Area Forecast Discussion
Issued by NWS Sterling, VA

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541 FXUS61 KLWX 010121 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 921 PM EDT TUE MAY 31 2016 .SYNOPSIS...
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Several weak frontal boundaries will be in the area through Thursday. A stronger cold front will pass through from the west later Friday into Friday night. High pressure may briefly build into the area Saturday before another cold front approaches Sunday and passes through Sunday night into Monday.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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Rather weak surface pressure pattern across the area this evening with shortwave ridging aloft. The small showers that developed to the south and east of DC due to mesoscale boundaries have all but dissipated, and it looks like we should have a dry rest of the night. A prominent feature during the early evening was a dew point boundary, located between IAD and DCA, roughly oriented NNE to SSW...with dew points in the mid to upper 60s to the east, and in the 50s to the west (before rising due to decoupling). Temperatures which rose into the 80s for most of the area will drop into the 60s tonight...with some 50s in the cool spots and near 70F in the urban centers. Adjusted temps up a couple degrees where dew points are currently higher. With light winds and partly to mostly clear skies...potential for fog exists...though with lower dew points to start we might not get as widespread or dense as last night, especially in the western areas. Cloud cover and dew point trends will play an important role. Any fog will break early Wednesday. However...back door cold front will approach the area from the north and could spawn a stray shower or t-storm. Forcing and moisture is weak...mainly due to convergence in onshore flow between the front and remnants of Bonnie. Most hi-res models simulate widely scattered, light reflectivity. Have POPs trend east to west through the day as stable air pushes onshore. Temps may also be a little cooler with more clouds but generally still a decent day. Highs again mostly in the 80s.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... Back door cold front appears to regain some strength and push southwest into the area Wednesday night into Thursday...with further modest decrease in temperatures. This may try to keep north and east portions of CWA dry...while further SW spotty showers/storms will again be possible though with low coverage once again. Stronger cold front will approach from the west on Thursday night and cross the area Friday. This system will bring better concentration and coverage of rain and storms. However...forcing aloft is not great even if CAPE looks decent...so probably looking at marginal severe if any. Highs again in the vicinity of 80. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Weak high pressure briefly builds in Friday night-Saturday, keeping most of the area dry through the day. Attention then turns to upper trough digging into the NE Sunday. Guidance still differs with respect to amplitude/positioning/timing, which will have a big influence on impacts for our area. Depending on evolution, shear/thermo profiles could be favorable for severe thunderstorms. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
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With light winds and partly to mostly clear skies, areas of fog possible again later tonight into Wednesday morning. Have introduced IFR vsby at MRB (climo) and CHO (where higher dew points currently reside, and have MVFR at the rest of the terminals except DCA. Like last night, not out of question IAD could drop lower right around dawn. On the whole, fog is not looking as dense as last night. Weak boundary pushes toward area on Wednesday and may spark an isolated shower or perhaps a thunderstorm, likely moving roughly east to west. Predicted coverage and intensity preclude TAF mention ATTM. IFR or lower conditions possible Wednesday night into Thursday morning with onshore marine layer...then more isolated/scattered showers/t-storms Thursday afternoon mainly MRB/CHO. Winds generally less than 10 knots through Thursday, ranging from NE-SE. Better coverage of showers/t-storms late Thursday night and Friday with stronger front. Winds become more SW for a time. Another stronger cold front approaches Sunday with another chance of thunderstorms across the area.
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&& .MARINE...
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Sub-SCA winds expected through at least Wednesday with surface flow changing from roughly southerly this evening to a more easterly component less than 15 knots on Wednesday. Near-SCA conditions possible Wednesday night into Thursday behind a back door cold front. Another cold front passing through the waters Friday into Friday night will bring better coverage of showers and thunderstorms. Showers and thunderstorms are possible Sunday with another stronger cold front. Gradient winds also increase near SCA conditions Sunday near and behind frontal passage.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...RCM NEAR TERM...ADS/RCM SHORT TERM...RCM LONG TERM...MSE AVIATION...ADS/MSE/RCM MARINE...ADS/MSE/RCM

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