Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 301927 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 327 PM EDT TUE JUN 30 2015 .SYNOPSIS...
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LOW PRESSURE WILL SLIDE EASTWARD OVER THE EASTERN GREAT LAKES TODAY. A COLD FRONT WILL SLIDE SOUTHEAST INTO THE MID ATLANTIC LATE ON WEDNESDAY...AND THEN STALL ACROSS THE REGION ON THURSDAY. THE STALLED FRONT WILL LINGER IN THE AREA THROUGH THE WEEKEND BEFORE LIFTING NORTHWARD AGAIN ON MONDAY.
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&& .NEAR TERM /THROUGH WEDNESDAY NIGHT/...
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SVR TSTM WATCH 372 IN EFFECT FOR METRO BALT AND N-CENTRL MD TIL 8PM AND SVR TSTM WATCH 377 IN EFFECT FOR THE REST OF THE CWFA TIL 9PM. LLVL CNVRGNC AND NOSE OF THTE RDG THE DRIVING MECHANISMS ATTM ACRS NERN CWFA. DIURNAL HEATING...DIFFERNETIAL HEATING BNDRYS...TRRN CIRCULATIONS...AND LEE TROF ALL PROVIDING LIFTING MECHANISMS FOR THE REST OF THE AREA. ENVIRONMENT CONTAINS MORE THAN ENUF CAPE/SHEAR /2000 J/KG SBCAPE AND 40 KT EFFECTIVE BULK SHEAR/. THIS SUGGESTS THAT TSTM DVLPMNT WL BECOME MORE NMRS IN THE SHEN VLY/BLURDG BEFORE 21Z. THESE STORMS WL THEN MIGRATE TWD THE I-95 CRRDR TWD THE END OF THE WATCH PD. THERE IS POTLENTIAL THAT STORMS MAY LINGER BYD EXPIRATION OF WATCH. IF SO...A LCL EXTENSION MAY BE CONSIDERED IN CONJUNCTION WITH SPC. THE PRIMARY THREAT WOULD BE DAMAGING WIND GUSTS. GIVEN THE MAGNITUDE OF THE SHEAR...A CPL SUPERCELLS NOT OUT OF THE QUESTION. WHILE THERE SHOULD BE AN OVERALL EASTWARD PROGRESSION AND DIURNAL WEAKENING OF ACTIVITY THIS EVENING...MODELS MAINTAIN ELEVATED INSTBY OVERNIGHT AND DECENT SHEAR TNGT. MID/UPPER LEVEL TROUGH WILL BE APPROACHING TOWARD DAYBREAK. THEREFORE SOME SHOWERS AND STORMS MAY LINGER WELL INTO THE OVERNIGHT PERIOD. MIN TEMPS IN THE LOWER/MID 60S WEST AND UPPER 60S/LOWER 70S EAST. THE TROF WL EMERGE OVER THE ERN SHORE BY WED MRNG. A CDFNT WL BE APPROACHING...ATTENDENT FM LOPRES THAT WL BE TRACKING ACRS QUEBEC BY THAT TIME. HWVR...THE CDFNT LOOKS QUITE WEAK...AND AM STRUGGLING TO FIND FORCING MECHANISMS. AMS WL STILL BE QUITE MOIST BUT NOT THAT UNSTBL. MID LVL LAPSE RATES WL BE DECENT. WL HOLD ONTO LOW END CHC POPS...HIER THAN MAV/MET...AND CONT TIL SUNSET. AM NOT MAKING ANY SUBSTANTIVE CHANGES TO TEMPS ATTM. WL STILL BE IN THE WARM SECTOR TMRW...SO TEMPS WL BE SLGTLY MUGGY WITH HIGHS MID-UPR 80S.
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&& .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
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LOW PRESSURE WILL MOVE ACROSS THE UPPER MISSISSIPPI RIVER VALLEY THURSDAY MORNING WHILE A COLD FRONT REMAINS STALLED ACROSS MUCH OF THE EASTERN SEABOARD. SHOWERS ARE EXPECTED TO MOVE INTO THE HIGHLANDS THURSDAY AFTERNOON AS LOW PRESSURE MOVES ALONG THE STALLED FRONTAL BOUNDARY. FCST MODELS HAVE SLOWED DOWN THE PROGRESSION OF SHOWERS MOVING INTO THE REGION. SHOWERS WILL SPREAD ACROSS THE MID- ATLANTIC THURSDAY NIGHT. HEAVY SHOWERS ARE EXPECTED AS ENHANCED LIFT OCCURS IN THE ENTRANCE REGION OF A UPPER LEVEL JET. DUE TO THE TIME OF DAY AND LACK OF INSTABILITY ALOFT...THUNDERSTORMS ARE NOT EXPECTED AT THIS TIME.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/...
