Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221427 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1025 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/...
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AS OF 1025 AM FRIDAY... PERTURBED NORTHWESTERLY FLOW CONTINUES OVER THE REGION TODAY BETWEEN A MID-LEVEL RIDGE OVER THE DEEP SOUTH AND A TROUGH OVER THE NORTHEAST. A LEAD...DECAYING DISTURBANCE CROSSING WV HS AIDING AN AREA OF MOSTLY LIGHT SHOWERS NOW OVER SOUTHWESTERN VA. AHEAD OF THIS FEATURE...AMPLE SUNSHINE OVER CENTRAL NC WILL ALLOW TEMPS TO RISE INTO THE LOW TO MID 90S...BASED ON H85 TEMPS OF 19-20C PER REGIONAL RAOBS. DEWPOINTS SHOULD AGAIN MIX OUT INTO THE MID/UPPER 60S...ESPECIALLY ACROSS THE SOUTHWESTERN AND WESTERN AREAS WHERE 925MB DEWPOINTS ARE AT A RELATIVE MIN. MLCAPE VALUES AREA FORECAST TO RANGE FROM 1000 J/KG IN THE WEST TO NEAR 2000 J/KG IN THE EAST. A BELT OF STRONGER NORTHWESTERLY MID-LEVEL FLOW WILL SHIFT SOUTHEAST ACROSS VA AND THE NORTHERN PORTIONS OF NC AS A SPEED MAX CROSSES THE CENTRAL APPALACHIANS. EFFECTIVE BULK SHEAR SHOULD REACH AROUND 25- 30 KTS NORTHEAST OF THE TRIANGLE THIS AFTERNOON AND EVENING...WHICH COMBINED WITH MODERATE INSTABILITY WILL SUPPORT THE POTENTIAL FOR SOME STRONG MULTI-CELL CLUSTERS. THE BIGGEST UNCERTAINTY CONTINUES TO BE WITH CONVECTIVE INITIATION AHEAD OF THE DISTURBANCE. IF THE SHOWERS AHEAD OF THE DISTURBANCE HOLD TOGETHER INTO THE NORTHERN PIEDMONT IN THE NEXT 2-3 HOURS...THEY MAY LIMIT DESTABILIZATION. HOWEVER... WITH TIME EXPECT ADDITIONAL STORMS TO POPS UP AND PROPAGATE TOWARD THE SOUTH-SOUTHEAST TOWARD WHAT SHOULD BE MODEST DCAPE ACROSS THE SOUTHERN TIER...FURTHER ENHANCING THE THREAT OF SOME DAMAGING WIND GUSTS. LINGERING SFC OUTFLOW AND SURFACE FRONT DROPPING SOUTH INTO THE AREA WILL SUPPORT SMALL TO SLIGHT POPS OVERNIGHT. LOWS IN THE UPPER 60S NE TO LOWER 70S SE.
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&& .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 /12Z FRIDAY THROUGH TUESDAY/... AS OF 648 AM FRIDAY... 24-HR TAF PERIOD: 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/BLS SHORT TERM...CBL/KRD LONG TERM...KRD AVIATION...CBL/VINCENT

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