Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 240652 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 152 AM EST SAT JAN 24 2015 .SYNOPSIS... LOW PRESSURE OVER THE GULF COAST REGION WILL RAPIDLY LIFT NORTHEAST ALONG THE SOUTHEAST ATLANTIC COAST TONIGHT...AND PUSH OFF THE MID ATLANTIC COAST ON SATURDAY. HIGH PRESSURE RETURNS BRIEFLY ON SUNDAY...TO BE FOLLOWED BY LOW PRESSURE FROM THE NORTHWEST CROSSING THE REGION SUNDAY NIGHT THROUGH MONDAY. && .NEAR TERM /THROUGH TODAY/... CURRENT ANALYSIS REVEALING DEEPENING SFC LOW PRESSURE CENTERED OVER SRN GA...WITH SFC HIGH OFF THE DELMARVA COAST. SW FLOW PREVAILS ALOFT WELL OUT AHEAD OF AMPLIFYING MID/UPPER LEVEL TROUGH ALONG THE GULF COAST. PRECIP SHIELD HAS OVERSPREAD MUCH OF THE CWA THROUGH THE EVENING HOURS...WITH THE HIGHEST AMOUNTS (UP TO ~0.5IN) OVER THE NW PIEDMONT COUNTIES. THE CURRENT RADAR MOSAIC SHOWS THE BACK EDGE OF THE INITIAL RAIN SHIELD TRACKING ACROSS CENTRAL NC AND INTO THE VA PIEDMONT. RAPID UPDATE HIGH RES MODELS (HRRR/RAP) ALONG WITH THE 24/00Z NAM SHOW THE BACK EDGE PROGRESSING TOWARD THE COAST BY 09Z. MEANWHILE...A SECONDARY IMPULSE RIDES NE WITHIN THE SW FLOW ALOFT...WITH RAIN RETURNING FROM SW-NE BETWEEN ABOUT 09 AND 12Z. FOR THE OVERNIGHT HOURS...THE MAIN CONCERN WILL BE THE POTENTIAL FOR MODERATE TO LOCALLY HEAVY RAIN. FOLLOWING A BLEND OF WPC AND SREF GUIDANCE FOR RAIN OVERNIGHT YIELDS TOTALS OF 1.00 TO 1.50" THROUGH 12 Z...WITH AN ADDITIONAL 0.25-0.50" EXPECTED DURING THE DAY SAT. THIS AS STRONG UPPER JET/RRQ FORCING INCREASES DEEP UVM LATER THIS EVENING AND OVERNIGHT. GFS/NAM PROG ~60 KT SOUTHERLY LOW LEVEL JET BETWEEN 900-800 MB FROM 03-06Z...AND AS SFC LOW SLIDES OFF THE NC/SE VA COAST BETWEEN 06-12Z WILL SEE RAPID CYCLOGENESIS AND PRESSURE FALLS. HAVE ADDED MENTION OF HEAVY RAIN TO ALL AREAS...HIGHEST CONFIDENCE ACRS THE SE ZONES AFTER MIDNIGHT...THOUGH SOME OF THE MODELS ARE SHOWING A SECONDARY AREA OF HEAVY RAIN OVER NW SECTIONS DUE TO FRONTOGENESIS. TEMPS OVERNIGHT WILL BE STEADY IN THE MID-UPPER 30S MOST AREAS...BUT WILL LIKELY RISE A BIT THROUGH THE 40S/LOW 50S OVER FAR SE VA/NE NC. DRY SLOT ENTERS AREAS WEST OF I-95 PRIOR TO DAYBREAK SO WILL RAMP POPS DOWN AFTER 06Z-09Z THERE. GIVEN TRACK OF SFC LO PRES ON MDLS THROUGH CSTL NE NC THEN OUT TO SEA...CONCERN ON SAT WILL BE DRY SLOT ARRIVING FM THE SW...RESULTING IN BULK OF PCPN WINDING DOWN/ENDING