I'm Still Here!

Friday, January 27, 2012
10:05 P.M.

Hey everybody, I'm just writing this to let you all know that I am still updating my blog from time to time! However, I'm swamped with work right now, so don't fret if you don't see many posts in the next week (or two). I'll still post occasionally.

Thanks!
Charlie

Snow Update

Thursday, January 19,

5:20 P.M.

Hi everybody, this is just a quick update... the snow has stuck around longer than forecast, and freezing rain has mainly impacted areas south of Seattle, sparing the Seattle area itself. The snow has been going on all day here, and I'd say UW got about 2 inches out of this storm, maybe a little more.

I'm actually expecting another inch or two before we are done, as the precipitation, after briefly dipping south, is starting to rise back up north again. Temperatures have been below freezing all day here, and I doubt they will warm up significantly overnight. Friday morning should see a significant warm up, but temperatures may very well not get above freezing in some spots until daybreak. If this pans out, schools will likely be canceled.

05:25pm PST Wed 19 Jan 2012

One thing that makes me think that the cold air may stay around longer is the fact that both the surface temperatures and temperatures aloft are decreasing. Take a look at the latest profiler from Sand Point. This graphic shows the temperatures recorded throughout the atmosphere at different times of the day. As you can see, the air aloft is much warmer than the air at the surface due to relatively warm and moist Pacific air over-running the colder, drier, arctic air below. Still, the most recent sounding, the black one, is noticeably cooler aloft than the other soundings today.

Even though the event is not over, it'd be great to have some more preliminary snow totals!!!

Thanks,

Charlie

Ice Storm Warning

Thursday, January 19, 2012
11:06 A.M.

As if snow wasn't bad enough...

After the major snowstorm yesterday, another storm was forecast, but precipitation was only supposed to make it to Olympia. The models turned out being wrong with this storm, and precipitation is located all the way to the eastern entrance to the Strait of Juan De Fuca.

11:22am PST, Thu 19 Jan 2012

The upper atmosphere has warmed up significantly since yesterday morning, particularly south of Seattle, yet the lower atmosphere has largely remained below freezing. This type of setup can create freezing rain, which is more disruptive and hazardous to the region than snow. Snow can make the roads very slick, but freezing rain turns them into an ice rink.

Many places south of Seattle are reporting freezing rain right now, and the NWS has issued an ice storm morning for much of the Puget Sound region and southwestern Washington. This is the first ice storm warning issued since 1996, where Seattle got 2 feet of snow before everything first changed to freezing rain, and then rain. While this storm is not expected to have as much of an impact on the region as the December 1996 one, it will be very disruptive to the region. Ice not only creates slick roads, it accumulates on trees and power lines, bringing them down and causing power outages. Many places have reported over a half-inch of ice so far. Let's take a look at some pictures from around the region!

Kent, Washington - Photo Credit - Kristen Jordan

Issaquah, Washington - Photo Credit - Stephanie Schlosser

Auburn, Washington - Photo Credit - Mark Haley

Auburn, Washington - Photo Credit - Mark Haley

Auburn, Washington - Photo Credit - Mark Haley

However, there is some good news. At the UW campus, the freezing rain has changed to a steady, accumulating snow. It looks like the snow may extend a bit further south than the NWS was expecting it to at this point, so places Seattle north could easily see up to two additional inches if it keeps snowing, with no changeover to freezing rain or rain. 

Things should gradually warm up a bit overnight, and they will really warm up Friday. On an interesting note, some of the models have been indicating a change to colder weather in "la-la land" on the models (so far out that you can't put much stock in the results) but it is at the very least interesting to see. I will keep you updated if the arctic outbreak looks more likely.

Thanks for reading! Stay safe out there.

Charlie

Post Your Snow Totals!!!

Wednesday, January 18, 2012
9:50 A.M.

Hello everybody! It snowed last night and most places in Washington are still seeing snow right now! The models this morning actually came more in line with what I was predicting last night and are now predicting more snow for the Puget Sound lowlands. A couple more inches will fall in the Puget Sound region today before the snow tapers off this afternoon. It will remain below freezing today and overnight, so much of the snow on the roads right now will stay there through Thursday. Schools will likely be closed tomorrow.

Valid 04:00 am PST Thu, 19 Jan 2012 - 24hr Fcst - UW 4km 12z 1/18/2012 WRF-GFS - 24 hour snowfall

Olympia got HAMMERED with this storm... my roommate is from Olympia and one of his friends is reporting 13 inches of snow. Warning: everybody who's not in Olympia will be pretty jealous...

