Thoughts on the upcoming storm...

THE SET-UP

Low pressure will track from the Gulf states to along the North Carolina coast this evening, then quickly out to sea Monday morning.  Colder air will infiltrate the Commonwealth from the northwest during the day, and with a storm track to our south, will set the stage for a wintry mess across the region.  There are a couple of things that concern me and put up a red flag in regards to potential snow accumulations:

1) A potential warm layer aloft...water temperatures along the coast are quite warm and any easterly component to the wind aloft will bring milder air than forecast by the models
2) The warm ground and near surface (air) temperatures...the snow probably won't stick right away, and temperatures are forecast to remain above the freezing mark for much, if not all of the event
3) Any rain that occurs may cause puddles/standing water, particularly in areas south and east of Richmond

All of these elements will retard the accumulation of snow on the ground, and contribute to a very uncertain forecast.  I'm not convinced this will be a major snowfall, and it certainly will be a wet snow, with some big flakes out there!

THE TRANSITION FROM RAIN TO SLEET TO SNOW

Clearly, there will be a mix and changeover time for everyone, even along the coast.  This transition time could vary depending on any warm layer aloft (prolonging mixed precipitation/sleet) and how fast the colder air slides south and east.  An upper level trough will help to drive this colder air to the coast, but may not move through until late at night.  While much of the precipitation may start as rain & sleet, a period of mixed precipitation (rain, sleet and snow) will likely take a few hours to make the complete transition to snow.  So here's a possible timeline for the mix/changeover windows...

North & west of Richmond (Goochland/Louisa/Hanover):  Between 2PM & 6PM
Metro Richmond & along I-95, as well as inland on the Northern Neck:  Between 4PM & 8PM
Northern Neck (closer to the coast):  Between 6PM and 10PM
Middle Peninsula & Eastern Shore, as well as South Central VA:  Between 8PM and midnight
Hampton Roads: After midnight

POTENTIAL ACCUMULATIONS

As mentioned above, while I think it will snow, I have concerns over how fast and how much it may accumulate, due to various factors.  With that in mind, I'll give you my thoughts on "potential" accumulations.  Much of this will come after dark.

East of I-95 from Richmond south (including the Tri-Cities and Williamsburg):  1-3 inches
West of I-95 (including Ashland, the West End and much of Chesterfield):  2-4 inches
Western Goochland/Hanover and points west:  3-6 inches
Coastal Northern Neck/Middle Peninsula/Eastern Shore:  1-2 inches
Hampton Roads:  Dusting to 1 inch

Much of this accumulation may be slushy due to temperatures above freezing through much of the event.  However, early Monday morning just prior to sunrise, temperatures will lower to near 30 degrees (upper 20s away from the city), so any wet/slushy areas could turn icy.  Be aware of this if you're out & about very early Monday morning.  Temperatures will then rise by 9AM or so, with plenty of sunshine.

Stay tuned for any forecast updates @ richmondforecast.com!