BEFORE ANY AIR COLD ENOUGH FM THE PCPN ENDING AS MIXED SN/RA OR ALL SN (IN THE AFTN/EVE). GFS/NAM/ECMWF ALL SHOW A BRIEF PERIOD OF STRONGER FORCING AS THE UPPER SYSTEM PUSHES THROUGH THE REGION SAT AFTN. WHILE BNDRY LAYER WOULD BE FAIRLY WARM...COULD SEE A BRIEF PERIOD WHERE PRECIP COULD TURN TO SNOW OR RAIN/SNOW MIX IN HIGHER PRECIP RATES. THUS WILL KEEP MENTION OF RA/SN IN BY AFTN ACRS N/W 1/2 OF THE CWA GIVEN THE UNCERTAINTY. HIGHS SAT 40-45 F (ARND 50 F CSTL NE NC). IT COULD BE A TAD WARMER THAN THIS IF SKIES CLEAR A LITTLE EARLIER AND TEMPS RISE A FEW DEGREES PRIOR TO SUNSET. && .SHORT TERM /TONIGHT THROUGH MONDAY/... LATEST 12Z SUITE OF THE GFS/NAM/ECMWF CONTINUE TO TREND FASTER/MORE PROGRESSIVE AND THE W/NW FLOW ALOFT SHOULD ALLOW FOR RAPID DRYING OF ANY LEFTOVER MOISTURE. WILL FORECAST DRY CONDITIONS UNDER PARTLY CLOUDY TO MOSTLY CLEAR SKIES SAT NIGHT OTHER THAN A CHC FOR SNOW BRIEFLY IN THE EVENING ON THE MD ERN SHORE/NRN NECK. LOWS 30-35 F. PARTLY SUNNY WITH HIGHS IN THE LWR 50S S TO THE MID 40S N ON SUN IN ADVANCE OF NEXT CLIPPER SYSTEM. MUCH COLDER AIRMASS APPROACHES FROM THE WNW SUN NIGHT INTO MON...AS CLIPPER SYSTEM TRAVERSES THE CENTRAL/SRN APPALACHIANS SUN NIGHT AND SLIDES ESE THROUGH SRN VA/NC AND OFFSHORE THROUGH THE DAY MON. MODELS DIFFER SOMEWHAT AS TO HOW FAST COLD AIR ARRIVES...GFS SLOWEST/NAM/ECMWF A BIT FASTER ON MON. WILL CARRY HIGH CHC TO LIKELY POPS AND RAIN CHANGING TO SNOW ON MON. THIS IS BY FAR LOOKING LIKE OUR BEST CHC FOR ACCUMULATING SNOW THUS FAR THIS WINTER FOR MUCH OF THE CWA. HIGHS MON IN THE 40S S TO THE 30S N (WITH TEMPS LIKELY TO BE STEADY OR SLOWLY FALL THROUGH THE DAY). STAY TUNED. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... HIGHLY AMPLIFIED/MERIDIONAL FLOW WILL PERSIST THRU THE EXTENDED PERIOD...CHARACTERIZED BY A DEEP/ANOMALOUS NRN STREAM UPPER TROUGH OVER THE ERN CONUS AND BLOCKY FLOW OVER THE WRN ATLANTIC. TO BEGIN THE EXTENDED...LOW PRESSURE PROGGED TO LIFT AWAY FROM THE MID-ATLANTIC COAST TUES MORNING AS THE NEXT IN A SERIES OF NRN STREAM SHORTWAVES DIGS OVER THE CNTRL CONUS. SHORTWAVE DIGS OVER THE TN/KY VALLEYS AND INTO THE CAROLINAS TUES MORNING. ASSOCIATED AREA OF LOW PRESSURE DROPS SOUTH OF THE REGION. HEIGHT FALLS IN TANDEM WITH MOIST SOUNDINGS WILL RESULT IN ADDITIONAL PRECIP THRU MON NIGHT. MODELS HAVE COME INTO BETTER AGREEMENT...SO HAVE INCREASED POPS TO SOLID