Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 222349 RRA AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 745 PM EDT FRI AUG 22 2014 .SYNOPSIS...A COLD FRONT WILL MOVE SOUTH THROUGH THE STATE SATURDAY AFTERNOON AND NIGHT. HIGH PRESSURE WILL THEN BUILD SOUTH INTO THE REGION FOR EARLY NEXT WEEK. && .NEAR TERM /OVERNIGHT/... AS OF 745 PM FRIDAY... EARLIER SMALL CLUSTERS OF THUNDERSTORMS HAVE MOVED SE OF OUR REGION THIS EVENING. THE ACTIVITY UPWIND APPEARS TO BE DISSIPATING AS IT COMES OVER THE HIGHER TERRAIN IN SW VA/WVA. CONVECTIVE PARAMETERS OVER CENTRAL NC ARE NOT FAVORABLE FOR ADDITIONAL DEVELOPMENT OTHER THAN ON AN ISOLATED BASIS. CONVECTION UPWIND SHOULD ALSO DISSIPATE AS IT MOVES EAST OF THE MOUNTAINS THIS EVENING AND OVERNIGHT. THEREFORE... WE WILL LOWER POP TO A SLIGHT (15-20) PERCENT CHANCE FOR ANY ONE GIVEN SPOT FOR 0.01 OVERNIGHT. OTHERWISE... PARTLY TO MOSTLY CLOUDY WITH PLENTY OF MID AND HIGH RESIDUAL CONVECTIVE DEBRIS CLOUDINESS FROM UPWIND CONVECTION. LOWS 68-73. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 220 PM FRIDAY... A WEAK BOUNDARY...POTENTIALLY OUTFLOW INDUCED...FORECAST TO MOVE INTO THE AREA TONIGHT WILL SETTLE ACROSS THE SOUTHERN PORTIONS OF THE AREA...WHILE THE TRUE COLD FRONT REMAINS TO OUR NORTHEAST. AHEAD OF THE FRONT...H85 TEMPS REMAIN ABOVE 18C...THOUGH MIXING SHOULD STOP SHORT OF THAT LEVEL WITH PW NEAR 2 INCHES. PERIODS OF HIGH CLOUDS IN NORTHWEST FLOW ALOFT SHOULD ALSO TEMPER HIGHS A BIT...ESPECIALLY ACROSS THE NORTHEAST AS THE FRONT BEGINS TO PUSH INTO THE AREA LATE IN THE DAY. COOLER GUIDANCE GIVES A WIDE RANGE OF TEMPS FROM LOWER 90S SOUTHWEST TO MID 80S NORTHEAST. DUE TO THIS...INSTABILITY WILL BE GREATEST ACROSS THE SOUTHEAST...WITH MARGINALLY STRONGER SHEAR BACK TO THE NORTHEASTER CLOSER TO THE FRONTAL ZONE. THERE IS STILL THE POTENTIAL FOR ANOTHER DISTURBANCE TO APPROACH FROM THE NORTHEAST...WHICH COMBINED WITH INCREASINGLY CONVERGENT LOW LEVEL FLOW AND HIGH PW...SHOULD LEAD TO A BETTER CHANCE OF SHOWERS AREAWIDE. THE BACKDOOR COLD FRONT WILL MAKE ITS WAY INTO THE AREA LATE SATURDAY AND OVERNIGHT...WITH DRYING ALOFT BEHIND THE FRONT ZONE. MOIST NORTHEASTERLY FLOW WILL LIKELY LEAD TO FAIRLY WIDESPREAD STRATUS...AND POSSIBLY A FEW LIGHT SHOWERS AS A SHORTWAVE ROTATES SOUTH ACROSS THE AREA. LOWS WILL BE IN THE UPPER 60S NORTHEAST TO LOWER 70S SOUTHWEST. 