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FXUS61 KLWX 301521 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1021 AM EST Thu Nov 30 2023

SYNOPSIS
High pressure will continue to push offshore this afternoon allowing for warmer conditions. Light rain chances return Friday as an area of low pressure approaches from the Ohio River Valley. Additional waves of low pressure look to bring excess cloud cover and precipitation chances to the region this weekend into early next week.

NEAR TERM /THROUGH TONIGHT/
Some mid-level and high clouds are gradually fanning out across the northern half of our CWA late this morning. Sunshine will be plenty with occasional cirrus clouds streaking across the sky over the Virginia Piedmont and some upslope stratocumulus in the northern Appalachians this afternoon. It will be dry this afternoon and tonight ahead of wetter Friday. Highs this afternoon will be mainly in the lower to middle 50s with some upper 40s in the mix. Moisture is expected to increase on a south to southwest flow ahead of Friday's cold front.

Additional clouds later this afternoon into tonight will keep our tonight's temperatures from plummeting too far into the cold. Lows in the mid to upper 30s expected across the region with some upper 20s in the western valleys and parts of central Virginia. No precipitation is expected with dry air remaining in place as broad high pressure pushes further offshore.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
We will be looking at several weak waves of shortwave energy to round out the workweek and into the weekend. The first wave comes in the form of an area of low pressure and it's associated front set to approach from the Ohio River Valley Friday. Most locations will start out dry Friday as it will take sometime for the atmospheric column to moisten. Shower activity will start west of the Allegheny Front late Friday morning before pushing toward the metros throughout the afternoon. While we anticipate mainly rain at the start and during the middle of the event, some pockets of cold air in some valleys cannot rule a little light snow or sleet on the front end or at the start. No accumulation is expected with a quick changeover to rain showers as temperatures warm through the morning and afternoon hours. Any rain shower activity is likely to be light and short duration given most of the energy associated with this system will remain north of the area. Rainfall amounts will remain less than a quarter of an inch.

Friday temperatures will start in the low to mid 30s west of the Blue Ridge with upper 30s further east. High temperatures Friday afternoon will warm back into the upper 40s and low 50s with increased southwesterly flow. Breezy conditions will also return with south to southwesterly winds at 10 to 15 mph gusting up to 25 mph at times Friday afternoon and evening.

Shower chances decrease Friday night into Saturday as the best isentropic lift works north of the region. Southwesterly flow will continue aloft as broad upper level troughing remains over the central CONUS. At the surface, will be caught between the northern stream trough and an area of low pressure/warm front lifting northward from the Gulf Coast. The combination of these two features will keep a low end chance for showers in place over most of the forecast region with higher chances west of the Allegheny Front and to the south across the southern MD/northern neck of VA where better forcing resides. Cloud cover will also be in abundance with a notable warm surge as the warm front lifts in Saturday afternoon.
High temperatures will push into the upper 50s and low to mid 60s.
Lows Saturday night will fall into the mid to upper 40s and low 50s.

LONG TERM /SUNDAY THROUGH WEDNESDAY/
Showers seem likely Sunday-Sunday evening as heights fall across the region ahead of a negatively-tilted s/w trough moving across the OH River Valley and the northern mid-Atlantic and sfc low pressure develops overhead. Colder air begins to filter in Sunday night as NW flow strengthens as low pressure deepens offshore. Snow showers late Sunday night into Monday may accumulate several inches of snow across the higher terrain before shortwave ridging builds in briefly on Tuesday.

A second shortwave trough diving from the Central Plains into the OH River Valley Tue into Wed will reinforce the trough pattern across the East bringing temperatures back to slightly cooler than normal and a second and more significant round of snow showers/squalls across the Appalachian region Wednesday. This could also bring the first measurable snow, albeit light to locations east of the mountains. Conditions should begin to improve Wed night and the second half of next week as trough axis shifts east.

AVIATION /15Z THURSDAY THROUGH MONDAY/
VFR conditions with some mid-level and high clouds at the northern terminals this afternoon into this evening. CIGS will remain between 6-12 kft with south/southwest winds occasionally gusting up to 15 kts this afternoon/evening.

An area of low pressure will move to the north and west of the area Friday into Friday night. Periods of sub-VFR conditions remain possible at some of the TAF sites. This includes a period of MVFR ceilings and showers especially during the late morning and afternoon period Friday. South to southwesterly winds will continue Friday gusting between 15 to 25 kts Friday afternoon/evening. Some LLWS is possible during the afternoon period especially at terminals west of the Blue Ridge.

Sub-VFR conditions will remain possible at times Saturday and Sunday as additional waves of low pressure push through. Winds will remain out of the south and southwest Saturday with gusts under 10kts. Higher gusts are likely at terminals along and west of the Allegheny Front.

Occasional showers Sunday as low pressure passes overhead. MVFR cigs are likely on Sunday across the main terminals as low clouds remain stubborn on easterly flow. Conditions should improve later Sunday evening as NW flow takes over.

MARINE
SCAs remain in effect later this afternoon into this evening due to southerly channeling. Additional SCAs are possible Friday as an area low pressure moves north and west of the waters. This will lead to a brief uptick in winds during the late morning and late afternoon hours. Sub- SCA level winds are expected on Saturday and Sunday. Winds will remain out the south Saturday before becoming light and variable Sunday.

SCA conditions likely Sunday night through Tuesday in NW flow. Risk of gales seems low at this time.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 3 PM this afternoon to 3 AM EST Friday for ANZ531>534-537-539>543.

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