Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 280802 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 400 AM EDT TUE JUL 28 2015 .SYNOPSIS...A SERIES OF PERTURBATIONS ALOFT INTERACTING WITH A MOIST AND UNSTABLE AIR MASS WILL TRIGGER SCATTERED THUNDERSTORMS...MAINLY DURING THE AFTERNOON AND EVENING HOURS...THROUGH THE REMAINDER OF THE WORK WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 400 AM TUESDAY... NORTHWESTERLY FLOW ALOFT CONTINUES DOWNSTREAM OF THE SOUTHERN PLAINS CENTRAL U.S. RIDGE...WITH NUMEROUS ILL-DEFINED DISTURBANCES STREAMING ACROSS THE CENTRAL AND SOUTHERN APPALACHIANS. MOISTURE RECOVERY ALSO CONTINUES IN EARNEST AS PW HAS RECOVERED TO NEARLY 2 INCHES IN THE PAST 24 HOURS...WITH SOUTHEASTERLY FLOW BETWEEN A RIDGE AXIS ALONG THE MID-ATLANTIC COAST AND AN INVERTED TROUGH OFF THE SOUTHEAST COAST. DEWPOINTS IN THE LOWER 70S THIS MORNING AREN`T FORECAST DROP MUCH TODAY GIVEN WEAK BOUNDARY LAYER FLOW/MIXING...WHICH SHOULD YIELD SLIGHTLY BETTER INSTABILITY THAN YESTERDAY...WITH MLCAPE OF 1000-2000 J/KG PROJECTED ACROSS THE WESTERN/NORTHERN PIEDMONT AND LESSER AMOUNTS TO THE SOUTHEAST. DIFFERENTIAL HEATING..ALONG WITH THE AFOREMENTIONED DISTURBANCES ALOFT AND A WEAK LEE TROUGH WILL BE THE PRIMARY TRIGGERS...WHICH AGAIN FAVORS THE NORTHERN/WESTERN PIEDMONT FOR AFTERNOON STORMS THAT WILL HAVE A PRIMARY THREAT OF HEAVY RAIN AND LOCALIZED FLOODING GIVEN WEAK STEERING FLOW. HIGHS 89-94. 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.
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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
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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.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 245 PM MONDAY... MEDIUM RANGE MODELS ARE IN GENERAL AGREEMENT IN SHOWING A MID LEVEL RIDGE CENTERED ACROSS THE CENTRAL/SOUTHERN PLAINS AND LOWER MS RIVER VALLEY TO START THE PERIOD (WEDNESDAY)... THEN RETROGRADING IT WESTWARD ACROSS THE WESTERN U.S. BY LATE WEEK. THE MID LEVEL RIDGE IS FORECAST TO BUILD NORTH/NORTHWESTWARD AS IT RETROGRADES... HELPING TO AMPLIFY THE MID/UPPER LEVEL FLOW PATTERN ACROSS THE CONUS. THIS SHOULD YIELD BROAD MID LEVEL TROUGHING FOR CENTRAL NC LATE WEEK INTO EARLY NEXT WEEK... WITH A SURFACE COLD FRONT PUSHING INTO THE AREA FROM THE NORTH AND WEST LATE THURSDAY INTO FRIDAY. HOWEVER... THE STRONGER FLOW ALOFT WILL REMAIN TO THE NORTH OF CENTRAL NC... YIELDING GENERALLY WEAK DEEP LAYER SHEAR. QUESTIONS STILL REMAIN IF THE FRONT WILL PUSH THROUGH THE AREA OR SETTLE ACROSS SOUTHEASTERN PORTIONS OF CENTRAL NC... AND RESULTANT HOW LONG PRECIP CHANCES WILL CONTINUE ACROSS CENTRAL NC. FOR NOW WILL TO TREND THE FORECAST TOWARDS AN UNSETTLED PATTERN FOR LATE THURSDAY THROUGH SUNDAY... WITH THE POTENTIAL FOR HIGH MOISTURE CONTENT AIR TO ADVECT INTO THE FROM THE NORTHEASTERN GULF OF MEXICO ALONG WITH POTENTIALLY A FEW WEAK DISTURBANCES LIFTING NORTH-NORTHEASTWARD AND ACROSS SOUTH/EASTERN PORTIONS OF THE FA. HOWEVER... DEPENDING ON HOW FAR SOUTH AND EAST THE BOUNDARY MAKES IT WILL DETERMINE HOW MUCH OF THE AREA SEE A GOOD CHANCE FOR SHOWERS AND STORMS OVER THE WEEKEND... ALONG WITH THE POTENTIAL FOR HEAVY RAIN. THUS... WILL LIMIT POPS TO CHANCE FOR NOW BUT RAISE THEM A BIT... WITH THE HIGHEST POPS SOUTH/SOUTHEAST THIS WEEKEND. HIGH TEMPS AHEAD OF THE FRONT ON WEDNESDAY AND THURSDAY ARE EXPECTED TO BE NEAR NORMAL... GENERALLY AROUND 90 TO THE LOWER TO MID 90S. HIGH BEHIND THE FRONT WILL GENERALLY BE IN THE MID TO UPPER 80S... WITH A FEW LOCATIONS TOUCHING THE LOWER 90S... DEPENDING ON THE PRECIP. LOWS AHEAD OF THE FRONT AREA EXPECTED TO BE IN THE LOWER TO MID 70S. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... AS OF 150 AM TUESDAY... CONVECTION HAS DIMINISHED OVER CENTRAL NC AND THE ONLY REMAINING STORMS ARE NORTH OF THE NC-VA BORDER. THE REST OF THE NIGHT SHOULD BE QUIET WITH REGARDS TO CONVECTION...WITH STRATUS POSSIBLE IN A FAIRLY WELL ESTABLISHED SOUTHEASTERLY RETURN FLOW. GIVEN THIS RETURN FLOW AND LOW-LEVEL MOISTENING...ALONG WITH EARLIER CLUSTERS OF STORMS OVER THE WESTERN PIEDMONT...STRATUS MAY END UP BEING MORE WIDESPREAD WEST OF KRDU AND IMPACT KGSO/KINT. HOWEVER...THESE SIGNALS ARE MIXED IN MODEL GUIDANCE...AND CONFIDENCE IS STILL LOW GIVEN THE LACK OF DEVELOPMENT SO FAR. PATCHES OF HIGH CLOUDS WILL ALSO CONTINUE TO STREAMING FROM THE NORTHWEST...WITH SOME MVFR/IFR VSBYS POSSIBLE IN AREAS WHERE SKIES ARE CLEAR FOR AN EXTENDED AMOUNT OF TIME. WHAT STRATUS THAT FORMS WILL BURN OFF QUICKLY THIS MORNING AND SCATTERED STORMS WILL BE POSSIBLE AGAIN THIS AFTERNOON...WITH SLIGHTLY HIGHER CONFIDENCE IN STORMS IN THE VICINITY OF KGSO/KINT/KRDU. OUTLOOK: EARLY MORNING STRATUS AND/OR FOG WILL BE POSSIBLE WEDNESDAY AND THURSDAY WITH AFTERNOON STORMS...MAINLY WEST...EACH DAY. A COLD FRONT WILL THEN MOVE INTO THE AREA ON FRIDAY...POTENTIALLY STALLING OVER EASTERN NC THIS WEEKEND. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...22 SHORT TERM...22 LONG TERM...BSD AVIATION...22

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