... A strong area of high pressure, originating from Canada, will build to our north today through Thursday night. Meanwhile, an area of low pressure will develop over the Gulf of Mexico Friday and track north, across the eastern United States, as high pressure departs offshore. Low pressure will then move across the area Saturday, with another area of low pressure approaching Monday into Tuesday.
NEAR TERM /THROUGH THURSDAY/... Strong high pressure will continue to build across the region this afternoon through Thursday. With the high originating from Canada, the air mass is quite chilly, but not excessively or unusually cold for this time of year, with temperatures generally 10 degrees below normal or so. Low temperatures overnight will dip down into the low to mid 20s, with the normal colder spots potentially getting into the teens.
With high pressure set up north of the region tomorrow, temperatures will even be a little colder than today, with highs in the mid to upper 30s. No precipitation to speak of though, and winds will be light, so even wind chills won't be an issue. So just a dry, chilly day across the area.
SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... High pressure will slide offshore Thursday night, as low pressure develops along the Gulf Coast and heads north toward the region. A wedge of cold air will remain through much of Friday morning, especially in the valleys west of the Blue Ridge. This could create some problems with freezing rain at the onset of the event Friday morning, when warm advection precipitation is likely to begin across the area. The most significant risk of freezing rain appears to be along the I-81 and I-64 corridors, where the precipitation arrives earlier and the cold air lingers the longest. Farther north and east of these areas, thinking that surface temperatures should warm just quick enough to avoid any major issues, but certainly can't rule out some light accumulations north and east of I-64. Right now, generally thinking this will be a light event, with less than a tenth of an inch along the I-81 and I-64 corridors, and perhaps a couple hundredths farther north and east, if conditions line up just right.
Outside of the freezing rain threat comes a soaking rain event starting Friday night, continuing into Saturday morning, as low pressure moves over the area. Periods of moderate rain can be expected overnight Friday. Additionally, some guidance indicates there could be some cold air still in place in western MD, where cold air climatologically hangs around longer, so can't rule out some freezing rain in the valleys in that area Friday evening/night.
LONG TERM /SATURDAY THROUGH TUESDAY/... Low pressure overhead Saturday will move off to the north later Saturday morning and afternoon. A soaking rain will be around to start, but a dry slot will work its way into the area during this time, and this may cause a lull in the precipitation. Confidence in timing the lull of precipitation remains low at this time. A second round of precipitation will be possible Saturday evening into early Sunday morning due to forcing by the upper level low passing over our area and the surface low's associated cold front. Some upslope wintry precipitation can be ruled out over and along the higher elevations.
High pressure will build back into our region Sunday through early Monday morning. Clear skies along with cooler temperatures in the mid 40s during the day and the 20s and 30s overnight. A warm front is forecast to lift through our region Monday morning. Overruning precipitation will be possible as this frontal boundary moves through our region. As high pressure is in place over the Northeast US, models have been hinting at a cold air damming situation. As the warm front lifts through our area, this precipitation could potentially fall as wintry precipitation. We will need to continue to track the model trend. Models have the damming setup breaking early Tuesday as the main cold front moves through our area. A brief warm up into the 40s will lead to rain Tuesday afternoon. It looks like the cold front is forecast to fully move through our area by Tuesday evening with cooler temps building back into our area Tuesday overnight into Wednesday.