Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 250753 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 353 AM EDT THU SEP 25 2014 .SYNOPSIS... COASTAL LOW PRESSURE WILL CONTINUE TO DEVELOP OFF THE DELMARVA PENINSULA THIS MORNING...AND WILL VERY SLOWLY MOVE OUT TO SEA TO THE EAST NORTHEAST THIS AFTERNOON AND TONIGHT. GREAT LAKES HIGH PRESSURE WILL SLOWLY BUILD INTO THE REGION FRIDAY...AND REMAIN THROUGH THE WEEKEND. LOW PRESSURE WILL APPROACH THE REGION DURING THE FIRST HALF OF NEXT WEEK. && .NEAR TERM /UNTIL 9 AM THIS MORNING/... STILL A THREAT OF SOME HEAVY RAIN IN SOME SPOTS THAT SEE ENHANCED BANDING. THERE HAVE BEEN A FEW SPOTS UNDER THE BANDS THAT HAVE SEEN AROUND A QUARTER INCH IN AN HOUR...BUT THOSE ARE ISOLATED. MOST OF THE REGION UNDER LIGHT RAIN...ALTHOUGH VERY LITTLE AT ALL OVER THE SHEN VALLEY AND POTOMAC HIGHLANDS EARLY THIS MORNING. THE STRONG EAST WINDS IN THE LOW LEVELS OFF THE ATLANTIC ARE SHIFTING TO OUR NORTH AND BECOMING MORE NORTHEASTERLY BY LATE MORNING. GIVEN THE LITTLE RAIN THAT HAS FALLEN SO FAR...THE DRY GROUND FROM NOT MUCH RAIN OVER THIS MONTH...AND THE ONLY FEW HOURS LEFT OF POSSIBLE HEAVIER RAIN AT TIMES...DO NOT SEE A REASONABLE CHANCE OF FLOODING RAINS AT THIS POINT. THEREFORE WILL BE CANCELING THE FLOOD WATCH THAT WOULD HAVE EXPIRED AT 6AM ANYWAY. WILL CONTINUE TO MONITOR IN THE VERY OUTSIDE CHANCE THAT SOMETHING MORE SUBSTANTIAL BEGINS TO MATERIALIZE...BUT BETWEEN THE ABOVE...AND THE FORECAST QPF BY THE EURO NAM GFS SREF AND WPC ENSEMBLE PROBABILISTIC QPF...EXPECT THIS RAIN IN THE BALT WASH METRO WILL BE MEASURED IN TENTHS OF AN INCH..AND NOT INCHES. && .SHORT TERM /9 AM THIS MORNING THROUGH 6 PM FRIDAY/... SEEING A SIZABLE SHIFT IN THE MODELS ON HOW SLOWLY THIS LOW WILL KICK OUT. MADE SIGNIFICANT SHIFTS IN THE FORECAST INTO FRIDAY KEEPING CLOUDS IN LONGER AND RAIN SHOWER CHANCES IN LONGER. EXPECT THE GREAT LAKES HIGH WILL MUSCLE IN AS THE DAY GOES ON FRIDAY...BUT UNTIL THEN SKIES WILL BE SLOW TO CLEAR AND SHOWER CHANCES WILL LINGER...ESP CLOSE TO THE CHES BAY. THIS IS BORNE OUT IN THE GFS NAM EURO AND WPC PROBABILISTIC QPF FIELDS...ALBEIT AT SLIGHTLY DIFFERENT SPEEDS OF MOVING IT OUT. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... HIGH PRESSURE REMAINS CENTERED OVER SRN ONTARIO FRIDAY NIGHT AND SATURDAY (WITH NORTH FLOW) BEFORE DRIFTING EAST TO NEW ENGLAND FOR SUNDAY (WITH AN ONSHORE FLOW) PER 00Z GFS/ECMWF. QUIET WEATHER IN THIS TIME WITH HIGH CLOUDS LINGERING FRIDAY INTO SATURDAY. WORTH NOTING THAT THE NLY FLOW SATURDAY IS ACTUALLY WARM AIR ADVECTION FROM CONTINENTAL AIR WRAPPING AROUND THE GREAT LAKES HIGH. BELIEVED MOS CONSENSUS OF LOW 80S FOR MAX TEMPS FOR