Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 261436 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1036 AM EDT Tue Jul 26 2016 .SYNOPSIS...
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A front will become stationary across the area today, then drift southward on Wednesday. Another cold front is expected early next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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A weak front is stalled across the area. Winds are light and from the N or NW. Aloft, very weak CAA is also in place, with 850 mb temperatures falling just below 20C. However, a warm start and some sun have allowed temperatures to warm to near 90 by 10 AM. Mid level clouds are advancing from the west, which will filter sunshine into the afternoon. Nevertheless, another hot day is in store with temperatures in the mid 90s and heat indices near or above 100 for much of the area. The heat advisory for southern counties looks to be in good shape based on the latest trends. Showers and thunderstorms are expected to develop this afternoon, and the going forecast looks largely on track based on latest guidance. Coverage will range from isolated near the MD/PA border to scattered across Central VA. A weak shortwave approaching from the Ohio Valley may help initiate storms. A few storms may become strong to severe across the central Shenandoah Valley, Central Foothills and southern Maryland where instability is higher. Poor lapse rates will once again be a limiting factor. Weak shear profiles will also keep strong storms isolated. While heavy rain will be possible due to high PWAT, there should be enough flow to keep storms moving. Coverage will diminish into the evening however any ongoing thunderstorms will likely continue as little change is airmass is expected.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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Zonal flow continues across the region Wednesday. The cold front is expected to move south Wednesday and into central and southern VA. There is some guidance that keeps the front northward along the east coast and therefore dewpts may not drop as much across central VA and southern Maryland. Thunderstorm coverage is expected to be less on Wednesday with a few forming across the higher terrain. If dewpts do not drop across the east coast a few thunderstorms will be possible in the afternoon. Activity will diminish into Thursday. The front lingers near the region Thursday and isolated showers and thunderstorms are possible in the afternoon and evening. A shortwave trough will approach the area Thursday night and coverage will likely become more widespread and heavy rain is possible.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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Guidance shows heights falling across the region through the end of the week especially in the Thu-Fri evening time frame as a shortwave-trough digs across the eastern Great Lakes. Both the ECMWF and GFS show a low pres center tracking from the Carolinas newd to south of Long Island during the weekend with periods of rain affecting the area Fri into Mon. Widespread total rainfall amounts of an inch or more are likely during this period. Ignoring the GFS precip output which appear spurious generating a large area of 1-3 inches in a 6-hr period over northern VA and MD. Based on ensembles, the period of best rainfall potential appears to be in the Fri-Sat time frame. By Mon night, most guidance show a front clearing the area with enough dry air to suppress precip chances and enough cooler air to keep temps below 90F at least in northern areas.
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&& .AVIATION /15Z TUESDAY THROUGH SATURDAY/...
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VFR conditions expected this morning. Scattered showers and thunderstorms are expected this afternoon and evening with higher chance at CHO. Coverage will be isolated at best for MRB-Baltimore and confidence is low to put in TAFs at this time. Activity will likely diminish tonight and vfr conditions are expected. Isolated SHRA/VCTS expected Wednesday and Thursday afternoon. Sub-VFR conditions possible in activity. Risk of showers and t-storms will likely continue into the weekend as area remains under a very warm and moist air mass. Drier air not likely to make into the area until early next week.
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&& .MARINE...
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A cold front has stalled across the waters this morning. N/NW winds this morning may become southerly this afternoon, especially for the southern waters. Showers and thunderstorms possible today mainly across the southern half of the waters. Gusty winds are possible and SMW may be issued. Winds become nrly tonight and Wednesday. Isolated showers and thunderstorms possible Wednesday and Thursday afternoons. Sub-SCA conditions expected Fri through Mon, but higher winds and waves can be expected near thunderstorms.
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&& .CLIMATE...
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Records were either broken or tied at all three main airports yesterday. A record high temperature of 100F degs was set yesterday at Dulles breaking the old record of 98F set in 2010. A record high temperature of 100F degs was set yesterday at BWI airport tying the old record of 100 set in 2010. A record high and a record high minimum were set at DCA yesterday. A record high of 100F was set tying the old record of 100F degs set in 1930. A record high minimum of 81F degs was set breaking the old record of 79F set in 1965.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Heat Advisory until 8 PM EDT this evening for MDZ016>018. VA...Heat Advisory until 8 PM EDT this evening for VAZ036-037-050- 055>057. WV...None. MARINE...None.
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&& $$ SYNOPSIS...LFR NEAR TERM...ADS/HAS SHORT TERM...HAS LONG TERM...LFR AVIATION...ADS/HAS/LFR MARINE...ADS/HAS/LFR CLIMATE...LFR

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