This discussion is based upon the FIRST guess snow map and the early morning Friday at midday data.
Every forecast and especially every winter forecast involving snow / ice always has its Tricky portions. The area which is right on the knife’s edge…where the potential for a busted forecast of either more snow than forecasted or less snow than forecasted or too .
In this particular event that area is going to be in and around the Richmond Metro area.. In order to understand why this particular region of the Mid-Atlantic is tricky with this event we have to understand the nature of this event.
1. The data from early this morning to midday continues to show that the event is going to develop during the evening hours on Saturday in North Carolina which is actually a little faster compared to what the data was showing yesterday and the day before.
2. The second most important point is that the event occurs during the pre-dawn hours of Sunday when the temperatures will be at their coldest. If this event were to begin after sunrise in Virginia Maryland and Delaware and southern New Jersey.. temperatures would probably be 35–39 degrees so the precip would either be a rain snow mix for all rain for many areas.
But because the precipitation begins before dawn and it comes in fairly heavy — the falling snow (and rain changing the snow) will keep the temperatures in check during the hours of Sunday morning from 1 or 2 a.m. until 10 or 11 a.m. in Virginia … western North Carolina and Maryland. BUT as soon as the moderate to heavy snowfall comes to an end ….it will warm up enough so that it becomes a rain ir snow mix or just plain light rain in much of central and northeast Virginia …southern Maryland/ and a good portion of the Delmarva.
It is possible that northwest portions of South Carolina -Greenville-Spartanburg could see 1–2 two inches of snow -even on the northern suburbs of Charlotte when the event begins in that location on Saturday evening.
3. This is a fairly fast-moving event . This also strongly implies that any snow forecast over 8 inches any portion of the Middle Atlantic or southern New England is probably going to not verify. The LOW is simply moving too fast. Because it is coming in faster ….it also ends sooner so that skies actually clear out by midday in much of Virginia and North Carolina and the temperatures s bounce up to near 45° in western North Carolina and 40–45 in much of the Virginia Piedmont as well as central and northeast Virginia… and near 40° Sunday afternoon DC Baltimore the eastern panhandle of West Virginia and central Maryland.
This is going to make measuring the snowfall quite tricky, For all locations in western North Carolina …central eastern and northern Virginia …. the snow ratio is not going to be 10 to 1 . It will be more like 7 to 1 or 5 to 1. In other words a damp heavy wet snow. This means that the snow is going to compact right away so whatever fall… in a few hours later maybe down to 2 or 3 inches.
The model data in and around the Richmond Metro Area shows significant hours of heavy snow and if the atmosphere was cold enough the snow would easily be 3 to 6 inches in around the Richmond Metro area with maybe even a few pockets of 7 inches up towards has Ashland and Tappahannock and King William County. But again with the temperatures just staying at 32 or 33 degrees early Sunday morning — from 3am to 9am — the snow ratio is not going to be the regular 10 to 1. There could be 2 or 3 inch difference in snow totals between what say Short pump on the west side of Metro Richmond sees versus the airport see… or between say western Chesterfield County and Prince George and Hopewell.
In Southwest Virginia and the Southern half of the Shenandoah Valley this looks. solid 3 to 6 or 4 to 8 inch snowfall. The snow will break in sw Virginia FIRST and race up the southern portions of the Shenandoah valley. The issue in western and northern Virginia ….Maryland …Delaware… Philadelphia and New Jersey is the axis of the heaviest snow. Some models take it right up the Shenandoah Valley in the DC Baltimore and Philly BUT other models have the access of heaviest snow on the south side of DC Baltimore in Philly into southern New Jersey/ and Long Island NY.
This places is locations such as Winchester and the eastern panhandle of Virginia Hagerstown and Frederick on the border between seeing anywhere from 2 inches to as much as 5 or 6. As the LOW pressure area continues to move away from the North Carolina coast and intensify… the snow shield should become more uniform and most of central and northern New Jersey …eastern third of Pennsylvania … southeast New York and southern New England should see a very nice 4 to 8 inch snowfall.
In New York City … southern New England …the model data is somewhat uncertain. The British model has a nice 4 to8 inch snow in NYC / Long Island central and e\stern Connecticut …Rhode Island …and eastern Massachusetts . So does the high resolution midday Canadian model . But the midday and early morning GFS models do not have that much snow in southern New England nor does the early morning and midday European model. So it is possible that I might have to adjust my 4 to 8 inch snow band in eastern and southeastern New England in further updates
In the middle of Atlantic region Sunday evening will see cooling temperatures but not a hard freeze — until after midnight. Then the arctic front arrives and temperatures tumble quite rapidly. Temperatures may be as low as the single digits or around 10 degrees in much of the Shenandoah Valley and Southwest Virginia on Monday morning — -and in the teams in the Virginia Piedmont up into northern Virginia DC Baltimore . Reading may be as low 18 or 20 degrees in the Richmond Metro Area into the western portion of the Northern Neck and southern Maryland as well as the Delmarva. So any snow which has not been removed or melted will freeze after midnight in the pre-dawn hours of Monday.
In eastern Pennsylvania temperature readings in the single digits are likely as well as in the interior portions of New Jersey ….Southeast New York…. western Connecticut by dawn Monday
Further down the road you should be prepared for the potential of a significant winter storm sometime around February 13 or 14. SEE BELOW
The Polar Vortex is coming south. This represents the central core of arctic air which is normally found in Hudson’s Bay Canada or Northern Canada. From time to time the PV decides to come southward because of something else in the jet stream which forces the feature to drop southward.
If you recall several Winters ago we saw a lot of media coverage about the polar vortex coming southward. Well it is going to come south again , As it does so it will drive a series of Arctic cold fronts southward. Temperatures on the morning of February 8 and 9th will be 20 degrees below zero or colder in the Dakotas Minnesota and Wisconsin
By February -10 the PV will be located just north of Minnesota on the north side of the Great Lakes . . The arctic cold front will move through New England on February 9 and the Mid-Atlantic on February 10
With each day turning progressively colder. The front will stall in Georgia and Alabama And waves of LOW pressure may \ develop on the front bringing significant snow and ice i to Tennessee North Carolina Virginia Maryland Delaware Pennsylvania New Jersey. Right now this has the potential to be the storm of the winter with regard to snowfall for the Middle Atlantic region.
Beyond that there was another mass of Arctic HIGH developing in northwest Canada which threatens to come down into the northern CONUS after said FEB 16 .