Photo credit: Dylan Glebe

Below are observations over Washington as of 9:53 A.M. Nearly all places are seeing NE winds with the exception of southern Washington, where the winds are from the SE. The "rain" is posted on the right, but all of it has been in the form of snow save perhaps Vancouver, Washington, which is right by the border.

I've heard of some preliminary snow totals, and as expected, the heaviest snow was in southwest Washington. Toutle got 18 inches, Centralia got 17 inches, Winlock got 15 inches... incredible stuff. In addition, winds gusted at over 100mph on the Oregon Coast last night.

Seattle might not have gotten the brunt of the storm, but we got a pretty good amount, and I'm content with that. Now, I'm gonna go play in it!

PLEASE post your snow totals, along with your elevation and location, on the comments down below!!!

Enjoy the snow,
Charlie

Models Pessimistic, Charlie Optimistic

Tuesday, January 17, 2012
10:05 P.M.

So, the latest model runs have come in, and they are moving the storm even further south. For snow lovers who live in Seattle, this is bad news. However, I've been watching the radar, and I believe that we will see more snow than is currently forecast by the models. I'm still expecting less than 4 inches north of Seattle, 4-7 inches from Tacoma to Seattle, and over 7 inches south of Tacoma, despite the fact that the newest WRF-GFS model gives Everett to Tacoma a paltry 1-3 inches of snow. The southern Cascades in southern Washington and northern Oregon will receive feet of snow with this storm, so if you are bummed out that we didn't end up getting one of the biggest snowfall events in years around here, just head to the mountains. You can be standing in feet of snow, maybe bring a picture of the Space Needle along with you, and you can at least pretend that Seattle is experiencing a true "Snowmageddon."

Many of you are probably frustrated with how the forecasts have changed so much, particularly how they have gone back down after first proclaiming that Seattle would be in for the snow event of a lifetime. I'm not sure if these next few images will calm your nerves or just get you angry at our weather models, but I think it is important for the populace to understand how much a situation can change in such a short amount of time.

Let's take a look at the progression of this event on the UW WRF-GFS model. Here, I am showing the different 24-hour snowfall forecast maps starting from when the event was 84 hours out and ending with the current snowfall forecast over our area over the next 24 hours.

Things were starting to look interesting on Sunday morning's run. At first, the models showed the low coming north, quickly scouring out any cold air but also dumping several inches in northern spots like Bellingham.

Valid 04:00 pm PST Wed, 18 Jan 2012 - 84hr Fcst - UW 12km 24 hour snowfall - initialized 12z Sun, 15 Jan 2012

Sunday night? uh oh, major snow. Still a lot of snow to our north.

Valid 04:00 pm PST Wed, 18 Jan 2012 - 72hr Fcst - UW 12km 24 hour snowfall - initialized 00z Mon, 16 Jan 2012

Then comes Monday morning's run. Close to a foot over Seattle. Simply amazing.

Valid 04:00 pm PST Wed, 18 Jan 2012 - 60hr Fcst - UW 12km 24 hour snowfall - initialized 12z Mon, 16 Jan 2012

Monday night's run was very different, but it still suggested a lot of snow for Seattle. This was probably our worst-case scenario. The low was shown to go to our south, bringing down cold air, yet still be close enough to give lots of snow to Seattle. Honestly, this was when I started freaking out. A major snowstorm, possibly the biggest since 1996 in Seattle, and maybe before that for Sea-Tac.

Valid 04:00 pm PST Wed, 18 Jan 2012 - 48hr Fcst - UW 12km 24 hour snowfall - initialized 00z Tue, 17 Jan 2012

Then came this morning's run. A major letdown. All of the heavy snow has moved to our south. Still, we had pretty significant amounts nonetheless... I'd take 2-6 inches any day!

Valid 04:00 pm PST Wed, 18 Jan 2012 - 36hr Fcst - UW 12km 24 hour snowfall - initialized 12z Tue, 17 Jan 2012

Tonight's run was a crusher though... the snow has moved even further south!

Valid 04:00 pm PST Wed, 18 Jan 2012 - 24hr Fcst - UW 12km 24 hour snowfall - initialized 00z Wed, 17 Jan 2012

And that's the evolution of our snowstorm prediction. Looking at last night's model run, it's easy to get pretty excited, but the models had a poor handling on this storm and are now giving us paltry amounts as compared to what they were showing before.

Forecast models are our best tool of predicting weather in the future, and model predictions will get better in the future around here, especially as ensemble forecasting continues to be developed. Still, models are models. Let's take a look at what is actually happening out there!!!

