Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 280906 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 406 AM EST SUN DEC 28 2014 .SYNOPSIS...
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A COLD FRONT OVER OHIO WILL MOVE INTO THE AREA TODAY. LOW PRESSURE WILL MOVE ALONG THE STALLED FRONT THIS AFTERNOON AND EVENING... PUSHING THE FRONT SOUTH OF THE AREA. ANOTHER LOW PRESSURE SYSTEM WILL MOVE ACROSS THE CAROLINAS MONDAY AND MONDAY NIGHT. STRONG HIGH PRESSURE WILL BUILD OVER MUCH OF THE COUNTRY BY TUESDAY...AND GRADUALLY PUSH EASTWARD DURING THE REST OF THE WORK WEEK.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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AS OF 08Z...1025MB SFC HIGH IS APPROACHING BERMUDA WHILE 999MB SFC LOW IN QUEBEC. THE ASSOCIATED COLD FRONT IS HALFWAY ACROSS OHIO WITH SUBTROPICAL AIR OVER THE MID-ATLANTIC. AN UPR TROUGH AXIS IS OVER THE SRN GREAT PLAINS. TEMPERATURES HAVE RISEN OVER THE CWA WITH AN INCREASE IN CLOUD COVER WITH TEMPERATURES IN MIXED AREAS IN THE UPR 40S TO AROUND 50F. SOME POCKETS OF UPR 30S PERSIST IN DECOUPLED AREAS. RAPID INCREASES INTO THE MID OR POSSIBLY UPR 50S ARE POSSIBLE THIS MORNING WITH 14C AIR AT 925MB OVER THE AREA. HOWEVER... THICKENING CLOUDS SHOULD GENERALLY KEEP MAX TEMPS IN THE LOW TO MID 50S OVER THE AREA. THE LAST LEADING SHOWERS (FOR NOW) ARE MOVING EAST ACROSS THE NRN BALTIMORE METRO. ONLY ISOLATED SHOWERS ARE EXPECTED AHEAD OF THE COLD FRONT THROUGH THE MID-MORNING HOURS. THE COLD FRONT IS PROGGED BY THE 06Z HRRR TO REACH THE POTOMAC HIGHLANDS IN THE MID-MORNING HOURS. FORWARD PROGRESS WILL SLOW FROM THERE AS SHORTWAVE TROUGHS SPREAD NORTHEAST UP THE PARENT UPR TROUGH. WIDESPREAD LIGHT RAIN IS EXPECTED ACROSS THE AREA THIS AFTERNOON WITH QPF GENERALLY LESS THAN TWO TENTHS INCH.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
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PERIODIC LIGHT RAIN WILL DRIFT SOUTH WITH THE FRONTAL BOUNDARY INTO MONDAY. PERHAPS AN ADDITIONAL TENTH INCH RAIN...PARTICULARLY SOUTH OF DC. NORTHWEST WINDS INCREASE TO AROUND 10 MPH TONIGHT WITH COLD AIR ADVECTION RESULTING IN MIN TEMPS OF LOW 30S FOR NRN AND WESTERN FRINGES...MID TO UPR 30S ELSEWHERE. RAIN ENDS AS SNOW FOR THESE FRINGE AREAS NEAR THE MASON-DIXON LINE AND FOR RIDGES. NO SNOW AMOUNTS WERE ADDED AS OF YET WITH LOW POPS...BUT THERE IS THE POSSIBILITY OF A DUSTING...PARTICULARLY AT HIGH ELEVATIONS. 21Z SREF WAS EAGER TO HAVE HIGH POPS IN FOR MOST OF THE CWA THROUGH MONDAY. HOWEVER...WENT WITH CONSENSUS OF NAM/GFS/ECMWF WITH HAVING LIKELY POPS FOR RAIN LIMITED TO SRN MD MONDAY MORNING. LOW LEVEL FLOW IS MORE NELY MONDAY AFTERNOON...WHICH WOULD PROMOTE CHANCE POPS FOR RAIN/SNOW MIX OVER TERRAIN THE SWRN PART OF THE CWA. NO WINTRY ACCUMULATION THERE EITHER WITH JUST CHANCE POPS.