Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 260228 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 928 PM EST WED FEB 25 2015 .SYNOPSIS... LOW PRESSURE OVER THE GULF STATES WILL TRACK ALONG THE CAROLINA COAST TONIGHT AND NORTHEAST FROM CAPE HATTERAS THURSDAY MORNING. AN UPPER LEVEL TROUGH CROSSES THE GREAT LAKES THURSDAY NIGHT. HIGH PRESSURE WILL THEN BUILD THROUGH SATURDAY. THE NEXT COLD FRONT WILL CROSS THE AREA SUNDAY NIGHT INTO MONDAY. A WARM FRONT LIFTS INTO THE AREA TUESDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... HEADLINE EXPANSION WITH WINTER STORM WARNING FOR SOUTHERN MARYLAND AND NORTH-CENTRAL VIRGINIA (ALONG WITH OUR NEW-THIS-WINTER CENTRAL VA BLUE RIDGE ZONE) AND ADVISORIES NOW FOR THE SHENANDOAH VALLEY NORTH TO WINCHESTER AND JEFFERSON COUNTY WV. PLEASE EXCUSE SLOW UPDATES FOR THINGS SUCH AS OUR WINTER MAPS AS PROCESSES ARE STILL SLOW IN THE WAKE OF OUR SOFTWARE UPGRADE ON MONDAY. AS OF 02Z...SATELLITE DEPICTION OF DEVELOPING LOW/COMMA CLOUD SHIELD SPANS FROM SRN IL TO THE DELMARVA DOWN TO THE FL PANHANDLE. SFC LOW CENTER IS 1001MB OVER THE FL PANHANDLE. THIS WILL QUICKLY TRACK ENE ACROSS SRN GA TO ALONG (BUT OFF) THE CAROLINA COAST THROUGH THE REST OF THE OVERNIGHT. LIGHT ONSHORE FLOW HAS BEGUN OVER THE AREA...THOUGH DEWPOINTS ARE STILL AT OR BELOW 20F. AMBIENT TEMPS ARE DROPPING BELOW FREEZING AND WETBULBS LOOK TO BE IN THE MID 20S. RADAR MOSAIC SHOWS WIDESPREAD PRECIP ACROSS NC JUST STARTING TO ENTER VA. SNOW ONSET LOOKS A LITTLE LATER DUE TO THIS DRY AIR IN PLACE. SWRN ZONES ONSET MIDNIGHT TO 1AM...SRN MD 1AM TO 2AM...DC METRO AND SHEN VLY 3AM TO 5AM...BALTIMORE MORE LIKE 5AM TO 7AM. MODERATE TO LOCALLY HEAVY BANDS WILL DEVELOP LATE TONIGHT ON THE FAR NWRN SIDE OF THE LOW AND AFFECT CENTRAL VA TO CENTRAL MD. LOW LEVEL ELY FLOW WILL UPSLOPE ON THE PIEDMONT TO THE BLUE RIDGE (HENCE CNTRL VA BLUE RIDGE IN WARNING). WILL NEED TO WATCH WRN/NRN EDGE OF PRECIP FOR POSSIBLE FURTHER EXPANSION OF ADVISORY HEADLINES. CRITERIA FOR NRN SHEN VLY IS 2IN BUT ONE INCH ON A WEEKDAY MORNING RUSH WOULD BE IMPACTFUL SO IT SHOULD WARRANT THE ADVISORY. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... THIS WL BE A FAST MOVG SYSTEM...TRACKING WELL OUT TO SEA BY LATE MRNG. SNOW EXPECTED TO END BY (OR BEFORE) NOON. AFTERNOON BRKS IN THE CLDS SHOULD APPEAR...BUT STILL TEMPS SHOULD BE WELL BLO NRML AGN. HIGHS XPCTD TO BE IN THE L30S. WINDS OUT OF THE N AT 10-15 MPH WL KEEP WIND CHILLS IN THE TEENS. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... MID/UPPER LEVEL TROUGHING WILL DOMINATE THE EASTERN TWO-THIRDS OF THE CONUS THROUGH FRIDAY NIGHT. THE LOCAL AREA WILL BE ON THE CYCLONIC SIDE OF A STRONG UPPER LEVEL JET AND A PERTURBED MID LEVEL FLOW. THIS WILL LEAD TO GENERALLY CLOUDY...UNSETTLED CONDITIONS. 850MB TROUGH AXIS PASSES THURSDAY EVENING...LEADING TO CAA. MOST FAVORABLE TIME FOR MOIST UPSLOPE FLOW WILL BE DURING THE EVENING AND THUS ADDED LIKELY POPS TO THE FAVORED AREAS. INDICATIONS THAT SNOW SHOWERS MAY ALSO SPREAD EAST OF THE ALLEGHENIES DURING THE EVENING IN THIS PERIOD OF MORE FAVORABLE LIFT. HAVE HIGHEST POPS GENERALLY WEST OF THE BLUE RIDGE. MID LEVEL TROUGH AXIS APPROACHES ON FRIDAY...ALTHOUGH UNLIKE SOME RECENT CASES...IT WILL BEGIN TO SHEAR OUT ALONG THE OHIO VALLEY. HOWEVER...COMBINED WITH STEEP LOW LEVEL LAPSE RATES INTERSECTING THE DGZ...IT MAY BE ENOUGH TO PRODUCE FLURRIES OR SNOW SHOWERS ON FRIDAY. MOISTURE PROFILES WILL BE THINNING THOUGH...SO QUESTIONABLE HOW ROBUST