Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 220721 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 320 AM EDT FRI AUG 22 2014 .SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES WILL DIVE SOUTHEAST INTO OUR REGION FROM THE OHIO VALLEY AND MIDWEST. A BACK-DOOR COLD WILL SETTLE SLOWLY SOUTH THROUGH THE AREA OVER THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 320 AM FRIDAY... SHORTWAVE VORT DISTURBANCES DIVING SOUTH DOWN THE BACKSIDE OF THE DIGGING UPPER TROUGH OFF THE MID-ATLANTIC COAST WILL CONTINUE TO INFLUENCE THE WEATHER THROUGH SATURDAY. ASSOCIATED HEIGHT FALLS WILL EVENTUALLY PUSH A COLD FRONT THROUGH THE AREA SATURDAY AND INTO SATURDAY NIGHT. TODAY AND TONIGHT: WEAKENING AREA OF CONVECTION OVER OHIO AND THE BULK OF ITS REMNANT VORTICITY ENERGY IS FORECAST TO MOVE ACROSS VIRGINIA LATE THIS MORNING AND THEN OFF THE DELMARVA COAST THIS AFTERNOON. WHILE WEAKER ENERGY ALOFT COULD HELP TO SUPPORT CONVECTION THIS AFTERNOON...APPEARS THAT SOUTHEASTWARD DRIFTING OUTFLOW FROM STORMS IN CENTRAL/SOUTHERN VA WILL BE THE MAIN FOCUS FOR CONVECTION LATE THIS AFTERNOON AND EVENING. THIS WILL HIGHEST CHANCE POPS ACROSS THE NORTH/NORTHEAST TIER...WITH LOWER CHANCE/SLIGHT CHANCE POPS ACROSS THE SOUTHERN ZONES OWING TO WEAKER SUPPORT ALOFT AND WITH WHAT LIKELY BE INCREASING CIN AS WE MOVE INTO THE EVENING AND OVERNIGHT HOURS. LINGERING SFC OUTFLOW AND SURFACE FRONT DROPPING SOUTH INTO THE AREA WILL SUPPORT SMALL TO SLIGHT POPS OVERNIGHT. MODERATE TO STRONG DESTABILIZATION IS EXPECTED AGAIN ACROSS THE NC COASTAL PLAN REGION WHERE BL DEWPOINTS SHOULD HOLD IN THE LOWER 70S...AWAY FROM THE DOWNSLOPE MIXING EFFECTS IN THE WEST. WITH A BELT OF MODEST 35KT NWLY FLOW EXPECTED TO EXTEND ACROSS VA/NC... COULD SEE A FEW STRONG TO SEVERE THUNDERSTORM CAPABLE OF PRODUCING DAMAGING THUNDERSTORM WIND GUSTS. HIGH RANGING FROM 90 NE TO 95 SOUTH. LOWS IN THE UPPER 60S NE TO LOWER 70S SE. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 320 AM FRIDAY... SATURDAY AND SATURDAY NIGHT: HIGH PRESSURE OVER NEW ENGLAND WILL BEGIN TO RIDGE SOUTH DOWN THE MID-ATLANTIC SEABOARD WHICH SHOULD PUSH THE BACK-DOOR FRONT SLOWLY SOUTH INTO THE AREA ON SATURDAY. AS USUAL...TIMING OF THESE BACK-DOOR FRONTS THIS TIME OF YEAR IS SUSPECT(USUALLY SLOWER IS BETTER)...WITH DIURNAL HEATING AND RESULTANT DESTABILIZATION AIDING IN SCATTERED COVERAGE. THE LATE ARRIVAL OF A SHORTWAVE TROUGH ROTATING SOUTHWARD DOWN THE BACK-SIDE OF THE UPPER TROUGH SATURDAY NIGHT MAY EVEN SUPPORT A FEW ANAFRONTAL SHOWERS OVERNIGHT. COOLER ON SATURDAY WITH CLOUDS AND NELY FLOW NORTH OF THE FRONT. HIGHS RANGING FROM LOWER/MID 80S NORTH TO LOWER 90S SOUTH. LOWS SATURDAY NIGHT IN THE UPPER 60S TO LOWER 70S. SUNDAY AND SUNDAY NIGHT: AS THE UPPER AIR PATTERN AMPLIFIES (RIDGE BUILDING OVER THE MISSISSIPPI RIVER VALLEY...TROUGH DEEPENING ACROSS THE WESTERN ATLANTIC) ON SUNDAY...CENTRAL NC WILL BE UNDER NORTHWEST/NORTHERLY FLOW ALOFT. AT THE SURFACE...A COLD FRONT WILL BE SHUNTED SOUTH OF THE REGION AS HIGH PRESSURE BEGINS TO RIDGE DOWN FROM THE NORTHEAST. AS THIS OCCURS...DRIER AIR WILL FILTER INTO THE REGION THROUGHOUT THE DAY...BUT SOME DEEP MOISTURE WILL REMAIN IN PLACE...MOSTLY ACROSS THE SOUTH AND WEST WHERE PWAT VALUES ARE PROGGED TO HOVER BETWEEN 1.5-1.75 INCHES THROUGH SUNDAY NIGHT. GIVEN THIS AND THE LINGERING FRONT...AND THE POSSIBILITY OF ANY WEAK DISTURBANCES MOVING OVER THE AREA WITHIN THE NORTHWESTERLY FLOW ALOFT...WILL MAINTAIN SLIGHT CHANCE TO CHANCE POPS...HIGHEST ACROSS THE SOUTH AND WEST. IN FACT...NORTHEASTERN PORTIONS OF THE FORECAST AREA MAY STAY DRY. TEMPS WILL RANGE FROM NEAR 80 DEGREES TO THE MID 80S...WITH OVERNIGHT LOWS GENERALLY IN THE MID 60S. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 300 AM FRIDAY... THE HIGHLY AMPLIFIED PATTERN WILL PERSIST THROUGH EARLY NEXT WEEK... WITH THE UPPER RIDGE GRADUALLY BUILDING EAST TOWARDS THE REGION. THE COLD FRONT WILL BE PUSHED WELL TO OUR SOUTH AS A SURFACE HIGH PRESSURE RIDGE BECOMES FIRMLY ENTRENCHED OVER THE AREA. MUCH DRIER AIR IS PROGGED TO BE IN PLACE...WITH PWAT VALUES EXPECTED TO FALL BELOW 1 INCH. ALL OF THIS WILL LEAD TO MOSTLY DRY CONDITIONS THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. THE STRONG UPPER RIDGE WILL FINALLY FLATTEN OUT/SHIFT OFFSHORE AS THE NEXT UPPER TROUGH/SURFACE FRONT APPROACHES THE AREA LATE THURSDAY INTO FRIDAY...BRINGING INCREASING PRECIP CHANCES BY THE END OF THE WEEK. LOW LEVEL THICKNESS VALUES WILL GRADUALLY FALL THROUGH EARLY NEXT WEEK AS THE UPPER TROUGH DEEPENS DOWN THE WESTERN ATLANTIC. IN ADDITION...NORTHEASTERLY SURFACE FLOW WILL PERSIST AS HIGH PRESSURE RIDGES INTO THE AREA FROM THE NORTHEAST. ALL OF THIS WILL RESULT IN BELOW NORMAL TEMPS...WITH UPPER 70S TO LOW/MID 80S EXPECTED FOR SUNDAY AND EARLY NEXT WEEK. TEMPS WILL BEGIN TO MODERATE TUESDAY AND ESPECIALLY INTO WEDNESDAY/THURSDAY AS THE UPPER RIDGE SHIFTS EAST... WITH MID/UPPER 80S EXPECTED BY THE END OF THE PERIOD. OVERNIGHT LOWS WILL FOLLOW THE SAME PATTERN...WITH MOSTLY MID/UPPER 60S (MAYBE SOME LOWER 60S IN THE COOLER LOCATIONS) FOR THE FIRST HALF OF THE PERIOD AND THEN MORE IN THE WAY OF MID/UPPER 60S. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 135 AM FRIDAY... 24-HR TAF PERIOD: AS DEBRIS CLOUD COVER SCATTERS OUT...MOSTLY MVFR VFR FOG AND/OR LOW CEILINGS ARE EXPECTED TO DEVELOP OVERNIGHT GIVEN VERY MUGGY/HUMID AIRMASS. THE EXCEPTION WILL BE AT FOG-PRONE KRWI...WHERE A BRIEF PERIOD OF LIFR TO IFR CONDITIONS ARE POSSIBLE. VFR CONDITIONS SHOULD RETURN BY 13Z TO 14Z. SHORTWAVE DISTURBANCES MOVING INTO THE AREA WITHIN THE NW FLOW ALOFT WILL SUPPORT SHOWERS AND STORMS THIS AFTERNOON AND EVENING...WITH THE BEST CHANCE AT THE RDU/RWI TERMINALS. ITS POSSIBLE THAT CONVECTION COULD PERSIST WELL INTO OVERNIGHT HOURS...ESPECIALLY ACROSS THE NE AS A COLD FRONT ATTEMPTS TO DROP SOUTH INTO THE AREA. LOOKING AHEAD: DIURNAL CONVECTION IS EXPECTED AGAIN ON SAT... ENHANCED BY THE PASSAGE OF A BACK DOOR COLD FRONT FROM THE NORTH/NE SAT EVE/NIGHT. WIDESPREAD IFR CEILINGS ARE EXPECTED IN THE WAKE OF THE BACKDOOR COLD FRONT SAT NIGHT/SUN MORNING...POSSIBLY PERSISTING THROUGH THE DAY AND INTO SUN NIGHT. DRY SURFACE HIGH PRESSURE BUILDING DOWN THE MID-ATLANTIC SEABOARD WILL SECURE DRY VFR CONDITIONS THROUGH EARLY NEXT WEEK. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...CBL NEAR TERM...CBL SHORT TERM...CBL/KRD LONG TERM...KRD AVIATION...CBL/VINCENT

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