Valid 10:47pm PST Wed, 18 Jan 2012

We've got a FAT blob of moisture headed up our way from the southwest, and the good thing is that it is looking more impressive here than it did on our models. Ever since the two WRF-GFS runs today, I've been thinking that the models have been underestimating the strength of the jet stream propelling this thing into our area. You can see some heavier precip around the edge of the front, and if I had to guess why these features are there, I'd say it is because the warm air is rising over the cold wedge of air that I was showing to you in the cross-section diagrams of my previous post. It's a great thing to see, and I'm very happy that the precipitation is this far north this early. The mark of a really good forecaster is the ability to pin down amounts in the short term when models are of little use just by looking at radar imagery. By looking at this radar image, I'd expect snowfall amounts exceeding those shown in the WRF-GFS above, which is why I have forecast 4-7 inches of snow from Everett to Tacoma. Taken at face value, the WRF-GFS shows anywhere from 1-3 inches from Everett to Tacoma.

Now, let's take a look at the bigger picture.

I'm going to show three different images here from different times throughout the day. These images show the water vapor in the atmosphere, which is often more useful than standard infrared satellite maps for picking out centers of low pressure, as low pressure centers tend to develop a "dry slot" right by the low as they develop.

01:00 pm PST Tue 17 Jan 2012

This image was taken at 1 P.M. this afternoon. That huge blob of moisture is what is headed towards us. 

06:00 pm PST Tue 17 Jan 2012

5 hours later, the front is moving in. Notice how defined the leading edge has become as it has moved into our area. Again, I am hypothesizing that the reason for this increase in definition is because of the warm, moist air riding above the cold wedge of arctic air extending back into Canada. I've only taken atmos 101 though, so don't quote me on that.

10:30 pm PST Tue 17 Jan 2012

Now, the high level clouds are completely over our area, and we are just waiting for the surface precipitation to catch up! In case you didn't catch on, this system is moving pretty dang fast, being driven by a very strong jet stream aloft.

Let's go over some quick gradients and surface observations now, and then I gotta get out of here!!! 

These gradients were given to me by my friend and fellow weather nerd Nicholas Efthimiadis.

The BLI (Bellingham) to YWL (Kelowna) gradient is currently -10.7, meaning the pressure in Bellingham is 10.7 degrees lower than the pressure in Kelowna. Remember, wind always flows from high pressure to low pressure, and over terrain, it follows a fairly direct, "as-the-crow-flies" path. Hence, tons of frigid air is making it's way from the interior of BC to Bellingham. Indeed, the last time I checked, the temperature at the Bellingham airport was 11 degrees Fahrenheit. Cold stuff!

The OLM (Olympia) to BLI (still Bellingham!) gradient is currently -1, meaning that Western Washington is now experiencing light northerly winds. Expect those to become pretty strong tomorrow, especially up by Bellingham.

Now, the surface observations in our state as of 11 P.M.

11 degrees, clear, and light (~5mph) winds out of the NNW at BLI, with temperatures slightly above freezing at Sea-Tac. Right now, the Willamette Valley is getting snow and they have temperatures in the low 30s, but they will change over to rain in the next couple hours.

My weather station is reporting a balmy 36 degrees with 255% humidity. I wouldn't put too much stock in it.

Do some snow dances, I have a feeling they might be working. :)

Charlie

Small Changes, Big Effects

Tuesday, January 17, 2012

11:39 A.M.

 Valid 04:00 pm PST Wed, 18 Jan 2012 - 36hr Fcst - UW 4km 12z WRF-GFS 24-hour snowfall

As I was looking over the models and the spread in forecasts being made by different people and organizations, I was thinking about some changes that should be implemented in UWs Atmospheric Sciences Department. In order to apply for a Ph.D, aspiring graduates must have forecast at least one Seattle snow event to an overall "standard" set by the department. If they forecast it well enough, they can go ahead with their Ph.D if all of their other prerequisites are met. If they don't quite make the cut, they can always wait for next winter.

As hard as it is to forecast this stuff, it's even harder when the media gets involved. Newspapers and tv stations will often feature these huge articles on how much snow the Seattle area will get. What did the Seattle Times say for today? "Megastorm Looms for Area." Sound pretty scary, and it is sure to attract a lot of readers. It turns out that it may have been a bit premature though, at least for Seattle. As a forecaster, you find yourself being the hero or the goat based on how accurate your forecast is, especially if it is catered towards certain types of weather the public is wishing for (i.e. snow). 

