Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 041805 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 204 PM EDT FRI SEP 4 2015 .SYNOPSIS...A BACKDOOR COLD FRONT WILL APPROACH FROM THE NORTH LATE TODAY...THEN PUSH SOUTHWARD THROUGH THE AREA TONIGHT...BEFORE SETTLING TO OUR SOUTH ON SATURDAY. HIGH PRESSURE WILL EXTEND INTO THE REGION FROM THE NORTH OVER THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1058 AM FRIDAY... A WEAK COLD FRONT OVER THE MID-ATLANTIC STATES WILL DROP SOUTH INTO THE AREA LATE THIS EVENING. MOISTURE FLUX CONVERGENCE ALONG THE FRONT COUPLED WITH WEAK SHORTWAVE IMPULSES EMBEDDED ON THE BACK SLIDE OF THE DEPARTING SHORTWAVE TROUGH OFF THE SOUTHEAST COAST WILL SUPPORT SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND THROUGH THE EVENING. DESPITE MODERATE INSTABILITY OF 1500-2000 J/KG OF MUCAPE...DEEP LAYER SHEAR REMAINS VERY WEAK...LESS THAN 10 KTS. THUS...EXPECT A NON-ZERO SEVERE THREAT. THE MAIN THREAT FROM ANY STORM WILL BE LOCALLY HEAVY/SLOW MOVING STORMS OWING TO HIGH PWS OF 1.75-1.8" AND WEAK WIND ALOFT. THE PRESENCE OF WEAK LIFT/FORCING ALOFT COULD SUPPORT ISOLATED SHOWERS INTO THE EARLY MORNING HOURS SATURDAY...MAINLY ACROSS THE WESTERN PIEDMONT AS DRIER AIR ALOFT SPREADS INTO THE AREA FROM THE EAST. EXPECT ONE MORE DAY OF WARM ABOVE-NORMAL TEMPERATURES IN ADVANCE OF THE BACK-DOOR FRONT LATER THIS EVENING. HIGHS IN THE UPPER 80S TO LOWER 90S. NELY LOW-LEVEL FLOW AS SURFACE HIGH PRESSURE RIDGES SOUTH DOWN THE MID-ATLANTIC REGION COULD SUPPORT AREAS STRATUS OVERNIGHT. LOWS IN THE MID 60S TO AROUND 70. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 325 AM FRIDAY... SURFACE HIGH PRESSURE WILL BUILD/EXTEND SOUTHWARD INTO THE REGION ON SATURDAY AND SATURDAY NIGHT... WITH A FAIRLY DEEP NORTHEAST TO EASTERLY FLOW AS THE SURFACE FRONT SETTLES TO THE SOUTH OF CENTRAL NC. THIS SHOULD YIELD A RATHER CLOUDY PERIOD... WITH THE POTENTIAL FOR SOME SCATTERED SHOWERS AND PERHAPS A FEW ISOLATED STORMS AS A WEAK MID LEVEL LOW IS FORECAST TO LINGER JUST TO THE SOUTH OF CENTRAL NC. WILL GO ON THE COOL SIDE OF GUIDANCE GIVEN THE CAD-LIKE SURFACE PATTERN AND CLOUD COVER... WITH HIGH TEMPS SATURDAY EXPECTED TO RANGE FROM THE UPPER 70S NW TO THE MID 80S SE. MORE OF THE SAME IS EXPECTED ON SATURDAY NIGHT... WITH LOW TEMPS BY SUNDAY MORNING IN THE MID TO UPPER 60S. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 325 AM FRIDAY... AT THE BEGINNING OF THE PERIOD...THE UPPER AIR PATTERN WILL FEATURE A WEAK UPPER LEVEL LOW OVER THE SE U.S. COAST AND AN UPPER LEVEL HIGH OVER THE NORTHERN MID ATLANTIC. AT THE SURFACE...A RIDGE OF HIGH PRESSURE WILL ALIGN FAIRLY CLOSE TO THE APPALACHIANS. THIS SET-UP WILL SUPPORT A FAIRLY DEEP E-NE FLOW OVER CENTRAL NC. THIS FETCH ORIGINATES OFF THE ATLANTIC...SO APPEARS THAT WE WILL HAVE A DECENT SUPPLY OF MOISTURE FLOWING