Area Forecast Discussion
Issued by NWS Sterling, VA

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997 FXUS61 KLWX 250909 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 409 AM EST Sat Feb 25 2017 .SYNOPSIS...
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A cold front will cross the area today. High pressure will return to the area Sunday through early next week. A warm front will then lift north into the area Tuesday into Wednesday followed by another cold front Wednesday night.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Weather story for today: Severe storms possible, especially east of the Blue Ridge, while cold front brings sharp weather changes. A cold front is crossing the Ohio Valley this morning, trailing low pressure over Lake Huron. With southerly winds established locally, temperatures are very warm for this time of year, in the 50s and even 60s. Low clouds and fog have failed to form as aggressively as models suggested, although there has been a recent trend downward from Baltimore to Westminster. Wouldn`t think this would have an impact on sensible weather, but if thicker cloud cover can develop, it could affect temperatures and destabilization later today. At this time, most lightning strikes are south of the Ohio River, so would expect the weakening band of showers to continue to progress toward the mountains by daybreak. The cold front will march eastward across the area through the day. Ahead of it, temperatures have a good shot of topping out in the upper 60s to lower 70s on breezy south winds. While the showers may break apart somewhat, am expecting a reinvigorated line to form east of I-81 around the midday hours, as the strong low level forcing encounters increasing instability (possibly around 1000 J/kg MLCAPE near the I-95 corridor). Parameters such as updraft velocity/helicity and max lightning suggest the strongest storms will be east of US-15 after 2 PM. Strong unidirectional deep layer shear will support some bowing segments, and instability should be sufficient to bring down higher winds aloft. SPC has thus highlighted the eastern portion of the area in a Slight Risk. While strong to damaging winds will be the main threat, mid-level lapse rates are fairly steep, so the strongest updrafts could also contain some hail. Brief locally heavy rain will also be possible, but no problems are expected due to fast movement and dry conditions. The line of storms will push east of the Bay between 5-8 PM. Temperatures will fall quickly as the front passes, and westerly winds will increase with gusts of 30-40 mph possible. The best surge of winds may come during the early evening. Lows will ultimately bottom out in the 30s, with some 20s west of the Blue Ridge. A period of upslope snow showers could produce localized amounts up to an inch west of the Allegheny Front.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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High pressure moves in from the west Sunday, allowing winds to gradually relax. Highs will be much cooler but closer to normal in the mid 40s to lower 50s. Lows will fall back to the upper 20s and 30s Sunday night as the high begins to move east. While no well defined system is expected for Monday into Monday night, there will be increased isentropic lift, and an inverted trough may develop along the Carolina coast to SE VA. Will have gradually increasing chances of showers through the period, highest S/E of DC Monday night. Temperatures will gradually warm back up as well.
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&& .LONG TERM /TUESDAY THROUGH FRIDAY/...
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Another system will slowly lift northeast across the Plains and Great Lakes Tuesday through Wednesday night. This system will push a warm front back northward across the region Tuesday and Tuesday night, with solid warm sector weather expected by Wednesday afternoon. Showers will be possible through this entire period. Then the cold front will cross the region Wednesday night with more showers and perhaps a stray thunderstorm. This system looks a little weaker than the current one but not a whole lot so we may have some of the same concerns. After the system passes, we turn notably cooler Thursday and Friday as Canadian high pressure tries to build in. A weak clipper could even try to sneak across the area at the end of the week but this is highly uncertain. There is a small potential that this system could even try to bring a little snow, but odds again are quite small at this point. In any case, after all this mild weather, the slightly cooler than normal weather expected for the end of this week will feel pretty cold.
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&& .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
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Given current trends low cloud fog potential is iffy at best this morning, with the best chances of MVFR or briefly lower at BWI. The main story today will be a sharp cold front crossing the area this afternoon. Expect a line of showers/storms to accompany the front, which could pose brief IFR conditions and strong wind gusts above 40 kt. Winds will sharply shift to the west behind the front, with 30-35 kt gusts possible through mid- evening or so. Winds gradually diminish through Sunday as high pressure builds. No major impacts are forecast Monday and Monday night, although there will be increasing chances for some light rain showers. Potential for sub-VFR conditions Tuesday through Wednesday night as a warm front moves north followed by a cold front, with showers reducing visibility along with low clouds possible.
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&& .MARINE...
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Southerly flow 10-15 kt should increase through mid morning. In first period forecast, have Gale Warning starting at 10 AM, although strongest gusts will be later. Sharp cold front will move eastward this afternoon, accompanied by strong showers and storms with 40+ kt wind potential. Winds also shift to west, with continuing gusts near gale force possible through the evening. The main story is the sudden onset, which may catch boaters off guard after the mild morning. SCA conditions then continue through Sunday afternoon. Brief lull Sunday night with high pressure, but southerly winds could again reach SCA criteria on Monday into Monday night. System moving through Tuesday/Wednesday may result in continued SCA conditions as southerly flow continues.
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&& .CLIMATE...
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Record high maximum and minimum temperatures for February 25: BWI 83F (1930), 52F (1930) DCA 84F (1930), 54F (1891) IAD 79F (2000), 47F (2000) 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 24th) DCA: 47.1 BWI: 43.7 IAD: 44.5 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 Feb 24) DCA: 43.7 BWI: 40.3 IAD: 40.7 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 24th) DCA: 0.16 BWI: 0.46 IAD: 0.25
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 1 AM to 4 PM EST Sunday for ANZ530>543. Gale Warning from 10 AM this morning to 1 AM EST Sunday for ANZ530>543.
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&& $$ SYNOPSIS...RCM NEAR TERM...ADS SHORT TERM...ADS LONG TERM...RCM AVIATION...ADS/RCM MARINE...ADS/RCM CLIMATE...BAJ/DFH/RCM

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