This morning's forecast models showed the storm coming in slightly further south on Wednesday. Seattle would still be on the cold side of the storm and would receive snow, but the heaviest amounts would be shifted southward. Seattle would not bear the brunt of the snow... instead, places like Centralia would. Now, I'm expecting less than four inches north of Everett (with Bellingham getting nothing), 4-7 inches from Tacoma to Seattle, and over 7 inches south of Tacoma. Isolated spots in Southwestern Washington could pick up over a foot of snow, and the Southern Cascades (in Washington and Oregon) will see apocalyptic amounts measured in feet. This is slightly different than what other forecasts are calling for... Cliff Mass of the University of Washington was calling for 2-6 inches from the storm, while the National Weather Service is predicting anywhere from 5-10 inches of snow from Tacoma to Everett with higher amounts to the south and lower amounts to the north.

This is a very complicated forecast, and I am going to show you some model charts I have never shown you before to give you a better idea of what is in store for us. First, let's look at some ensemble charts.

There are two general types of models: operational and ensemble. Operational models take the atmosphere at one point in time and run equations to predict the weather into the future. These models usually run at 00z and 12z GMT, with the NOAA models also running at 06z and 18z. I commonly post pictures from operational models on my blogs... in fact, the picture at the very top is from this morning's operational UW WRF-GFS. Ensemble models, on the other hand, take a whole bunch of operational models and combine them into one giant "supermodel" by averaging the statistics from each model run together. With ensemble models, we are able to express not only an "average solution" for the runs but also identify areas where different models deviate with respect to the average solution.

Take a look at the ensemble chart below. It shows the sea level pressure (SLP) expected at 7 A.M. Wednesday. Unfortunately, this chart is from last night's 00z ensemble runs (I couldn't get to the one for the 12z runs for today for some reason) but it is still useful because it identifies uncertainties in the track of the storm that will impact us.

Valid 07:00 am PST Wed, 18 Jan 2012 - 39hr Fcst - UW 12km UWME Mean & Spread" SLP Standard Deviation and Mean

This chart shows two things, the deviations in SLP (marked by gray shading) and the ensemble mean (average) for the SLP (marked by blue isobars). Here, we see a low pressure system approaching the mouth of the Columbia, which is in line with the 12z WRF-GFS run from this morning and supports relatively less snow in Seattle (2-6 inches) compared to previous model runs. The really important thing to look at there though is the shading, which dictates the spread in the SLP predictions of each of the ensemble members. South of the Columbia, the shading is light, denoting little disagreement with the models in regard to SLP predictions. North of the Columbia, however, there is greater uncertainty, meaning that the models are predicting a larger spread of surface pressures there. By looking at this chart, a meteorologist can immediately know that most runs indicate a pretty similar SLP structure to the south of the center of the low pressure system, but that the models are in less agreement of the pressure configuration north of the low. In fact, some ensemble members may even take the whole low pressure system and shove it up to the north. 

I don't use ensemble models as much because they aren't very convenient for making a quick forecast and our  operational models generally do a pretty good job, but they are very useful when the operational models are in complete disagreement because they give you specifics on where they are disagreeing while still providing you with a great average of all the solutions that is many times far more accurate than any of the operational models. Ensemble forecasting is the way of the future... in fact, UW has an ensemble system dedicated to the layman called "Probcast" (you can find it @ "UW Probability Forecast" on my list of weather likes on the right) that is generally very accurate.

Second, let's look at some cross sections!!! Cross sections look at a vertical slice of the atmosphere over a large region and show the characteristics of it at a certain time. Cross sections are very important to look at right now because we are in the midst of an overrunning event, where warm, moist Pacific air overruns cold, arctic air. 

There are a lot of things to look for in these charts, but I first want you to look at the far right section of the chart, which represents Bellingham and the mountains north of it. The left side of the chart goes south past Olympia. 

In this first chart, notice how there is a "wedge" of blue lines at the surface. This, folks, is the beginning of a strong, northeasterly wind pouring into our region as the storm approaches.

Valid 04:00 am PST Wed, 18 Jan 2012 - 24hr Fcst - UW 4km 12 WRF-GFS Orting, WA, to Vancouver, BC

Tomorrow morning, some moisture arrives in gusto, which you can see by the colorful shaded area in the top left. Cold air is still pouring into Western Washington from the north. 

 Valid 10:00 am PST Wed, 18 Jan 2012 - 30hr Fcst - UW 4km 12 WRF-GFS Orting, WA, to Vancouver, BC

Look now though! There is so much cold air that it has displaced the moisture and created a sort of "block" preventing much moisture from coming further north! So while the north gets extremely cold air, this cold outflow will actually make it more difficult for the moist air off of the Pacific to encroach and bring more snow to the area. It will be very important to monitor the ways these different air masses interact. If the arctic "wedge" ends up being weaker, it will be easier for more moisture to make it further north. On the other hand,  if the arctic air ends up overpowering the maritime air, places to the north of Everett or so may see much less snowfall than is forecast. 

