Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221838 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 238 PM EDT MON SEP 22 2014 .SYNOPSIS...AN UPPER LEVEL LOW WILL DEVELOP OVER THE CAROLINAS TONIGHT...AND WILL SLOWLY WEAKEN OVER THE REGION THROUGH MID-WEEK. MEANWHILE...AT THE SURFACE...A STALLED FRONT WILL LINGER ALONG THE SOUTHEAST COAST AS HIGH PRESSURE EXTENDS INTO THE AREA FROM THE NORTH. && .NEAR TERM /THROUGH TUESDAY NIGHT/...
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AS OF 1045 AM MONDAY... TODAY: STOUT SHORTWAVE VORTMAX DIVING ESE TOWARD THE SOUTHERN APPALACHIANS AND ROUNDING THE BASE OF THE AMPLIFYING EASTERN US TROUGH WILL DECELERATE AND WILL CLOSE AND EVENTUALLY BECOME CUT-OFF OVER THE CAROLINAS OVERNIGHT. IN RESPONSE... SURFACE COLD FRONT...WHICH IS CURRENTLY IN THE PROCESS OF EXITING THE FORECAST AREA...WILL STALL OUT ALONG THE COAST. RAIN CHANCES: THE FAR SE COUNTIES WILL HAVE THE POTENTIAL FOR SOME SHOWERS THROUGH LATE MORNING(ANOTHER HOUR OR SO)...WITH DRY CONDITIONS THROUGH THE REMAINDER OF THE AFTERNOON AS DRIER AIR IN THE WAKE OF THE FRONTAL PASSAGE SURGES SOUTH. THEN LATE TONIGHT...LIGHT RAIN WILL ATTEMPT TO SPREAD BACK INLAND ACROSS THE EXTREME SE COUNTIES(SAMPSON/WAYNE COUNTIES)AS A WEAK WAVE DEVELOPS ALONG THE OFFSHORE FRONTAL ZONE...TRIGGERING WEAK OVERRUNNING. ISENTROPIC LOOKS FAIRLY WEAK...AND THUS EXPECT PREDOMINATELY CLOUDS WITH SOME LIGHT RAIN/SPRINKLES POSSIBLE. TEMPERATURES: COLD ADVECTION WILL BE PRESENT IN THE WAKE OF THE FRONTAL PASSAGE THROUGH THE REMAINDER OF THE DAY AND TONIGHT. UNDER SUNNY SKIES HIGHS RANGING LOWER TO MID 70S NW TO NEAR 80S SE. LOW TEMPERATURES TONIGHT WILL NOT BE QUITE AS COOL AS ORIGINALLY THOUGHT OWING TO THE RETURN OF CLOUDS...AT LEAST ACROSS THE COASTAL PLAIN AND CENTRAL PIEDMONT. LOWS RANGING FROM LOWER 50S N/NW PIEDMONT TO UPPER 50S/NEAR 60 SOUTHEAST. THE LATEST MODEL GUIDANCE SUGGESTS THAT ROBUST SHORTWAVE ENERGY APPROACHING THE REGION TODAY WILL DIG FURTHER SOUTH AND AMPLIFY INTO AN UPPER LOW OVER SC TONIGHT... BECOMING CUT-OFF FROM THE NORTHERN STREAM AND STALLING OVER CENTRAL PORTIONS OF THE CAROLINAS THROUGH TUE NIGHT. IN THE LOWER LEVELS... AN INVERTED TROUGH WILL BE PRESENT IN VICINITY OF THE STALLED BAROCLINIC ZONE ALONG OR JUST OFFSHORE THE CAROLINA COAST WHILE AN INVERTED RIDGE EXTENDS SOUTHWARD INTO CENTRAL/WESTERN PORTIONS OF THE CAROLINAS FROM HIGH PRESSURE TO THE NORTH. THE 00Z GFS/NAM KEEP PRECIP LARGELY SOUTH/EAST OF CENTRAL NC TUE/TUE NIGHT...HOWEVER... THE LATEST 00Z ECMWF SHOWS THE COASTAL FRONT MOVING INLAND TUE NIGHT WITH WIDESPREAD PRECIPITATION OVERSPREADING CENTRAL NC FROM THE SOUTH/SE BY WED MORNING. WITH SUCH A LARGE DIFFERENCE IN THE 00Z OPERATIONAL GUIDANCE QPF...FORECAST CONFIDENCE IS BELOW AVERAGE. AT THIS TIME...WILL ADJUST THE FORECAST FOR CENTRAL NC TO REFLECT MOSTLY CLOUDY TO OVERCAST SKIES...COOLER TEMPERATURES (PERHAPS STRUGGLING TO EXCEED THE 60S TUE AFTERNOON) AND A CHANCE FOR RAIN IN THE SOUTHEAST COASTAL PLAIN...THOUGH PRECIP CHANCES MAY NEED TO BE EXTENDED WEST TO INCLUDE THE ENTIRE CWA TUE NIGHT IF THE 12Z GFS/NAM GUIDANCE TRENDS TOWARD THE 00Z ECMWF.