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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BASICALLY THE EXTENDED BOILS DOWN TO TWO PRECIP SYSTEMS AT THE START AND END OF THE LONG TERM WITH COLD HIGH PRESSURE SANDWICHED IN BETWEEN. MON AND MON NIGHT...STILL SOME UNCERTAINTY BASED ON MODEL SPREAD OF PRECIPITATION FOR MON. 00Z/NAM AND GFS SOLNS SHOW MOST OF THE PRECIP SLIPPING SOUTH AND EAST OF THE CWA EARLY MONDAY AM. BUT 00Z/ECMWF LINGERS SOME MOISTURE ACROSS SRN TIER OF ZNS. KEPT SLIGHT TO CHANCE POPS IN FOR MON OVER THE CWA...AND WITH TEMPS COLD ALOFT BUT BOUNDARY TEMPS ABOVE FREEZING...MENTIONED RAIN/SNOW MIX POSSIBLE. BY MON NIGHT...LINGERING MOISTURE ACROSS SOUTHERN TIER OF ZONES WARRANT CHANCE POPS...WITH LIKELY POPS IN FAR SW PORTION OF CWA ACROSS HIGHLAND COUNTY AND SRN PENDLETON COUNTIES...AND COLD ENOUGH THERE FOR ACCUMULATING SNOW AROUND AN INCH IN UPSLOPE AREAS. TUE...COLD AIR LOFT IS A CERTAINTY AS THE LARGE POLAR AIR MASS SETTLES OVER MUCH OF THE CONUS EAST OF THE ROCKIES. THE 00Z/NAM AND 03Z/SREF ARE AGAIN SHOW BEING AGGRESSIVE WITH A WEAK DISTURBANCE THAT THE 00Z/GFS/ECMWF/UKMO SOLNS SHOW A MUCH WEAKER AND FLATTER SYSTEM THAT STAYS SOUTH. AT THIS POINT ANY PRECIP AMOUNTS TUE WILL BE LIGHT BUT COULD BE IN FORM OF SNOW. WED-FRI...HIGH PRESSURE DOMINATES WITH SEASONABLY COLD WEATHER AND DRY CONDITIONS. LATE FRI-SAT...NEXT SYSTEM WILL APPROACH FROM THE SOUTHWEST AS MODELS SHOW A LARGE LOW PRESSURE SYSTEM MOVING FROM THE CENTRAL PLAINS LATE FRI MOVING INTO THE UPPER GREAT LAKES ON SAT. THIS SYSTEM LOOKS LIKE IT COULD BRING A WINTRY MIX INITIALLY FRIDAY NIGHT WITH THE EXPECTED TRACK OF THE LOW NORTHWEST OF THE CWA... LOTS OF WARM AIR WILL BE ADVECTED INTO THE AREA...CHANGING PRECIP TO LIQUID BY SAT MORNING. OF COURSE...TIMING AND POSITION AND TRACK OF THE LOW IS LOW CONFIDENCE AT THIS POINT.
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&& .AVIATION /09Z SUNDAY THROUGH THURSDAY/...
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VFR CONDS THROUGH THE MORNING AS RAIN ASSOCIATED WITH A COLD FRONT APPROACHES FROM THE OHIO VALLEY TODAY. MVFR CONDS THIS AFTERNOON IN MAINLY LIGHT RAIN. FRONT STALLS/DRIFTS SOUTH TONIGHT...SO CONDS CONTINUE TO LOWER WITH IFR POSSIBLE...BUT KEPT 06Z TAFS WITH MVFR CIGS. LIGHT WLY FLOW TODAY...NWLY FLOW UP TO 10 KT TONIGHT...NLY FLOW 10 KT MONDAY. MVFR TO IFR CIGS/VSBYS MON AND MON EVENING. VFR CONDITIONS TUE THROUGH THU...WITH POSSIBLE MVFR CIGS IN SNSH- ACTIVITY TUE.
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&& .MARINE...
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LIGHT SWLY FLOW VEERS NWLY TODAY AS A COLD FRONT CROSSES THE WATERS THIS AFTERNOON AND EVENING. COULD BE A NLY SURGE WITH GUSTS AROUND 18 KT LATE TONIGHT. DID NOT RAISE AN SCA DUE TO UNCERTAINTY...BUT ONE OUT OF SANDY POINT IS POSSIBLE INTO MONDAY. MON-WED...EXPECT WINDS TO REMAIN BELOW SCA LEVELS. PRECIP ON MON PUSHES SOUTH AND EAST LATE MON. HIGH PRESSURE BUILDS IN TUE AND CONTINUES THROUGH END OF THE WEEK.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...BAJ NEAR TERM...BAJ SHORT TERM...BAJ LONG TERM...SMZ AVIATION...BAJ MARINE...BAJ/SMZ

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