Valid 04:00 pm PST Wed, 18 Jan 2012 - 36hr Fcst - UW 4km 12 WRF-GFS Orting, WA, to Vancouver, BC

This has been a very long post, and I hope you got something out of it. I'll offer another review of the models tonight. Here, I wanted to give you my general forecasts and introduce you to some concepts about ensemble forecasting and the interaction between arctic air and Pacific air. Later tonight, I'll get down to business and talk about updated forecasts... maybe I'll even include some real time stats to reflect the battle between the two different air masses! 

Charlie

I'm Losing Sleep...

Monday, January 16, 2012
1:03 P.M.

I've tried to be as objective as possible with these forecasts, because while Seattle freaks out over the "s" word, it needs to be made clear to the public that there are drastically different types of snow events in Washington and not all of them are serious.

Now, it is looking more and more likely that we will experience a major snow event starting later tonight and likely persisting into Wednesday or even beyond.

Don't believe me? Check out what the National Weather Service office here in Seattle had to say this morning.

"VERY HIGH IMPACT WINTER WEATHER IS EXPECTED THROUGH 
WEDNESDAY NIGHT OR THURSDAY. SNOWFALL AMOUNTS AT SEATAC COULD EXCEED 
ANYTHING SEEN SINCE NOVEMBER 1985...A TOP 5 RECORD 24 HOUR SNOWFALL 
AMOUNT. "
I wasn't around in November 1985, but I have heard that it was a very snowy time for Western Washington. I did a little research and actually found a surface chart for November 21, 1985. It outlines a nearly perfect scenario for snow here, and although our scenario will be considerably different, the two share some key similarities.

This map shows the surface analysis at 5 P.M. PST, November 21st, 1985 over the Pacific Northwest. There are TWO key things on this map that are telling of a major snow event over Western Washington. First of all, there is a large dome of high pressure up in Canada with very cold air at the surface and a strong pressure gradient through the Fraser River Valley. Second, there is a low pressure system to the south of Puget Sound, drawing even more cold, northeasterly winds from the Fraser River Valley into the state while providing lift for precipitation.

The event being forecast is different from the November 1985 event in that it the air in the area will not be as cold and the storm coming in will come more from the west off of the Pacific instead of coming in from a more northerly track like the 1985 storm. However, we still do have cold air to our north and a big, juicy storm coming to our south. Whenever this happens, there is the possibility for significant snow in the lowlands.

The forecast for the next couple days is very complex, so I am going to break it up into three parts.

Part 1: Today into tonight - isolated snow showers

Part 2: Tonight into Tuesday afternoon - increasing snow showers associated with an arctic frontal boundary

Part 3: Tuesday night into Wednesday - possible major, widespread overrunning event

Part 1:

Today into tonight is expected to be the most benign event of the four for the Seattle area. A small disturbance is directing unstable, westerly flow into our area, generating snow showers in spots. The Olympics, however, are shadowing the Central Puget Sound region, particularly Seattle. Expect these showers to slightly increase throughout the day, but the Seattle area will likely remain largely snow-free for today outside of a couple isolated showers. Take a look at the image below and notice how the Puget Sound area is high and dry while Bellingham and Olympia are getting pounded.

02:03 pm Monday, January 16, 2012

Part 2:

SEATTLE/BREMERTON AREA-TACOMA AREA-HOOD CANAL AREA-
235 PM PST MON JAN 16 2012
.WINTER STORM WATCH REMAINS IN EFFECT FROM MIDNIGHT PST TONIGHT
THROUGH TUESDAY AFTERNOON...
...WINTER STORM WATCH REMAINS IN EFFECT FROM LATE TUESDAY NIGHT
THROUGH WEDNESDAY EVENING...

* SOME AFFECTED LOCATIONS...SEATTLE...TACOMA...BREMERTON...
  SHELTON.

* TIMING...SNOW ACCUMULATIONS ARE POSSIBLE TONIGHT THROUGH TUESDAY
  AS COOLER UNSTABLE AIR CONTINUES OVER THE AREA. LOCAL
  ACCUMULATIONS UP TO 3 INCHES ARE POSSIBLE. A MUCH MORE
  SIGNIFICANT WINTER STORM IS LIKELY LATE TUESDAY NIGHT THROUGH
  WEDNESDAY OR WEDNESDAY NIGHT. SNOW WITH THIS SYSTEM WILL BE
  WIDESPREAD AND HEAVY.

