Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 280139 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 939 PM EDT MON JUL 27 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 /00Z TUESDAY THROUGH SATURDAY/... AS OF 815 PM MONDAY... LATEST RADAR TRENDS INDICATE BULK OF SHOWER ACTIVITY REMAINS ACROSS WESTERN NC...INVOF KGSO AND KINT...WITH HI-RES NWP MODELS INDICATING THE STORMS DIMINISHING BY 03Z. PER FCST SOUNDINGS AND STATISTICAL GUIDANCE...SOUTHEASTERN AREAS WILL SEE THE BEST CHANCE OF MORNING LOW CLOUDS/STRATUS...WITH CEILINGS AT KFAY EXPECTED TO LOWER TO IFR/LIFR. ADDITIONALLY...ANY AREAS THAT SEE HEAVY RAINFALL THIS EVENING COULD SEE LOCALLY DENSE FOG. ANY STRATUS/FOG SHOULD LIFT INTO A BROKEN FLAT CU LAYER BY MID-LATE MORNING. EXPECT MAINLY DIURNAL SCATTERED SHOWERS AND STORMS AGAIN TUESDAY AFTERNOON...WITH THE PIEDMONT AIRPORTS(KGSO/KINT/KRDU)ONCE AGAIN THE FAVORED AREAS. OUTLOOK: THE PROBABILITY FOR EARLY MORNING FOG AND STRATUS WILL REMAIN RELATIVELY HIGH THROUGH THE REMAINDER OF THE WEEK. ISOLATED TO SCATTERED SHOWERS AND STORMS WILL BE POSSIBLE EACH AFTERNOON/EARLY EVENING...WITH HIGHEST CHANCE POPS IN THE WEST THROUGH THURSDAY. THE BETTER RAIN CHANCES WILL SHIFT TO EASTERN AREAS ON FRIDAY AND INTO SATURDAY AS A WEAK SURFACE FRONT COULD POTENTIALLY STALL NEAR THE COAST. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...ELLIS SHORT TERM...WSS LONG TERM...BSD AVIATION...CBL

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