Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 050750 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 350 AM EDT TUE MAY 5 2015 .SYNOPSIS... COLD FRONT SINKS SOUTH TODAY...STALLING NEAR THE MASON-DIXON LINE THROUGH TONIGHT BEFORE PUSHING FURTHER SOUTH ON WEDNESDAY. HIGH PRESSURE IS EXPECTED TO RETURN TO THE REGION LATE IN THE WEEK WHILE LOW PRESSURE DEVELOPS OFF THE CAROLINA COAST. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... REGION REMAINS ON THE WESTERN PERIPHERY OF HIGH PRESSURE NEAR BERMUDA THIS MORNING. THE HIGH WILL PUSH TO THE SOUTH AND EAST TODAY AS A COLD FRONT CURRENTLY POSITIONED OVER WESTERN NY DIPS SOUTH...EVENTUALLY STALLING NEAR THE MASON-DIXON LINE LATER TODAY. THIS FRONT WILL BE THE FOCUS OF PCPN DEVELOPMENT TODAY AS NEAR ZONAL FLOW SETS UP ALOFT WITH MINIMAL ASSISTANCE OF FORCING. THE HIGH COMBINING WITH SUBSIDENCE ALOFT KEEPING MOSTLY CLEAR SKIES EARLY THIS MORNING. VERY LIGHT RAIN SHOWERS NOTED OVER SW PA AS OF 07Z ASSOCIATED WITH A WEAK VORT MAX. WILL MAINTAIN ISO SPRINKLES IN FOR THE NW CORNER...BUT OVERALL NOT EXPECTING PCPN TO REACH THE CWA TILL MID DAY AS THE FRONT NEARS THE REGION. THINKING DIURNAL HEATING ALONG WITH THE FRONTAL BOUNDARY WILL BE THE TRIGGERING SOURCE FOR SHOWERS AND ISO TSTMS TODAY. AS SUCH...HAVE GONE WITH LIKELY POPS FOR NORTHERN FRINGE OF THE CWA BY LATE AFTN...THEN TAPERED POPS OFF TO THE SOUTH. HAVE INCLUSION OF THUNDER FOR THE AFTN/EARLY EVENING...THEN JUST SHOWERS FOR THE OVERNIGHT WITH THE LOSS OF DAYTIME HEATING. ANOTHER WARM DAY FOR THE ENTIRE REGION AS HIGHS REACH INTO THE 80S. DEPENDING ON THE TIMING OF THE FRONT...COULD SEE TEMPS FLUCTUATE A FEW DEGREES. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... COLD FRONT EXPECTED TO HAVE STALLED BY THE MASON-DIXON BY TONIGHT...THEN BEGINS TO SINK TO THE SOUTH AGAIN AFTER 12Z WED AS THE UPPER LVL TROUGH OVER THE NORTHEAST DEEPENS JUST ENOUGH TO PUSH THE FRONT TO THE SOUTH. MOVEMENT TO THE SOUTH WILL BE MINIMAL THOUGH AS THE FLOW ALOFT QUICKLY TRANSITIONS INTO A BUILDING RIDGE. TONIGHT LOOKS TO BRING A PERIOD OF DRY WX FOR ALMOST THE ENTIRE AREA...WITH LINGERING SHOWERS JUST ALONG THE I-95 CORRIDOR AND EAST. PCPN CHC INCREASES AGAIN TOMORROW WITH THE FRONTAL BOUNDARY PROVIDING YET AGAIN A TRIGGERING MECHANISM FOR SHOWERS. WITH WINDS TURNING E-NE BEHIND THE FRONT THOUGH INJECTING IN A MORE STABLE ATMO...THINKING THIS WILL MINIMIZE THE THUNDER THREAT. AS SUCH...HAVE JUST GONE WITH SLIGHT CHC AROUND MID DAY OF THUNDER...THEN TAPERED TO THE SOUTH AND WEST TO AREAS OUT AHEAD OF THE FRONT THAT WITH A S- E FLOW HAVE A BETTER CHC OF OF WARMING MORE/REMAINING MORE UNSTABLE. HIGH PRESSURE BUILDS SOUTH