Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 222005 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 405 PM EDT TUE APR 22 2014 .SYNOPSIS...
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A COLD FRONT WILL CROSS THE REGION THIS EVENING. COOL CANADIAN HIGH PRESSURE BUILDS BACK OVER THE REGION WEDNESDAY AND THURSDAY. A SERIES OF WEAK FRONTS WILL CROSS THE AREA FRIDAY INTO THE WEEKEND.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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LATEST WX ANALYSIS FEATURES A WEAK LEE TROUGH DEVELOPING ACRS THE PIEDMONT AS SEEN IN OBS/PRESSURE FALLS. ACTUAL COLD FRONT STILL ALONG WEST SLOPE OF THE APPALACHIANS. DEEP LAYER WSW FLOW WILL GRADUALLY SHIFT TO THE WNW AFTER MIDNIGHT. SOME SCATTERED SHOWERS ON RADAR OVER INTERIOR SECTIONS BUT MUCH OF THIS HAS NOT EVEN BEEN MEASURABLE THUS FAR. THINK BEST CHC FOR ANY MORE SIGNIFICANT PRECIP WILL COME W/ THE FRONT BETWEEN ABOUT 6 AND 10 PM (CURRENTLY SOME CONVECTION IS BECOMING MORE WIDESPREAD OVER SW PA). THE WSW DRYING FLOW E OF THE MTNS MAY KEEP THIS FROM MAKING IT INTO AKQ CWA HOWEVER. HAVE INCLUDED SOME LIKELY POPS OVER FAR WRN SECTIONS INTO ERLY EVENING...AND NRN ZONES THROUGH 02Z. HAVE ALSO CONTINUED WITH ISOLATED TSTMS BUT IN GENERAL THERE IS NOT A LOT OF SUPPORT FOR SEVERE WX GIVEN A SHORT WINDOW WITH ML CAPES EVEN GETTING TO 500-1000 J/KG THROUGH 01Z. DEEP LAYER SHEAR IS ONLY ON THE ORDER OF 25-30 KT AS WELL...BUT CAN`T RULE OUT AN ISOLATED STORM WITH GUSTY WINDS TO 40-45 MPH GIVEN THE DEEP MIXING. QPF AMOUNTS WILL GENERALLY BE LESS THAN ONE TENTH TO ONE QUARTER OF AN INCH. SHOWERS/ISO THUNDERSTORMS PUSH OFFSHORE LATE THIS EVENING W/ A QUICKLY CLEARING SKY THROUGH MIDNIGHT, AS COOL CANADIAN HIGH PRESSURE BUILDS IN FROM THE NW. WELL MIXED ATMOSPHERE SHOULD PREVENT TEMPS FROM FALLING AS QUICKLY AS PROGGED BY COOLER MAV GUIDANCE...SO HAVE OPTED TOWARDS WARMER ENVELOPE OF MOS GUIDANCE ACROSS THE BOARD. EARLY MORNING LOWS GENERALLY IN THE UPPER 40S INLAND AND OVER THE EASTERN SHORE...TO LOW 50S SE COAST.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
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MODIFYING CANADIAN HIGH PRESSURE BUILDS IN FROM THE NW ON WED...WITH A BREEZY TO WINDY AND VERY DRY DAY EXPECTED. BUFKIT SOUNDINGS SUGGEST FREQUENT GUSTS TO 35-40 MPH ON THE ERN SHORE AND 25-35 MPH ELSEWHERE (SEE FIRE WX SECTION BELOW). SKIES WILL BE MAINLY CLEAR ALTHOUGH A FEW SCATTERED CU WILL PERSIST ACRS THE ERN SHORE DUE TO COLD POOL ALOFT ON THE BACK SIDE OF THE UPPER TROUGH (LOCATED JUST OFFSHORE). LOCAL THICKNESS TOOLS INDICATE HIGHS ONLY IN THE LOWER TO MIDDLE 60S OVER THE LOCAL AREA. HOWEVER, WITH DEWPOINTS WILL MIX INTO THE UPR 20S/LOW 30S (YIELDING