... The remnants of Ian, along with an upper-level low, will move to the East Coast tonight into early Monday. Light to moderate rain will continue across the region during this time. A coastal low is expected to develop off of the East Coast Monday, before propagating westward into Tuesday bringing more shower activity to the region. High pressure builds into the region Wednesday ushering in drier conditions. Temperatures briefly warm up mid- week ahead of a strong cold front moving through on Friday.
NEAR TERM /THROUGH MONDAY/... Light to moderate rain continues mainly east of I-81 this evening. A coastal low is expected to develop off of the Eastern Seaboard tonight. Gusty winds expected over the eastern half of our CWA, especially along and east of I-95 and perhaps a little farther to the west. A Wind Advisory remains in effect for Anne Arundel, Calvert, and St. Mary's Counties through midday Monday where NE winds will be coming off the bay. Sustained winds will be between 20-30mph, with gusts up to 45-50 mph. Weak cold air advection at the surface will drop temperatures tonight to the mid to upper 40s, with upper 30s in the Allegheny Mountains.
SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... The large coastal low that develops off the Eastern Seaboard is going to remain in place for Monday and Tuesday. Periods of rain or showers is expected in much of our eastern zones. A few models don't have this nearly stationary closed low moving out until mid-morning Wednesday. Temperatures will be well below normal as afternoon highs only reach the mid to upper 50s. High pressure builds into the western half of the area Tuesday afternoon. The rain threat will linger east of the Blue Ridge through Tuesday night and perhaps early Wednesday morning.
Nighttime temperatures will also be well below normal. As a matter of fact, models indicate that higher elevations in western Maryland and eastern West Virginia show temperatures dropping into the 30s.
LONG TERM /WEDNESDAY THROUGH SUNDAY/... A trend continues in the 12Z guidance suite to slow the eastern progression of the upper low and associated surface cyclone away from the Mid Atlantic coast. This means that some areas, especially near and east of I-95, could still be dealing with clouds and a little lingering rain on Wednesday. While the latest NBM has highs near 70 for the metros, it's important to note the cloudier solutions result in another day of upper 50s/lower 60s.
The next shortwave digging into the Great Lakes on Thursday will provide the necessary movement in the pattern to kick the coastal low farther away. Return flow will develop and likely result in the warmest day of the week for many areas as highs return to seasonal normals in the mid 70s.
The aforementioned trough will cause low pressure to track near or north of the St. Lawrence Valley with its trailing cold front reaching the area sometime Friday into early Saturday. A slower progression will mean another warm day for Friday (which is looking increasingly likely) while a faster/stronger front would bring cold advection during the day. Either way, moisture return ahead of the front will be weak and the best forcing will be north of the area. The chance of showers will be mainly limited to the Appalachians.
Dry conditions and below normal temperatures are expected next weekend as upper level troughing remains overhead and high pressure slowly builds in from the west. Will have to monitor for potential frost/freeze issues depending on the strength of cold advection as well as winds/clouds (in relation to radiational cooling).