Thursday, December 19, 2013

Oh Heck Yeah!

Thursday, December 19, 2013
8:32 p.m.

OK, so when I saw the latest model run, I absolutely jumped for joy. Why? Because the newest WRF-GFS model run upped the forecast snow amounts. At first, this model gave us a lot of snow, but then it sharply pulled back. Now, it’s trending whiter again. Let’s take a look at how this trending has turned out.
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This was last night's run, and was as close to a Snowmageddon as the models ever came to showing. Half a foot just to the north of Seattle? Please sir, may I have another? 

But then came this morning's run. I cried.

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Snow amounts decreased three-fold over north Seattle. Those poor folks in Tacoma weren't getting any. I got over myself fairly quickly... this was never expected to be the snow event of the century, and I honestly didn't even think it was gonna happen... but still. It's like walking out of a test feeling great about your performance, and then seeing that you failed it. OK, maybe not failed it, but didn't perform as well as you thought you would.

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Then came this evening's run (and the numbers are still rolling in). It definitely wasn't as good as last night's run, but it was significantly better than this morning's run. There's that 6-inch bulls-eye over North Seattle. In any event, things look snowy tomorrow morning, especially from Northern Seattle northward. Kids - don't do your homework.

By the way, this snow event is brought to you by evaporative cooling. When the atmosphere is dry like it is right now, it acts like a "sponge" in that it absorbs some precipitation that falls from the sky. It takes energy to evaporate this precipitation and turn it into water vapor - heat energy - and this cools the atmosphere. If the atmosphere was moist, we'd be talking about a cold rain.

You can see that the moisture starts to come in around 4 a.m.

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By 7 a.m., it has solidly engulfed our area.

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This model says the front will pass through Western Washington from south to north during mid-morning and probably cross Seattle around 10 a.m. Afterwards, it looks like some precipitation may keep falling in the form of rain as showers and a possible convergence zone set up. Showers will be sparse in nature up north, and Seattle and the central Puget Sound region will probably be shadowed by the Olympics. The westerly flow behind the front will be VERY conducive, however, to orographic snowfall in the Cascades, so hopefully the Summit and Snoqualmie can open before too long. All in all, I'm not expecting too much rain, which is a good thing, because rain on snow is just really, really depressing.

Southern Washington, however, will receive more rain. The same thing goes for Oregon. With the exception of the Longview-Vancouver area perhaps picking up an inch, however, the snowfall doesn't look to be all that spectacular. Excepting that region, Olympia southward to Salem look to pick up trace amounts.

I'll probably wake up early to see the snow and/or I'll stay up late to see what happens, either by choice or by instinct. Either way, I'll keep you posted.

At this point, my LAWES rating is 5.3d

5 = 80-100% chance of snow with snow observed in area (Victoria, BC earlier this evening)
.3 = 2-6 inches of snow
d = 3 or more models consistent

Have a good one folks!

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