Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 280554 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 153 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/... AS OF 925 PM MONDAY... DIURNALLY INDUCED CONVECTION IS BEGINNING TO DISSIPATE WITH THE EXCEPTION OF AN AREA OF PERSISTENT RAINFALL IN THE SOUTHWEST PIEDMONT COINCIDENT WITH TWO CONVERGING SURFACE BOUNDARIES...AIDED BY SOME DIVERGENCE ALOFT...AS SEEN CLEARLY IN THE WATER VAPOR IMAGERY. WHILE THIS ACTIVITY COULD PERSIST FOR A LITTLE WHILE...GENERALLY EXPECT IT TO WEAKEN OVER THE NEXT COUPLE OF HOURS. WHILE CENTRAL NC REMAINS ON THE BACK/FRONT SIDE OF AN UPPER LEVEL TROUGH/RIDGE...WATER VAPOR SHOWS ANOTHER SURGE OF DRY AIR ALOFT MAKING A SOUTHWARD PROGRESSION THROUGH VA AT THIS TIME. TO THE WEST OF THIS HOWEVER...A STEADY STREAM OF MOISTURE SHOULD CONTINUE TO FEED INTO THE WESTERN COUNTIES OF THE CWA. HIGH RESOLUTION MODELS WEAKEN CONVECTION THROUGH THE OVERNIGHT HOURS BUT THE HRRR HOLDS ONTO SOME RAINFALL IN THE SW PIEDMONT FOR LONGER THAN THE WRF SIMULATIONS WHICH IS NOT OUT OF THE QUESTION AT THIS POINT. WILL START TO SEE POCKETS OF FOG AND LOW STRATUS IN RAIN MOISTENED AREAS AS WELL AS POSSIBLY IN THE EASTERN COUNTIES CLOSER TO SUNRISE. LOW TEMPERATURES TONIGHT IN THE LOW TO MIDDLE 70S...COOLEST IN THE NE COUNTIES WHERE UPPER LEVEL CLOUDINESS MAY CEASE ONCE/IF DRY AIR ALOFT ARRIVES. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 325 PM MONDAY... A WEAK SFC TROUGH WILL REMAIN STALLED IN VICINITY OF THE WESTERN PIEDMONT. ALOFT...AN UPPER RIDGE CENTERED OVER THE SOUTHERN PLAINS BRIEFLY AMPLIFIES INTO THE WESTERN LAKES...VEERING FLOW ALOFT OVER CENTRAL NC TO A NWLY DIRECTION. WEAK PERTURBATIONS EMBEDDED IN THIS FLOW ALOFT INTERACTING WITH THE STALLED SFC TROUGH AND AVAILABLE MOISTURE/INSTABILITY SHOULD TRIGGER SCATTERED CONVECTION...MAINLY IN THE AFTERNOON AND EVENING HOURS. PROBABILITY OF SCATTERED CONVECTION APPEARS BEST IN VICINITY OF THE STALLED SFC TROUGH IN THE WESTERN PIEDMONT...AND IN VICINITY WHERE THE PERTURBATIONS ALOFT TRACK THROUGH THE REGION. THUS...POPS WILL VARY FROM SOLID CHANCE(SCATTERED) ACROSS THE NORTHERN PIEDMONT-NORTHERN COASTAL PLAIN TO SLIGHT CHANCE(ISOLATED)OVER THE FAR SOUTHERN COUNTIES. BULK OF CONVECTION WILL DIMINISH WITH LOSS OF HEATING TUESDAY EVENING THOUGH A FEW SHOWERS MAY OCCUR WELL INTO THE NIGHT DUE TO PERTURBATIONS IN THE NW FLOW ALOFT INTERACTING WITH THE MOISTURE RICH AIR MASS OVER OUR REGION. WHILE A STRONG OR SEVERE STORM CANNOT BE RULED OUT TUESDAY AFTERNOON...BULK OF CONVECTIVE PARAMETERS POINT TOWARD MOST OF THE STORMS REMAINING BELOW SEVERE CRITERIA. MAX TEMPS TUESDAY HIGHLY DEPENDENT ON EXTENT OF EARLY MORNING CLOUDS AND TIMING OF AFTERNOON CONVECTION. FAVORING PARTIAL SUN TO OCCUR FOR MOST OF THE LATE MORNING-EARLY AFTERNOON...BOOSTING TEMPS WELL INTO THE 80S-AROUND 90. IF LOW CLOUDS LINGER PAST NOON OR CONVECTION DEVELOP BY NOON-2 PM...THAN MAX TEMPS MAY END UP BEING 3-5 DEGREES COOLER THAN FORECAST. MIN TEMPS TUESDAY NIGHT 70-74. && .LONG TERM /WEDNESDAY 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/...
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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.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...ELLIS SHORT TERM...WSS LONG TERM...BSD AVIATION...22

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