Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 130820 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 420 AM EDT SUN APR 13 2014 .SYNOPSIS...
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HIGH PRESSURE WILL REMAIN ANCHORED OFF THE EAST COAST THROUGH MONDAY. A COLD FRONT WILL GRADUALLY MOVE THROUGH THE REGION LATE MONDAY NIGHT INTO TUESDAY...WITH HIGH PRESSURE BUILDING INTO THE AREA FOR THE SECOND HALF OF THE WEEK.
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&& .NEAR TERM /THROUGH MONDAY/...
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HIPRES IS PARKED OVER THE WRN ATLANTIC. A WARM FRONT IS LOCATED OVER THE NORTHEAST STATES. THE MID-ATLANTIC REGION WILL BE SITUATED DEEP INTO THE WARM/MOIST SECTOR AND IN SLY RETURN FLOW AROUND THE HIGH. SFC DEWPOINTS HAD INCREASED INTO THE 50S OVNGT. 11-3.9U SAT AND SFC OBS AT NAK/NHK CAPTURED THE DEVELOPMENT OF STRATUS ALONG THE WRN SHORE OF THE CHSPK. THE HRRR AND LOCAL ARW- WRF4N MODELS HAVE HAD A DECENT HANDLE ON THE LOW CLOUDS THOUGH APPEAR TO BE TOO AGGRESSIVE WITH LOW VSBYS AND FOG. STRATUS SHOULD BE CONFINED TO THE WRN SHORE AND WILL MIX OUT BY MID MRNG. YDA WAS WARM BUT FCST H8-H9 TEMPS TDA ABOUT 3C WARMER...WHICH SHOULD TRANSLATE TO HIGHS IN THE UPPER 70S AND LOWER 80S ACROSS MUCH OF THE REGION. A BAY BREEZE SHOULD DEVELOP THIS AFTN DUE TO A SIGNIFICANT TEMP/DENSITY GRADIENT INLAND AND OVER THE CHSPK BAY WHERE WATERS TEMPS ARE STILL IN THE 50S. SYNOPTIC SLY WINDS WILL BE STRONG ENOUGH TO PREVENT THE COOL MARINE AIR FROM ADVECTING MUCH INLAND. TRIED TO REFLECT THIS IN FCST TEMP/WIND GRIDS- HIGHS STRUGGLE TO REACH 70F ALONG THE IMMEDIATE WRN SHORE OF MD. LOW- AND MID-LVL SUBSIDENCE UNDER THE RIDGE WILL YIELD DRY CONDITIONS TDA. HIPRES WILL RETREAT FURTHER OFFSHORE TNGT AS A COLD FRONT ADVANCES EWD INTO THE MIDWEST/GREAT LAKES REGIONS TNGT. MOIST SLY WINDS 5-15 MPH WILL PERSIST AFTER SUNSET...KEEPING TEMPS MILD TNGT AND FOG POTENTIAL LOW. FCST MIN TEMPS IN THE UPPER 50S/LOWER 60S FAVORED THE WARMER BIAS CORRECT MET/NAM GUIDANCE. STRATUS MAY DEVELOP AGAIN NEAR THE CHSPK BAY. THE COLD FRONT WILL APPROACH THE WRN SIDE OF THE APPALACHIANS ON MON. HEIGHT FALLS ALOFT AHEAD OF THE AMPLIFY CENTRAL CONUS TROUGH WILL SPREAD EWD TOWARD THE ERN SEABOARD DURING THE DAY AND SLY LLVL JET WILL TRANSPORT MOISTURE INTO THE REGION. HOWEVER...POPS WERE KEPT LOW AND COVERAGE LIMITED TO THE MTS AS THE MAIN SYNOPTIC LIFT REMAINS UPSTREAM OF THE CWA. NOT MUCH INSTABILITY PRESENT ON MON DUE TO THE PRESENCE OF A MID-LVL CAPPING INVERSION. THE MID-LVL SUBSIDENCE INVERSION WEAKENS LATE IN THE DAY ACROSS THE WRN HIGHLANDS...WHERE SLIGHT CHANCE OF TSTMS WERE MENTIONED. TEMPS EXPECTED TO REACH THE MID TO UPPER 70S ACROSS MUCH OF THE AREA DESPITE INCREASING CLOUD COVER.