* SNOW ACCUMULATIONS...AT THIS TIME UP TO 3 INCHES ARE POSSIBLE ON
  TUESDAY. TEMPERATURES WILL REMAIN STEADY OR GRADUALLY FALL
  DURING THE AFTERNOON HOURS...SO ROADWAYS MAY FREEZE. A MUCH MORE
  SIGNIFICANT WINTER STORM IS LIKELY LATE TUESDAY NIGHT THROUGH
  WEDNESDAY EVENING. WEDNESDAYS STORM MAY BRING 6 TO 14 INCHES OF
  SNOW.

* MAIN IMPACT...EXTREME TRAVEL DIFFICULTIES ARE POSSIBLE.

If you read closely, you'll notice that the National Weather Service actually has two winter storm watches over our area right now! One of them is for an arctic front that will sweep through tomorrow, and the other is for the bigger storm late Tuesday into Wednesday. Part 2 is concerned with the first winter storm watch tonight through tomorrow afternoon.

As we move into Monday night, an arctic front will start to move south through Whatcom and Skagit Counties, reaching the Seattle area at or after the morning commute. Even though tomorrow's communte could be tough, it is hard to know if schools will close at this point because the peak of the snow will strike after 5 A.M., which is when most schools have to make their decisions about whether to stay open or close. Schools aside, I'm forecasting anywhere from 1-5 inches of snow across much of Puget Sound from tonight to tomorrow afternoon. Arctic fronts can be very hit-or-miss, so it is definitely possible that some places may see no snow at all. Right now, it looks like the highest amounts will be in Snohomish Country, but we'll have a much better clue of what we can expect snow-wise from this feature later tonight. I don't want to go to classes as much as the next guy, but it'd be smart to plan for school in the morning just because of the uncertainty associated with this feature. 

Based on the model below, the front should get to Seattle around 10:00 A.M. tomorrow, but I wouldn't be surprised if it came in earlier. As I said before, these arctic fronts have a mind of their own.

Valid 10:00 am PST Tue, 17 Jan 2012 - 30hr Fcst - UW 4km 12z WRF-GFS 3-hour snowfall

That said, it sure doesn't look like I'll have to do any work Tuesday night. Which leads me on to Part 3.

Part 3:

Oh boy. This is the part of the forecast I have been losing sleep over. And after this afternoon's models, I don't think sleep will be possible.

First off, let's take a look at the models. Remember, the things you need for a major snowstorm are high pressure and cold air to the north and a juicy Pacific low pressure system making landfall to our south, giving us heavy precipitation while drawing in cold air from the north.

Here is the latest 18Z NAM:

Valid 05:00 pm PST Wed, 17 Jan 2012 - 54hr Fcst - UW 4km 12z WRF-GFS 3-hour snowfall

Look at that! A big low pressure system right at the Columbia River, and higher pressure over Southern B.C.!

But it gets even better! Another storm goes to our south, possibly giving more snow Seattle northward.

Valid 11:00 am PST Thu, 18 Jan 2012 - 69hr Fcst - NAM 6-hour precip, 1000-500mb thickness, SLP

Now, the 18z GFS.

Valid 11:00 am PST Wed, 17 Jan 2012 - 48hr Fcst - GFS 6-hour precip, 1000-500mb thickness, SLP

Again, a juicy storm comes right to our south! And once again, another storm comes to our south, possibly prolonging the snow event for many areas.

Valid 8:00 am PST Thu, 18 Jan 2012 - 66hr Fcst - GFS 6-hour precip, 1000-500mb thickness, SLP

Us forecasters have a lot on our plates right now. It's very exciting to even be talking about an event like this, and it will be great to watch it on the coastal radar. These posts are long, but for an event that doesn't come around too often, it's worth it. :)

Charlie

The Spiel on Snow After the Spiel on Snow

Sunday, January 15, 2012
9:47 P.M.

I gave a schpeal on snow this morning, and now it's time I give another one. Many places around Seattle saw significant accumulations today while other places saw very little snow. My brother reports that my house down by Lake Washington between the floating bridges got 4 inches today, but the college dorm where I am currently staying only got an inch. I went up to Whidbey Island today to update my weather station (more on that later) and while Whidbey did not see any steady snow like the Seattle metropolitan area did, it had some highly localized snow showers that were interesting and fun to watch. It always amazes me how localized these showers can be. My mom and I were driving down one of the numerous highways on South Whidbey today and we drove from clear skies to heavy snow in less than 50 yards.

