Friday, December 8, 2017

Winter Weather Advisory - First Snow of Season

Well folks...I'll eat my words from yesterday.

Yesterday morning I had posted that the chances of snow looked pretty slim and prospects were pretty muddy going forward.

Well...yesterday, the models trended west with the system that is expected to slide off the east coast. For this reason, a more "significant" snowfall is seemingly likely. While this won't be an outright snowstorm, a light to moderate event is likely. One thing to note is that the cutoff will be quite sharp. In other words, you will not have to go far to go from 4 inches of snow to nothing. We'll get into the specifics below.

As mentioned above, a coastal storm system will track off of the east coast later tonight and tomorrow. With the storm track now expected to be a little to the west of prior forecasts, snow will become likely very late tonight and throughout the day tomorrow. The upper level portions of this storm system have improved a lot over the past 24 hours. Snow will become likely by the wee hours of Saturday morning. The National Weather Service has issued a Winter Weather Advisory, which is in effect from tonight until 4:00pm Saturday afternoon.

The purple areas are under a Winter Weather Advisory for this potential storm. This *may* be extended farther to the west with more model data arriving later this morning/this afternoon.
Heavy snow is NOT expected. However, light to at times moderate snow will be likely. The best chance at a little more snow will be to the south and east of the metro areas (this much has not changed). What HAS changed is the expected western extent. Light snowfall may make it as far west as the Blue Ridge. There may also be some upslope farther west over the mountainous areas of the area.


The 06z GFS model forecast for the storm. You can see the snow backs pretty far to the west on this model.
Road accumulations should be minor due to temperatures hovering around or just above freezing - but slick conditions are still possible...especially given the low sun angle at this time of year.

Total snow accumulations south and east of the area will be 2-4 inches in spots. In the immediate I-95 corridor, 1 inch to as much as 3 inches may be possible. Farther west, the accumulations will taper down to an inch or less or a coating in the farthest west areas.

The 06z run of the 3km NAM model shows a bit more of an eastern snow profile. However, snow still gets into most areas...except for the far western zones.
The RGEM (Canadian regional model) is showing a very robust solution. I'm not sure this will happen. 
What's the potential of this being a busted forecast?

I would say that we are probably pretty close to the "maximum potential" for this snow event. It's a fairly quick hitting event, which prevents it from being a more significant event. There IS, however, the potential for the storm to cut east again, which would reduce totals significantly. SNow is notoriously hard to get in this area.

Will post updates as we draw closer. Stay tuned!

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