... Low pressure will develop over the central United States and lift into the Great Lakes today. A warm front developing east of this area of low pressure over the Carolinas is expected to lift northward across the Mid-Atlantic today. The aforementioned low will drag its trailing cold front through the region Tuesday into Wednesday. Strong Arctic high pressure will build from the Great Lakes toward the Mid-Atlantic Wednesday night through Thursday night, then shift offshore of New England as low pressure develops over and approaches from the southeastern United States.
NEAR TERM /THROUGH TONIGHT/... Rain showers/drizzle associated to a warm front/isentropic lift are moving along southern and central Maryland. Upper level trough will continue to push over the eastern CONUS as front approaches from the west today with southerly flow advecting warm and moist air into our region. Rain showers/drizzle are also observed over the Potomac Highlands.
Low pressure will develop over our area along the warm front that is sitting to our east and will move NE and away form us into the evening. Short term guidance and soundings supports that rain showers/drizzle over south/central MD and the Potomac Highlands will continue through early this morning before widespread rain moves into our region mid Monday morning and into the afternoon.
Rain showers are expected for most areas on Monday night as forcing from the front moves away from us, with highest chance over central MD and the Potomac Highlands.
Temperatures will be above normal today and tonight. High and low temperatures will be in the 40s and 50s.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Surface cold front will move across our area on Tuesday and showers will redevelop into Tuesday night. The front should be east of our area by Tuesday evening but the upper jet dynamics and a mid level energy ahead of a trough will allow for anafrontal precipitation. Cold and dry air advection behind the front will have an impact on the p-type on Tuesday night. A changeover from rain to snow could occur Tuesday night, assuming there is still enough moisture in the column.
If things come together, the most likely areas for snow accumulations are over higher elevation. Highest amounts are about 5 inches at the ridgetops, with up to 3 inches elsewhere (see winter weather website). This of course will depend if cold air moves in fast enough, so there is still some uncertainty with this.
Precipitation will end on Wednesday as Arctic high pressure builds in from the west on Wednesday into the night.
LONG TERM /THURSDAY THROUGH SUNDAY/... Guidance is in relatively good agreement, better than last night, regarding the end of week and weekend. High pressure likely dominates on Thursday, with chilly temperatures but dry conditions. By Friday, low pressure developing near the Gulf coast may start to spread precipitation into the region, but this is more likely Friday night. With the chilly air mass in place, some mixed precipitation, perhaps even freezing rain, will be possible mainly west of the Blue Ridge. By Saturday, the low lifts northward to our west, likely scouring out the cold air and bringing temperatures back above normal across much of the area, though rain showers will continue. As low pressure then moves further away to the north and east by Sunday, drier weather should return, but with little cold air behind the system, temperatures look more likely to remain on the plus side of normal.