CHANCE POPS...ESPECIALLY NORTH AND EAST OF RICHMOND. THERMAL PROFILES INDICATE THAT PRECIP WILL TRANSITION TO PREDOMINATELY SNOW THRU THE NIGHT...REACHING SE VA/NE NC AFTER MIDNIGHT. STILL TOO EARLY TO KNOW FOR SURE...BUT LIGHT ACCUMULATIONS ARE POSSIBLE. WILL CARRY SLIGHT CHANCE-LOW END CHANCE POPS TUES AS THE SHORTWAVE DIGS SOUTH OF THE LOCAL AREA...BUT EXPECT BRUNT OF MEASURABLE PRECIP TO BE OFFSHORE. THEREAFTER...MODELS IN GOOD AGREEMENT WITH PUSHING THE TROUGH AXIS OFFSHORE LATE TUES NIGHT-WEDS MORNING. ANOTHER AREA OF LOW PRESSURE EXPECTED TO FORM OFFSHORE TUES NIGHT...BUT INCREASING NWLY FLOW WILL LIMIT THE AMOUNT OF MOISTURE OVER THE REGION. SFC HIGH PRESSURE WILL BEGIN TO BUILD INTO THE REGION IN CONFLUENT FLOW ALOFT WEDS-WEDS NIGHT...RESULTING IN DRY CONDITIONS. NRN AND SRN STREAM ENERGY APPROACHES THE REGION THURS...AS AN ASSOCIATED COLD FRONT REACHES THE CNTRL APPALACHIANS LATE THURS-THURS NIGHT. MAINTAINED SLIGHT CHANCE POPS ACROSS THE NORTH THURS NIGHT. BELOW NORMAL TEMPS PERSIST THRU THE PERIOD WITH HIGHS TUES-WEDS IN THE MID-UPPER 30S. TEMPS REBOUND THURS-FRI INTO THE LOW-MID 40S. COLDEST NIGHT WILL BE TUES NIGHT...WITH LOWS IN THE UPPER TEENS TO LOW 20S. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... LOW PRESSURE SYSTEM ALONG THE SE COAST TONIGHT WILL MOVE TO A POSITION OFF THE DELMARVA COAST BY SUNRISE THIS MORNING. LATEST OBS REFLECT IFR TO LIFR CONDITIONS ACROSS THE REGION EARLY THIS MORNING, AND EXPECT THESE CONDITIONS TO PERSIST THROUGH MID- MORNING. THE SFC LOW WILL MOVE ALONG THE CAROLINA COAST OVER THE NEXT FEW HOURS, BACKING THE WINDS TO THE NNW INLAND AT RIC/SBY, BRIEFLY VEERING WINDS TO THE SSW OVER SE COASTAL TERMINALS EARLY TODAY. A BRIEF LULL IN PCPN IS UNDERWAY AT RIC, AND HV GONE WITH A BREIF PERIOD OF DZ BEFORE PCPN FILLS BACK IN BEFORE DAWN. WINDS REMAIN MORE NORTH AND NORTHWEST BY MID-MORNING AND THROUGH THE AFTERNOON, WITH THE REMAINING MOISTURE SWINGING OFF THE COAST BY 16-20Z. AS THE UPPER LOW PULLS ACROSS THE AREA, SOME OF THE LINGERING SHOWERS COULD CHANGE TO SNOW SHRAS AS PCPN ENDS BY LATE MORNING (PRIMARY AREA OF CONCERN WOULD BE RIC. HAVE HELD THIS OUT OF THE TAF FOR NOW, BUT WILL MONITOR FOR 12Z ISSUANCE. ONCE THE MOISTURE CLEARS BY LATE AFTN/EVENING...WILL SEE A RETURN TO VFR CONDITIONS TONIGHT THROUGH SUNDAY. OUTLOOK: ANOTHER WEATHER SYSTEM WILL IMPACT THE AREA MONDAY INTO TUESDAY. THIS