Final Call for Saturday

(Update 11:30am)

Cold air (both at the low and mid levels) is having a tough time eroding.  I think it's safe to say most areas end up exceeding (or at least on the higher side of) expected totals.

End Update

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(Posted 2/20 8 pm)

After going through all the data today, here's what I'm looking at accumulation wise for Saturday.  This is a tricky setup and confidence is definitely lower than usual.  There are a few caveats that will effect snowfall for some (discussed below).

Thoughts for the Shenandoah Valley

Timing: Snow showers should break out between 8-11am.  These will become steadier and heavier towards lunchtime and continue into the afternoon.  As warm air surges in aloft, snow will begin to changeover to more of a sleet/snow/freezing rain mix.  There's some uncertainty regarding just when this occurs but my best guess would be sometime during the evening (5-8pm or so).  Most places switch over to a light plain rain Saturday night before things come to an end but it looks like the bulk of the precipitation has already fallen by this point. 

Amounts: With a northern jog today allowing the initial axis of steadier overrunning precipitation to move right over the area, I've bumped up the entire Shenandoah Valley to 4-8" with as much as 10" possible across the western highlands.  Fortunately, this increase in snow has lessened the ice threat with only up to a glaze expected.  

Some Additional Thoughts Across the State: 

• I do have some concerns regarding effects dry air will have on the initial overrunning band.  This latest arctic blast has left dew points well below zero area wide.  With this overrunning band expected to move in from the west, the combination of very dry air and Appalachian Mountain influence may shred up some of the precipitation.  Not only would this delay onset but also lead to the lower side of the 4-8".   We'll know this outcome based off mid-morning radar and observations.  
• You'll also notice the pretty dramatic cutoff draped across the southern Shenandoah Valley/portions of the New River Valley.  There will be a very tight snowfall gradient here with 50 miles one way or the other making a huge difference.  There hasn't been great consistency concerning just where this sets up so my confidence here (Blacksburg, Roanoke, Lynchburg, Covington) is below average.
• There have been a few models consistently wanting to expand the higher totals east of the Blue Ridge to include areas like Charlottesville, Fredericksburg, and DC.   Strong mid level flow out of the south along I-95 should be too much for snow to remain the dominant precipitation type into the afternoon.  Normally I would take this and run with it but we're coming off historic cold with remaining snow pack which may slow this erosion.  Something to keep in mind if you live in those areas.