Snow Update

Will Try An Experiment Today--A 4 PM NOWCAST
At 4 PM I will do a nowcast on this blog...describe what is happening at that time and what is expected over the next few hours.

Perhaps can help you decide whether to go home early or cancel that evening event. But my real reason is that I think that the missing ingredient in forecasting today is very frequent local updates.



New runs are in. The latest high-resolution run shows light snow hitting Seattle between 5 and 6 PM and perhaps could hold out until 10 PM before it turns to rain. Could be some freezing rain at the tail end.

Here is some graphics I have never shown...model prediction of temperature and snow at 1000 ft. The red lines are snow mixing ratio at 1000 ft (related to snow intensity). The colors indicate temperature (red...too warm for snow, etc). Showing 1000 ft because it takes about that distance for snow to melt. If no snow at 1000 ft, there wont be anything at sea level. Click on them for bigger image.

Here is 5 PM. Puget Sound clear--snow coming into coast.


7 PM. Snow over Seattle and west. Much less snow east of city and south (easterly winds are bad for snow on east side)


9 PM: Still some snow from Seattle north and west. Upslope flow is giving much more snow SE of the Olympics.


Midnight...its over folks...except for the far north. RAIN and warm.

NW Washington and the Kitsap will get hit much harder than Puget Sound country. Could the timing be off an hour or so? You bet. Could the distribution be slightly different? Sure. But I bet these graphics provide the key story plots

And we can watch the winds and temperature change aloft in real-time using the Sand Point Profiler....

here is the latest plot (time on x axis, height in meters on y):Red lines are temperature and wind barbs in blue. Good easterly flow and temps just below freezing (you have to add one to these temperatures, which are in degrees centigrade for reasons I don't want to get into).
You can view this in real time at:

http://www.atmos.washington.edu/cgi-bin/latest.cgi?profiler

And check the latest weather radar imagery..you will see everything unfold. Or keep your eyes on Seattle RainWatch (will be SnowWatch tonight!):

http://www.atmos.washington.edu/SPU/

So bottom line: if you are in Seattle and you get home by 4 PM you will have no problem. By 5-6 light snow should hit. Over by midnight, probably sooner. Tomorrow's commute will be fine.