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MAIN STORY THROUGH THE EXTENDED IS CONT CHCS FOR UNSETTLED WX...AS STUBBORN FRONTAL BOUNDARY REMAINS NEAR/OVER OUR AREA. THERE REMAINS CONSIDERABLE UNCERTAINTY AND MODEL DISAGREEMENT WITH REGARDS TO FRONTAL LOCATION THROUGH THE EXTENDED. AS SUCH...IT IS DIFFICULT DETERMINE THE SPATIOTEMPORAL EXTENT OF ANY ACTIVITY AND DETERMINE CONVECTIVE VS SHOWER CHCS. MILLION DOLLAR QUESTION IS WHAT WILL THE WX BE LIKE ON SAT...FOR NOW HAVE KEPT CHC POPS AND THUNDER...THOUGH THERE IS CERTAINLY BUST POTENTIAL WITH THIS...AS FRONT COULD BE FAR ENOUGH TO OUR SOUTH...WHICH WOULD LIMIT INSTABILITY (ELEVATED). AS MENTIONED YESTERDAY...TEMPS PROGGED TO REMAIN AOB CLIMO NORMS THROUGH THE EXTENDED...WITH A GRADUAL WARMING TREND THROUGH THE PERIOD. DEWPOINTS ALSO EXPECTED TO REMAIN AOB 70F...SO NOT EXPECTING CONDITIONS TO BE VERY OPPRESSIVE.
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&& .AVIATION /19Z TUESDAY THROUGH SUNDAY/...
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VFR CONDS PREVAILING ATTM. TSRA DVLPMNT WL BE IN THE NEIGHBORHOOD...BUT CONFIDENCE IN IMPACT AT A TERMINAL A BIT MORE UNCERTAIN. AM USING VCTS TO COVER THRU EVENING PUSH...AND WL INCL A TEMPO FOR SPECIFICS ONCE ITS MORE CERTAIN A TERMINAL WL BE DIRECTLY AFFECTED. POTL FOR WINDS GUSTS 40-50 KT IN THE STRONGEST STORMS. BELIEVE OVERALL INTENSITY WL DECLINE OVNGT...BUT SUSPECT THERE WL BE SOME ACTIVITY. FLGT RESTRICTIONS WL THEREFORE REMAIN PSBL... BUT MORE LKLY MVFR. HWVR...CONFIDENCE NOT HIGH IN STORM EVOLUTION. TSRA CVRG LOOKING MUCH LWR ON WED...AS TROF WL BE EAST OF TERMINALS. A WEAK CDFNT WL BE DROPPING SWD IN THE AFTN-EVNG. ITS ENTIRELY PSBL THAT THERE WL BE NO TSRA AT ALL. TAFS VFR W/ CIGS BKN-OVC050-060. SUB-VFR CONDITIONS POSSIBLE THURSDAY NIGHT AS RAIN MOVES INTO THE REGION MAIN CONCERN THROUGH EXTENDED IS POTENTIAL FOR SCATTERED THUNDERSTORMS EACH DAY...WITH SUB-VFR CONDS POSSIBLE NEAR TSTMS. VFR CONDS EXPECTED OUTSIDE OF TSTMS.
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&& .MARINE...
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S/SE CHANNELING OCCURING OVER THE WATERS ATTM. SCA REMAINS IN EFFECT. SEVERE THUNDERSTORM WATCH ALS IN EFFECT FOR ALL WATERS FOR THE POTENTIAL OF STRONG WIND GUSTS. GRADIENT WINDS WILL DIMINSH OVERNIGHT. SW FLOW THROUGH WED AROUND 10 KT...ALTHOUGH MAY BE SLIGHTLY STRONGER TOWARD TANGIER SOUND. LOWER CHANCE OF STORMS THROUGH WED. SHOWERS WILL OVERSPREAD THE REGION THURSDAY NIGHT AND MAY CAUSE REDUCED VSBYS. WINDS EXPECTED TO REMAIN BELOW SCA CRITERIA THROUGH THE EXTENDED...THOUGH WILL NEED TO MONITOR AS FRONT WILL BE NEAR AREA EACH DAY. SHOWERS AND TSTMS ARE ALSO POSSIBLE EACH DAY...WHICH COULD IMPACT MARINE CONCERNS
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&& .TIDES/COASTAL FLOODING...
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WATER LVLS RUNNING ABT A FOOT ABV ASTRO NORMS. THE LOWER OF THE TWO HIGH TIDES ROLLING IN NOW...WHICH WL KEEP LEVELS BELOW ADVY CRITERIA. HWVR...ISSUES WUD RESULT FROM THE NEXT TIDE...MIDNGT TO NOON. TOO SOON TO ISSUE ADVY ATTM...BUT ONE MAY BE REQD BEFORE EVNG OVER.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT WEDNESDAY FOR ANZ531>534- 537-539>543. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ530- 535-536-538. && $$ SYNOPSIS...HTS NEAR TERM...HTS SHORT TERM...HAS LONG TERM...MSE AVIATION...HTS/HAS/MSE MARINE...HTS/HAS/MSE TIDES/COASTAL FLOODING...HTS

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