BALT-WASH METRO WHICH SHOULD BE A COUPLE DEGREES HIGHER THAN KCHO WHICH IS FARTHER DOWNSTREAM OF THE WARM AIR ADVECTION. MAX/MINS ABOVE NORMAL THROUGH THIS WEEKEND AS THE CONTINENTAL AIR PERSISTS. CUTOFF LOW OVER THE DEEP SOUTH DRIFTS EAST/NORTHEAST MONDAY... STRUGGLING TO DISLODGE THE HIGH PRESSURE OVER THE NERN CONUS. POPS SLOWLY INCREASE MONDAY THROUGH TUESDAY BUT NOTHING ABOVE LOW CHANCES AS OF THIS TIME. THE 00Z GFS ALSO BRINGS A LOW FROM THE GREAT LAKES WHICH MAY PROVIDE A BOOST IN POPS SHOULD IT BE A FEATURE CARRIED ONTO FUTURE RUNS. && .AVIATION /07Z THURSDAY THROUGH MONDAY/... WITH THE COASTAL LOW SLOW TO MOVE OUT...EXPECT WIDESPREAD IFR CONDITIONS THIS MORNING AND AGAIN THURSDAY NIGHT FROM LOW CIGS. MRB TAF SITE IS THE ONLY ONES EXPECTED TO REMAIN MVFR THIS MORNING...BUT EVEN THAT WILL BE MONITORED SINCE IT WILL BE JUST OVER THE THRESHOLD. HIGH PRESSURE/VFR PREVAILS FRIDAY NIGHT INTO MONDAY. LIGHT NLY FLOW FRIDAY NIGHT/SATURDAY BECOMES ONSHORE SUNDAY INTO MONDAY. WEAK LOW APPROACHES FROM THE SOUTHWEST INTO THE MIDDLE OF NEXT WEEK. && .MARINE... NORTHEAST WINDS GUSTING 23 TO 29 KT AT MANY SITES ON THE MIDDLE AND UPPER MARYLAND CHESAPEAKE BAY EARLY THIS MORNING. HI RES MODELS HAVE THAT SUBSIDING A BIT TOWARDS DAWN AS THE LOW LVL JUST SHIFTS NORTH. HAVE THAT REFLECTED IN THE FORECAST...BUT GIVEN HOW CLOSE THAT IS TO GALE THRESHOLD...WILL MONITOR TO MAKE SURE THE LOW AND THE WINDS DONT STRENGTHEN MORE THAN EXPECTED THIS MORNING. SMALL CRAFT CONDITIONS WILL LAST UNTIL FRIDAY MORNING ON THE BAY...AND UNTIL LATE TODAY ON THE POTOMAC. HIGH PRESSURE LINGERS OVER THE NRN MID-ATLANTIC FRIDAY NIGHT THROUGH SATURDAY...THEN PERSISTS OVER NEW ENGLAND INTO MONDAY. LIGHT NLY FLOW FRIDAY NIGHT/SATURDAY BECOMES ONSHORE SUNDAY INTO MONDAY. WEAK LOW APPROACHES FROM THE SOUTHWEST INTO THE MIDDLE OF NEXT WEEK. && .TIDES/COASTAL FLOODING... ANOTHER THING TO MONITOR THIS MORNING. THANKFULLY...THE LEVELS HAVE STAYED LOW ENOUGH TO REMAIN BELOW MINOR FLOODING LEVELS AND ARE NOT PRESENTING ANY PROBLEMS. WITH THE WINDS GRADUALLY BECOMING NORTH FROM NE...NOT EXPECTING THE ANOMALIES TO INCREASE. HOWEVER...LIKE MANY OTHER THINGS THIS MORNING...GIVEN HOW CLOSE MANY ARE TO MINOR TIDAL FLOODING...WILL CONTINUE TO KEEP AN EYE ON IT FOR POSSIBLE MINOR TIDAL FLOODING ISSUES AROUND HIGH TIDE TIMES. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM EDT FRIDAY FOR ANZ530>534-537- 539>541-543. SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ535- 536-538-542. && $$ SYNOPSIS...CAS NEAR TERM...CAS SHORT TERM...CAS LONG TERM...BAJ AVIATION...BAJ/CAS MARINE...BAJ/CAS TIDES/COASTAL FLOODING...CAS

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