Area Forecast Discussion
Issued by NWS Sterling, VA

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858 FXUS61 KLWX 271943 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 243 PM EST Mon Feb 27 2017 .SYNOPSIS...
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A warm front will lift north across the area through Tuesday, followed by a strong cold front late Wednesday and Wednesday night. After a brief period of high pressure Thursday, an area of weak low pressure will cross the region Friday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Weak upper level disturbance passing near the region along with warm air advection has provided for an overcast mid level deck of clouds through the day. There have been some light radar echoes during the day, but no reports of actual rain across our area, so most of what`s being seen is likely mid clouds or virga and not reaching the ground. However, light rain is being observed across parts of central West Virginia and now into far western Maryland, and that may make it as far east as Martinsburg and Winchester before ending tonight. System pulls east overnight with chances for rain ending. Overcast skies to start will see some clearing towards morning. Lows from the upper 30s to mid 40s.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
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Strong warm air advection moves overhead Tuesday as the warm front crosses the region. The day should start partly sunny but see an increase in clouds through the day. Chances for showers and possibly a few thunderstorms increase in the afternoon and evening as ongoing activity moves in from the west. Temperatures will rise into the 60s area-wide. Showers and few thunderstorms Tuesday evening should wane overnight. However, there will be continued chances for a few showers/thunderstorms through the night with deep moist southwest flow, marginal instability, and elevated mixed layer moving overhead. Lows in the 50s to around 60F. Significant weather day possible Wednesday. Deepening low pressure center will be passing through the eastern Great Lakes Tuesday night and into Wednesday with a trailing cold front moving towards and through the Mid-Atlantic states later Wednesday and into Wednesday night. Some morning showers/thunderstorms may be ongoing across the area, mainly north, but most of the activity will likely be associated with a cold frontal passage later Wednesday afternoon and evening. Temperatures will soar in the warm sector out ahead of the front well into the 70s to around 80F with dew points in the 50s to near 60F. This should help generate MLCAPE values into the 500-1000 J/KG range. At the same time, very strong southwest flow will move overhead, with 0-6KM shear increasing to 60-70 knots. Equally impressive is the 850mb flow maxing out at about 50-60 knots. These factors will help set the stage for potential severe weather late Wednesday and Wednesday evening ahead of the cold front. The Storm Prediction Center has already placed our region in a Slight Risk for severe thunderstorms. After cold front passes, will see gusty northwest winds take over later Wednesday night with falling temperatures. Some upslope snow showers also possible late near the Allegheny Front. Lows Wednesday night from the upper 30s to mid 40s.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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Upslope snow showers over the Appalachian Mountains early Thursday. Weak high pressure will move overhead Thursday afternoon and evening before moving offshore Thursday night. An upper level disturbance is expected to approach the region from the Great Lakes and bring a chance for a little rain or snow Friday. An associated surface cold front will bring a re-inforcing shot of colder air into the region Friday afternoon through Friday night. A chance of lingering snow showers or sprinkles Friday night. Temperatures will be seasonably chilly. High pressure will build into the region Saturday through Sunday, keeping dry conditions and chilly temperatures across the region. As the high moves east late Sunday and Sunday night, a dry front is expected to move through the area. On Monday, high pressure will be south of us as a warm front pushes northward helping to spread clouds and perhaps some sprinkles across the region.
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&& .AVIATION /19Z MONDAY THROUGH SATURDAY/...
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VFR expected into Tuesday afternoon. Broken to overcast deck of mid level clouds expected for the remainder of today and tonight with no precip or fog anticipated. Rain and sub- VFR threat increases later Tuesday afternoon and evening. Gusty thunderstorms with sub-VFR cigs and vis are also likely later Wednesday and Wednesday night as a strong cold front passes. Some thunderstorms may become strong to severe. Winds will be increasing out of the south, light today, but steady and gusty by Wednesday afternoon, then turn gusty from the NW after the front passes Wednesday night. VFR conditions expected Thursday and Thursday night. MVFR conditions possible with a chance for a little rain or snow Friday. VFR conditions then return for Friday night and Saturday. Winds gusty out of the northwest early Thursday become west 5 to 10 knots Thursday night. Winds west 10 to 15 knots gusts 20 knots Friday, and turning back southerly Saturday.
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&& .MARINE...
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Generally sub-SCA winds expected for the remainder of today, tonight, and into Tuesday. A few gusts to near 20 knots are possible. SCA then goes into effect at 4 PM Tuesday as southerly winds increase late in the day and overnight. Southerly winds increase further Wednesday with gale conditions possible. In addition, there is the potential for strong to severe thunderstorms late Wednesday and Wednesday evening as a cold front crosses the region. Winds then turn northwest Wednesday night with gale conditions possibly continuing. Gale conditions possible into Thursday morning will gradually weaken through the day, with lighter winds Thursday night. Small craft advisories possible again Friday. No marine hazards Friday night and Saturday.
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&& .CLIMATE... Another period of unseasonably warm weather is forecast to culminate in near-record warmth ahead of a cold front late Wednesday. Here is a list of record daily warm temperatures for March 1st (Wednesday). Site Record High Record Warm Low DCA 80 (1976) 57 (1910) BWI 80 (1972) 53 (1910) IAD 77 (1972) 43 (1997/1987/1976) Here are updated February and Winter records. A warm Tuesday will ensure the warmest February at all three sites. Warmest Februaries (average temperature) DCA BWI IAD 1. 46.9 (1976) 44.0 (1976) 42.1 (1990) 2. 45.2 (1990) 43.9 (1949) 41.1 (1976) 3. 44.7 (1997) 43.3 (1890) 41.0 (1998) 4. 44.3 (2012) 42.7 (1932) 40.9 (2012) 5. 43.9 (1949) 42.6 (1909) 40.5 (1997) Feb 2017 (through the 26th) DCA: 47.4 BWI: 44.0 IAD: 44.8 Warmest Winters (Dec 1-Feb 28/29) DCA BWI IAD 1. 44.7 (1931-32) 45.3 (1931-32) 40.0 (2011-12) 2. 44.3 (1889-90) 44.4 (1889-90) 39.7 (2001-02) 3. 43.3 (2011-12) 42.4 (1948-49) 39.4 (1997-98) 4. 43.2 (2001-02) 41.9 (1949-50) 39.0 (2015-16) 5. 42.8 (1949-50) 41.3 (1879-80) 38.3 (1990-91) Winter 2016-17 (through the 26th) DCA: 43.8 BWI: 40.4 IAD: 40.8 Driest Februaries (total precipitation) DCA BWI IAD 1. 0.35 (2009) 0.26 (2009) 0.25 (1978) 2. 0.42 (1978) 0.36 (2002) 0.35 (2009) 3. 0.47 (2002) 0.56 (1978) 0.46 (2002) 4. 0.62 (1901) 0.63 (1977) 0.49 (1977) 5. 0.66 (1977) 0.65 (1901) 0.68 (1968) Feb 2017 (through the 26th) DCA: 0.34 BWI: 1.21 IAD: 0.33 && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 4 PM Tuesday to 6 AM EST Wednesday for ANZ530>543.
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&& $$ SYNOPSIS...MM NEAR TERM...MM SHORT TERM...MM LONG TERM...KLW AVIATION...MM/KLW MARINE...MM/KLW CLIMATE...LWX

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