COULD AGAIN CAUSE SOME MVFR TO IFR CEILINGS ALONG WITH A CHANCE FOR SOME WINTRY PRECIPITATION...MOST LIKELY RAIN SHOWERS CHANGING TO SNOW SHOWERS MONDAY INTO TUESDAY. HIGH PERSSURE BUILDS OVER THE REGION FROM THE WEST FOR MID TO LATE WEEK...WITH VFR CONDITIONS EXPECTED FOR MUCH OF THE PERIOD. && .MARINE... HIGH PRESSURE REMAINS OVER THE WATERS THIS AFTERNOON WITH ELY WINDS AOB 10 KT. WAVES GENERALLY 1-2 FT AND SEAS 2-3 FT. HIGH PRESSURE PUSHES OFFSHORE THIS EVENING AS LOW PRESSURE LIFTS NEWD OVER THE SE COASTAL PLAINS. GRADIENT WINDS RAMP UP AS WINDS BECOME SELY IN ADVANCE OF THE LOW. LOW PRESSURE WILL LIFT OVER THE LOWER BAY LATE TONIGHT...PULLING AWAY FROM THE COAST SAT MORNING. WHILE WAA WILL ACCOMPANY THE INCREASING LOW LEVEL WINDS...A BRIEF PERIOD OF SCA CONDITIONS ARE EXPECTED IN THE BAY/SOUND/COASTAL WATERS WITH THE STRONGEST PRESSURE GRADIENT AS THE LOW LIFTS OVER THE WATERS EARLY TONIGHT. A BRIEF LULL IN SCA WINDS EXPECTED AS THE LOW LIFTS OVER THE WATERS LATE TONIGHT. AS THE LOW LIFTS NEWD AWAY FROM THE WATERS AND THE TRAILING COLD FRONT SWEEPS THRU THE AREA...LOW LEVEL CAA WILL RESULT IN A NWLY SURGE SAT MORNING THRU SAT AFTERNOON. SEAS WILL BUILD FIRST IN THE SRN WATERS...REACHING 4-6 FT THIS EVENING...AND 4-6 FT IN THE NRN WATERS AFTER MIDNIGHT. WINDS BECOME MORE WLY SAT AFTERNOON AS LEE SIDE TROUGHING DEVELOPS AND CAA WANES. SCA HEADLINES FOR THE BAY/RIVERS/SOUND RUN THRU THE DAY SAT. SEAS REMAIN 4-6 FT (UP TO 7 FT IN THE NRN WATERS) THRU THE DAY...SUBSIDING THRU SAT EVENING. HIGH PRESSURE BUILDS OVER THE SE STATES SUN WITH SUB-SCA CONDITIONS OVER THE WATERS. LOW PRESSURE PROGGED TO CROSS THE WATERS MON...INTENSIFYING AS IT MOVES OFFSHORE. SCA CONDITIONS ARE EXPECTED MON AFTERNOON INTO TUES. LOW END GALES POSSIBLE OVER THE COASTAL WATERS. STRONG NWLY WINDS WILL PERSIST THRU TUES NIGHT AS THE WATERS REMAIN BTWN LOW PRESSURE OVER THE WRN ATLANTIC AND HIGH PRESSURE BUILDING OVER THE OH VALLEY. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 7 PM EST THIS EVENING FOR ANZ635>638. SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ630>634. SMALL CRAFT ADVISORY UNTIL 1 AM EST SUNDAY FOR ANZ654-656-658. SMALL CRAFT ADVISORY UNTIL 4 AM EST SUNDAY FOR ANZ650-652. && $$ SYNOPSIS...LKB NEAR TERM...AJZ/LKB SHORT TERM...LKB LONG TERM...SAM AVIATION...MAM MARINE...SAM

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