PBS's update on WB:
My update FOR THE MIDDLE ATLANTIC
...this is why we never say never...and yes, "beware the caboose"
Thermal boundary/baroclinicity looks to only reach southern Virginia to just off the Long Island coast late today and this evening...strong shortwave now over E TX will eject ENE and cause the first big snow of 2022 east of the Mississippi River...
Major winter storm appears highly likely beginning in the Smoky Mountains, then spreading into SW and central Virginia, and southern Maryland, as well as the central Delmarva Peninsula beginning in NC/TN this evening, then after midnight further northeast in the central and southern Mid-Atlantic States.
This situation is ever-changing, and there's no evidence this event climbs another 75 miles north, as the thermal boundary looks pinned in VA/NC, then south of the Northeast/Mid-Atlantic coast. However, adjustments will be made by NWS et al today, and I would not be surprised if Winter Storm Watches were expanded northward in Virginia and Maryland, as well as Delaware and New Jersey (maybe far SE PA?) after the 12Z model package suite.
A winter storm of the moderate/heavy category is likely along a swath just north of the major area (by major, I'm talking 12"+) Right now, the immediate Washington area (Fairfax/Prince William/Prince Georges/Montgomery) look to be on the northern edge of the heavy snow, amounts in excess of 6" look likely (highest on non-paved surfaces), especially from southern Montgomery County, southward. 6"+ snow looks likely over southern New Jersey. This is subject to some adjustment.
Amounts of at least 4"-6" may occur from extreme SE PA through central NJ to southern/eastern LI.
I'll give my opinions after the full 12Z suite, but suffice to say, this looks to be the largest snowstorm for some areas of southern Maryland and the Northern Neck (the area just south of the Tidal Potomac River, but north of the James River), in Virginia.
Rich precipitable water values will linger over the Southeast and southern Mid-Atlantic today, then the shortwave (now initiating precipitation in east TX) will move ENE and ignite heavy lift/upward motion over central Tennessee, northern 'Bama, and into N Georgia mountains...possibly into northern suburbs of Atlanta. From there, the thermal boundary will serve as a focus for a 1.5"+ QPF event for the lower Mid-Atlantic Region. Snow rates of 1" to possibly 2"/hour may occur in banding Monday morning over portions of Delaware, Maryland, and Virginia, especially from the foothills of the Blue Ridge to the coast.
Short range modeling take the 850 mb low-pressure from around ATL to the coastal VA/NC border by midday Monday, 1/3/22. General synoptic meteorology rule is the heaviest snow is around 150 miles NW of that low. No doubt, that looks to work out in this scenario, and I still think there's a very sharp cut-off. The Northeast immediate south coastal areas are now in the equation, as enhancement off the warm Atlantic waters will tend to overcome dry, cold advection n the mid and low levels out of the North. However, the area from LI to central Jersey, to PHL metro, to NE MD, is a very tough call on QPF. That's going to depend on a) where the thermal boundary sets up tonight, and b) how easily the dry, cold air is overcome along that area by the intense lift on the northern edge of the precipitation shield. There may be places 50 miles north of a 4" snow that see not a flake.
Temperatures? P-type? While it's bloody warm now (850 mb temps. +12C to +15C from central VA to GA)...the cold air now stretching from NE OH to SE MO will be dragged southward later today and especially tonight, at all levels, as the low-center intensifies over N Georgia. I expect rain to spread into N VA, the Washington area, and Lower Southern Maryland within a couple hours of midnight, but transition to IP, then S/S+ from north to south.
Freezing rain is falling in parts of western Louisiana and east Texas this morning after incredible warmth and humidity...that just ended overnight. Things can change on a dime.
@tornadoTom and @ty454 and @jmshank it's hard to see how this is not a heavy snowstorm for you all.
Intense precipitation rates during Monday morning's rush hour (the day after the long holiday period) look to cause problems. While ground temperatures are very warm, the falling temperatures and heavy snow should overwhelm roadways by dawn, or soon after, in most places. Wind 15-25 mph (but 25-35 mph over the coastal areas, into central VA/southern VA and southern Maryland) will help to cause cooling of road surfaces and force snow to adhere. Also, this looks like a pasting with power outages likely and tree damage, as temperatures will start above freezing, then fall to the 28F-31F range in most areas east of the mountains.
I would like to wait another 5-7 hours for numbers and swaths, but at this time, it appears HIGHLY LIKELY, amounts in excess of 12" will occur in the bullseye, somewhere in Virginia and Maryland...with 6"+ amounts likely over the Smoky Mountains and in the Shenandoah Valley of Virginia, down into SW VA and the New River Valley area. Higher snow amounts are expected in the mountains of Virginia and southern/southeastern West Virginia, as well as in the Smokey Mountains of TN and NC.
One last point: as surface high pressure builds in Monday Night over eastern Maryland and central Virginia/southern Virginia, radiational cooling is expected to result in air temperatures dropping into the teens over the heavy snow cover.