Here is a brief list of snow totals from today, just to give you an idea of the variability in snow totals around here! This list was compiled by Scott Sistek of KOMO, and you can find Scott Sistek's current discussion and forecast for the future here.

Kirkland - 7.5"
Bothell -  7"
Mill Creek - 7"
North Bend - 5"
Marysville - 4"
La Conner - 4"
North Seattle - 2.5"
West Seattle - 2"

Here's a picture from one of my favorite websites, the UW SnowWatch website. You can find it @ http://www.atmos.washington.edu/SNOWWATCH/.

 UW SnowWatch 09:39pm Sun 15 Jan 2012 24-hour snowfall

The amounts on this picture are estimated, but the general shading gives you a good overall picture of who saw the heaviest snow. The dorm I live in is right by Portage Bay, which got significantly less snow than Capitol Hill and areas east. Kirkland and Bothell were the big-time winners from this storm.

Here are some pictures of snow from around the Sound today! All of these were taken by members of the "Pacific Northwest Weather" group on Facebook, which is a group of local weather enthusiasts who love to discuss weather models and share weather-related stories/photos from across the Pacific Northwest and beyond. If you aren't a member, you should definitely look into joining! Check it out @ http://www.facebook.com/groups/109882929060639/. 

Issaquah, ~3 P.M. Photo credit: Stephanie Schlosser

Seattle, ~3 P.M. with 4 inches of snow. Look at the Bank of America Tower in the background! Photo credit: Nick Vaughn

"My attempt at making a snowman. I've guess I've lost those skills" - Nicholas Efthimiadis, North Seattle ~ 3 P.M.

One more thing... it is ICY out there tonight, so be very, very careful when you are driving! Roadway ice is the #1 weather-related killer in the Pacific Northwest by a long shot, so please be careful out there, and don't end up like this...

Portland, ~4 P.M. Photo Credit: Jeff Raetz

So, what can we look forward to now?

It's tough to say, because the forecast, particularly for Tuesday-Wednesday, has been so unclear over the past few days that NOAA has actually sent out aircraft over the Pacific to obtain additional observations to plug into their models with the aim of getting a more accurate forecast. NOAA does this with hurricanes all the time, but I've never heard of them doing something like this before. Getting a model consensus on this Tuesday-Wednesday storm will be critical, because since the models diverge on the strength and location of the low, they also differ wildly on more extended forecasts for the rest of the country, with some models keeping the arctic air bottled up in Canada while others blanket the eastern half of the country with snow.

The forecast for tomorrow into Tuesday morning is still difficult, but it is much, MUCH easier than the late Tuesday-Wednesday time frame, so let's start with it first.

Valid 04:00 pm PST Tue, 17 Jan 2012 - 48hr Fcst - UW 4km 00z WRF-GFS 24-hour snowfall

This shows the 24-hour snowfall forecast in our area from 4 P.M. Monday to 4 P.M. Tuesday. Tomorrow, the snow will be a little late to start around our area, but it should start picking up in places by the afternoon. Still, it will be pretty spotty, with some places getting dumped on while other places receive nothing, and Seattle could very well be "snow-shadowed" by the Olympics tomorrow and receive very little snow. It will be important to watch the radar tomorrow, as it will prove to be the best tool for predicting snowfall amounts several hours into the future, although the models are in reasonable consensus about bringing some heavier snow through the area into Tuesday morning. We'll just have to see how this situation plays out.

Now, let's talk Tuesday-Wednesday.

I'm getting tired, so I'm just gonna give you the basics. The GFS model gives us several inches of snow before  shifting to heavy rain. 

Valid 04:00 pm PST Wed, 18 Jan 2012 - 72hr Fcst - UW 4km 00z WRF-GFS 24-hour snowfall

This scenario would give Seattle around 2-6 inches of snow, but it would all change to rain and wash away, so I'm not particularly excited about it.

The other American model, the NAM, is showing a strong system making landfall on the central Oregon coast. Such a landfall would give Seattle cold temperatures, but little precipitation. Portland, on the other hand, would see over 6 inches of snow.

Valid 01:00 pm PST Wed, 18 Jan 2012 - 69hr Fcst - 00z NAM 6-hour precip, SLP

Now, the Euro...

I'm a little nervous about putting the latest run of the European Model up because it would generate dangerously high expectations for snow in Seattle, and the last thing I want is a bunch of people frustrated with me because they didn't get the foot of snow the Euro promised them.

I'm going to show two shots from the latest Euro... one is the 3-hour snowfall over our area at 60 hours, and the other is the three hour snowfall at 72 hours. 

