... A pressure trough will cross the area tonight. High pressure will gradually build in from the west during the middle of the week. A cold front will cross the region by week's end.
NEAR TERM /THROUGH TONIGHT/... Coastal low pressure will continue to move to the east this afternoon while an upper level trough axis approaches from the west. A second weak surface low and attendant surface trough is located beneath the upper trough and will cross the area through tonight. The pressure pattern in between is very weak, and the air has essentially been stagnant from MRB/HGR through IAD, resulting in the persist low clouds and haze. These clouds have been eroding away from the west and east, but will quickly be replaced by additional clouds ahead of the disturbance aloft. Rain showers have already reached ROA/LYH, and will continue to spread north this evening. There's pretty good model agreement that the showers will weaken some with northward extent, before fading/exiting between midnight and 3 AM. Some locations near/east of the central Virginia Blue Ridge could get up to a quarter inch of rain, but otherwise amounts will be light.
The rain will serve to resaturate the lower atmosphere, so additional low clouds and/or fog may develop late tonight. Currently thinking stratus will have formed first and thus will be predominant, though fog could occur if clearing is quick behind the rain. There's a low chance of some flurries or light freezing drizzle in the upslope areas late tonight, but don't think there will be notable accumulation at this time. Lows will be in the mid to upper 30s, east of the Blue Ridge, and closer to freezing to the west.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Any fog/low clouds should mix out by mid morning. However, Upper level troughing will remain overhead on Tuesday and there will be enough moisture associated with it to likely result in mostly cloudy skies. The daylight hours should be dry though, with slightly warmer temperatures in the upper 40s to mid 50s. A vort max and weak surface trough will rotate across the area during the evening. Low level moisture will be lacking, but there could be enough lift to produce a few light showers or sprinkles, especially toward central Virginia and out in the mountains. Light upslope precipitation will continue into Wednesday morning, with any wintry accumulations being very minimal.
Upper troughing finally pushes to the east Wednesday with ridging at the surface and aloft building in from the west. There may be enough moisture in the northwest flow to keep some clouds around, but should be more sunshine overall than Tuesday. Temperatures will be fairly seasonal with a more Pacific airmass, though radiational cooling could allow some below freezing temperatures Wednesday night.
LONG TERM /THURSDAY THROUGH MONDAY/... Surface high pressure and ridging aloft will reside over the Eastern Seaboard Thursday before shifting off the coast Thursday night. At the same time, low pressure will track northeastward from the Central U.S. into the Great Lakes, lifting a warm front through the Mid Atlantic Region. A few showers will be possible Thursday night as a result, with temperatures running on the mild side for this time of year. The cold front associated with the aforementioned low will push into our area on Friday, continuing the chance for showers as temperatures rise into the 50s & 60s.
Model guidance is at a bit of a disagreement thereafter in terms of the placement of the frontal boundary as another area of low pressure tracks northeastward along it. As a result, will maintain POPs in the forecast for the first half of the weekend as the area of low pressure tracks through the region. Depending on how much cold air is able to filter in behind the front Friday night, could see a mix of rain/snow showers, with our mountains areas favored for any wintry precipitation. Rain showers will be advertised Saturday/Saturday night with drier conditions expected the second half of the weekend in the wake of the low/front. Slightly below normal temperatures can be expected through the weekend.