Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 250900 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 400 AM EST WED FEB 25 2015 .SYNOPSIS... A WEAKENING COLD FRONT MOVES THROUGH TODAY WITH HIGH PRESSURE BUILDING IN ITS WAKE. LOW PRESSURE TO THE SOUTH IMPACTS THE AREA TONIGHT THROUGH THURSDAY. AN UPPER LEVEL TROUGH CROSSES THE GREAT LAKES THURSDAY NIGHT. HIGH PRESSURE WILL THEN BUILD THROUGH SATURDAY NIGHT. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... GENERALLY DRY AND QUIET CONDITIONS TODAY. LOW PRESSURE TREKKING THROUGH SOUTHERN CANADA DRAGS AN ASSOCIATED COLD FRONT THROUGH THE REGION LATER TODAY...THOUGH GENERAL CONSENSUS AMONGST THE 00Z MODELS HAS THE FRONT WEAKENING/DISSIPATING AS IT PASSES THROUGH. WESTERLY FLOW PERSISTS FOR MOST OF THE DAY...WHILE TEMPS SHOULD WARM UP INTO THE 30S ACROSS MOST OF THE AREA. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... MAIN CONCERN FOR TONIGHT THROUGH TOMORROW WILL BE AN APPROACHING LOW PRESSURE TO THE SOUTH. WINTER WEATHER ADVISORIES HAVE BEEN ISSUED FOR THE SOUTHERN TIER OF THE CWA TO ACCOUNT FOR THE AREA OF HIGHEST CONFIDENCE OF REACHING AT LEAST 2 INCHES. THIS GOES INTO EFFECT TONIGHT...AND LASTS THROUGH THURS MORNING. INITIALLY EXPECTING DRY CONDITIONS TONIGHT. USED A BLEND OF THE 00Z NMM/ARW FOR TIMING OF PCPN TONIGHT. UNSURE OF THE EXACT START TIME AS DRY AIRMASS IN PLACE...HOW QUICKLY CAN THE ATMO MOISTEN UP. GENERALLY THINKING PCPN MOVES INTO THE SOUTHWESTERN CORNER BETWEEN 02-05Z...THEN SPREADING TO THE EAST AND NORTH THROUGH THE REMAINDER OF THE NIGHT. SOME DISCREPANCIES ON HOW FAR NORTH THE PCPN MAKES IT...WITH THE NAM SUGGESTING POSSIBLY MAINLY DRY CONDITIONS RIGHT ALONG THE MASON-DIXON. STRONGEST SHORTWAVE ENERGY SEEMS TO PIVOT ACROSS SOUTHEASTERN VA...WITH EVEN A HOLE OF SUBSIDENCE SHOWING UP ON THE 00Z GFS AND NAM ACROSS THE NW CORNER OF THE CWA. HAVE ALIGNED THE HEAVIEST PCPN AXIS (WHICH COMES OUT TO ABOUT 2 INCHES TOTAL FOR SNOW) ALONG THE BETTER FRONTOGENIC FORCING EXTENDING ACROSS EXTREME SOUTHERN MD...AND INTO PORTIONS OF THE PIEDMONT. WHILE THE MODELS HAVE TRENDED FARTHER WITH THE ACTUAL LOW...THE NORTHERN PERIPHERY OF THE HEAVIER PCPN HAS REMAINED FAIRLY CONSTANT AND AS SUCH WILL KEEP WITH THE TREND OF THE ONE INCH LINE COMING UP TO DC SOUTH TO CULPEPER. NORTH OF THIS LINE IT LOOKS LIKE WOULD STRUGGLE TO EVEN REACH HALF AN INCH...AND WITH SOME UNCERTAINTY OF IF THE PCPN EVEN PUSHES THAT FAR NORTH...HAVE MAINTAINED CHC POPS UNTIL HIGHER CONFIDENCE. AS THE LOW PUSHES OFFSHORE...AND THE UPPER LVL FORCING PIVOTS ALONG THE EASTERN SEABOARD...HAVE THE PCPN TAPERING OFF OVER THE WESTERN SECTIONS BY MID MORNING THURS...WITH LINGERING PCPN OVER THE EASTERN HALF THROUGH THE EARLY PART OF THE AFTN. COULD SEE SOME SNOW SHOWERS THURS AFTN OVER THE ALLEGHENY FRONT WITH WESTERLY FLOW COMBINING WITH A DECENT PASSING SHORTWAVE...RESULTING IN UPSLOPING SHOWERS. HOWEVER...NOT EXPECTING MUCH MORE THAN HALF AN INCH WITH THESE SHOWERS. TEMPERATURE GUIDANCE WAS VERY INCONSISTENT FOR HIGHS ON THURSDAY. HIGH CONFIDENCE LOW TEMPS TONIGHT ALL WELL BELOW FREEZING...SO NOT EXPECTING A P-TYPE ISSUE. SIDED WITH THE COOLER MET/MAV BLEND ON TEMPS FOR THURS...KEEPING EVERYWHERE MAINLY IN THE 20S...EXCEPT FAR SOUTHWESTERN AREAS WHICH COULD SEE THE LOWER 30S. