Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281903 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 300 PM EDT TUE JUL 28 2015 .SYNOPSIS...A SERIES OF PERTURBATIONS ALOFT INTERACTING WITH A MOIST AND UNSTABLE AIR MASS WILL TRIGGER ISOLATED TO SCATTERED THUNDERSTORMS...MAINLY DURING THE AFTERNOON AND EVENING HOURS...THROUGH THE REMAINDER OF THE WORK WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1105 AM TUESDAY... JUST MINOR TWEAKS REQUIRED TO THE NEAR TERM FORECAST. NAMELY TO RAISE MAX TEMPS A DEGREE OR TWO ACROSS THE EAST AND SOUTH SECTIONS...AND TO CONCENTRATE THE HIGHEST POPS (30-40%) ACROSS THE WESTERN-NW PIEDMONT. 12Z UPPER AIR ANALYSIS DEPICTS A HIGHLY AMPLIFIED RIDGE EXTENDING FROM THE SOUTHERN PLAINS INTO THE GREAT LAKES. THIS YIELDS A NWLY MID-UPPER LEVEL FLOW OVER CENTRAL NC. WATER VAPOR IMAGERY SUGGEST A FEW VORT MAXIMA CIRCULATING AROUND THE RIDGE OVER THE LOWER OH AND EASTERN TN VALLEYS. PER TRAJECTORIES...THESE SYSTEMS SHOULD REMAIN WEST OF OUR AREA THIS AFTERNOON AND TONIGHT. IN THE LOWER LEVELS...A WEAK SFC TROUGH WAS POSITIONED OVER THE FAR NW PIEDMONT INTO SOUTH CENTRAL VA. CONFLUENCE ALONG THIS FEATURE WAS VERY WEAK. MESO-ANALYSIS INDICATES A NARROW RIBBON OF HIGHER MOISTURE/MODEST INSTABILITY IN VICINITY OF THIS FEATURE. THIS APPEARS TO BE THE FAVORED REGION FOR CONVECTIVE INITIATION LATER TODAY. DIFFICULT TO DISCERN ANY TRIGGER MECHANISM ALOFT. THUS BELIEVE BULK OF CONVECTION WILL BE INITIATED BY AFTERNOON HEATING. THUS EXPECT ONLY ISOLATED COVERAGE ALONG AND EAST OF HIGHWAY 1 WITH A SLIGHTLY BETTER COVERAGE ANTICIPATED IN VICINITY OF THE YADKIN RIVER VALLEY AND THE FAR NW PIEDMONT. MAY NEED TO RE-EVALUATE POP FOR THE TRIAD REGION AS 40-50% MAY BE TOO HIGH. STRONG HEATING THIS MORNING HAS PUSHED TEMPS WELL INTO THE 80S BY MID-LATE MORNING. IN EXPECTATION OF ISOLATED CONVECTION...THE SOUTHERN PIEDMONT AND SANDHILLS SHOULD REACH THE LOW-MID 90S WITH NEAR/LOWER 90S EXPECTED ELSEWHERE. -WSS PERSISTENCE WOULD SUGGEST STORMS MAY CONTINUE TO PERCOLATE ON OLD OUTFLOW BOUNDARIES THROUGH MIDNIGHT...STAYING CONFINED TO THE PIEDMONT. LOWS WILL AGAIN BE IN THE LOWER 70S. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 400 AM TUESDAY... THE CENTRAL U.S. RIDGE WILL BE SUPPRESSED A BIT ON WEDNESDAY BY A SHORTWAVE CROSSING THE GREAT LAKES...LEADING A LITTLE MORE NORTHERLY FLOW ALOFT OVER OUR AREA AND LESS IN THE WAY OF UPPER DISTURBANCES TO ENHANCE CONVECTIVE COVERAGE. FORECAST SOUNDINGS CONTINUE TO SHOW SLIGHTLY BETTER INSTABILITY OVER WESTERN NC AND MOST NWP FAVORS THE WESTERN HALF OF CENTRAL NC FOR AFTERNOON CONVECTION...THOUGH NORTHERLY STEERING FLOW MAY LIMIT THE BEST COVERAGE TO THE FAR WESTERN PIEDMONT. WEAK MID-LEVEL FLOW WILL CONTINUE TO LIMIT THE SEVERE WEATHER THREAT. HIGHS WILL BE BE WITH A DEGREE OR TWO OF TODAY`S VALUES...89-94. LOWS WEDNESDAY NIGHT IN THE LOWER 70S. && .LONG TERM /THURSDAY THROUGH MONDAY/...
