Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 270759 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 359 AM EDT MON APR 27 2015 .SYNOPSIS... AN UPPER LEVEL TROUGH TO THE NORTH WILL MOVE THROUGH THE AREA TODAY. HIGH PRESSURE WILL MOVE INTO THE AREA TUESDAY. LOW PRESSURE IS EXPECTED TO TRACK ACROSS THE SOUTHEASTERN U.S. DURING THE SECOND HALF OF THE WEEK. && .NEAR TERM /TODAY/... CLR SKIES ATTM...BUT THAT WL CHG AS CLDS ACROSS PA TRACK SWD INTO THE CWA. THIS IS IN ASSO W/ AN UPR LVL SHORT WV EMBEDDED IN WHAT IS A SOMEWHAT UNUSUAL SYNOPTIC PTTN FOR LATE APR W/ A CLOSED LOW SPINNING IN THE GULF OF ME. RW WL BE PSBL..PRIMARILY ACROSS THE NWN 1/3 OF THE FCST AREA LATE THIS MRNG THRU MID AFTN. AS HAS FRQNTLY BEEN THE CASE LATELY TEMPS XPCTD TO BE BLO NRML. W/ THE CENTRAL SHEN VLLY BEING THE LAST TO CLD OVR TEMPS SHOULD RISE TO THE M60S...BUT MUCH OF THE RMDR OF THE FCST AREA WL TOP OUT IN THE U50S/L60S. && .SHORT TERM /TONIGHT THROUGH TUESDAY/... THE SYNOPTIC PTTN IS GOING TO BE SLOW TO CHG THRU TUE: THE AFOREMENTIONED UPR LOW LOOKS TO SPIN SLOWLY OUT TO SEA. HIGH PRES WL WORK ITS WAY INTO THE MID ATLC DURG TUE. LOWS TNGT WL BE IN THE L40S. W/ MORE INSOLATION TUE TEMPS SHOULD CLIMB BACK INTO THE U60S - STILL A FEW DEGS BLO NRML. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... AN ACTIVE AND COMPLEX STORM SYSTEM APPROACHING FROM THE GULF COAST REGION IS CERTAIN FOR THE SECOND HALF OF THE WORK WEEK. MODEL DIVERGENCE FOR THE SYSTEM AS IT NEARS THE AREA TOWARD MID WEEK ADDS UNCERTAINTY. THE 00Z VERSION OF THE ECM KEEPS A MORE SRN-STREAM SYSTEM AND KEEPS IT AS MORE OF AN OPEN WAVE UPON ARRIVING OVER THE ATLC COAST WED INTO THU. INSTEAD OF AN INTENSIFICATION OF THE SYSTEM FROM A BACK SIDE UPPER VORT DIVING DOWN FROM THE GREAT LAKES REGION...IT PUSHES THE SYSTEM OFF THE COAST. THE GFS HOWEVER HAS QUITE THE AGGRESSIVE DEPICTION IN ITS 00Z RUN...TAKING A DEEPENING UPPER CUT OFF LOW OVER THE OHIO VLY AND SLIDING IT INTO THE BACK SIDE OF THE PRECIP SHIELD OVER THE CAROLINAS AT ABOUT THE SAME TIME. THE ADDITION OF THIS POTENT UPPER VORT DIVING DOWN OUT OF SRN CANADA ADDS THE ENERGY THE SYSTEM WOULD NEED TO DO AN INTENSE PHASING...SIMILAR TO SYSTEM IN THE MIDDLE OF WINTER OVER THE MID- ATLC. THIS AGGRESSIVE SOLN BRINGS AN INTENSE SFC LOW HUGGING THE DELMARVA COAST LATE THU INTO FRI. GUSTY WINDS OVER THE BAY AND A COLD RAIN OVER THE REST OF THE MID-ATLC. RAISED POPS INTO THE MED CHANCE CATEGORIES FROM LATE WED INTO EARLY FRI...BUT STILL NOT CONFIDENT IN GFS SOLN W/ THE INTENSITY/DURATION AND ALL THE PROPER FACTORS COMING TOGETHER FOR SUCH AN INTENSE STORM SYSTEM. BLENDED SOME OF THE BIAS-CORRECTED VALUES AND LEANED ON THE EURO IN A LONG- TERM BLEND OF VARIOUS WX ELEMENTS FOR THIS TIME PERIOD. WILL MONITOR TRENDS. THE MORE AGGRESSIVE AND RECENT GFS RUN KEEPS THE SYSTEM OVER THE AREA FOR MUCH OF THE DAY FRI WHILE THE EURO HAS A BULK OF THE FEATURE WELL OFF THE COAST BY THEN. EITHER WAY...A MULTI-DAY PERIOD OF HIGH PRESSURE WILL RETURN FROM THE WEEKEND AND LIKELY INTO EARLY NEXT WEEK. && .AVIATION /07Z MONDAY THROUGH FRIDAY/... VFR CONDS XPCTD TDA THRU TUE. A FEW RW ARE XPCTD LATE THIS MRNG/AFTN BUT CVRG WL BE LOW SO NOT SPECIFICALLY MENTIONED IN THE TAFS. WINDS WL GUST TO A20 KTS FM THE NW LATE THIS MRNG/AFTN. LOW CONFIDENCE IN THE POSSIBLE EFFECTS OF A LOW PRESSURE SYSTEM THAT WILL APPROACH THE AREA DURING THE MIDDLE OF THE WEEK. POSSIBLY A COUPLE OF DAYS OF RAIN AND GUSTY WINDS...BUT A LESS INTENSE SOLN WOULD BE FOR THE SYSTEM TO PASS JUST SOUTH OF THE AREA AND SLIDE OFF THE ATLC COAST. && .MARINE... SCA HAS BEEN XTND FOR THE MAJORITY OF THE WATERS THRU TUE. LOW PRES IN THE GULF OF ME TDA WL TRACK SLOWLY E...BUT W/ HIGH PRES MOVG INTO THE RGN TUE THE PRES GRAD WL RMN IN PLACE AND G20 XPCTD THRU MID AFTN TUE. A POTENT LOW PRESSURE SYSTEM OVER THE DEEP SOUTH EARLY THIS WEEK WILL HAVE THE POTENTIAL TO BRING SMALL CRAFT AND POSSIBLY GALE CONDITIONS TO THE WATERS FROM LATE WED INTO FRI. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 4 PM EDT TUESDAY FOR ANZ530>534-537>543. SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 8 PM EDT THIS EVENING FOR ANZ535-536. && $$ PRODUCTS...WOODY!/GMS

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