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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AS OF 230 PM MONDAY... FORECAST CONFIDENCE REMAINS SOMEWHAT BELOW NORMAL FOR THE MIDDLE OF THE WEEK AS THERE CONTINUES TO BE SOME DISAGREEMENT AMONG THE MODELS...ALTHOUGH THERE IS SOME MODEL CONVERGENCE TOWARDS A MORE UNSETTLED PERIOD. THE LOW LEVEL FLOW AROUND THE HIGH WILL INCREASE AND BEGIN TO GRADUALLY TAKE ON MORE OF AN EAST OF NORTHERLY COMPONENT (AS HIGH PRESSURE SHIFTS OFF THE NORTHEAST COAST) ALLOWING MOISTURE TO RETURN TO THE AREA. IN ADDITION...MODELS CONTINUE TO HINT AT A WEAKNESS ALOFT AND ASSOCIATED INVERTED TROUGH DEVELOPING NEAR THE SOUTHEAST COAST (ALTHOUGH TO VARYING DEGREES AMONG THE MODELS). THIS WOULD INCREASE CLOUDS AND PRECIP CHANCES (ESPECIALLY ACROSS EASTERN NC). THE MORE CONSISTENT ECMWF SHOWS A CLOSED LOW ALOFT ACROSS THE SOUTHEAST WHICH IN TURN RESULTS IN A STRONGER INVERTED TROUGH AND THEREFORE MORE ENHANCED PRECIP/CLOUD COVER. THE GFS NOW ALSO SHOWS A CLOSED LOW ALOFT OVER THE AREA...BUT IT IS FURTHER OFFSHORE (AND MORE PROGRESSIVE) WITH THE INVERTED TROUGH...THUS IT IS STILL THE DRIER SOLUTION. WILL CONTINUE TO FOLLOW MORE CLOSELY TO THE MORE CONSISTENT ECMWF (AND EC ENSEMBLE MEAN). REGARDLESS...CLOUDY AND COOLER CONDITIONS WILL PERSIST... WITH RAIN CHANCES INCREASING (ESPECIALLY ACROSS THE EAST). HIGHS ARE EXPECTED TO STAY IN THE LOW TO MID 70S (WITH SOME UPPER 60S POSSIBLE) AND OVERNIGHT LOWS MOSTLY IN THE MID/UPPER 50S TO LOWER 60S.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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AS OF 230 PM MONDAY... SOME DRYING IS EXPECTED BEGINNING FRIDAY...BUT ESPECIALLY INTO THE WEEKEND AS THE UPPER LOW FILLS IN WHILE RIDGING TRIES TO BUILD EAST. THIS WILL CAUSE THE INVERTED TROUGH TO WEAKEN/DISSIPATE. HOWEVER... WILL NOT REMOVE POPS ALTOGETHER AS THERE WILL BE STILL BE A WEAKNESS ALOFT OVER THE AREA AND MOISTURE WILL NOT DECREASE SIGNIFICANTLY. WITH THE ABOVE IN MIND...TEMPS WILL UNDERGO SOME MODERATION...AND ARE EXPECTED TO RETURN TO NEAR NORMAL VALUES. OUR NEXT SYSTEM MAY APPROACH THE AREA EARLY NEXT WEEK...BUT AS CAN BE EXPECTED (GIVEN THE LOW CONFIDENCE IN THE MEDIUM RANGE FORECAST)...THERE IS A LOT OF UNCERTAINTY IN THE EXTENDED RANGE.
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/... AS OF 205 PM MONDAY... 24-HR TAF PERIOD: DRY LOW-LEVEL AIR FILTERING IN THE AREA FROM THE NORTH...IN THE WAKE OF THIS MORNINGS COLD FRONTAL PASSAGE WILL SECURE VFR CONDITIONS THROUGH THE PERIOD. THE FRONT WILL STALL JUST OFFSHORE...ALONG THE SOUTHEAST COAST TONIGHT THROUGH MID-WEEK AS CLOSED/CUT-OFF LOW DEVELOPS OVER THE CAROLINAS. THIS WILL SPREAD MOISTURE IN THE 5-10KFT LAYER BACK INLAND TONIGHT THROUGH TUESDAY WITH INCREASING RAIN CHANCES ACROSS THE SOUTHEAST...AND POSSIBLY EASTERN/CENTRAL PIEDMONT. WINDS SHOULD REMAIN OUT OF THE NORTH AT 5-10KT THROUGH THE PERIOD. LOOKING AHEAD: PROXIMITY TO CUT-OFF UPPER LOW OVER THE CAROLINAS ALONG WITH INVERTED SFC TROUGH ALONG THE COAST WILL LIKELY RESULT IN A CONTINUATION OF BROKEN TO OVERCAST CLOUD COVER WITH BETTER RAIN CHANCES EXPECTED ALONG THE SOUTHEAST NEAR KFAY WITH THE POTENTIAL FOR SOME SUB-VFR CEILINGS TUESDAY NIGHT AND INTO WEDNESDAY. ELSEWHERE...VFR CONDITIONS ARE LIKELY TO PREVAIL FURTHER INLAND OVER CENTRAL NC AS DRY AIR SURFACE RIDGE EXTENDS SOUTH INTO PIEDMONT. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...CBL NEAR TERM...CBL/VINCENT SHORT TERM...KRD LONG TERM...KRD AVIATION...CBL

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