INTO OUR AREA. THIS SUGGEST AN ENHANCED POTENTIAL FOR EXTENSIVE CLOUD COVER ON SUNDAY...POSSIBLY CONTINUING INTO MONDAY. MODEL GUIDANCE HAS BEEN FAIRLY CONSISTENT IN ITS DEPICTION OF A WEAK UPPER LEVEL DISTURBANCE MOVING ONSHORE EARLY SUNDAY THEN DRIFTING WEST-SW SUNDAY AFTERNOON-SUNDAY NIGHT. THIS FEATURE INTERACTING WITH AVAILABLE MOISTURE AND MODEST INSTABILITY MAY SUPPORT A FEW SHOWERS AND ISOLATED T-STORMS BY SUNDAY AFTERNOON. AIR MASS TO THE WEST-NW OF RALEIGH MAY BE QUITE STABLE...SO CHARACTER OF PRECIP MAY BE MORE STRATIFORM RATHER THAN SHOWERY. PATTERN CHANGES LITTLE FOR MONDAY THOUGH MAY START TO SEE A SOUTHWESTWARD DRIFT TO THE UPPER LEVEL LOW AND AN EVENTUAL WEAKENING OF THE MOISTURE FEED OFF THE ATLANTIC. ALSO...DIFFICULT TO DISCERN ANY NOTABLE FEATURE ALOFT TO ORGANIZE OR ENHANCE PRECIP ACTIVITY. THUS...EXPECT SHOWER COVERAGE TO BE LESS MONDAY COMPARED TO SUNDAY. AFTERNOON TEMPS SUNDAY AND MONDAY WILL AVERAGE SLIGHTLY BELOW NORMAL. IF CLOUDS/PRECIP MORE EXTENSIVE THAN CURRENT THINKING...MUCH OF THE PIEDMONT WILL STRUGGLE TO REACH 80 DEGREES SUNDAY. MAX TEMPS SUNDAY 80 NW TO LOW-MID 80S EAST-SE...AND LOWER 80S NW TO MID 80S EAST-SE MONDAY. MIN TEMPS IN THE 60S. THE UPPER LEVEL LOW RETROGRADES WEST-SW THROUGH MID WEEK. THIS ALLOWS THE BERMUDA HIGH TO RE-ASSERT ITSELF INTO THE SE U.S. THIS SUGGEST A RETURN TO MORE LATE SUMMER CONDITIONS WITH CONVECTIVE ACTIVITY MAINLY DRIVEN BY DIURNAL HEATING AND AFTERNOON TEMPS 3-6 DEGREES ABOVE NORMAL. EXPECT THE WARMEST/HOTTEST DAYS TO OCCUR WEDNESDAY AND THURSDAY. AN APPROACHING S/W IN THE NORTHERN STREAM MAY BRING AN INCREASED THREAT FOR SHOWERS AND T-STORMS LATE THURSDAY INTO FRIDAY. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AS OF 204 PM FRIDAY... 24 HR TAF PERIOD: A WEAK UPPER LEVEL DISTURBANCE COUPLED WITH THE APPROACH OF A BACKDOOR COLD FRONT WILL SUPPORT SCATTERED TO NUMEROUS SHOWERS AND STORMS ACROSS THE AREA THIS AFTERNOON AND EVENING. BRIEF PERIOD OF IFR TO MVFR CONDITIONS WILL BE POSSIBLE WITH THE STRONGER STORMS. WHILE COVERAGE/POPS SHOULD DECREASE AFTER SUNSET...ISOLATED SHOWERS WILL BE POSSIBLE WELL INTO THE OVERNIGHT HOURS...ESPECIALLY NEAR WESTERN TERMINALS(KINT AND KGSO). NELY FLOW IN THE WAKE OF THE BACK-DOOR COLD FRONT PASSAGE WILL SUPPORT WIDESPREAD STRATUS LATE TONIGHT AND INTO THE DAY ON SATURDAY. CEILINGS ARE EXPECTED TO IMPROVE SLOWLY ON SATURDAY...LIFTING TO LOW END VFR BY THE LATE MORNING/EARLY AFTERNOON. OUTLOOK: DEEP FETCH OF EASTERLY MARITIME FLOW WILL SUPPORT EARLY MORNING STRATUS AND SCATTERED SHOWERS AND STORMS THROUGH THE WEEKEND. RAIN CHANCES SHOULD BECOME MORE CENTRALIZED TOWARD THE COASTAL PLAIN MONDAY THROUGH WEDNESDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BSD/26 NEAR TERM...CBL SHORT TERM...BSD LONG TERM...WSS AVIATION...CBL

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