Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 202000 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 300 PM EST Tue Feb 20 2018 .SYNOPSIS...
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Southerly flow south of a warm front will bring near record warmth to the region through Wednesday. A cold front will pass through Wednesday night into Thursday before stalling out to our south Thursday night. The boundary may return north as a warm front Friday into Saturday before a stronger cold front passes through from the west on Sunday.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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Current surface analysis depicts the warm front which was to our south this morning has redeveloped well to our north. Warm air has flooded the region and we are at record high temperature readings for this date across the region as of this writing. Southwesterly flow will continue through Wednesday as a cold front approaches from the northwest and high pressure slowly retreats off the coast, with a strong ridge aloft. Temperatures will drop this evening with some radiational cooling, though the southwest winds will limit this to some extent. Nevertheless, with high dew points in the 50s and some drop in winds, expect some patchy fog, low clouds and even a little drizzle to redevelop, especially near the bay. Otherwise, it will be extremely mild, with lows in the 50s to near 60. After low clouds/fog burn off on Wednesday, it will be exceptionally warm again with another day of highs in the 70s to low 80s. As a cold front approaches from the northwest later in the day, some showers become possible west of the Blue Ridge, but odds are not high. Increasing clouds from the west during the afternoon could limit insolation, keeping all-time February records from being touched, but the potential for this does exist. See climate section for details. In addition to the warmth, it will be breezy again, with southwest winds potentially gusting up to 30 mph.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
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Cold front slide southeast into the CWA during the evening and settles south of us by the overnight hours. Showers will be weak and scattered at first, but as a wave of low pressure rides east along the now stalled out front to our south, rain will become more widespread on Thursday. As the wave passes east Thursday night and cold high pressure passes by to our north, some chilly air may make its way into the northern portions of the CWA which might bring a risk of freezing rain. For now have held temps just above freezing, but this potential will need to be re- evaluated. With the colder air moving in almost continuously from Wednesday night through Thursday night, temperatures will be dropping or steady just about the entire time, starting out in the 70s early Wednesday evening, spending most of Thursday in the 50s and 40s, and then dropping into the 30s Thursday night.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/...
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Cold air damming will be in place Fri with light rain and/or drizzle as a warm front tries to lift through the area. There will likely be a lull in precip Fri night into Sat behind warm frontal passage with next chance of rain on Sat as a another frontal zone associated with a stronger low over the mid MS valley establishes across the area. Warm front might not be able to clear the entire fcst area Sun before low pressure and associated front become occluded Sun afternoon over Lk Huron. The front should clear the fcst area by 00Z Mon at the latest with a drying trend taking place early next week. Temps will remain generally in the 50s with warm overnight lows due to abundant cloud cover and high moisture content.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/...
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VFR through this evening as gusty southwest winds start to diminish by sunset. Low clouds/fog/drizzle may redevelop across the terminals east of the Blue Ridge (CHO/IAD/DCA/BWI/MTN) later tonight, with many different solutions pointing to a return of IFR cigs and MVFR vis, so have gone that way with the TAFs. MRB may stay VFR cigs, but could also see some dense fog develop if winds go calm. Low clouds/fog/drizzle break later in the morning Wednesday and we turn out pretty much like today, with VFR conditions and a gusty southwest wind. Sub-VFR conditions possible at times on Wednesday night as a cold front blows through and winds shift northerly. Sub-VFR is more likely Thursday as a wave of low pressure brings some rain to the region. Conditions may improve a bit Thursday night if enough dry air works southward from high pressure to our north. Possible flight restrictions Fri into Sat due cold air damming signature and widespread precipitation.
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&& .MARINE...
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SCA continues into this evening all waters. Winds should diminish a bit after sunset, but isolated gusts near SCA could occur overnight. Winds likely ramp back up to SCA levels on Wednesday so SCA goes back into effect mid morning through afternoon. Cold front brings a wind shift Wednesday night, with SCA possible on northerly flow in parts of the bay on Thursday. SCA conditions possible Sunday into Monday with a passing wave of low pressure and accompanying cold front.
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&& .CLIMATE...
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Some all-time February highest minimum temp records could be in jeopardy, but it depends on how quickly a cold front moves through Wednesday night. If the Wednesday calendar day low does not drop below 60 degrees, it would be the first time not dropping below 60 at DCA in February since 1891, and only the sixth time on record in the entire meteorological winter season. Even a low 56 or higher at DCA would be the warmest low in the month of February since 1976. The all-time February highest minimums are: 61 at DCA/Washington (2/17/1891) 58 at BWI/Baltimore (2/17/1891) 55 at IAD/Dulles (2/17/1976) - records only go back to 1960 at IAD In addition, its not out of the question that all-time February maximum temperatures are tied or broken. 84 at DCA/Washington (2/25/1930) 83 at BWI/Baltimore (2/25/1930) 79 at IAD/Dulles (2/24/1985 and 2/25/2000) - records only go back to 1960 at IAD It goes without saying that daily records are in jeopardy. A table of those records follows. Tuesday`s highs have already been tied or broken: Record warm daily maximum temperatures Tue 2/20 Wed 2/21 DCA 76 (1930) 75 (1953) BWI 76 (1930) 74 (1930) IAD 70 (1971) 70 (1997) Record warm daily minimum temperatures Tue 2/20 Wed 2/21 DCA 59 (1939) 51 (1954) BWI 57 (1939) 49 (1981) IAD 46 (1981) 45 (1981)
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 8 PM EST this evening for ANZ530>543. Small Craft Advisory from 9 AM to 6 PM EST Wednesday for ANZ530>543.
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&& $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...LFR AVIATION...RCM/LFR MARINE...RCM/LFR CLIMATE...LWX/RCM

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