MINIMUM RH VALUES IN THE MID 20S INLAND) AND WITH DOWNSLOPE FLOW COMPONENT, BUMPED TEMPS INTO THE MID TO UPPER 60S INLAND ALL ZONES (NOT MUCH DIFFERENCE AT THE COAST DUE TO STRONG NW FLOW). HIGH PRESSURE BEGINS TO BUILD IN FROM NW WED NIGHT UNDER CLEAR SKIES. EARLY MORNING LOWS THU MORNING IN THE MID-UPPER 30S ALONG/W OF I-95 TO THE UPPER 30S TO LOWER 40S ELSEWHERE (DO NOT EXPECT A FREEZE AND PROBABLY TOO DRY FOR MUCH IN THE WAY OF FROST). DRY AGAIN ON THU AS HIGH PRESSURE SLIDES OVER THE REGION, BEFORE SLIDING OFF OFF THE CAROLINA COAST LATE THU/ERY FRIDAY. HIGHS THURS GENERALLY IN THE UPPER 60S (A LITTLE COOLER NEAR THE COAST). ONCE AGAIN, MIN RH VALUES FALL INTO THE 20S THU AFTN BUT WINDS WILL BE LIGHTER. NEXT FAST MOVING WAVE OF MOISTURE MOVES IN FROM THE W ON FRI. HAVE BLENDED THE FASTER GFS AND SLOWER NAM/ECMWF FOR NOW...WITH CHC POPS ALL ZONES AT SOME POINT...MAINLY FROM LATE MORNING THROUGH LATE AFTN. WARMER SSW FLOW SHOULD PUSH HIGHS WELL INTO THE 70S.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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PROGRESSIVE FLOW WILL BEGIN TO EVOLVE INTO A HIGHLY AMPLIFIED/BLOCKY PATTERN OVER THE CONUS DURING THE EXTENDED...LIKELY RESULTING IN A COOL/WET PERIOD BY EARLY NEXT WEEK. MEDIUM RANGE GUIDANCE TENDS TO STRUGGLE WITH BLOCKY FLOW...AND THIS IS NO EXCEPTION. TRENDED TOWARD ENSEMBLE AND WPC GUIDANCE TO SMOOTH OUT DIFFERENCES IN THE MODELS. OVERALL...UPPER PATTERN WILL BE CHARACTERIZED BY AN ANOMALOUS UPPER TROUGH OVER THE WRN CONUS...HIGH PRESSURE RIDGING FROM THE GULF STATES INTO THE NORTHWEST TERRITORIES AND ANOTHER UPPER TROUGH OVER SE CANADA AND NEW ENGLAND. WHILE MEANINGFUL DIFFERENCES EXIST IN THE MODELS...A SECOND (DRY) COLD FRONT IS PROGGED TO CROSS THE LOCAL AREA ON SAT. THIS FRONT WILL BRING COOLER/DRIER AIR TO THE REGION ON SUN. A STATIONARY BOUNDARY WILL THEN SET UP OVER THE MID-ATLANTIC REGION (DEPENDING ON THE MODEL IT COULD BE FROM THE CAROLINAS NWD TO THE MASON DIXON LINE). THIS BOUNDARY WILL BE THE FOCUS OF PRECIP EARLY NEXT WEEK. MEANWHILE...A BROAD AREA OF LOW PRESSURE OVER THE PLAINS WILL PROGRESS EWD SUN-TUES...TAPPING INTO GULF MOISTURE. WILL MAINTAIN SLIGHT CHANCE POPS SUN NIGHT-TUES BASED ON UNCERTAINTY...BUT INCREASE TO LOW-END CHANCE POPS TUES NIGHT AS THE UPPER/SFC LOW GETS CLOSER. HAVE TRENDED TO THE COOLER SIDE OF GUIDANCE WITH HIGHS GENERALLY IN THE MID-UPPER 60S SUN-TUES. OVERNIGHT LOWS GENERALLY IN THE UPPER 40S-LOW 50S.