Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 290055 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 855 PM EDT TUE OCT 28 2014 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OFFSHORE THROUGH TONIGHT. A COLD FRONT WILL PASS THROUGH THE AREA WEDNESDAY AND HIGH PRESSURE WILL RETURN FOR THURSDAY. LOW PRESSURE AND ITS ASSOCIATED COLD FRONT WILL PASS THROUGH THE AREA FRIDAY INTO SATURDAY BEFORE CANADIAN HIGH PRESSURE BUILDS OVERHEAD EARLY NEXT WEEK. && .NEAR TERM /THROUGH WEDNESDAY/...
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HAVE CIRRUS STREAMING THROUGH THE CWA THIS EVENING FOR PARTLY TO MOSTLY CLOUDY SKIES. SHOWERS HAVE BEEN MOVING INTO NORTHERN/CENTRAL WEST VIRGINIA. THEY ARE STILL AT LEAST 2-3 HOURS AWAY FROM THE POTOMAC HIGHLANDS. SHOWERS APPEAR TO BE AHEAD OF THE COLD FRONT RIGHT NOW...WHICH IS APPROACHING THE OHIO/WEST VIRGINIA LINE. CLOUDS WILL THICKEN AND LOWER THROUGH THE NIGHT...WITH SHOWERS SLOWLY PROGRESSING EASTWARD LIKELY ONLY MAKING IT NEAR THE BLUE RIDGE LATE TONIGHT. FRONT MAY WIND UP BECOMING MORE ANAFRONTAL BY WEDNESDAY...WITH A WIND SHIFT OCCURRING BEFORE THE BULK OF THE SHOWERS. HAVE MAINLY LIKELY POPS FOR A FEW HOUR WINDOW FOR SHOWERS...LIGHT AMOUNTS OF QPF EXPECTED. RE-POPULATED GRIDS THROUGH WEDNESDAY TO CAPTURE THE LATEST TRENDS OF OBS AND GUIDANCE /PARTICULARLY SREFS/.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... A SHORTWAVE TROUGH WILL MOVE TOWARDS THE MID- ATLANTIC WEDNESDAY NIGHT AS THE COLD FRONT MOVES SOUTH AND EAST OF THE REGION. SFC HIGH PRESSURE WILL MOVE INTO THE REGION DURING THIS TIME. CLOUDS WILL LIKELY MOVE OVER THE HIGHLANDS AS THE TROUGH CROSSES THE REGION INTO THURSDAY. NRLY WINDS BEHIND THE COLD FRONT WILL CONTINUE TO BRING DRY AIR INTO THE REGION LEADING TO DRY CONDITIONS. A STRATO-CU DECK IS EXPECTED BY THURSDAY AFTERNOON. FCST MAX TEMPS WILL RANGE FROM THE UPPER 50S TO LOW 60S. HIGH PRESSURE WILL DETERIORATE OVER THE AREA THURSDAY NIGHT. BROAD TROUGHING ACROSS THE EASTERN CONUS WILL THEN INCREASE SIGNIFICANTLY IN AMPLITUDE THROUGH THE DAY FRIDAY AND FRIDAY NIGHT AS THE UPSTREAM SIDE OF THE TROUGH DIGS NEARLY MERIDIONALLY. THE ASSOCIATED SURFACE LOW WILL DEEPEN AS IT PASSES OVER THE GREAT LAKES DURING THIS TIME. AT THE BASE OF THE HIGH AMPLITUDE TROUGH...OPERATIONAL ECMWF SHOWS AN UPPER LEVEL LOW BECOMING CLOSED OVERNIGHT FRIDAY...WHILE THE GFS IS LESS INCLINED TO CLOSE THE LOW. THE PRIMARY EFFECT OF THIS DIFFERENCE LOCALLY IS UNCERTAINTY IN TRACK AND TIMING OF THE EFFECTS OF THE SURFACE LOW. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... FORECAST REFLECTS EXPECTATION THAT THE LOW WILL BEGIN TO WORK PRECIP INTO THE FORECAST AREA FRIDAY BUT THE BEST CHANCES WILL BE FRIDAY NIGHT AND INTO SATURDAY AS THE LOW PASSES OVER OR JUST WEST OF THE CWA ON A SOUTHEASTWARD TRACK. GIVEN THE TRACK OF THE LOW AND THE HIGH AMPLITUDE TROUGH OVERHEAD SATURDAY AND SUNDAY COULD SEE TEMPS 10 TO 20 DEGREES BELOW NORMAL. SOME SNOWFALL ACROSS THE HIGHEST ELEVATIONS...SPECIFICALLY THE POTOMAC HIGHLANDS...IS POSSIBLE...ELSEWHERE SHOULD SEE MOSTLY LIGHT RAIN SHOWERS. GUSTY WINDS ARE POSSIBLE SATURDAY AND SUNDAY AS THE SURFACE LOW MOVES OFF THE CAROLINA COAST AND THEN RETURNS NORTHEASTWARD UP THE COAST. HIGH PRESSURE WILL FILL IN BEHIND THE LOW AND TEMPS WILL REBOUND CLOSER TO NORMAL BY THE MIDDLE OF NEXT WEEK. