Revised LAWES Scale

Friday, January 13, 2012
3:11 P.M.

Don't judge me... this is the most relevant picture I could find.

I first invented my LAWES scale in November of 2010. It has been hailed as one of the most innovative weather scales of the 21st century by the followers of this blog ever since, but I have noticed a couple of its shortcomings over time, and it is time I update my LAWES scale to address these.

First, I made my LAWES level 3 more specific, replacing "a few days" with "5 days." Second, I added a new level that was between the old levels of 3 and 4 (now 3 and 5). The new level is now LAWES Level 4, and adds specificity to the scale by saying that the models are in a reasonable consensus about getting snow in 1-3 days. The percentages for LAWES Level 5 (previously Level 4) have been updated as well; there is now an 80-99% chance of snow with this scenario.

It's not over yet! I also added a .0 to the second part of the LAWES scale to describe situations where it doesn't make sense to forecast snow totals because the potential event is too far out. This was desperately needed, as I felt I couldn't properly use my scale when a snow event seemed to be lurking but the exact details were unclear. I also changed the range of snow predicted for each level more accurately reflect uncertainty in the art of forecasting, particularly the art of forecasting snow in Western Washington.

Remember, the first part of the scale explains the probability of snow, and the second part explains the amount of snow forecast. For example, a level 5.5 would mean that there is a 80-99% chance of snow and the snowfall totals would generally range from 6 inches to a foot. That is a pretty high LAWES level. Sometime in the future, I'd like to type that as an actual prediction and not as an example!

The scale predictions are centered around the Seattle metropolitan area, but they generally apply to all of Western Washington. When a situation nears, I will start to outline snowfall predictions for certain areas, as it is not uncommon for some places to get a foot of snow while places 30 miles away get absolutely nothing, especially with Puget Sound Convergence Zone events.

I'll print both scales below, so you can see the changes. The revised scale is on the bottom.

Old Scale:


LAWES level 0: You are on a planet that has the ingredients necessary for snow
LAWES level 1: Models are showing a chance of snow beyond a week out, 0-20% chance of snow
LAWES level 2: Models are showing a chance of snow within a week, 20-40% chance of snow
LAWES level 3: Models are all showing a scenario that would easily produce snow within a couple days, 40-60% chance of snow
LAWES level 4: Places around the area are already getting snow AND snow is forecasted for Seattle, 60-99 % chance of snow
LAWES level 5: Snow is occurring, 100% chance of snow (derp)

Ending in:
.1 - 0-2 inches of snow
.2 - 2-4 inches of snow
.3 - 4-6 inches of snow
.4 - 6-8 inches of snow
.5 - over 8 inches of snow
.6 - board the next plane to Panama


New Scale:

LAWES Level 0: You are on a planet that has the ingredients necessary for snow
LAWES Level 1: Models are hinting a chance of snow beyond a week out, 0-20% chance of snow
LAWES Level 2: Models are showing a chance of snow within a week, 20-40% chance of snow
LAWES Level 3: Models are showing a scenario that would produce snow within 5 days, 40-60% chance of snow
LAWES Level 4: Models are in consensus about a snow event 1-3 days out, 60-80% chance of snow
LAWES Level 5: Places around the area are already getting snow AND snow is forecasted for Seattle, 80-99% chance of snow
LAWES Level 6: Snow is occurring, 100% chance of snow (derp)

Ending in:
.0 - the event is too far out to pin down snow totals
.1 - up to 2 inches of snow
.2 - up to 4 inches of snow
.3 - 2-6 inches of snow
.4 - 4-8 inches of snow
.5 - 6-12 inches of snow
.6 - board the next plane to Panama

Tell me what you think of the new scale! And, if you have any suggestions for improving it, let me know!

Now, let's move on to our forecast.

We have several different snow events on the horizon. Our first shot at snow begins Saturday and lasts into Wednesday. I'd give us a LAWES rating of 4.1. Places will probably get snow, but it won't be that much and it will be hard to pinpoint which places will see the highest amounts. A Puget Sound Convergence Zone will probably form, meaning that places between north Seattle and Everett could see higher amounts... possibly much higher if it lasts for a long time. It is very hard to forecast the locations of these convergence zones though, so anywhere from Burien to Mt. Vernon should be on the lookout for one of these zones.

I personally think that most lowlands will get more snow than is advertised here. Due to the spotty nature of this incoming storm, some places will see no snow, but I believe Seattle could receive up to 2 inches with this storm. The models tonight will give us more details.

The real interesting stuff comes in next week. Some models have hinted at over a foot of snow for Seattle!!!

Ok, I probably shouldn't have said that, because now people are gonna run around and say that I forecast a foot for Seattle and then get mad at me when we get rained on. I do believe that we could get some significant snow next week though.

For now, I'm giving our snow chances next week a LAWES 5.3. I'll have more details after tonight's model runs, and I'll post again either tonight or tomorrow.

Thanks for reading!!!
Charlie