Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 270121 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 920 PM EDT TUE MAY 26 2015 .SYNOPSIS...THE WESTERN EXTENT OF BROAD SURFACE HIGH PRESSURE...AND A SEASONABLY MOIST AIR MASS...WILL PREVAIL OVER THE REGION FOR THE WORK WEEK. && .NEAR TERM /OVERNIGHT/...
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AS OF 920 PM TUESDAY... AN AREA OF CONVECTION LIFTING NE ACROSS UPSTATE SC AND SW NC BEING MAINTAINED BY A MID LEVEL TROUGH AND ATTENDANT SPEED CONVERGENCE ALONG WITH UPPER DIVERGENCE...CENTERED MAINLY OVER THE SOUTHERN APPALACHIANS. THE 00Z GSO SOUNDING DEPICTS A FAIRLY SUBSTANTIAL CAP BETWEEN 750-700MB...A BIT STRONGER THAN PREDICTED BY THE NEAR TERM MODELS. EXPECT THIS AREA OF CONVECTION TO GRADUALLY WEAKEN AS IT ENCOUNTERS THE SLIGHTLY MORE STABLE AIR MASS OVER THE WESTERN PIEDMONT...BUT COULD STILL SEE A FEW SHOWERS LATE THIS EVENING INTO THE OVERNIGHT IN VICINITY OF THE TRIAD. OTHERWISE VARIABLY CLOUDY SKIES AND A LIGHT BUT PERSISTENT SLY SFC WIND WILL RESULT IN A MILD (THOUGH SLIGHTLY HUMID) NIGHT. MIN TEMPS MAINLY IN THE UPPER 60S.
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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 305 PM TUESDAY... INSTABILITY OVERALL INCREASES ACROSS CENTRAL NORTH CAROLINA WEDNESDAY...WITH SURFACE-BASED CAPE RISING TO JUST OVER 1000J/KG WHILE MLCAPE THROUGH THE LOWEST 3KM IS GENERALLY 500J/KG OR SO. LIFTED INDICES ARE FORECAST TO BE SLIGHTLY LOWER COMPARED TO TODAY... TO NEAR -5C WEDNESDAY AFTERNOON VERSUS ABOUT -3C. ALOFT...THERE IS FORECAST WEAK AND BROAD DIFFLUENCE AND WEAK CONVERGENCE AT 850MB...ALTHOUGH CERTAINLY THE NAM AND TO A LESSER EXTENT THE GFS FORECAST MODEST LIFT OVER CENTRAL NORTH CAROLINA FOR WEDNESDAY AFTERNOON. WINDS ALOFT ARE WEAK...AND ANY PIEDMONT TROUGH SHOULD BE SOMEWHAT WEAK AS WELL...LEADING TO A DAY WHERE SCATTERED MOSTLY DISORGANIZED SHOWERS AND THUNDERSTORMS SHOULD OCCUR AS THE DAY PROGRESSES. ONCE AGAIN...0-3KM SHEAR IS LOW AND 850MB AND 925MB WINDS ARE RELATIVELY LIGHT BY AFTERNOON...10 TO 20KT. HIGHS IN THE 80S. OVERNIGHT...BUFR SOUNDINGS FROM BOTH THE NAM AND GFS SHOW INCREASING STABILITY AS SURFACE HIGH PRESSURE IS FORECAST TO BUILD SOMEWHAT BACK WEST. FOR THIS FORECAST WILL DIMINISH CHANCES EAST TO WEST AND RETAIN A SLIGHT CHANCE OF SHOWERS IN THE OVERNIGHT HOURS ONLY TOWARD THE YADKIN RIVER ESPECIALLY FOR FORECAST CONSISTENCY...BUT IF THE NAM BUFR SOUNDINGS VERIFY IN PARTICULAR CENTRAL NORTH CAROLINA SHOULD HAVE BELOW SLIGHT CHANCE POPS AFTER 06Z. LOWS IN THE MID TO UPPER 60S. && .LONG TERM /THURSDAY THROUGH TUESDAY/... AS OF 210 PM TUESDAY... THE REMNANT MOISTURE AND SHEAR AXIS FROM THE SYSTEM CURRENTLY OVER THE MISS RIVER VALLEY WILL MOVE EAST AND BECOME CENTERED OVER CENTRAL NC BY THURSDAY. WHILE THE BEST MID/UPR ENERGY WILL HAVE LIFTED WELL TO OUR NORTH...THERE SHOULD BE ENOUGH MOISTURE AND FORCING FOR AT LEAST SCATTERED AFTERNOON/EVENING SHOWERS/TSTMS. INSTABILITY AND SHEAR VALUES SUGGEST SUB-SEVERE ACTIVITY. THE UPPER RIDGE OFF THE EAST COAST WILL THEN REBUILD OVER THE SOUTHEAST COASTAL REGION FRIDAY THROUGH THE WEEKEND...AND