Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 240724 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 324 AM EDT Sat Sep 24 2016 .SYNOPSIS... A cold front will pass through the area today. High pressure returns for tonight through Sunday before moving off the coast Monday. A cold front will pass through the area overnight Monday into Tuesday. An upper-level low may impact the area during the middle portion of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Cold front dropping southward from Pennsylvania will cross the region this morning and into the afternoon hours. The frontal passage will be mainly dry, although an isolated spot shower or two is possible across northern Maryland this morning, and then over the higher terrain this afternoon. Otherwise, will see a wind shift to the north and an increase in clouds. High temperatures will be noticeably cooler, with highs in the mid to upper 70s for most, with low 70s possible in NE MD, and mid 80s in central Virginia where front gets hung up and takes longer to pass. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/... High pressure will nose into the region tonight with continued north to northeast flow. This will lead to much cooler temperatures with lows generally 50-60F. Locations from the DC Metro north and east should see clearing skies, with clouds likely getting hung up in southern and western areas, especially in the higher terrain with light northeast upslope flow and some trapped low level moisture. There may even be some patchy fog/drizzle or a light shower west of the Blue Ridge. Surface high pressure will continue to build across the northeastern US on Sunday, providing for mostly sunny skies for much of the region. Exception will be across portions of central/western VA and into eastern WV where more clouds may still hang on in the light easterly flow. Highs generally in the 70s. The high will begin to shift offshore Sunday night, promoting stronger easterly flow, which will likely lead to the development of a low stratus deck of clouds, especially in western areas. Again some patchy fog/drizzle or an isolated shower possible west of the Blue Ridge. Lows mainly in the 50s. A frontal system will then approach on Monday and cross the region late Monday night. This will bring a period of rain showers to the region, mainly Monday night. Highs Monday in the 70s, with lows Monday night a bit milder ahead of the front, in the low to mid 60s. && .LONG TERM /TUESDAY THROUGH FRIDAY/... A cold front will move off to the east Tuesday and high pressure will likely build overhead briefly for later Tuesday and Tuesday night. Mainly dry and seasonable conditions are expected. A cutoff upper-level low will pass through the area Wednesday through Thursday...and there is even some indication that it could hang around until Friday. The exact location of the upper-level low is very important. If it remains to the north and east...then a westerly flow will allow for dry and seasonable conditions over our area for most of this time. However...if the low drops farther south and west...then it will tap into moisture from the Atlantic at the same time coastal low pressure develops near the Mid- Atlantic Coast. This would bring plenty of clouds along with chances for rain. Latest forecast will be a blend of these two solutions...but will lean slightly toward the first scenario which keeps the upper-level low to the north. This lines up with most other guidance. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... Cold front crossing the region this morning will bring increased clouds to the area today. A period of MVFR ceilings likely at BWI/MTN/MRB in the 12-18z timeframe. Ceilings currently forecast to remain above 3000 feet at DCA/IAD, however there is the possibility for a period of MVFR ceilings at these sites as well. Conditions will improve to VFR area-wide after 18z. Later tonight, an MVFR stratus deck likely develops at CHO with a slight chance of some patchy fog/drizzle. Otherwise, VFR expected elsewhere into Sunday. Winds light and variable early this morning will turn north/northeasterly following frontal passage, with speeds up to about 10 knots. Additional development of sub-VFR conditions (primarily ceilings) possible Sunday night into Monday, mainly MRB/CHO. Another period of sub-VFR conditions possible Monday night in rain showers with frontal passage. A cold front will move off to the east Tuesday and VFR conditions are likely as high pressure builds into the area. An upper-level low may impact the area during the middle portion of next week. Details are highly uncertain at this time. && .MARINE... As a cold front crosses early this morning, will see a surge of wind, with gusts up to about 20 knots with and behind the front. Thus, a Small Craft Advisory remains in effect until 2 pm. Winds taper off this afternoon. An additional wind surge is possible tonight into Sunday morning with near-SCA conditions possible once again. Sub-SCA conditions then return by Sunday afternoon and Sunday night. Southerly winds will then be on the increase Monday and Monday night ahead of an approaching cold front, with SCA conditions possible. A cold front will move off to the east Tuesday. A small craft advisory may be needed for portions of the waters Tuesday morning...but high pressure should briefly build overhead for later Tuesday into Tuesday night. An upper-level low may develop overhead...and this may cause coastal low pressure to develop depending on how strong this system is and exactly where the upper-level low tracks. Details are highly uncertain at this time...but a small craft advisory may be needed for portions of the waters Wednesday night and Thursday. && .TIDES/COASTAL FLOODING... Anomalies remain elevated, but a northerly flow should keep water levels below minor flooding thresholds through tonight. However, winds will shift to the east and southeast Sunday through Monday night. Minor tidal flooding is possible...especially Monday into Monday night when the onshore flow will be strongest. && .CLIMATE... Unusually warm weather has persisted over the area for quite some time. Autumn-like temperatures will finally make an appearance over the weekend likely bringing low temperatures at DCA below 60 degrees for the first time since June 9th, or 106 days ago. The record most consecutive days at or above 60 degrees in the Washington DC area is 112 set in 2012. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 6 AM this morning to 2 PM EDT this afternoon for ANZ530>534-537>543. && $$ SYNOPSIS...BJL NEAR TERM...MM SHORT TERM...MM LONG TERM...BJL AVIATION...BJL/MM MARINE...BJL/MM TIDES/COASTAL FLOODING...BJL CLIMATE...DFH is the U.S. government's official web portal to all federal, state and local government web resources and services.