Area Forecast Discussion
Issued by NWS Sterling, VA

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380 FXUS61 KLWX 191855 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 255 PM EDT Wed Jul 19 2017 .SYNOPSIS...Weak high pressure will build into the region through Thursday, followed by the potential for weak disturbances Friday through Sunday. An upper level trough of low pressure will move over the northeastern US to start the new week. && .NEAR TERM /THROUGH TONIGHT/...Convective coverage today has been significantly less than yesterday. Experimental GOES-16 low-level water vapor imagery shows much drier air today than yesterday which is greatly limiting deep convection to just isold showers. Tranquil and very warm muggy tonight with lows in the 70s in many areas and upper 70s in urban areas. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...As heights rise a bit more and h85 temps rise into the low 20s (C), expect even less convective coverage tomorrow than today. In addition, a light w to nw sfc flow will develop lowering sfc dewpoints and boosting temps in the mid to upper 90s hottest over western MD, ern WV panhandle and wrn VA. Due to advection of lower dewpoints, heat indices will likely fall below any heat advisory criteria. Still hot nonetheless. Slight risk of some nocturnal MCS activity to make it into western MD, but activity is likely to dissipate as it crosses the Appalachians. Hotter on Friday as h85 temps peak at 22C. A light sw flow over Fredericksburg, southern MD and the urban areas will likely keep sfc dewpoints higher with heat indices filtering around the 105 degree threshold. Temps west of the Blue Ridge could hit the century mark with heat indices filtering with the new heat index criteria there of 100F. Some convection can`t completely be ruled out, but model guidance do not show good chances. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... A front will stall across central Virginia Saturday. There is a chance for showers and thunderstorms along this front. Highs will once again reach the middle 90s in many areas. The front will move north of the region as a warm front Saturday night, keeping the chance for showers and thunderstorms present over much of the region. Upper level energy from the west will set up a trough of low pressure on the leeside of the Appalachians Sunday into Sunday night. Additional showers and thunderstorms could form along this trough but could mainly be isolated to scattered. Highs will reach the middle to upper 90s. A cold front will approach the region Monday before pushing across the region Monday night. Showers and thunderstorms will develop along and ahead of this front. Some thunderstorms could be strong to severe as wind shear increases some. Highs will reach the be in 90s again, until the front ushers in cooler and drier air Monday night. Broad high pressure will build in from the west and northwest Tuesday through Wednesday. Temperatures will be nearly 10 degrees cooler than previous days with a comfortable relative humidity with respect to mid-Summer days and nights. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/...VFR conditions tonight through Fri with light and variable winds. Mvfr to ifr conditions possible with showers and thunderstorms Saturday through Sunday night. Ifr conditions would be mainly in heavy thunderstorms. Winds southwest 5 knots Saturday. Winds light and variable Saturday night. Winds southwest 5 to 10 knots Sunday, becoming northwest around 5 knots Sunday night. && .MARINE...Isolated t-storms possible today through Fri. No marine hazards expected Saturday through Sunday night. Winds southwest 5 to 10 knots Saturday and Saturday night. Winds southwest 10 knots Sunday and Sunday night. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...KLW AVIATION...LFR/KLW MARINE...LFR/KLW

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