Update snow with the most powerful tools available

The most powerful technology for prediction is the aggregation of many high-resolution forecasts.

The UW modeling effort has one of the most advanced and largest (most forecasts–about 25), far superior to the National Weather Service system. Such aggregation systems are useful for representing the uncertainty of forecasts.

Let me show you what it predicts for a few snow-related locations. The accumulated snowfall is on the Y-axis and the time is on the x-axis (in GMT/UTC, 18 is 10am, 06 is 10pm Pacific time). The depth of the snow will be less than the amount of snowfall.

Each line is a separate forecast, and the black line is the average of all (usually a good forecast).

At Seattle-Tacoma Airport, there was about 3.5 inches of total snowfall, but the uncertainty was great, from 0.5 inches to 8 inches. Uncertainty is closely associated with the marginal temperature for the event. Snow starts tonight.

In Bellingham, it snowed more and the predictions were more agreeable. Why more sure? Because Bellingham is near the cold air source (the Fraser River Valley) and the air is cold enough it is almost certain.

In contrast, Olympia is expected to have much LESS snow, because warm air from the Pacific Ocean is more likely.

Wenatchee will see some light snowfall, but less uncertainty (temperature shouldn’t be an issue).

Same goes for the Stampede Pass, which is expected to be around 8 inches.

Another powerful tool is the regularly updated forecast of the NOAA/NWS HRRR model. Its 10 a.m. run time is in line with the above, with lots of snow in Northwest Washington and in the mountains, with a significant north-south slope as it snows over Puget Sound (less southerly). )

So prepare for tomorrow’s snow in NW Washington, central and northern Puget Sound, the Cascades, and the eastern slopes of that fence.