THESE WOULD BE. WOULD PREFER TO HAVE LESS-VAGUE WORDING IN THE FORECAST AS THERE PROBABLY WILL NOT BE A CONTINUOUS CHANCE OF SNOW SHOWERS FROM THURSDAY NIGHT THROUGH FRIDAY...BUT AT THIS TIME THERE IS LITTLE TO PINPOINT TO HELP IN NARROWING DOWN TIMING. TEMPS STRUGGLE TO CLIMB THROUGH THE 20S AND LOWER 30S ON FRIDAY. HIGH PRESSURE BUILDS IN FROM WEST FRIDAY NIGHT AS UPPER FLOW FLATTENS. WITH DIMINISHING WINDS AND CLEARING SKIES...TEMPERATURES WILL FALL QUICKLY. SINGLE DIGITS OR LOWER POSSIBLE ALONG PA BORDER AND WEST OF BLUE RIDGE...TEENS EAST. WILL HAVE TO BE COGNIZANT OF SNOWPACK EFFECT IF RADIATIONAL COOLING MAXIMIZED...AS WELL AS WIND CHILLS BELOW ZERO IF A BREEZE STAYS IN PLACE. LARGE HIGH PRESSURE GRADUALLY MOVES OVER THE AREA SATURDAY INTO SUNDAY. AIRMASS SLOWLY MODIFIES AS PRECIPITATION BEGINS TO OVERRUN A WARM FRONT LATE SUNDAY INTO MONDAY. A WINTRY MIX IS POSSIBLE AT THE ONSET DEPENDING ON HOW QUICKLY COLD AIR ERODES AT THE SURFACE. COLD HIGH PRESSURE BRIEFLY NOSES OVER THE AREA LATE MONDAY INTO TUESDAY BEFORE A MORE POTENT STORM SYSTEM APPROACHES TUESDAY NIGHT INTO WEDNESDAY. LOOKS LIKE THERE MAY BE SOME DEEPER COLD AIR AND MORE PRECIP TO DEAL WITH IN THIS SECOND SYSTEM SO MORE SUBSTANTIAL WINTRY PRECIP IS POSSIBLE AND BEARS WATCHING IN SUBSEQUENT FORECASTS. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... VFR CONDS THROUGH MIDNIGHT..THEN CIGS/VSBY EXPCTD TO DIMINISH FROM S TO N AS SNOW DVLPS ACROSS THE MID ATLC. IFR CONDS EXPECTED AT ALL TAF SITES EXCEPT KMRB ON FRINGE OF STORM TRACKING ALONG NC COAST LATE TONIGHT. CONDITIONS SLOWLY IMPROVE THROUGH THE MORNING. KEPT IFR INTO THE LATE MORNING...EXPECT IFR AT LEAST THROUGH MID- MORNING. LOW CONFIDENCE THURSDAY NIGHT-FRIDAY WRT ISOLATED/SCATTERED SNOW SHOWERS. IF THEY MATERIALIZE BRIEF CIG/VSBY REDUCTIONS ARE POSSIBLE. VFR MORE CERTAIN BY FRIDAY NIGHT. WINDS IN NW QUADRANT THURSDAY NIGHT-FRIDAY NIGHT GENERALLY LESS THAN 10 KT. MAINLY VFR SAT-SUN AM W/ SLY FLOW AOB 10 KT. SUB-VFR POSSIBLE BY SUN NIGHT AS FRONTAL SYSTEM APPROACHES FROM THE WEST. && .MARINE... SCA IN EFFECT FOR NELY FLOW ALL WATERS XCPT UPR PTMC AFTR 4 AM...AND THEN ALL WATERS AFTR 10 AM THU. N/NW FLOW PREVAILS THURSDAY NIGHT-FRIDAY NIGHT. STRONGEST WINDS ARE FORECAST FOR LATE FRIDAY NIGHT BUT IT LOOKS LIKE GUSTS GENERALLY STAY BELOW SCA LEVELS. HIGH PRESSURE MOVES OVERHEAD WITH WEAK GRADIENT SAT- SUN...AND SUB-SCA CONDITIONS ARE EXPECTED DURING THIS TIME. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST THURSDAY FOR DCZ001. MD...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST THURSDAY FOR MDZ013-014. WINTER WEATHER ADVISORY FROM 3 AM TO NOON EST THURSDAY FOR MDZ004>006-011-503>508. WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO NOON EST THURSDAY FOR MDZ016>018. VA...WINTER STORM WARNING UNTIL NOON EST THURSDAY FOR VAZ508. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST THURSDAY FOR VAZ026-038>040-050>054-502-507. WINTER WEATHER ADVISORY UNTIL NOON EST THURSDAY FOR VAZ025-036- 037. WINTER WEATHER ADVISORY FROM 3 AM TO NOON EST THURSDAY FOR VAZ027-029-030-501-505-506. WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO NOON EST THURSDAY FOR VAZ055>057. WINTER WEATHER ADVISORY FROM 5 AM TO 11 AM EST THURSDAY FOR VAZ028-031. WV...WINTER WEATHER ADVISORY FROM 5 AM TO 11 AM EST THURSDAY FOR WVZ053. MARINE...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. && $$ UPDATE...JACKSON PREVIOUS...WOODY!/ADS/DFH

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