... High pressure will move off the coast through tonight. A cold front will pass through the area Saturday. High pressure will build across the area Sunday and Monday. Multiple waves of low pressure and a slow moving front may affect the area during the middle of next week.
NEAR TERM /THROUGH TONIGHT/... 10:30 AM Update: Cold start to the day with mostly sunny conditions across the area aside from some high cirrus clouds tracking across western portions of the CWA. Clouds will continue to increase over the remainder of the day ahead of the next system moving in from the west. Near seasonable temperatures are expected for the afternoon (40s and 50s).
Previous Discussion Follows:
Fair weather conditions are expected today with 1035 mb high pressure situated overhead. The ridge of high pressure will gradually slide east this afternoon and evening before heading off the coast tonight. Return flow will increase out of the south providing a nice boost in temperature after a cold start in the 20s and 30s this morning. Most locations will top out around 50 degrees which is seasonable for this time of year. Mostly sunny skies will start the day with mid to high level clouds encroaching from the west by mid to late afternoon. These clouds are in association with our next cold front that looks to push through late Friday night into Saturday.
00z hi-res and synoptic model guidance continue to show good agreement in keeping most of the region dry Friday night as the front slowly moves in. The exception to this will be along and west of the Allegheny Front where better jet dynamics and upper level forcing can be found. Shower activity will remain light in these locations with any widespread precipitation holding off until Saturday morning and afternoon as the front pushes through.
Expect breezy conditions to develop Friday afternoon into Friday night as the gradient tightens. The incoming front to the west combined with departing high pressure will lead to increased southerly winds especially along the ridges/over the waters. Expected sustained speeds of 10-20 mph in these locations with periodic gusts 30-40 mph. This is largely due part to a 850 mb LLJ out ahead of the main front running 40-50 kts 5kft off the surface. Confidence remains moderate in to how much of the wind mixes to the surface Friday night with some lag per the guidance. Confidence increase though into Saturday for widespread breezy conditions.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Rain returns along with breezy conditions for the first half of Saturday as another cold front pushes through the region. Widespread rain chances look to be during the morning and early afternoon Saturday with chances decreasing during the evening hours. Rainfall amounts will be on the order of a tenth to a quarter of an inch with a localized heavier pockets along and east the I-95 corridor. Winds will also remain an issue along and ahead of the front Saturday. 00/06z hi-res/ensemble guidance continues to suggest northwesterly gusts upwards of 40-50 mph along the Allegheny Front and crest of the Blue Ridge Saturday afternoon and evening where the gradient will be at it's tightest. The potential for a Wind Advisory may be needed in these areas as confidence continues to increase for advisory level gusts. Areas further east will likely see gusts of 20 to 30 mph due to downsloping flow. Locally higher gusts near advisory level are possible, confidence remains lower due to a slightly more relaxed gradient.
The front clears the area Saturday evening into Saturday night allowing high pressure to build back in. Cold and dry conditions will return along with less wind heading into the beginning of next week.
High temperatures Saturday will surge into the upper 50s and low 60s ahead of the front with increased southerly flow. By Sunday, expect highs in the mid to upper 40s for most with 30s over the mountains. Lows Saturday and Sunday nights will bottom out in the mid to upper 20s.
LONG TERM /MONDAY THROUGH THURSDAY/... A progressive split flow pattern, with troughing dominant in central Canada and ridging dominant over the Gulf of Mexico, makes for an uncertain and potentially unsettled long term period. However, Monday is expected to be dry and seasonable as high pressure moves off the coast.
The first wave will approach Monday night into Tuesday. Most areas will only see rain. However, things such as precipitation onset time, the amount of nocturnal cooling, and low level wetbulb profiles could result in some mixed precipitation mainly along and west of the Blue Ridge.
Model guidance varies in the timing and placement of additional waves through the middle of the week, although temperatures should be warm enough for all rain through at least Wednesday. A cold front eventually settles across the area, although the magnitude of post- frontal cold advection, as well as any additional waves of moisture, remain uncertain. This leads to some ambiguity in the forecast, both in the long duration of chance PoPs and in snow creeping into northwestern areas by Wednesday night. It won't necessarily precipitate every single period through the middle of the week, and any postfrontal wintry weather will be contingent on cold air and moisture overlapping. Therefore, monitoring the forecast for future updates is advised. Temperatures do likely drop some toward the end of the week regardless of precipitation chances.