Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 020634 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 234 AM EDT SAT MAY 2 2015 .SYNOPSIS... LOW PRESSURE WILL PULL AWAY FROM CAPE HATTERAS TONIGHT. HIGH PRESSURE WILL BUILD SATURDAY AND SATURDAY NIGHT BEFORE DROPPING TO OUR SOUTH EARLY NEXT WEEK. A COLD FRONT MAY IMPACT THE AREA DURING THE MIDDLE PORTION OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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...UPDATE TO INCLUDE DENSE FOG ADVISORY FOR CENTRAL SHENANDOAH VALLEY. THE PREVIOUS DISCUSSION FOLLOWS... VERTICALLY STACKED LOW PRESSURE IS LOCATED EAST OF CAPE HATTERAS THIS EVENING...WITH A VERY SLOW EASTWARD DRIFT. SFC HIGH PRESSURE IS BUILDING INTO THE OHIO VALLEY. BETWEEN THE TWO...A CONVERGENCE ZONE EXISTS...WHICH SLIPPED FROM THE APPALACHIAN CREST TOWARD THE I-81 CORRIDOR EARLIER THIS EVENING. THE REMAINING FEW SHOWERS THAT WERE PRODUCED IN THIS ZONE HAVE BEEN STEADILY WEAKENING WITH LOSS OF DAYTIME HEATING...WITH ANY CHANCE OF A SHOWER ENDING BY MIDNIGHT. A DRIER AIRMASS IS LOCATED WEST OF THE MOUNTAINS AND IS FORECAST TO MAKE GRADUAL EASTWARD PROGRESS OVERNIGHT. HOWEVER THE SLOW MOVEMENT OF THE COASTAL LOW WILL PREVENT CLOUDS FROM CLEARING QUICKLY. WHERE SHOWERS OCCURRED EARLY THIS EVENING IN THE SHENANDOAH VALLEY/CENTRAL VA...DEWPT DEPRESSIONS ARE MUCH SMALLER. ALREADY HAVE 2-5 SM VSBY AT FRONT ROYAL AND NEW MARKET. MAINTAINED THE MENTION OF PATCHY FOG ACROSS THE S/SW CWA AND MAY NEED TO EXPAND IT NORTH. FORECAST SOUNDINGS DO NOT LOOK PARTICULARLY FAVORABLE FOR FOG AND WHEN COMBINED WITH THE DRY AIR ADVECTION...HAVE LOW CONFIDENCE ON HOW MUCH/HOW LONG OF AN ISSUE ANY FOG WILL BE. SEE LITTLE REASON TO ADJUST LOW TEMPS AT THIS TIME. EXPECT 40S WILL BE FAIRLY COMMON AREAWIDE.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH MONDAY/... THE CONVERGENT AXIS WL CONT TO MV EWD SAT AS HIPRES BLDS. IN DAYTIME HEATING...THAT MAY ONCE AGN YIELD A FEW SHRA...PRIMARILY IN THE AFTN. AT THAT POINT...THE AXIS SHUD BE ORIENTED ROUGHLY OVER I-95. LTST POP GDNC BACKING OFF A BIT...BUT STILL SEE THE SIGNAL IN WIND FIELDS AS WELL AS QPF OUTPUT. WL CONT W/ SCHC POPS. THE STRUGGLE W/ BE IN CLDCVR WHICH OTRW WL BE QUITE LMTD IN NW FLOW WITH DEWPTS IN THE 40S. BENIGN WX BEGINS SAT NGT AS RDG BLDS AND SKIES CLR. WENT A BIT ON THE HIGH SIDE OF MOS FOR TEMPS...BOTH MAXT AND MIN-T. HIGH PRESSURE WILL MOVE OVERHEAD SUNDAY INTO MONDAY BRINGING MAINLY CLEAR AND SEASONABLY WARM CONDITIONS. HIGHS SUNDAY WILL TOP OUT IN THE 70S OVER MOST OF THE AREA...EXCEPT NEAR 80 OVER THE CENTRAL VIRGINIA PIEDMONT AND IN THE DOWNTOWN AREAS...AND UPPER 60S OVER THE HIGHER TERRAIN. LOWS SUNDAY NIGHT WILL DROP INTO THE UPPER 40S AND 50S. AS HIGH PRESSURE SHIFTS OFFSHORE OF THE CAROLINA COAST...A SOUTHWESTERLY RETURN FLOW WILL BEGIN TO ESTABLISH ITSELF ON MONDAY LEADING TO SLIGHTLY WARMER AND MORE HUMID CONDITIONS. HIGHS WILL BE IN THE 70S TO LOWER 80S...WHICH IS ABOUT 5 TO 10 DEGREES ABOVE NORMAL FOR THE BEGINNING OF MAY. