Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 230856 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 356 AM EST TUE DEC 23 2014 .SYNOPSIS... WEAK LOW PRESSURE WILL TRACK UP THE MID-ATLANTIC COAST TODAY. STRONGER LOW PRESSURE WILL PUSH NORTH ALONG THE APPALACHIANS ON WEDNESDAY...SENDING A COLD FRONT EASTWARD WEDNESDAY NIGHT. BREEZY CONDITIONS WILL FOLLOW THE FRONT ON THURSDAY...THEN HIGH PRESSURE WILL BUILD BACK INTO THE REGION TO CLOSE OUT THE WEEK. && .NEAR TERM /THROUGH WEDNESDAY/... HIGH PRESSURE REMAINED WEDGED THROUGH THE MID-ATLANTIC OVERNIGHT...WHILE LOW PRESSURE WAS LOCATED ACROSS SOUTHEAST VIRGINIA. WEDGE LOOKS LIKE IT WILL HOLD STRONG TODAY/TONIGHT AS LOW PRESSURE WEAKENS AS IT MOVES NORTHEAST. FOR THE TIME BEING...MUCH OF THE MEASURABLE PRECIP HAS EXITED THE CWA WITH AREAS OF DRIZZLE LEFT IN ITS WAKE ESPECIALLY OVER WESTERN/CENTRAL MD AND EASTERN WV. WITH SOME MESONETS STILL 30-32F...THERE ARE LIKELY POCKETS OF FREEZING DRIZZLE OCCURRING WHICH IS WHY FREEZING RAIN ADVISORY WAS EXTENDED TIL 6 AM LATE LAST EVENING. NEXT BATCH OF MEASURABLE RAIN OVER SOUTHWEST VIRGINIA WILL LIFT NORTHEAST THROUGH DAYBREAK. CONCERN IS WHETHER TEMPERATURES WILL BE ABLE TO RISE ANY BEFORE THIS AFFECTS THOSE AREAS THAT ARE NEAR FREEZING. IF THIS DOESN/T HAPPEN...MAY NEED TO EXTEND THE ADVISORY A FEW HOURS LONGER AND POSSIBLY EVEN CONSIDER THROWING IN A COUPLE MORE COUNTIES. WILL CONTINUE TO MONITOR TEMPERATURES CLOSELY. OTHERWISE...TEMPERATURES SHOULD VERY GRADUALLY RISE TODAY. PREFER THE LOWER MET GUIDANCE GIVEN THE SYNOPTIC SITUATION. RAIN IN THE MORNING LIKELY BECOMES MORE OF A DRIZZLE/FOG SET UP THIS AFTERNOON/EARLY EVENING BEFORE THE NEXT ROUND OF RAIN COURTESY OF ISENTROPIC LIFT ARRIVES THIS EVENING. BY THEN...TEMPERATURES ACROSS THE ENTIRE CWA SHOULD BE WARM ENOUGH FOR LIQUID. IN FACT...TEMPERATURES MAY BE STEADY OR SLOWLY RISE OVERNIGHT. LOW LEVEL JET STRENGTHENS ON WEDNESDAY...PUSHING A PLUME OF NEAR 1.5 INCH PW/S INTO THE MID-ATLANTIC. PERIODS OF MODERATE RAIN MAY BE HEAVY AT TIMES. DESPITE DECENT WIND NOT TOO FAR OFF THE DECK...INSTABILITY IS EXPECTED TO RESIDE SOUTH OF THE CWA AND THUS SEVERE WX IS NOT EXPECTED. CONTINUED TO LEAN TOWARD THE LOWER SUITE OF GUIDANCE /MET/ FOR MAXIMA WEDNESDAY GIVEN THE EROSION OF THE WEDGE AND THEN PERIODS OF RAIN. THIS BRINGS 50S THROUGH THE CWA...BUT CONFIDENCE IN 60 OR ABOVE IS LOW. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... DEEPENING SFC LOW /PRESSURES FALLING THROUGH THE 980S MB/ AND VIGOROUS UPPER LEVEL TROUGH WILL BE LIFTING THROUGH THE GREAT LAKES THURSDAY NIGHT. THE TRAILING COLD FRONT WILL CROSS THE CWA. USED A BLEND OF THE 00Z ECMWF AND GFS FOR MOST OF THE WX ELEMENTS AS THEY MIRROR THE MODEL CONSENSUS. THIS PUSHES THE FRONT OFF THE DELMARVA BY 12Z. SHOULD SEE A SHARP CUT OFF IN PRECIP BEHIND THE FRONT...BUT LINGERED SOME POPS IN THE EAST AFTER DAYBREAK IN CASE A SLOWER SOLUTION TAKES PLACE. MODELS ARE INDICATING A HUNDRED OR TWO J/KG OF MUCAPE AHEAD OF THE FRONT...ALTHOUGH IT MAY NOT BE DEEP ENOUGH TO CONSISTENTLY PRODUCE THUNDER. THEREFORE KEPT THE SLIGHT CHANCE OF THUNDER IN THE EAST WHERE A SLIGHTLY MORE UNSTABLE PROFILE WILL EXIST. NONETHELESS...PRECIP WILL BE A MORE SHOWERY DURING THIS TIME FRAME...AND WITH UNSEASONABLY HIGH PWAT VALUES...SOME MODERATE TO HEAVY ELEMENTS OF RAIN COULD EXIST. FOR AN AREAL AVERAGE THOUGH...IT APPEARS AMOUNTS WILL BE UNDER A HALF INCH. 40-50 KT WINDS WILL BE LOCATED A FEW THOUSAND FEET ABOVE MSL...BUT THE TEMP PROFILE WILL NOT BE SUPPORTIVE OF THESE MIXING DOWN CONSISTENTLY. HOWEVER...WILL HAVE TO MONITOR THE WIND FORECAST FOR THE PEAKS...AS IT MAY BE CLOSE TO ADVISORY CRITERIA. EVEN THOUGH TEMPERATURES WILL BE FALLING IN THE WEST BEHIND THE FRONT...ONLY THE HIGHEST ELEVATIONS HAVE A CHANCE OF SEEING A CHANGEOVER TO SNOW ONCE THE UPSLOPE ENVIRONMENT TAKES OVER. TIGHT PRESSURE GRADIENT WILL BE IN PLACE THURSDAY...SO EXPECT BREEZY CONDITIONS IN A CAA/DOWNSLOPE ENVIRONMENT. GOOD CONSENSUS ON 20-30 KT GUSTS. SCT/BKN STRATOCU MAY BE MORE PREVALENT IN THE NORTHERN PART OF THE CWA. THE MOST FAVORABLE TIME FOR UPSLOPE RAIN/SNOW SHOWERS WILL BE IN THE MORNING...WITH MOISTURE PROFILES THINNING DURING THE AFTERNOON AS HIGH PRESSURE BUILDS IN FARTHER. WHILE HIGH TEMPERATURES WILL BE COOLER THAN WEDNESDAY...THEY WILL STILL BE ABOVE NORMAL. HIGH PRESSURE WILL BE CENTERED OVER THE CAROLINAS BY LATE THURSDAY NIGHT. WINDS WILL DIMINISH AND LOWS WILL DROP TO EITHER SIDE OF FREEZING. && .LONG TERM /FRIDAY THROUGH MONDAY/... HIGH PRESSURE WILL DRIFT OFF THE MID ATLANTIC COAST FRIDAY AND SATURDAY. TEMPERATURES WILL BE ABOVE NORMAL. A COLD FRONT WILL APPROACH FROM THE WEST SATURDAY NIGHT...BUT IT WILL BE MOISTURE STARVED WITH A THE HIGHEST CHANCE OF LIGHT PRECIP IN THE MOUNTAINS. MODEL SOLUTIONS THEN DIVERGE WITH HOW TO HANDLE UPPER LEVEL ENERGY EMERGING FROM THE DESERT SOUTHWEST AND HOW IT INTERACTS WITH THE FRONT WHICH BECOME MORE PARALLEL TO THE UPPER FLOW. WHILE THE FORECAST WILL SHOW A HIGHER CHANCE OF PRECIP SUNDAY...THE LATEST 00Z GUIDANCE SUGGESTS IT MAY BLEED OVER INTO MONDAY. TEMPERATURES WILL BE COOLER BEHIND THE FRONT AND THUS THERE COULD BE SOME PTYPE CONCERNS...BUT THERE WILL BE A LACK OF A TRUE ARCTIC AIR SOURCE. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... GIVEN THE WEDGE/CAD SCENARIO...FLIGHT RESTRICTIONS ARE EXPECTED DURING THE TAF VALID PERIOD DUE TO PERSIST FOG/DRIZZLE AND ALSO PERIODS OF RAIN. IFR IS LIKELY WITH THE POTENTIAL FOR LIFR PARTICULARLY TONIGHT. IFR IS LIKELY TO CONTINUE INTO WEDNESDAY AS EVEN IF THE WEDGE STARTS TO ERODE PERIODS OF MODERATE TO HEAVY RAIN WILL BRING POOR CONDITIONS. CAN/T RULE OUT THE POSSIBILITY OF LLWS ON WEDNESDAY AS WELL WITH STRENGTHENING SOUTHERLY LOW LEVEL JET. IFR OR LOWER CIGS REMAIN POSSIBLE INTO WEDNESDAY NIGHT UNTIL A COLD FRONT PASSES AROUND MIDNIGHT. PRIOR TO THE FRONT...SHOWERS MAY REDUCE VSBY AT TIMES AND LLWS MAY BE A CONCERN. THE FRONT WILL SHIFT WINDS TO THE WEST AND GUSTS WILL INCREASE ABOVE 20 KT. SOME WESTERLY WIND GUSTS UP TO 30 KT POSSIBLE THROUGH THURSDAY. WINDS DIMINISH THURSDAY EVENING WITH HIGH PRESSURE/VFR TO FOLLOW. && .MARINE... HIGH PRESSURE EXTENDS FROM NEW ENGLAND INTO THE MID-ATLANTIC. CURRENT WINDS ARE GENERALLY FROM THE NORTH...10 TO 15 KT DOWN THE BAY. SHIFT TO THE SOUTH IS EXPECTED OCCUR TONIGHT INTO WEDNESDAY. WINDS WILL INCREASE DURING THE AFTERNOON. BEST SOUTHERLY PUSH LOOKS LIKE EVENING...BUT GUIDANCE SUGGESTS 20 KT OCCURRING UP THE BAY IN THE AFTERNOON AND WILL RAISE SCA. SCA CONDITIONS LIKELY TO CONTINUE THROUGH WEDNESDAY NIGHT. SHOWERS WILL CONTINUE AND MAY MIX DOWN HIGHER GUSTS. A COLD FRONT WILL PASS LATE AT NIGHT OR JUST AFTER DAYBREAK THURSDAY. SCA CONDITIONS WILL CONTINUE AND SUSTAINED WINDS WILL INCREASE A BIT. MAY BE CLOSE TO GALES...BUT FORECAST AT THIS TIME WILL KEEP IT JUST SHY. WILL DEPEND ON HOW EFFECTIVE MIXING IS. HIGH PRESSURE WILL BUILD IN THURSDAY NIGHT WITH LIGHTER WINDS THROUGH FRIDAY NIGHT. GUSTS MAY APPROACH SCA CRITERIA SATURDAY AFTERNOON. && .TIDES/COASTAL FLOODING... WATER LEVELS WERE RUNNING 1/2 TO 3/4 FT ABOVE NORMAL. AS WINDS TURN TO THE SOUTH BY WEDNESDAY...ANOMALIES ARE EXPECTED TO INCREASE. AM NOT EXPECTING ANY MINOR TIDAL FLOODING ISSUES THROUGH WEDNESDAY MORNING...BUT WILL HAVE TO WATCH TIDES WEDNESDAY AFTERNOON/EVENING AS WATER LEVELS COULD GET CLOSE TO THOSE LEVELS IF ANOMALIES INCREASE OVER 1 FT. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR MDZ003>005-501-502. VA...FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR VAZ025>031. WV...FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR WVZ050>053-055-501>504. MARINE...SMALL CRAFT ADVISORY FROM 1 PM TO 6 PM EST WEDNESDAY FOR ANZ530>534-537>543. && $$ SYNOPSIS...BPP/ADS NEAR TERM...BPP SHORT TERM...ADS LONG TERM...ADS AVIATION...BPP/ADS MARINE...BPP/ADS TIDES/COASTAL FLOODING...BPP

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