Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 251748 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1248 PM EST Sat Feb 25 2017 .SYNOPSIS... 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. && .NEAR TERM /THROUGH TONIGHT/...
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Update... Earlier precipitation dissipated, but a band of thunderstorms have developed in Virginia along wind shift boundary...ahead of the cold front. Have used this feature as the catalyst for showers/thunderstorms this afternoon. All forecasts have been updated. Will be monitoring for severe thunderstorm potential. From previous discussion... Have an anonomously warm/humid air mass in place. In spite of approaching cloudcover, which may act to limit heating, would not want to discount heating potential. Therefore, am not backing down on temperature forecast. For that matter, little change made to overall forecast. Anticipate line of showers to reintensify upon diurnal heating. There is a well defined baroclinic boundary to drive convection, and heating will add the necessary instability/lift (1000 J/kg CAPE...in February). Believe that downward transport of momentum to be the primary threat. However, wet-bulb zero climatologically low (around 8500 ft) and lapse rates rather high, so any of the taller updrafts may contain a hail threat too. Current timing would place this activity near the Blue Ridge by noon, and the I-95 corridor around 3pm. HRRR/RAP depict good consistency temporally. By 6pm, all activity should be pushing onto the Eastern Shore. 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/... 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. && .LONG TERM /TUESDAY THROUGH FRIDAY/... 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. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... A sharp cold front will be crossing the terminals this afternoon. (MRB may be a pinch before noon.) 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. && .MARINE... Gale Warning now in effect, although strongest gusts will be later today. 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. && .CLIMATE... 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 && .LWX WATCHES/WARNINGS/ADVISORIES... 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 until 1 AM EST Sunday for ANZ530>543. && $$ SYNOPSIS...RCM NEAR TERM...HTS/ADS SHORT TERM...ADS LONG TERM...RCM AVIATION...ADS/HTS/RCM MARINE...ADS/HTS/RCM CLIMATE...BAJ/DFH/RCM

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