Area Forecast Discussion
Issued by NWS Sterling, VA

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863 FXUS61 KLWX 022002 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 302 PM EST Fri Dec 2 2016 .SYNOPSIS...
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High pressure will gradually move into the region through Sunday. An upper-level disturbance will pass through the area Sunday night and high pressure will briefly return for Monday. Coastal low pressure will impact the area Tuesday before high pressure briefly returns for Wednesday. A potent cold front will move through late next week.
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&& .NEAR TERM /THROUGH SATURDAY NIGHT/...
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Latest surface analysis shows high pressure stretching from North Dakota southeast to Alabama, with a low pressure centered just northwest of Caribou Maine. This puts our region in a steady NW flow which should continue through Saturday as both the high and low very gradually shift eastward. By Saturday night, the high pressure ridge to our west finally starts to move overhead and the winds should relax. Aloft, the NW flow will be enhanced by a passing shortwave later tonight before a ridge to the west starts building in Saturday night. The NW flow will remain fairly moist so expect skies to remain at least partly cloudy for much of the area this evening, perhaps clear a bit later tonight though some clouds may redevelop with the sunshine on Saturday. Meanwhile, we`ll also have some high clouds overhead especially later Saturday and Saturday night, so not really expecting a sunny start to the weekend. With wind do not expect it to get very cold tonight but temps will stay a bit lower tomorrow compared to today with cold advection ongoing. Better chance of radiational cooling on Saturday night with the high pressure ridge moving overhead and winds decreasing, but increasing high clouds may counteract that.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY/...
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Sunday the ridge passes east as a shortwave trough approaches from the west. This system has minimal surface reflection but warm air advection will allow clouds to dominate. The clouds will keep temps in the 40s in most spots. By Sunday night, there looks like enough forcing may be present for some light precipitation, though given the upper level pattern its certainly possible that most precip splits around us. Looking at latest guidance, most likely the metro area on S and E will end up with just plain rain, though N and W some snow is possible, especially across the higher terrain since lowest levels will be notably warmer. Guidance still wavers a bit on amounts, with the latest ECMWF notably wetter than the GFS. Given relatively warm antecedent conditions, any accumulations where it does snow would likely be limited to higher elevations, with valleys even all the way up to Hagerstown likely to struggle to accumulate any snow even if snow does make it to the surface. Lows on Sunday night will be in the 30s. Weak ridging returns on Monday with just some clouds and slightly warmer temps, with highs getting back into the 50s in parts of the area.
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&& .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
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Two main weather producers in the extended part of the forecast - a short wave Tuesday and a long wave late Thursday into Friday. GFS/Euro in agreement regarding the short wave moving out of the TN valley Tuesday morning...reaching the coast that evening. There will be a relative paucity of cold air as the wave approaches - Euro 850- 1000 thickness for Tuesday is currently AOA 1300 DM. It`s a long way out to try to get into specifics...but perhaps a wintry mix west of I-81 overnight then rain over the area for several hours Tuesday. This looks to be a fairly fast mover so no drought breaker. Highs Tuesday expected to reach mid 40s. Cold air will remain at bay during midweek. Larger long wave takes shape over the Rocky Mountains which will cause upper level flow in the Mid Atlantic to be from the southwest. Highs should be in the upper 40s to mid 50s. Lows in the mid 30s. It`s a week away but the second weather maker - the long wave, will likely be affecting the region Thursday bringing the chance of rain showers to the forecast area through Thursday night. Lows Wednesday night in the mid to upper 30s. Highs Thursday upper 40s/lower 50s. Cooler air moves into the area Thursay night as precip ends...lows in the 20s.
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&& .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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VFR likely thru late Sunday with high pressure crossing the area. Some clouds at 4-5kft expected through Saturday, then just high clouds Saturday night and much of Sunday before cigs lower again. No vis restrictions thru Sunday afternoon with no precip or fog expected. Winds gusting from the NW this afternoon at 20-25 knots may relax tonight before re-firing on Saturday. Lighter winds expected Sunday. Weak system moving in on Sunday night may reduce cigs and vis to MVFR or even perhaps IFR briefly. Precip most likely rain but a little snow could mix in at MRB. Returning to VFR Monday behind this system. Ceilings could drop into MVFR range Tuesday ahead of a fast moving system.
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&& .MARINE...
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SCA for all waters thru Saturday, then gradually dying off Saturday night as gradient relaxes under high pressure. Wind aloft increases tonight into Saturday and if there is enough mixing with the colder air moving over the warmer water, we may touch gale gusts. Uncertainty remains very high given its likely to be marginal if it even happens so have not raised gales just yet. Best chance would be later tonight into early Saturday. Otherwise dry conditions expected thru Sunday. Sub SCA winds expected Sunday night into Monday as a weak system passes with a little rain. Chances of rain Tuesday although winds still expected to remain below SCA values.
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&& .CLIMATE... Meteorological autumn 2016 has ended (it runs from September 1st through November 30th). It was unusually warm and dry across the much of the area. Below are preliminary temperature and precipitation rankings for this autumn. Washington DC area (Ronald Reagan National Airport, DCA) Temperature (warmest) Precipitation (driest) 1. 63.9 degrees (2016) 1. 1.83 inches (1930) 2. 63.3 degrees (2007) 2. 2.42 inches (1941) 3. 2.65 inches (2001) 4. 3.33 inches (1998) 5. 3.45 inches (1879) 6. 4.07 inches (1967) 7. 4.16 inches (2016) 8. 4.26 inches (1973) Records have been kept at DCA since August 1st 1941. Additional temperature records in the Washington DC area date back to 1872, and additional precipitation records date back to 1871. Baltimore MD area (Baltimore-Washington International Thurgood Marshall Airport, BWI) Temperature (warmest) Precipitation (driest) 1. 64.7 degrees (1931) Not in Top 20 (2016 was 29th driest 2. 63.4 degrees (1941) with 6.65 inches) 3. 63.3 degrees (1881) 4. 61.9 degrees (1946) 5. 61.8 degrees (1900) 6. 61.3 degrees (1970) 7. 61.1 degrees (1927) 8. 60.7 degrees (1947)* 9. 60.4 degrees (1930) 10. 60.3 degrees (1919) 60.3 degrees (1945) 60.3 degrees (1942) 13. 60.2 degrees (2016) 60.2 degrees (1985) *One day of missing data Records have been kept at BWI since January 1st 1950. Additional temperature records in the Baltimore MD area date back to 1872, and additional precipitation records date back to 1871. Dulles VA area (Washington Dulles International Airport, IAD) Temperature (warmest) Precipitation (driest) 1. 60.3 degrees (2007) 1. 3.96 inches (1998) 2. 60.0 degrees (2016) 2. 4.59 inches (1978) 3. 59.5 degrees (1985) 3. 4.61 inches (1965) 4. 4.97 inches (2016) 5. 5.31 inches (1981) Records have been kept at IAD since November 30th 1962. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until midnight EST Saturday night for ANZ531-532-538>540. Small Craft Advisory until 6 PM EST Saturday for ANZ530-535- 536-542. Small Craft Advisory until 6 AM EST Sunday for ANZ533-534-537- 541-543.
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&& $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...ABW AVIATION...RCM/ABW MARINE...RCM/ABW CLIMATE...DFH

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