Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 261908 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 307 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 /THROUGH TONIGHT/...
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AS OF 305 PM TUESDAY... THE LATEST SURFACE ANALYSIS SHOWED THE WESTERN END OF HIGH PRESSURE CONTINUING TO EXTEND OVER CENTRAL NORTH CAROLINA...WHILE WATER VAPOR IMAGERY SHOWED WEAK MID-LEVEL VORTICITY AND AN INCREASE IN MID-LEVEL MOISTURE OVER THE WESTERN CAROLINAS. PRECIPITABLE WATER VALUES HAD INCREASED TOWARD INTERSTATE 95 AND EAST DURING THE DAY...SUCH THAT THERE WERE FAIRLY UNIFORM VALUES AROUND 1.5 INCHES OVER CENTRAL NORTH CAROLINA AS THE LATE AFTERNOON APPROACHED. SCATTERED SHOWERS... AND ISOLATED THUNDER...OVER THE SOUTHERN COASTAL PLAIN SHOULD GENERALLY DECREASE THIS EVENING AS GFS AND NAM BUFR SOUNDINGS FORECAST LOW-LEVEL STABILITY INCREASING BY AROUND SUNSET. IN THE MEANTIME...ISOLATED SHOWERS OR A VERY ISOLATED STORM MAY FIND THEIR WAY ABOUT AS FAR NORTH AS U.S. 64 BASED ON A COMBINATION OF THE LATEST RADAR TRENDS AND THE HRRR WRF. WHILE AN ISOLATED SHOWER VERY LATE THIS AFTERNOON IS ALSO POSSIBLE OVER THE FAR WESTERN PIEDMONT...SCATTERED SHOWERS MAY BE A BETTER POSSIBILITY OVER THE WESTERN PIEDMONT AND TOWARD THE YADKIN RIVER LATER THIS EVENING WITH THE APPROACH OF THE WEAK MID-LEVEL WAVE COINCIDENT WITH FORECAST MOISTENING ON BUFR SOUNDINGS AND...AGAIN...HRRR WRF FORECASTS. 0-3KM SHEAR ON THE SPC MESOANALYSIS...AND AS FORECAST BY THE NAM AND GFS... IS LOW...SINGLE DIGITS KNOTS TO TEENS AT MOST...SO AS OF THIS WRITING DO NOT EXPECT ANY STRONG...DEEP CONVECTION. THE GFS WOULD SPREAD QPF FARTHER EAST THAN THE NAM AND THE HRRR WRF DEPICT...AND BASED ON THE STABILITY EVEN ON THE KRDU...KFAY...AND KRWI GFS BUFR SOUNDINGS OVERNIGHT...LEAN MORE TOWARD THE NAM AND RAP WHICH KEEP MEASURABLE PRECIPITATION FARTHER WEST DURING THE OVERNIGHT HOURS. AS ALSO NOTED IN THE AVIATION DISCUSSION BELOW...SREF MODEL PROBABILITIES OF LOW CLOUDS ARE HIGH ESPECIALLY WEST OF INTERSTATE 95 OVERNIGHT. HOWEVER...THE STATISTICAL GUIDANCE IS NOT AS BULLISH AND MODEL SOUNDINGS FROM THE GFS AND NAM DIFFER AS TO THE POTENTIAL OF LOW CLOUDS LATE. SINCE LOW CLOUDS OCCURRED MAINLY TOWARD THE YADKIN RIVER AND THE TRIAD EARLY THIS MORNING...THE OVERALL AIR MASS HAS MOISTENED...AND 925MB WINDS SHOULD BE FAVORABLE OVERNIGHT WITH VALUES OF 20 TO 30KT AS FORECAST BY THE GFS IN THE SOUTHWEST FLOW. AS A RESULT...BELIEVE THERE WILL BE AREAS OF LOW CLOUDS LATE TONIGHT CONTINUING INTO WEDNESDAY MORNING. OVERNIGHT LOWS 65 TO 70...SHY OF ANY RECORD HIGH MINIMUM VALUES FOR MAY 27.
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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
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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.
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&& .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 /18Z TUESDAY THROUGH SUNDAY/... AS OF 200 PM TUESDAY... FOR THE 18Z VALID TAF PERIOD...VFR CONDITIONS OUTSIDE OF ANY MOSTLY ISOLATED...DEEP CONVECTION SHOULD PERSIST THROUGH MUCH OF TONIGHT. AS OF THIS WRITING...ISOLATED TO SCATTERED SHOWERS WERE NOTED TOWARD KCTZ...AND DURING THIS EVENING WITH A WEAK SHORTWAVE MOVING NORTH OVER THE WESTERN CAROLINAS...ISOLATED TO SCATTERED SHOWERS MAY OCCUR MORE TOWARD THE TRIAD. THERE EXISTS A MODEST PROBABILITY OF IFR CONDITIONS IN LOW CLOUDS OVERNIGHT. SREF MODEL PROBABILITIES OF SUCH ARE HIGH ESPECIALLY WEST OF INTERSTATE 95...HOWEVER...THE STATISTICAL GUIDANCE IS NOT AS BULLISH AND MODEL SOUNDINGS FROM THE GFS AND NAM DIFFER AS TO THE POTENTIAL OF LOW CLOUDS LATE. SINCE LOW CLOUDS OCCURRED MAINLY TOWARD THE YADKIN RIVER AND THE TRIAD EARLY THIS MORNING...THE OVERALL AIR MASS HAS MOISTENED...AND 925MB WINDS SHOULD BE FAVORABLE OVERNIGHT...HAVE FORECAST IFR CONDITIONS BY 10Z IN THE TRIAD AND AT KRDU...WITH TEMPORARY CONDITIONS OF SUCH AT KFAY AND KRWI WHERE CONFIDENCE CURRENTLY IS NOT AS HIGH WITH LIGHTER 925MB WINDS AND LESSER PROBABILITIES EVEN ON THE AGGRESSIVE SREF. DURING WEDNESDAY MORNING...ANY IFR CONDITIONS SHOULD LIFT AT LEAST INTO MVFR...WITH SCATTERED SHOWERS BEGINNING TO DEVELOP TOWARD THE END OF THE TAF PERIOD. ANY SOUTHWEST WIND GUSTS SHOULD BE LIMITED TO THE LOWER TO MID TEENS KNOTS WITH MIXING WEDNESDAY AND BE BRIEF. BEYOND THE 18Z VALID TAF PERIOD...THE LATEST MODEL SOUNDINGS SUGGEST THAT LOW CLOUDS ARE 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...DJF SHORT TERM...DJF LONG TERM...RAH AVIATION...DJF

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