Valid 04:00 am PST Wed, 18 Jan 2012 - 60hr Fcst - 00z Euro 3-hour snowfall

You can see a huge band of snow streaming over our area. It moves slightly north, and then stalls directly over Seattle for 12 hours.

Valid 04:00 pm PST Wed, 18 Jan 2012 - 72hr Fcst - 00z Euro 3-hour snowfall

After this, we would warm up, but if this model run was correct, Seattle would see over a foot of snow. I do not think that will happen, but it is food for thought.

Finally, here's the deal on my weather station. I got it set up both on the Weatherlink website (http://www.weatherlink.com/user/charliep127/) and, most recently, at the Weather Underground website (http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KWACLINT8). Both of these links give you live access to the current weather conditions on Southern Whidbey Island. It's definitely something to check out!

Be sure to write any snow totals you got from today on the comments!!!

Charlie

The Spiel on Snow

Sunday, January 15, 2011
10:02 A.M.

I-5 by Northgate, Washington on Sunday morning - KOMO News

First off, I'd like to apologize for not posting a blog update yesterday. I was doing tons of math homework and review, because after jumping into Calculus 125 at the University of Washington, I've discovered that I have a lot of work to do to get back up to speed (I skipped Calculus 124 with AP credit). I'll be ok, but I will be spending a lot of time doing calculus. Strong math skills are essential to being a good meteorologist, so I'll be sure to put a lot of time into my math studies.

Now, I've finished my math and I'm ready for some real work: forecasting snow over the next few days.

Yesterday, much of Western Washington saw snow, but only a few places really got any accumulation. Remember how I talked about the shortcomings of the LAWES scale when dealing with local weather phenomena, such as convergence zones? While much of Western Washington escaped with less than one inch of snow, places around Everett got HAMMERED with snow. Take a look at the radar image from yesterday afternoon below, and note the strong convergence zone extending all the way from the northern Kitsap Peninsula through Everett and up into the Cascades.

Meanwhile, places to the north and south got very little snow while this convergence zone was roaring. In fact,  some places saw blue sky. Take a look at the visible satellite shot below.

02:10 pm PST Sat 14 Jan 2012

This shot captures the truest essence of a Puget Sound Convergence Zone. Not only is there a band of clouds where the zone is, but there are clear skies on either side of it. As the air converges and rises in the zone, it descends on either side of the zone, stifling clouds and precipitation. Yesterday's convergence zone was a textbook example of what a strong one looks like.

Snow totals in the Puget Sound lowlands ranged from 0-1.5 inches outside the zone to up to 4-5 inches in the zone.

Now, let's talk about today. We are seeing a rather weak low pressure system slide on through to our south, but in the meantime, it is giving us some snow showers. Take a look at the radar and satellite from this morning.

10:51 am PST Sun 15 Jan 2012

10:00 am PST Sun 15 Jan 2012

I know the pictures are out of sync, I'm just trying to write this really quickly. In the radar, you can see some showers around the area, but most importantly, you can see a weak area of convergence getting established over Seattle. There is another convergence zone over the Strait of Juan de Fuca. Neither of these zones are particularly strong, but they will give us precipitation. The National Weather Service is also predicting the northern zone to shift south throughout the day, bring showers along with it! On the satellite picture, you can see the center of the low right off the mouth of the Columbia River. It kind of looks like a tiny hurricane. Needless to say, it isn't.

The biggest factor in how much snow you will see today is your elevation and distance from the water. Places by the water will likely see snow, but it won't stick to roads. Places like Capitol Hill, on the other hand, could become quite snowy. If the temperature drops below freezing tonight like it is expected to, ice will be a major problem on the roads tomorrow.

I gotta go soon, but here's what I am predicting as far as snow goes for the future.

Today:  highly variable snow amounts ranging from 0-4 inches over the lowlands, with higher amounts over the hills and in persistent areas of convergence (LAWES 6.2)

Tomorrow: Snow picking up in the afternoon, LAWES 5.2

Things get interesting Tuesday, as a large system comes in to our south, spreading heavy precipitation over our area while bringing down cool, northerly air. The models are not in agreement on this scenario, as one brings it further north, giving us mostly rain. However, if a strong storm comes to our south on Tuesday, many places could receive up to 6 inches of snow. I don't feel comfortable forecasting a snowstorm yet, but as the models come into better agreement, I will let you know what's going on, because we could see a serious snowstorm mid-week.

I have to leave right now to go up to Whidbey Island, but I'll post more pictures and snow totals from various areas later on today. In the meantime, post your snow totals along with your location and elevation on the comments so that other people can see which areas are getting snow!

Thanks for reading,

Chuck