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... AN INTRUSION OF NRN STREAM ENERGY PROGGED TO IMPACT AREA THU NGT- FRI. WHILE THERES NOTHING SPECIFICALLY THAT JUMPS OUT...LLVL CAA... MID LVL PVA...RATHER AMPLE MEAN-LYR MSTR...AND A TAIL OF THE UPR LVL JET ALL SUGGEST LOTSA CLDS AT A MINIMUM. IF ITEMS ALIGN APPROPRIATELY...THEN FLURRIES PRBL AND A SHSN OR TWO PSBL. WENT A LTL MORE AGGRESSIVE ON POPS THU EVE /STILL CHC/...AND SCALED IT BACK OVNGT INTO FRI MRNG. IN THE BIG PICTURE...BLDG HIPRES SUGGESTS THAT THE ODDS FOR PCPN WL BE DIMINISHING THRU THE PD...AND WL BE HIGHLY UNLKLY BY FRI NGT. H8 TEMPS DROPPING INTO THE NEG TEENS /AGAIN/ SUGGEST THAT SHSN WUD BE THE ONLY PTYPE TO CONSIDER. NO CONFIDENCE WRT ACCUMS. IN A WORST CASE SCENARIO...SUPPOSE ITS PSBL. CERTAINLY WONT BE ADVERTISING THAT AS A PART OF A DETERMINISTIC FCST. ARCTIC HIPRES WL BE KEEPING WX QUIET THRU SAT NGT...ALBEIT COLD. NO BIG CHGS IN TEMP FCSTS. MAXT STRUGGLING TO RISE ABV FRZG...ALTHO SAT HAS A SLGTLY BETTER CHC. MIN-T DOWN IN THE TEENS AND LWR 20S. RADL COOLING AND THE CORE OF THE COLD AIR OVER AREA SAT MRNG IMPLY THAT SINGLE DIGIT OR SUBZERO LOWS PSBL W OF I-95. DEEP MEAN TROUGH WILL PERSIST OVER THE EASTERN CONUS THROUGH THE XTNDD PERIOD BUT ABATE SLIGHTLY BY THE MIDDLE OF NEXT WEEK. MEANWHILE...SUBTROPICAL RIDGING WILL BEGIN TO AMPLIFY OVER THE SOUTHEASTERN CONUS. THIS WILL SET THE STAGE FOR A COUPLE OF OVERRUNNING/PERHAPS MIXED P-TYPE EVENTS LATE IN THE WEEKEND INTO EARLY NEXT WEEK AS MODERATING AIRMASS ALOFT MOVES OVER RESIDUAL COLD AIR AT THE SURFACE. THE OVERALL PATTERN WILL BE FOR A TREND IN MODERATING TEMPERATURES THROUGH THE MIDDLE OF NEXT WEEK HOWEVER. && .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/... VFR CONDITIONS TODAY WITH HIGH PRESSURE BUILDING ACROSS THE REGION. W FLOW GENERALLY LESS THAN 10 KTS. LOW PRESSURE APPROACHING TONIGHT WILL BRING LIGHT SNOW...WITH SUB- VFR CONDITIONS EXPECTED. THE HEAVIEST SNOW SHOULD REMAIN TO THE SOUTH...WITH KCHO HAVING THE BEST CHC FOR SEEING IFR CONDITIONS WITH MOD-HEAVY SNOW LATE TONIGHT. PCPN CLEARS BY EARLY THURS AFTN...BRINGING CONDITIONS BACK TO VFR. WINDS WILL BE LIGHT/VRB TONIGHT...BCMG N TOMORROW...MAINLY LESS THAN 10 KTS. KDCA/KBWI/KMTN COULD SEE OCNL GUSTS TOMORROW. OUTLOOK... THU NGT-FRI MRNG...LOW CONFIDENCE. MAY BE SOME FLURRIES...AND WUDNT OUTRIGHT RULE OUT FLGT RESTRICTIONS DUE TO SHSN. FRI AFTN-SUN MRNG...VFR. SUN AFTN...MAINLY VFR..ALTHO CIGS SHUD BE LWRG AS PCPN CHCS INCREASE. && .MARINE... SUB-SCA CONDITIONS EXPECTED TODAY WITH HIGH PRESSURE. HAVE ISSUED A SCA LATE TONIGHT THROUGH THURSDAY WITH INCREASING NORTH FLOW AS LOW PRESSURE PASSES TO THE SOUTH. N/NWLY FLOW WL PREVAIL THU NGT-FRI. ATTM MIXED LYR DOES NOT APPEAR TO SUPPORT SCA CONDS. WIND FIELD INCREASES FRI NGT...AND THEN RELAXES AGN BY SAT AS HIPRES BLDS. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST THURSDAY FOR MDZ017. SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EST THURSDAY FOR MDZ508. VA...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 10 AM EST THURSDAY FOR VAZ025-036-037-508. WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST THURSDAY FOR VAZ050-056-057. WV...NONE. MARINE...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST THURSDAY FOR ANZ537. SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EST THURSDAY FOR ANZ530>534-537>543. SMALL CRAFT ADVISORY FROM 10 AM TO 4 PM EST THURSDAY FOR ANZ535-536. && $$ SYNOPSIS...SEARS/HTS NEAR TERM...SEARS SHORT TERM...SEARS LONG TERM...HTS/DH AVIATION...SEARS/HTS MARINE...SEARS/HTS

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