Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 041917 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 318 PM EDT FRI SEP 4 2015 .SYNOPSIS...A BACK-DOOR 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 300 PM 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 RAIN/SLOW MOVING STORMS OWING TO HIGH PWS OF 0.75-1.8" AND WEAK WINDS ALOFT. THE PRESENCE OF WEAK LIFT/FORCING ALOFT COULD SUPPORT ISOLATED SHOWERS WELL INTO THE EARLY MORNING HOURS SATURDAY...ESPECIALLY ACROSS THE WESTERN PIEDMONT AS DRIER AIR ALOFT SPREADS INTO THE AREA FROM THE EAST. 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 318 PM FRIDAY... SHORTWAVE ENERGY EMBEDDED IN THE BROAD WEST-EAST ORIENTED MID/UPPER LEVEL TROUGHINESS EXTENDING FROM THE SOUTHEAST US INTO WESTERN ATLANTIC WILL PROVIDE THE FOCUS FOR MAINLY DIURNAL SCATTERED SHOWERS AS DEEP FETCH OF EASTERLY MARITIME FLOW KEEPS A SEASONABLY MOIST AIRMASS(1.5- 1.75")IN PLACE ACROSS CENTRAL NC. EXTENSIVE NELY LOW-LEVEL CLOUDINESS WILL KEEP TEMPERATURES AT OR JUST BELOW NORMAL. HIGHS RANGING FROM UPPER 70S NW TO LOWER/MID 80S SOUTHEAST. LOWS SATURDAY NIGHT IN THE MID TO UPPER 60S. && .LONG TERM /SUNDAY THROUGH FRIDAY/... AS OF 300 PM FRIDAY... TO START OFF THE PERIOD...A BROAD UPPER LOW WILL BE OVER THE SOUTHEAST U.S. AND AN UPPER HIGH WILL BE OVER THE NORTHERN MID ATLANTIC. AT THE SURFACE...HIGH PRESSURE WILL BE RIDGING DOWN THE SPINE OF THE MOUNTAINS. ALL OF THIS WILL RESULT IN DEEP NORTHEASTERLY FLOW OVER THE AREA WHICH WILL PUMP MOISTURE IN FROM THE ATLANTIC...WITH PWAT VALUES PROGGED TO HOVER AROUND 1.6-1.7 INCHES. THIS COMBINED WITH ANY WEAK UPPER DISTURANCES ROTATING AROUND THE BROAD UPPER LOW WILL LEAD TO FAIRLY EXTENSIVE CLOUD COVER AND SCATTERED SHOWERS AND THUNDERSTORMS...ESPECIALLY ACROSS THE EAST WHERE INSTABILITY WILL BE BETTER. BY MONDAY...THE PATTERN IS NOT EXPECTED TO CHANGE ALL THAT MUCH. ALTHOUGH...THE UPPER LOW WILL SLOWLY START TO SHIFT TO THE SOUTH/WEST...THUS LOSING OUR MOISTURE FEED. HOWEVER...ENOUGH RESIDUAL MOISTURE WILL BE AROUND FOR DIURNAL TYPE SHOWERS/STORMS. GIVEN ALL THE CLOUDS AND PRECIP CHANCES...TEMPS WILL BE HELD DOWN...WITH GENERALLY LOW/MID 80S ON SUNDAY AND A FEW DEGREES WARMER ON MONDAY. OVERNIGHT LOWS WILL BE IN THE MID/UPPER 60S. BY THE MIDDLE OF THE WEEK...THE AFOREMENTIONED UPPER LOW WILL SHIFT EVEN FURTHER TO THE SOUTH/WEST...WHILE THE BERMUDA HIGH WILL DRIFT TOWARDS THE SOUTHEAST COAST. AS A RESULT...DIURNAL TYPE CONVECTION WILL OCCUR EACH DAY...WHILE TEMPS RISE TO ABOVE NORMAL ONCE AGAIN (MID/UPPER 80S TO NEAR 90 DEGREES). MODELS THEN SHOW A UPPER TROUGH/FRONT APPROACHING THE AREA BY THE END OF THE WEEK. THEREFORE...PRECIP CHANCES WILL GRADUALLY INCREASE LATE THURSDAY INTO FRIDAY...ALTHOUGH WILL NOT GO TOO HIGH AT THIS TIME GIVEN THE TIMING WILL LIKELY CHANGE BETWEEN NOW AND THEN. && .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...CBL LONG TERM...WSS AVIATION...CBL

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