... An area of low pressure will move northeast through the Ohio Valley tonight spreading clouds and rain across the Mid-Atlantic region. This Low will move off into the Atlantic Tuesday. Another area of low pressure will develop across the upper Mid- West Tuesday night then move northeast into southern Ontario. The associated cold front with second storm system will usher in some colder air for the second half of the week.
NEAR TERM /THROUGH TUESDAY/... As of 200 PM EST Monday...
An area of low pressure will move northeast through the Ohio Valley tonight spreading clouds and rain across the Mid-Atlantic region. This low is a southern stream system, of Pacific origin, and will introduce a milder airmass to the region. Temperatures tonight will remain relatively steady or may even continue to rise as flux of warm/moist air infiltrates the area from the southwest. Rain thus far today has been extremely light. Rain intensity is expected to increase with the best forcing for precip production occurring between 03Z/10PM and 09Z/4AM. Rain amounts of a quarter /0.25/ to a half inch /0.50/ can be expected with the heaviest amounts anticipated from the southern VA Blue Ridge (SW of ROA) into the North Carolina Piedmont. This system is moving relatively fast, so it should clear the area Tuesday morning with partial clearing anticipated for Tuesday afternoon. Winds aloft remain from the WSW Tuesday and with 85H temps close to +8 deg C, expecting a mild afternoon with highs in the 50s to lower 60s. Not out of the question for the piedmont to tease 65 provided we get a little sun.
SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 130 PM EST Monday...
Enjoy the warmth, it will not last.
A broad upper level trough will head eastward from the Plains on Wednesday, which will force a sharp cold front to cross over the Appalachian Mountains by Wednesday afternoon. Rain showers will accompany the frontal passage with the highest QPF in the mountains. These rain showers should transition to snow showers in the higher terrain as temperatures plummet rapidly behind the front, which raises concerns about a potential flash freeze for locations west of the Blue Ridge where any moisture on roads and sidewalks could quickly freeze and cause slick and icy conditions during late Wednesday evening. Not as much QPF is expected for the Piedmont, which lowers the confidence on potential flash freeze problems there.
Northwest winds will pick up during Wednesday night and Thursday as good cold air advection and pressure rises take place. There could be several surges in wind gusts throughout this time window as the 850 mb jet peaks around 45 knots on Wednesday night and boundary layer mixing will tap into the higher momentum air aloft during Thursday. Of course, the northwest flow will also allow upslope snow showers to persist in the higher elevations from Boone to Lewisburg. Although the air mass should dry out and allow the mountain snow showers to decay by Thursday night, the broad upper level trough firmly entrenched over eastern Canada will provide a cold night across the entire forecast area.
LONG TERM /FRIDAY THROUGH MONDAY/... As of 130 PM EST Monday...
A broad upper level trough will hold control across the eastern United States through Friday and Saturday. Confidence is high that northwest flow and cold air advection will persist throughout this time as indicated in the good agreement among the models. A shortwave disturbance swinging around the periphery of the broad upper level trough should cross overhead during Friday afternoon into Friday night. This shortwave disturbance should reinforce the cold air and offer more upslope snow showers to the higher elevations from Boone to Lewisburg. It will probably not be until Saturday before the upslope activity shuts off completely.
By Saturday night, high pressure should build overhead, and the broad upper level trough will finally loosen its grip over the Mid Atlantic as it departs offshore. Temperatures should begin to rebound on Sunday and more considerably on Monday as upper level ridging commences. The GFS is not quite as strong with this ridge as it allows the next low pressure system to approach the western fringes of the forecast area by the afternoon. However, the ECMWF keeps Monday drier and milder as it holds the low pressure system further west in the Plains. Given the fast bias of the GFS in the long range, the forecast for Monday will follow in close agreement with the ECMWF.