... High pressure will remain in control through Friday. A cold front will cross the area Saturday before returning north as a warm front Monday. Another cold front will cross the area during the middle portion of next week.
NEAR TERM /THROUGH TONIGHT/... Much like previous nights, the main concern through the remainder of the night and into early this morning will be fog. With a weak ridge of high pressure overhead, most locations have decoupled and gone calm. Temperatures have dropped to near the dewpoint in most locations. The formation of fog and/or low clouds is expected at most locations to the east of the Blue Ridge prior to daybreak. Like previous mornings, some of this fog could be dense. As a result, a Dense Fog Advisory has been issued for most locations to the east of the Blue Ridge. There are a few high clouds still present to our south across portions of central and southern Virginia. These high clouds could prevent the formation of fog across central Virginia.
Any fog will slowly burn off this morning. Given the relatively low sun angle this time of year, it may take until mid-morning or later in many spots for the fog to be completely gone. Thereafter, mostly sunny skies are expected, with just a few high clouds working in from the south. Highs today will be in the mid to upper 70s in most spots.
High clouds will be on the increase late tonight in advance of a cold front approaching from the west. A brief shower can't be ruled out close to daybreak along the Allegheny Front as the front moves through, but elsewhere dry conditions are expected. Low clouds may form again tonight, but the current thinking is that a weak southerly gradient wind, and high clouds moving in aloft will limit the formation of fog. Lows tonight will hold in the upper 50s to around 60.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... A cold front will progress through the area from northwest to southeast during the day on Saturday. A few showers may be ongoing as the front passes through the Allegheny Front around daybreak. Those showers are expected to rapidly fall apart within downslope flow as the front progresses to the east of the Allegheny Front. Decent daytime heating may ensue in advance of the front from central Virginia to southern Maryland. As a result, showers and possibly even a few thunderstorms may reform in the vicinity of the front around peak heating across those areas. Elsewhere, mainly dry conditions are expected, with just a brief passing shower possible as the front presses through. Highs on Saturday will range from the low 60s across far northwestern portions of the forecast area, to the upper 70s in central Virginia.
Cooler air will filter in Saturday Night as the front presses to our south. High pressure will build to our north Saturday Night, and then northeast on Sunday. With the high to our northeast, we'll start to gain an easterly component to the low-level flow. This will bring a marine influence into the area within the cold air damming regime. As a result, it will be a dreary day, with low clouds, drizzle, and much cooler temperatures. Temperatures will hold in the low 50s for most of the day Sunday.
LONG TERM /MONDAY THROUGH THURSDAY/... A subtropical ridge will build to our south for Monday while a longwave upper-level trough digs over the central CONUS into the Rockies. Guidance is in relatively good agreement that a cutoff low develops in the southern stream Tuesday through Thursday while a nearly zonal flow develops over our area in the northern stream.
For Monday, a boundary to our south to start will likely return north as a warm front in response to the upper-level ridge building to our southeast, and the upper-level trough developing to our west. Low clouds and fog/drizzle along with chilly conditions to start should give way to a milder afternoon. A stronger boundary (nearly stationary for Monday) will be just to our northwest. A few showers cannot be ruled out across our northern and western areas, but any shower coverage should be isolated to scattered since the bulk of the forcing will be off to our northwest.
That boundary will likely pass through as a cold front later Tuesday into Tuesday night as the zonal flow develops aloft. A few showers may be associated with the frontal passage, but precipitation amounts will be light, since the zonal flow will cut off moisture sources from the Gulf of Mexico and the Atlantic.
The cutoff low is most likely to get absorbed by the southern stream of the jet as troughing sets up over the western CONUS late next week. This system will have copious amounts of moisture with it, and this will bring a chance for a soaking rain late next week. Exact details regarding timing and exact track of the low remain uncertain at this time.