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&& .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
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MON NIGHT...THE 00Z/03Z ENSEMBLE MODEL GUIDANCE IN GENERALLY GOOD AGREEMENT ON POSITION OF THE APPROACHING COLD FRONT MOVING THROUGH THE GREAT LAKES/OHIO/TENNESSEE VALLEY EARLY IN THE PERIOD. MODELS ARE SLOWER WITH FRONTAL PASSAGE THEN WAS ADVERTIZED YESTERDAY...SO THE CWA WILL STILL BE IN A MILD SOUTHERLY REGIME THIS PERIOD. TUE AND TUE NIGHT...THE COLD FRONT WILL MOVE THROUGH DURING THE DAYTIME. STRONG COLD ADVECTION BEHIND THE FRONT WILL USHER IN MUCH COLDER CONDITIONS. RAIN WILL DEVELOP JUST AHEAD AND ALONG THE FRONT WITH AMOUNTS OF BETWEEN ONE HALF TO ONE INCH CWA WIDE...WITH SOME HIGHER AMOUNTS UP TO ONE AND ONE-HALF INCH POSSIBLE IN CONVECTION. INSTABILITY NOT HIGH OWING TO AMPLE CLOUD COVER...BUT SOME ELEVATED CONVECTION INSTABILITY OF 100-500 J/KG...SO THUNDERSTORMS POSSIBLE. TUE NIGHT...THERE COULD BE LINGERING POST-FRONTAL SHOWERS...AND ALONG AND WEST OF THE BLUE RIDGE...COLD AIR ALOFT COULD MEAN SOME SNOW MIXED IN WITH SHOWERS...BUT NOTHING APPRECIABLE EXPECTED FOR ACCUMULATIONS. 85H TEMPS FALL TO -6C TO -10C RANGE LATE TUE NIGHT. STRONG CAA WILL KEEP NW WINDS
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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WED...HIGH PRESSURE CENTER OVER THE OHIO VALLEY WILL MOVE EAST AND AND BE OVER THE REGION BY THE END OF WED. TEMPERATURES ON WED WILL BE UNSEASONABLY COOL BY A GOOD 10 TO 15 DEGF WITH BLUSTRY WINDS TO START THE DAY...GRADUALLY DIMINISHING BY LATE AFTERNOON. THU-FRI...HIGH PRESSURE WILL MOVE NORTHEAST AND FORM A RIDGE ALONG THE EASTERN SEABOARD BRINGING DRY WEATHER AND NORTH TO NORTHEAST WINDS. COOL TEMPS EXPECTED THUR...ALTHOUGH NOT QUITE AS COOL AS WED. TEMPS MODERATE A BIT MORE ON FRI. SAT...LOTS OF UNCERTAINTY AS WE HEAD TOWARD THE WEEKEND. RIGHT NOW IT LOOKS DRY FOR SAT...BUT VARIOUS MODEL SOLNS ARE SHOWING LOW PRESSURE SOMEWHERE OF THE EASTERN SEABOARD...OR GREAT LAKES... DEPENDING ON WHAT MODEL GUIDANCE ONE LOOKS AT. FOR NOW WILL DOWNPLAY PRECIP CHANCES AS UNCERTAINTY IS HIGH.
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&& .AVIATION /08Z SUNDAY THROUGH THURSDAY/...
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LOW CLOUDS HAVE DEVELOPED OVNGT ALONG THE WRN SHORE OF THE MD CHSPK BAY...RESULTING IN MVFR CIGS AT MTN. CIGS MAY LOWER TO IFR TOWARD DAYBREAK AT MTN AND TO MVFR AT BWI. TERMINALS FARTHER WEST WILL NOT BE IMPACTED BY ERY MRNG STRATUS. VFR TDA AND THIS EVE ACROSS ALL TERMINALS. SLY WINDS WILL GUST AROUND 20 KT THIS AFTN. STRATUS MAY DEVELOP ERY MON MRNG AGAIN NEAR THE BAY. VFR ON MON WITH SLY WINDS 15-25 KT. MON NIGHT VFR CONDITIONS INITIALLY...WITH LOWERING CIGS TO MVFR DURING THE OVERNIGHT. ON TUE...IFR CIGS AND VSBYS IN AREAS OF RAIN ALONG AND AHEAD OF THE FRONT...WITH BRIEF PDS OF TSTMS POSSIBLE. FRONT MOVES THROUGH TUE AFTERNOON...WITH CONDITIONS VFR EXPECTED LATE TUE THROUGH THE END OF THE WEEK. NW WINDS 15 TO 20 KT WITH GUSTS TO 25 KT LATE TUE NIGHT AND WED MORNING.
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&& .MARINE...
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SLY WINDS HAD DIMINISHED OVNGT TO UNDER 15 KT. WINDS WILL INCREASE THIS AFTN AS MIXING DEEPENS. SCA IN EFFECT FOR ALL OF THE WATERS THIS AFTN...TNGT AND NOW MON WITH SLY WINDS 20-25 KT. HOWEVER... WINDS MAY RELAX BRIEFLY LATE TNGT OUTSIDE OF THOSE MARINE LOCATIONS EXPOSED TO SLY CHANNELING. SCA LEVEL WINDS ARE EXPECTED MON NIGHT THROUGH WED. NEAR GALE FORCE WIND GUSTS POSSIBLE LATE TUE EVENING AND EARLY WED MORNING ON THE LOWER BAY AND LOWER TIDAL POTOMAC. WINDS DIMINISH BELOW SCA LEVELS BY LATE WED. THEN SMALL CRAFT ADVISORY LEVEL CONDITIONS ARE NOT LIKELY AGAIN THROUGH THE END OF THE WEEK.
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&& .TIDES/COASTAL FLOODING...
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NEGATIVE TIDAL ANOMALIES DECREASED LAST NGT AND ARE NOW NEAR ASTRONOMICAL NORM AS A RESULT OF SLY FLOW. EXPECT THIS TREND TO CONTINUE...LEADING TO POSITIVE ANOMALIES BETWEEN ONE-HALF AND ONE FOOT BY TNGT AND MON. CBOFS KEEPS ALL WRN SHORE FCST POINTS BELOW MINOR COASTAL FLOOD THRESHOLD THRU TNGT. WITH THE SOUTHERLY FLOW EXPECTED TO PERSIST THRU MONDAY NIGHT AND A FULL MOON UPCOMING... WATER LEVELS COULD APPROACH MINOR FLOOD CRITERIA AT THE MORE SENSITIVE LOCATIONS MONDAY AND MONDAY NGT. WILL ADD MENTION TO THE HWO.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 PM EDT MONDAY FOR ANZ530>543.
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&& $$ SYNOPSIS...JRK NEAR TERM...JRK SHORT TERM...SMZ LONG TERM...SMZ AVIATION...JRK/SMZ MARINE...JRK/SMZ TIDES/COASTAL FLOODING...JRK

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