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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VFR CONDITIONS GENERALLY EXPECTED TONIGHT. MAV/MET WERE ATTEMPTING TO BRING MVFR VIS IN FOG LATE TONIGHT/EARLY WEDNESDAY BUT WITH CLOUDS AND SOUTHERLY WINDS THIS IS LIKELY OVERDONE. SHOWERS MAY MAKE IT TO MRB LATE TONIGHT...THEN SPREAD EAST ACROSS THE TERMINALS WEDNESDAY. BRIEF MVFR IN -SHRA POSSIBLE BUT MUCH OF THE TIME WILL LIKELY BE GTE 6SM. HIGH PRESSURE MOVES INTO THE REGION WEDNESDAY NIGHT THROUGH THURSDAY. VFR CONDITIONS EXPECTED AT THIS TIME. CONFIDENCE IS LOW IN THE OCCURRENCE OF AVIATION HAZARDS THROUGH THE LONG TERM PERIOD.
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&& .MARINE...
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SOUTHERLY FLOW PERSISTS TONIGHT. TPLM2 JUST HAD A PEAK GUST 21KT LAST HOUR. SCA IN EFFECT AND CHANNELLING LIKELY KEEPS SCA WINDS THROUGH THE NIGHT. COLD FRONT MOVES THROUGH ON WEDNESDAY WITH A WIND SHIFT. SCA MAY NEED A BRIEF EXTENSION INTO WEDNESDAY MORNING BEFORE THE SHIFT TO THE NW...BUT CURRENTLY NW PUSH APPEARS TO BE BELOW SCA THRESHOLD DURING THE DAYTIME WEDNESDAY. A PRESSURE SURGE IS POSSIBLE BEHIND THE COLD FRONT SOMETIME LATE WED NIGHT INTO THURSDAY BUT THE TIMING IS UNCERTAIN AT THIS TIME. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED BEGINNING LATE FRIDAY NIGHT AND CONTINUING THROUGH THE DAY SATURDAY AS LOW PRESSURE MOVES OFF THE CAROLINA COAST. A GALE WARNING MAY BE NECESSARY SATURDAY EVENING AND NIGHT...AND POTENTIALLY INTO SUNDAY.
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&& .TIDES/COASTAL FLOODING...
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DESPITE SOUTHERLY FLOW...ANOMALIES HAVE ACTUALLY COME DOWN THE LAST SEVERAL HOURS. ANNAPOLIS WAS THE POINT OF CONCERN...BUT WITH ONLY ABOUT 1/3 FT ABOVE NORMAL NOW AND LITTLE INCREASE BETWEEN NOW AND HIGH TIDE WE ARE NOT EXPECTING MINOR TIDAL FLOODING DURING HIGH TIDE THIS EVENING NOR WEDNESDAY MORNING EITHER.
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&& .CLIMATE...
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UNUSUALLY WARM TEMPERATURES WERE OBSERVED ACROSS THE CWA THIS AFTERNOON. HIGH TEMPERATURES WERE AROUND 15 DEGREES F ABOVE NORMAL...MORE TYPICAL OF TEMPERATURES IN MID-SEPTEMBER...AND VERY CLOSE TO RECORD LEVELS. BELOW IS A TABLE OF TODAY/S HIGH TEMPERATURES COMPARED TO RECORD HIGHS FOR THE DATE. SITE...TODAY/S HIGH...RECORD HIGH FOR 10/29... DCA....80.............82 IN 1918.............. BWI....80.............82 IN 1946 AND 1945..... IAD....82.............83 IN 1984..............
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ532>534- 537-540>543.
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&& $$ SYNOPSIS...HAS NEAR TERM...BPP/HAS SHORT TERM...HAS/CEB LONG TERM...CEB AVIATION...BPP/HAS/CEB MARINE...BPP/HAS/CEB TIDES/COASTAL FLOODING...BPP CLIMATE...DFH

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