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/... BAND OF PRE-FRONTAL SHWRS NOW CROSSING THE PIEDMONT HAVE THE BEST CHC OF REACHING KRIC/KSBY OVER THE NEXT SVRL HRS SO HAVE ADDED A 2-3 HR TEMPO GROUP THERE. OTW...KEPT VCSH ACROSS SERN TAF SITES AFTR 20Z GIVING THE LATEST TRENDS OF THE PCPN WEAKENING AS IT CROSSES THE MTS. ALTHOUGH CONFIDENCE NOT HIGH ENOUGH TO PUT THUNDER IN ATTM... BEST LOCATION FOR ANY THUNDER TO OCCUR WOULD BE ACROSS SERN TAF SITES BEFORE 00Z. OTW...SCT-BKN MID LEVEL CLOUD COVERAGE EXPECTED AS THE ACTUAL COLD FRONT CROSSES THE AREA THIS EVENING. SKIES CLR BEHIND THE BOUNDARY AFTR 06Z. STRONG CAA SETS IN LATE TONIGHT AND WEDNESDAY MORNING WITH NW WINDS INCRG TO BTWN 15-25 KTS BY 12Z. HIGHER GUSTS POSSIBLE ALONG THE DELMARVA AND SERN COASTAL AREAS WEDNESDAY. VFR CONDITIONS CONTINUE THROUGH THURSDAY NIGHT. THE NEXT COLD FRONT CROSSES THE AREA FRIDAY WITH SCT SHWRS/TSTRMS. && .MARINE... SEAS HAVE FINALLY SUBSIDED BELOW 5 FT IN THE COASTAL WATERS THANKS TO SLY FLOW. HAVE CANCELLED SCA HEADLINES FOR THE COASTAL WATERS FOR THIS AFTERNOON AND EVENING. HOWEVER...THE LULL WILL BE SHORT LIVED AS ANOTHER COLD FRONT CROSSES THE WATERS LATE THIS AFTERNOON INTO THIS EVENING. SOLID SCA CONDITIONS EXPECTED AFTER MIDNIGHT AS A STRONG NWLY SURGE ARRIVES OVER THE WATER. STRONG GRADIENT WILL PRODUCE 35-40 KT 925MB WINDS TONIGHT AND WEDNESDAY OVER THE WATER. WILL LEAVE AS SCA ATTM...BUT WILL RE-EVALUATE FOR THE AFTERNOON FORECAST PACKAGE. PREV DISCUSSION... LIGHT WINDS AROUND 5 KT ARE GRADUALLY TURNING FROM EAST TO SOUTH AS SFC HIGH PRESSURE BEGINS TO SLIDE OFFSHORE. MEANWHILE...A SFC COLD FRONT WILL PUSH ACROSS THE OHIO VALLEY THIS MORNING AND THEN CROSS THE WATERS THIS AFTN/EVENING. AS THE FRONT APPROACHES THE WATERS THIS AFTN...WINDS WILL BECOME SW AND INCREASE TO 10-15 KT. A FEW GUSTS AROUND 20 KT MAY BE POSSIBLE OVER CHES BAY/CURRITUCK SOUND DURING THIS TIME...BUT AM STILL ANTICIPATING PREDOMINANT CONDITIONS TO BE SUB-SCA. MEANWHILE FOR TODAY...ONSHORE SWELL WITH 10-11 SECOND PERIODS WILL PREVENT SEAS FROM SUBSIDING BELOW 5 FT FOR THE GREATER PART OF TODAY...ESPECIALLY OUT NEAR 20 NM. THEREFORE SCA FLAGS FOR ALL COASTAL WATERS HAVE BEEN EXTENDED THROUGH TODAY. SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED DURING THE FRONTAL PASSAGE AND MAY BE CAPABLE OF PRODUCING LOCALIZED GUSTY WINDS OF 25-35 KT. THE FRONT CROSSES THE WATERS THIS EVENING AND PUSHES OFFSHORE AFTER MIDNIGHT TONIGHT. A PERIOD OF STRONG POST-FRONTAL SCA CONDITIONS ARE ANTICIPATED DUE TO A DECENT CAA SURGE LATE TONIGHT INTO WEDNESDAY. A FAVORABLE NW WIND DIRECTION WILL FURTHER ENHANCE WIND SPEEDS...BUT WILL GENERALLY PREVENT SEAS FROM BUILDING ANY HIGHER THAN 5-6 FT...WITH 3-4 FT WAVES ON THE BAY (LOCALLY UP TO 5 FT SRN BAY LATE TONIGHT) AND 2-3 FT ON THE RIVERS. WILL SEE A SECONDARY...ALBEIT WEAKER... COLD AIR SURGE WED NIGHT...FOLLOWED BY GRADUALLY IMPROVING MARINE CONDITIONS DURING THE DAY THU (ALTHOUGH TRENDS ARE A LITTLE SLOWER TO BUILD A SFC RIDGE INTO