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 /SUNDAY THROUGH FRIDAY/... AS OF 1250 PM FRIDAY... AN AMPLIFIED UPPER PATTERN WILL PERSIST THROUGH EARLY NEXT WEEK... WITH AN UPPER RIDGE GRADUALLY BUILDING EAST TOWARDS THE REGION. A COLD FRONT WILL BE SUPPRESSED SOUTH OF THE AREA BY LATE SUNDAY AS DRY AND COOLER SURFACE HIGH PRESSURE BECOMES FIRMLY ENTRENCHED DOWN THE ATLANTIC COAST. THERE WILL BE A LINGERING CHANCE OF SHOWERS SUNDAY AS THE FRONT SURGES SOUTH...FOLLOWED BY DRY CONDITIONS THROUGH THURSDAY. THE UPPER RIDGE WILL DEAMPLIFY/FLATTEN OUT AS THE NEXT UPPER TROUGH AND ASSOCIATED SURFACE FRONT APPROACHES THE AREA LATE THURSDAY INTO FRIDAY...BRINGING INCREASING PRECIPITATION CHANCES BY THE END OF THE WEEK. POST FRONTAL CONDITIONS WILL BE PLEASANT...WITH CONSIDERABLY COOLER TEMPERATURES AND LOWER HUMIDITY. LOW LEVEL THICKNESS VALUES WILL FALL THROUGH EARLY NEXT WEEK...TO THE TUNE OF 30 METERS EQUATING TO AROUND A 10 DEGREE COOL OFF. HIGHS SUNDAY THROUGH TUESDAY WILL BE WELL BELOW...5-7 DEGREES...NORMAL WITH UPPER 70S TO LOWER 80S OVER ALL BUT THE FAR SOUTHERN TIER WHICH MAY SEE MID 80S. TEMPS WILL BEGIN TO MODERATE WEDNESDAY THROUGH FRIDAY AS THE UPPER RIDGE SHIFTS EAST... WITH MID/UPPER 80S EXPECTED BY THE END OF THE WEEK. OVERNIGHT LOWS WILL FOLLOW THE SAME PATTERN...WITH MOSTLY LOW TO MID 60S EARLY NEXT WEEK WARMING TO MID AND UPPER 60S BY LATE WEEK. && .AVIATION /00Z FRIDAY THROUGH WEDNESDAY/... AS OF 735 PM FRIDAY... 24-HR TAF PERIOD: SCATTERED CONVECTION WILL PASS WITHIN 5-15 MILES OF THE FAY TERMINAL THROUGH 00Z. CONVECTION UPSTREAM OVER SOUTHERN WV AND SOUTHWEST VA AT 23Z WILL TRACK SOUTHEAST TOWARD THE INT/GSO TERMINALS THROUGH THE REMAINDER OF THE EVENING...THOUGH THIS ACTIVITY MAY WEAKEN OR ALTOGETHER DISSIPATE PRIOR TO REACHING THE TRIAD. ISOLD SHOWER ACTIVITY WILL REMAIN POSSIBLE AT ANY TERMINAL OVERNIGHT...THOUGH CONFIDENCE IS TOO LOW TO WARRANT ANY MENTION. PATCHY FOG AND/OR LOW CEILINGS WILL BE POSSIBLE AT ANY TERMINAL IF CLOUD COVER THINS OUT FOR SEVERAL HOURS PRIOR TO SUNRISE. WILL MENTION FOG DEVELOPING AT THE MORE CLIMATOLOGICALLY LIKELY FAY/RWI TERMINALS IN THE 07-12Z TIME FRAME. LOOKING AHEAD: GREATER CONVECTIVE COVERAGE IS EXPECTED ON SATURDAY AS A SERIES OF UPPER LEVEL DISTURBANCES TRACK S/SSE ACROSS THE CAROLINAS AND A BACK DOOR COLD FRONT PROGRESSES INTO CENTRAL NC FROM THE N/NE. IFR CEILINGS WILL BE POSSIBLE IN THE WAKE OF THE BACKDOOR COLD FRONT SAT NIGHT THROUGH MID-DAY SUNDAY...THOUGH COVERAGE AND DURATION REMAIN UNCERTAIN. AN UPPER LEVEL RIDGE CENTERED IN VICINITY OF THE SOUTHERN APPALACHIANS SHOULD RESULT IN BETTER-THAN-NORMAL CHANCES FOR VFR CONDITIONS MON-WED...THOUGH A PERSISTENT E/NE LOW- LEVEL FLOW MAY ALLOW ADEQUATE MOISTURE FOR LOW-TOPPED SHOWER ACTIVITY...ESP AT THE EASTERN TERMINALS (FAY/RWI). -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...PWB NEAR TERM...PWB SHORT TERM...BLS LONG TERM...MLM AVIATION...VINCENT

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