... Low pressure will move well out to sea tonight while an upper- level trough passes through the area. High pressure will gradually build into the area from the north and west through the middle of next week.
NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... An upper-level trough will move into the area from the west through this evening before moving off to the east later tonight. Low pressure will remain offshore while surface high pressure remains to the north.
Low-level moisture continues to wrap around the low offshore in a northerly flow, causing low clouds to continue across northern MD into the Washington and Baltimore Metropolitan areas. Farther southwest, clouds are slowly filling back in.
A northerly flow is expected to continue overnight as high pressure draws closer from the north. However, low-level moisture will likely remain trapped underneath the subsidence inversion, resulting in more low clouds for most areas. Some radiation fog is possible in the valleys of the Potomac Highlands into the central Shenandoah Valley where there are less low clouds to start this evening. A few showers and drizzle are still possible, mainly across northeastern MD and near the Chesapeake Bay where low-level moisture will be deepest.
SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... The trough that passes through our area tonight will develop into a cutoff low well off the New Jersey coast for Saturday. High pressure will continue to slowly build toward the area from the north. A north to northeast flow will continue to usher in some more low-level moisture, which will cause a stratocu deck for much of the time near and northeast of the Potomac River. Any low clouds/fog should give way to more sunshine farther south and west. Highs will range from the upper 60s to lower 70s across northeastern MD to the mid and upper 70s in the valleys of the Potomac Highlands as well as central Virginia.
High pressure will continue to build toward the area Saturday night, bringing dry conditions. Clouds should dissipate as drier air finally moves in from the north, but some fog is possible overnight.
The high will continue to slowly build overhead for Sunday through Sunday night. More sunshine is expected Sunday and this will allow for a warmer afternoon with highs in the mid 70s to near 80 for most areas. Dry conditions will persist Sunday night as well.
LONG TERM /MONDAY THROUGH FRIDAY/... Surface high pressure and a strong upper level ridge located overhead will provide the long term period with warm and dry conditions through midweek. As the upper level ridge erodes and an upper level trough pivots into the area, precipitation chances return to the forecast for the Alleghenies late Thursday. Otherwise, dry conditions are expected areawide with high temperatures topping out in the upper 70s for most with some reaching 80 degrees. Overnight low temperatures will be in the 50s and 60s for most.