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... HIGH PRESSURE TO THE SE WILL BE MOVING AWAY MON NIGHT INTO TUE. COLD FRONT WILL APPROACH FROM THE N TUESDAY BRINGING A FEW SHOWERS TO THE REGION. THUNDERSTORMS CANNOT BE RULED OUT DURING THE AFTERNOON AND EVENING HOURS ACROSS THE CWA. THE COLD FRONT WILL MOVE INTO THE REGION TUE NIGHT INTO WED BEFORE IT STALLS OVERHEAD WED INTO THUR. THIS MAY TRIGGER A FEW SHOWERS AND THUNDERSTORMS FOR WED AND THUR...ESPECIALLY DURING THE AFTERNOON AND EVENING HOURS. THE COLD FRONT WILL LIFT N AS A WARM FRONT ON FRI. WARM CONDITIONS WILL PERSIST TUES THROUGH FRI WITH MAX TEMPS APPROX 10 DEG ABOVE AVERAGE...REACHING THE 80S FOR MOST LOCATIONS. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... ONLY MRB MAY SEE A -SHRA BEFORE 03Z...AND THESE HAVE BEEN ON A WEAKENING TREND AND SHOULD NOT POSE AN IMPACT. OTHERWISE AREA IN BETWEEN LOW PRESSURE OFFSHORE AND HIGH PRESSURE IN OHIO VALLEY. CLOUD COVER WILL BE SLOW TO ERODE BUT CIGS GENERALLY BETWEEN 6-10KFT. CHO MAY SEE VSBY REDUCTION FOR PART OF NIGHT IN BR. HAVE MVFR MENTION LATE TONIGHT FOR NOW...BUT THIS MAY NEED TO START SOONER WITH LOW CONFIDENCE ON END TIME AS DRIER AIR WORKS IN. THINK MRB PROB IS LOWER BUT IS NONZERO. LIGHT/VRB WINDS. CONVERGENCE ZONE OVER WESTERN AREAS TODAY WILL SHIFT EASTWARD SATURDAY. LESS MOISTURE BUT A STRAY SHOWER COULD OCCUR AT THE METRO TERMINALS DURING MIDDAY/EARLY AFTERNOON. BORDERLINE SCT/BKN SKIES BUT BASE WOULD LIKELY BE AOA 5KFT. WINDS BECOMING NW LESS THAN 10 KT. VFR EXPECTED SATURDAY NIGHT. VFR SUN-MON. NWLY FLOW AOB 10 KT SUN BECOMES SWLY MON. VFR SHUD MAINLY PREVAIL TUE-WED. HWVR...THERE CUD BE A FEW SHRA/TSRA...WHICH MAY PRODUCE RESTRICTIONS IF/WHEN/WHERE THEY DVLP. && .MARINE... NOT MUCH OF A WIND HAZARD NEXT 36 HRS. WINDS NELY TNGT INTO TMRW... BCMG VRBL. SPDS ALL AOB 10 KT. A LIGHT GRADIENT WITH HIGH PRESSURE MOVING OVER THE WATERS WILL RESULT IN SUB-SCA WINDS SUNDAY INTO MONDAY. AS THE HIGH SHIFTS OFFSHORE...SOUTHWESTERLY FLOW WILL INCREASE WITH NEAR SCA GUSTS POSSIBLE BY MONDAY EVENING. && .TIDES/COASTAL FLOODING...
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A NORTHEAST FLOW HAS CAUSED TIDAL ANOMALIES TO INCREASE TO AROUND ONE-HALF TO ONE FOOT ABOVE NORMAL ACROSS THE CHESAPEAKE BAY AND TIDAL POTOMAC RIVER. THE NORTHEAST WINDS WILL CONTINUE THROUGH THIS MORNING...LIKELY KEEPING WATER LEVELS ELEVATED ACROSS THE BAY AND TIDAL POTOMAC RIVER. THE ANOMALIES SHOULD HOLD OR PERHAPS EVEN INCREASE A BIT THROUGH DURING THIS TIME. THIS WILL CAUSE WATER LEVELS TO COME CLOSE TO MINOR FLOODING THRESHOLDS...ESPECIALLY NEAR ANNAPOLIS WITH THE HIGH TIDE CYCLE THIS MORNING. DID NOT ISSUE AND ADVISORY SINCE CURRENT ANOMALIES SUGGEST THAT IT WILL FALL JUST SHORT...BUT IT WILL BE CLOSE. THE HIGH TIDE CYCLE LATE SATURDAY NIGHT INTO SUNDAY MORNING WILL ALSO CAUSE WATER LEVELS TO BE CLOSE TO MINOR FLOODING THRESHOLDS.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR VAZ025>027- 029-030. WV...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...HTS NEAR TERM...ADS SHORT TERM...HTS/DFH LONG TERM...IR AVIATION...ADS/IR/DFH MARINE...IR/HTS/DFH TIDES/COASTAL FLOODING...BJL/HTS

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