SHOULD HELP LIMIT THE COVERAGE OF SHOWER/TSTM ACTIVITY OVER OUR AREA FRIDAY AND SATURDAY. A COLD FRONT CROSSING THE MIDWEST ON FRIDAY IS PROGGED BY THE LATEST GFS TO DROP SOUTH ACROSS OUR AREA BY SUNDAY AND DISSIPATE OVER US BY MONDAY. DESPITE THE LIFT PROVIDED BY THIS FRONT...MODELS SUGGEST THE AFOREMENTIONED RIDGE OVER THE SOUTHEAST WILL KEEP THE BULK OF THE MOISTURE JUST TO OUR NORTH. NEVERTHELESS...THERE`S ENOUGH FORCING AND MOISTURE TO WARRANT A DECENT CHANCE POP ACROSS OUR AREA LATE IN THE WEEKEND INTO EARLY NEXT WEEK. AS FOR TEMPS...PERSISTENCE IS THE BEST FORECAST AT THIS POINT WITH LITTLE CHANGE IN THE AIRMASS. HIGHS IN THE MID TO UPPER 80S AND LOWS IN THE MID 60S EACH DAY DURING THE PERIOD. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... AS OF 830 PM TUESDAY... VFR CONDITIONS ARE EXPECTED TO CONTINUE THIS EVENING... WITH LOW TO MODERATE CONFIDENCE OF IFR/MVFR CONDITIONS EARLY WEDNESDAY MORNING... POSSIBLY LINGERING TO NEAR NOON WEDNESDAY AT KGSO/KINT. ISOLATED TO SCATTERED SHOWERS AND STORMS ARE EXPECTED ON WEDNESDAY AFTERNOON AS WELL. THE MID LEVEL RIDGE AXIS LOCATED NEAR THE COAST STILL HAD ENOUGH OF AN INFLUENCE TO SUPPRESS SHOWERS AND STORMS FOR THE MOST PART ACROSS THE AREA TODAY. HOWEVER... THIS FEATURE WILL CONTINUE TO SLOWLY SHIFT EASTWARD AND ALLOW A MORE FAVORABLE AIRMASS TO SLOWLY SHIFT FILTER INTO CENTRAL NC. IN FACT WE MAY SEE A WEAKENING BAND OF SHOWERS AND STORMS CURRENTLY LOCATED ACROSS FAR SOUTHWESTERN NC AND THE UPSTATE OF SC CONTINUE TO MOVE EAST AND NORTHWARD AND POSSIBLY AFFECT KGSO/KINT (THOUGH IN A WEAKEN STATE) IN THE 04Z TO 08Z TIME FRAME... WITH POSSIBLE MVFR CONDITIONS. ELSEWHERE OVERNIGHT... WE CANT ENTIRELY RULE OUT A FEW SHOWERS... BUT PROBABILITIES ARE WAY TOO LOW TO INCLUDE ANY MENTION OF CONVECTION IN THE TAFS. GIVEN THE CONTINUED MOISTENING LOW LEVEL FLOW EXPECT WE WILL LIKELY SEE SOME STRATUS AGAIN TONIGHT (MVFR/IFR CONDITIONS)... WITH THE HIGHEST PROBABILITIES ACROSS THE WESTERN PIEDMONT... KGSO/KINT. FURTHER EAST STILL THINK WE MAY SEE SOME MVFR/IFR CONDITIONS... BUT CONFIDENCE IS NOT AS HIGH. AFTER SUNRISE WEDNESDAY MORNING...ANY IFR CONDITIONS SHOULD LIFT AT LEAST INTO MVFR RANGE BY MID MORNING... WITH CIGS EXPECTED TO BE IN THE VFR RANGE BY EARLY AFTERNOON. SCATTERED SHOWERS AND STORMS ARE EXPECTED TO DEVELOP/MOVE INTO THE AREA TOWARDS WEDNESDAY AFTERNOON (GENERALLY ACROSS THE WESTERN PIEDMONT). THUS... GIVEN CONFIDENCE IN SEEING SOME SHOWERS AND STORMS IS HIGHEST IN THE NW PIEDMONT... WILL ONLY ADD A PROB30 GROUP AT KGSO/KINT FOR CONVECTION WEDNESDAY AFTERNOON. BEYOND THE 00Z VALID TAF PERIOD...LOW CLOUDS WILL BE POSSIBLE AGAIN THURSDAY MORNING...THOUGH WITH A BETTER PROBABILITY TOWARD KFAY AND KRWI RELATIVE TO THE REST OF CENTRAL NORTH CAROLINA. ISOLATED TO SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS ARE ALSO POSSIBLE. LOWEST CHANCES OF THOSE APPEAR TO BE SATURDAY WHEN THE AIR MASS IS RELATIVELY MORE STABLE COMPARED TO OTHER DAYS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DJF NEAR TERM...WSS SHORT TERM...DJF LONG TERM...RAH AVIATION...BSD/DJF

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