Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 251953 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 253 PM EST WED FEB 25 2015 .SYNOPSIS... HIGH PRESSURE IS MOVING OFFSHORE. LOW PRESSURE OVER THE GULF STATES WILL TRACK ACROSS NORTH CAROLINA TONIGHT AND RAPIDLY OFFSHORE THURSDAY MORNING. AN UPPER LEVEL TROUGH CROSSES THE GREAT LAKES THURSDAY NIGHT. HIGH PRESSURE WILL THEN BUILD INTO THE AREA THIS WEEKEND. && .NEAR TERM /TONIGHT/... WINTER CONTINUES IN THE MID ATLANTIC...LOW PRES OVR LA WL BE TRACKING RAPIDLY ENE ON A 120 KT JET...MOVG TO A POSN E OF HAT ARND 12Z THU. THE CWA WL ONCE AGN BE ON THE COLD SIDE OF THE LOW TRACK...WHICH WL KEEP THE P-TYPE AS ONLY SN. SNFL IS XPCTD TO DVLP IN THE CENTRAL SHEN VLLY LATE THIS EVE....MOVG INTO LWR SRN MD...THE DC AND BALT SUBURBS. PEAK SNFL RATE TIME IS XPCTD TO BE AFTR 4 AM...CONTINUING THRU THE MRNG RUSH. I`M NOT ENTIRELY SURE HOW FAR W THE ACCUMULATING SNOW IS GOING TO GET...BUT FEEL THAT SNOW WL FALL DURG THE MRNG DC/BALT COMMUTE HRS. AS A RESULT WE`VE UTILIZED THE "1 INCH AT RUSH HR" ADVSRY RULE. LOWS IN THE LM20S. && .SHORT TERM /THURSDAY/... THIS WL BE A FAST MOVG SYSTEM...TRACKING WELL OUT TO SEA BY LATE MRNG. BLV SNOW WL BE ENDING BY NOON. BLV LWR SRN MD IS WHERE THE GREATEST ACCUMS COULD BE - UP TO 4". CENTRAL SHEN VLLY COULD SEE 1-3"...FURTHER N AND W (UP TO THE BLU RDG) 1-2" AFTRWARDS 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 TUESDAY/... 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 /20Z WEDNESDAY THROUGH MONDAY/... VFR CONDS THIS EVE..THEN CIGS/VSBY EXPCTD TO DIMINISH AFTR MDNGT AS SNOW DVLPS ACROSS THE MID ATLC. IFR CONDS PSBL AT MAJOR AIRPORTS 5 AM-10 AM...BUT QUICKLY RECOVERING FOR THU AFTN. 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 KTS. SUB-VFR POSSIBLE BY SUN NIGHT AS FRONTAL SYSTEM APPROACHES FROM THE WEST. && .MARINE... SCA IN EFFECT FOR 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...SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EST THURSDAY FOR MDZ508. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST THURSDAY FOR MDZ013-014-016-018. WINTER WEATHER ADVISORY FROM 3 AM TO NOON EST THURSDAY FOR MDZ004>006-011-503>508. WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO NOON EST THURSDAY FOR MDZ017. VA...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO NOON EST THURSDAY FOR VAZ025-036-037-508. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST THURSDAY FOR VAZ038-039-051>055-502. WINTER WEATHER ADVISORY FROM 3 AM TO NOON EST THURSDAY FOR VAZ501-505-506. WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO NOON EST THURSDAY FOR VAZ050-056-057. WV...NONE. 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. WINTER WEATHER ADVISORY FROM 3 AM TO NOON EST THURSDAY FOR ANZ531. WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO NOON EST THURSDAY FOR ANZ537. && $$ PRODUCTS...WOODY!/ADS/DFH

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