BEHIND THE FRONT BY WED NIGHT...RESULTING IN A MAINLY DRY NIGHT. ANY LINGERING SHOWERS WED EVENING WILL TAPER OFF BY MIDNIGHT. TEMPS STILL WELL ABV NORMAL...GENERALLY IN THE 50S FOR OVERNIGHT LOWS...WITH POCKETS OF NEAR 60 IN THE METRO ARES. && .LONG TERM /THURSDAY THROUGH MONDAY/... RDGG REASSERTS ITSELF THU...NOT JUST AT THE SFC BUT ALSO ALOFT. THAT SETUP SHUD MAKE IT DFCLT FOR TSRA TO DVLP. HWVR...RESIDUAL MSTR WL LINGER...NOT JUST IN THE FORM OF DEWPTS IN THE UPR 50S/LWR 60S...BUT ALSO W/IN THE LYR. THEREFORE...XPCT A DECENT AMT OF CLDCVR. INSTBY PUSHED BACK TWD THE MTNS...WHERE OF COURSE TRRN BASED FORCING EXISTS TOO. IN THE END...OPTED TO KEEP A CHC SHRA/TSRA FOR THE VA PIEDMONT/ BLURDG CNTYS AS WELL AS APLCNS. CONFIDENCE NOT ALL THAT GREAT THOUGH. GIVEN LMTD INSTBY/FORCING...ANY ACTIVITY SHUD BE IN RAPID DECAY BY SUNSET. ITLL BE A SIMLR SETUP FRI-SAT. GIVEN SUCH A SMALL OPPORTUNITY...WL BE GOING W/ A DRY FCST FOR THESE TWO DAYS. INSTBY INCREASES SUN-MON AS RDGG SHIFTS OFFSHORE AND CDFNT APPROACHES FM THE WEST. THAT WL BE WHEN POPS /TSTMS/ APPEAR IN THE FCST...THO ITS A SLOWER PROGRESSION THAN FCST YDA. PTTN WL BE WARM THRUT THE XTNDD...W/ MAXT LWR-MID 80S. THU WL BE THE COOLEST DAY...AND TOOK FCST DOWN BY A DEGF OR TWO. GIVEN DEWPTS... MIN-T FOR A NUMBER OF DAYS. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... MAINLY VFR CONDITIONS FOR THE PERIOD. INCRSG HIGH LVL CLOUDS THIS MORNING...WITH SCT-BKN CU BY THIS AFTN WITH PCPN. BKN-OVC CONDITIONS CONTINUE TONIGHT THRU WED. WIND DIRECTION HARD TO PINPOINT TODAY WITH FRONTAL BOUNDARY OVER THE REGION. HOWEVER...WINDS WILL BE LIGHT...GENERALLY 7 KTS OR LESS. SCT-NUM SHRA MAINLY AFTR 18Z. ISO TSTM PSBL LATE AFTN...WILL MENTION WITH VCTS FOR NOW WITH LOW CONFIDENCE OF TIMING/LOCATION. BEST CHC FOR TSTM 19-23Z. CHC RW TONIGHT INCRSG IN COVERAGE ON WED. LESS CHC OF TSTM ON WED WITH ELY FLOW. MAINLY VFR THU-SAT. LOW CHC FOR A LTL PREDAWN FOG AT CLIMO FAVORED LOCATIONS. && .MARINE... SCA REMAINS IN PLACE FOR SOUTHERN TIDAL POTOMAC AND CENTRAL CHESAPEAKE BAY THRU 10Z WITH GUSTS 18-22KTS. WINDS DIMINISH AFTR DAYBREAK...SO ONLY KEEPING CHESAPEAKE BAY ZONES THRU THE MORNING. SUB-SCA CONDITIONS EXPECTED EVERYWHERE BY THIS AFTN...AND LASTING THRU WED NIGHT. FLOW WL BE LIGHT /10 KT OR LESS/ THRU THE END OF THE WEEK--ELY THU...SELY FRI...AND EVENTUALLY SLY BY SAT. NO FLAGS XPCTD. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR ANZ533-537. SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ534-543. && $$ SYNOPSIS...SEARS/HTS NEAR TERM...SEARS SHORT TERM...SEARS LONG TERM...HTS AVIATION...SEARS/HTS MARINE...SEARS/HTS

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