THE REGION SO IT WILL REMAIN FAIRLY BREEZY IN NW FLOW THROUGH THU AFTN FOR NRN COASTAL WATERS IN PARTICULAR). HIGH PRESSURE BUILDS OVER THE AREA FROM THE WEST BY LATE THU AFTN INTO FRI. SCA FLAGS FOR ALL COASTAL WATERS WERE EXTENDED THROUGH WED NIGHT FOR A COMBINATION OF WINDS AND SEAS. ADDITIONAL FLAGS WERE HOISTED FOR THE BAY/SOUND/RIVERS BEGINNING AFTER MIDNIGHT TONIGHT AND PERSISTING INTO EARLY WED EVENING TO ACCOUNT FOR THE STRONG NW SURGE TONIGHT AND CONTINUED BREEZY CONDITIONS ON WED BEFORE WINDS DIMINISH. && .FIRE WEATHER...
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A COLD FRONT WILL CROSS THE LOCAL AREA THIS EVENING...PRODUCING A FEW SHOWERS AND AN ISOLATED THUNDERSTORM. GENERALLY LESS THAN A TENTH OF AN INCH OF RAIN IS EXPECTED WHICH WILL HAVE LITTLE IF ANY IMPACT ON ALREADY DRY FUELS. GIVEN THE EXPECTED DRY AND BREEZY CONDITIONS WEDNESDAY...AND AFTER COORDINATION WITH STATE FIRE OFFICIALS/NEIGHBORING OFFICES...WILL GO AHEAD AND ISSUE A FIRE WX WATCH FOR WEDNESDAY AFTERNOON/EVENING FOR PORTIONS OF CENTRAL AND EASTERN VA AND THE LOWER MD EASTER SHORE. WINDS ARE EXPECTED TO BE THE STRONGEST (20-25 MPH WITH GUSTS TO 35-40 MPH) ALONG AND NORTH OF A LINE FROM FVX-PTB-LFI...AND THIS IS WHERE THE WATCH HAS BEEN ISSUED. FARTHER SOUTH...WINDS WILL NOT BE AS STRONG (10-20 MPH WITH GUSTS TO 25 MPH)...SO HAVE OPTED TO LEAN TOWARD AN SPS FOR INCREASED FIRE DANGER INSTEAD. WILL LET CURRENT LINE OF SHOWERS CLEAR THE LOCAL AREA THIS EVENING BEFORE ISSUING THE SPS. WILL LIKELY UPGRADE THE FIRE WX WATCH TO A RED FLAG EITHER LATE THIS EVENING OR OVERNIGHT. MIN RH VALUES WED AFTN WILL DROP TO BETWEEN 20-30% FOR MOST LOCATIONS. DRY CONDITIONS (MIN RH VALUES 20-25%) WILL OCCUR AGAIN ON THURSDAY. HOWEVER...WINDS ARE NOT EXPECTED TO BE AS STRONG. THIS WILL LIKELY PRECLUDE THE NEED FOR ANY FIRE WX STATEMENTS...EXCEPT FOR THE LOWER MD EASTERN SHORE WHERE WINDS MAY REMAIN ELEVATED.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...FIRE WEATHER WATCH FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING FOR MDZ021>025. NC...NONE. VA...FIRE WEATHER WATCH FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING FOR VAZ048-049-061>064-069>078-081>086-089>091- 094-099-100. MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 4 PM EDT THURSDAY FOR ANZ650-652-654-656-658. SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 7 PM EDT WEDNESDAY FOR ANZ633-635>638. SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM EDT THURSDAY FOR ANZ630>632-634.
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&& $$ SYNOPSIS...LKB NEAR TERM...LKB SHORT TERM...LKB LONG TERM...SAM AVIATION...MPR MARINE...BMD/SAM FIRE WEATHER...

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