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AS OF 300 PM TUESDAY... THE MAIN FEATURE FOR OUR AREA DURING THE LONG TERM PERIOD WILL BE THE DEEPENING LONG WAVE TROUGH OVER THE EAST. IT WILL BEGIN LATE THURSDAY AS THE TROUGH BEGINS DEEPENING OVER THE OHIO VALLEY AND MID ATLANTIC REGION...AND IN DOING SO WILL PUSH A COLD FRONT ACROSS OUR AREA THURSDAY NIGHT. WILL HAVE TO BEGIN RAMPING POPS UP ACROSS OUR WESTERN ZONES DURING THE AFTERNOON THURSDAY...BUT MOST OF DAYTIME THURSDAY SHOULD REMAIN DRY. THE BEST CHANCE FOR RAIN WILL BE THURSDAY NIGHT INTO FRIDAY MORNING...THEN RAIN CHANCES ENDING FROM W- E DURING THE AFTERNOON FRIDAY. TEMPS DURING THIS TIME NEAR NORMAL. FAIR WEATHER THEN APPEARS TO BE IN STORE FOR CENTRAL NC OVER THE WEEKEND WITH HIGH PRESSURE BUILDING TO OUR NORTH AND MUCH DRIER AIR OVER OUR REGION. THE PROGGED LOW LEVEL AIRMASS STILL APPEARS TO SUPPORT HIGHS AS WARM AS THE LOW 90S...SO LITTLE IF ANY RELIEF TEMPERATURE-WISE DESPITE HIGH PRESSURE BUILDING TO OUR NORTH. POPS EXPECTED TO REBOUND CLOSER TO DAILY CLIMO VALUES AS WE HEAD THROUGH EARLY NEXT WEEK AND PWAT SLOWLY RECOVERS. HOWEVER... COVERAGE SHOULD BE ISOLATED AT BEST GIVEN THE BETTER SYNOP FEATURES REMAINING BOTH TO OUR NORTH AND TO OUR SOUTH. IT`S WORTH NOTING THAT GIVEN THE LINGERING BOUNDARY AND LOW PRESSURE TO OUR SOUTH DURING THIS TIME...ANY SLIGHT NORTHWARD SHIFT IN THE PATTERN COULD MEAN HIGHER RAIN CHANCES FOR US DURING THE WEEKEND AND EARLY NEXT WEEK...ESP ACROSS OUR SOUTHERN ZONES. SO GIVEN OUR PROXIMITY TO THESE FEATURES...OUR CONFIDENCE IN THIS PART OF THE FORECAST ISN`T PARTICULARLY HIGH.
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&& .AVIATION /18Z TUESDAY THROUGH SUNDAY/... AS OF 125 PM TUESDAY... HIGH PROBABILITY THAT VFR CONDITIONS WILL PREVAIL AT MOST TAF SITES THROUGH WEDNESDAY AFTERNOON. THE EXCEPTION WILL BE A BRIEF PERIOD OF MVFR CONDITIONS THIS AFTERNOON THROUGH EARLY EVENING ASSOCIATED WITH SCATTERED CONVECTION. THIS OCCURRENCE IN MORE PROBABLE AT KGSO/KINT AND POSSIBLY KRDU. IN ADDITION...THERE MAY BE A HOUR OR TWO WINDOW OF IFR CONDITIONS EARLY WEDNESDAY MORNING ATTRIBUTED TO PATCHY FOG AND/OR LOW CLOUDS. THIS OCCURRENCE APPEARS MORE LIKELY AT KRWI AND POSSIBLY KFAY. OTHERWISE...CENTRAL NC WILL REMAIN IN A TYPICAL SUMMER PATTERN WITH VFR CONDITIONS INTERRUPTED BY BRIEF INSTANCES OF AFTERNOON-EVENING MVFR DUE TO CONVECTION...AND EARLY MORNING IFR CONDITIONS DUE TO PATCHY FOG AND LOW CLOUDS. AFTERNOON COVERAGE MAY BE ENHANCED FRIDAY AS A SFC FRONT DRIFTS SWD ACROSS THE REGION. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS/22 SHORT TERM...22 LONG TERM...RAH AVIATION...WSS

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