Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 310524 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 125 AM EDT THU JUL 31 2014 .SYNOPSIS...
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THE ATMOSPHERE ACROSS CENTRAL NC WILL BECOME VERY MOIST AND SLIGHTLY UNSTABLE. THIS WILL LEAD TO AN UNSETTLED WEATHER PATTERN FRIDAY...LASTING INTO THE WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 1015 PM WEDNESDAY... LOW LEVEL DEW POINTS HAVE COME UP INTO THE MID 60S (UP 10 DEGREES FROM 24 HOURS AGO)... AND CLOUDINESS HAS ALSO INCREASED AS WELL. THE MID AND HIGH CLOUDS ARE COURTESY OF THE UPPER JET. THE LOW LEVEL CLOUDINESS IS COURTESY OF THE INCREASE IN LOW LEVEL MOISTURE AND CONVERGENCE. THE CONVERGENCE IN RECENT HOURS HAS BECOME LIMITED TO THE LOCATIONS NEAR THE STATIONARY BOUNDARY OVER THE COASTAL PLAIN. EARLIER SHOWERS AND ISO THUNDERSTORMS HAVE DIED OFF. FOR THE REST OF THE NIGHT... EXPECT MOSTLY CLOUDY SKIES. LOWS GENERALLY IN THE LOWER TO MID 60S EXPECTED. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 245 PM WEDNESDAY... THE UPPER LEVEL TROUGH WILL REMAIN DRAPED ACROSS THE EASTERN CONUS ON THURSDAY. AT THE LOW LEVELS SOUTHERLY FLOW WILL BEGIN TO RETURN TO THE AREA...INCREASING MOISTURE IN THE SOUTHWESTERN CWA VIA RETURN FLOW. THIS PROCESS WILL TAKE A WHILE TO GET GOING HOWEVER AND MOST OF THE MORNING/EARLY AFTERNOON SHOULD REMAIN DRY WITH INCREASING CLOUD COVER FROM THE SOUTHWEST DURING THE DAY. AFTER 18Z...THE CHANCES FOR SHOWERS AND POTENTIALLY A THUNDERSTORM WILL INCREASE WITH MOST MODEL SIMULATIONS PRODUCING QPF BY 00Z FRIDAY AS PRECIPITABLE WATER VALUES BEGIN TO CLIMB TOWARDS TWO INCHES. INSTABILITY WILL BE VERY LIMITED THURSDAY AFTERNOON AND EVENING ALTHOUGH ABOUT 40 KTS OF BULK SHEAR WILL BE AVAILABLE. ANY SHOWERS/STORMS THAT DO COMMENCE THURSDAY AFTERNOON WILL HAVE A CHANCE OF CONTINUING THROUGH THE OVERNIGHT HOURS AS SOME ELEVATED INSTABILITY MAY BE PRESENT IN THE FORM OF A VORT MAX MOVING THROUGH ON THE EASTERN SIDE OF THE UPPER TROUGH FROM SOUTHWEST TO NORTHEAST. WITH INCREASE CLOUDS FROM THE SOUTHWEST...MAX TEMPS MAY BE HIGHEST IN THE NORTHEAST ON THURSDAY WITH TEMPS IN THE MID TO UPPER 80S AND ONLY LOWER 80S IN THE WEST AND SOUTHWEST. OVERNIGHT LOWS THURSDAY NIGHT WILL MODERATE INTO THE UPPER 60S. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... AS OF 315 PM WEDNESDAY... THE OVERALL PATTERN DURING THE LONG TERM PERIOD FEATURES AN EASTERN CONUS TROUGH AND A WESTERN U.S. RIDGE WHICH WILL SUPPORT NEAR OR COOLER THAN AVERAGE TEMPERATURES AND NEAR OR GREATER THAN NORMAL THREAT OF PRECIPITATION. THE BROAD EASTERN U.S. TROUGH SHARPENS ACROSS THE LOWER MISSISSIPPI VALLEY ON FRIDAY AND A STRENGTHENING INVERTED TROUGH/COASTAL FRONT DEVELOPS. AN INCREASINGLY MOIST ENVIRONMENT COMBINED WITH ISENTROPIC LIFT WILL PROMOTE A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS FRIDAY AFTERNOON AND EVENING THAT WILL LINGER BUT BECOME MORE SCATTERED FRIDAY NIGHT. THE UPPER TROUGH SHARPENS FURTHER OVER THE WEEKEND AS THE INVERTED TROUGH MOVES INLAND AND DEEP MOISTURE OVERSPREADS THE REGION. PRECIPITABLE WATER VALUES CLIMB TO AROUND OR JUST OVER 2 INCHES WHICH IS 2 STANDARD DEVIATIONS ABOVE CLIMATOLOGY DURING THE WEEKEND. THE AXIS OF GREATEST MOISTURE EXTENDING SOUTH-NORTHEAST ACROSS CENTRAL NC. NWP GUIDANCE ADVERTISE MULTIPLE DISTURBANCES IN THE SHARPENING UPPER TROUGH THAT WILL LIKELY ENHANCE PRECIPITATION COVERAGE AND INTENSITY ALTHOUGH IT IS DIFFICULT TO PIN POINT THE TIMING AND LOCATION AT THIS POINT. FOR NOW WILL INCLUDE LIKELY POPS FOR SATURDAY AND VERY HIGH CHANCE POPS FOR SUNDAY WITH THE GREATEST COVERAGE DURING THE AFTERNOON AND EVENING HOURS. BOTH THE GFS AND THE ECMWF SUGGEST A PORTION OF THE TROUGH WILL BREAK OFF AND MOVE ACROSS THE NORTHEAST ON MONDAY AND OFFSHORE TUESDAY WHILE A PORTION OF THE TOUGH LINGERS ACROSS THE LOWER MISSISSIPPI VALLEY. THIS SHOULD RESULT IN A DECREASE IN CONVECTIVE COVERAGE AND MORE TYPICAL CHANCES OF MAINLY AFTERNOON AND EVENING THUNDERSTORMS. ANOTHER DISTURBANCE DROPS INTO HE TROUGH ON WEDNESDAY BRING A COLD FRONT WITH IT THAT COULD ONCE AGAIN ENHANCE PRECIPITATION CHANCES FOR THE MID WEEK. HIGH TEMPS WILL GENERALLY RANGE IN THE UPPER 70S TO LOWER 80S ON FRIDAY THROUGH SUNDAY AN THEN MODERATE SLIGHTLY INTO THE LOWER TO MID 80S BY MID WEEK. MORNING LOWS WILL RANGE IN THE MID 60S TO NEAR 70 FOR MOST OF THE PERIOD. -BLAES && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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AS OF 120 AM THURSDAY... WHILE VFR CONDITIONS WILL PERSIST THROUGH THIS AFTERNOON...THERE MAY BE A BRIEF INSTANCE OF MVFR/IFR FOG BETWEEN 09Z-12Z IN THE VICINITY OF KRDU...KFAY AND KRWI. IN ADDITION...THERE MAY BE A PASSING SHOWER AND ASSOCIATED MVFR VISIBILITY IN THE KFAY VICINITY THROUGH 09Z OTHERWISE EXPECT MOSTLY CLOUDY SKIES ACROSS THE REGION THROUGH THURSDAY AFTERNOON THOUGH CLOUD BASES WILL REMAIN VFR. SURFACE WINDS WILL BE LIGHT AND VARIABLE. THERE WILL BE ISOLATED TO SCATTERED SHOWERS AND POSSIBLY A THUNDERSTORM DUE TO SURFACE HEATING AND A MARGINALLY MOIST AIR MASS. THE HIGHEST THREAT FOR THIS SCATTERED CONVECTION WILL BE SOUTH OF THE TRIAD TERMINALS AND WEST OF KFAY. FOR TONIGHT INTO MONDAY...EXPECT PERIODS OF ADVERSE AVIATION WEATHER CONDITIONS TO BEGIN LATER TONIGHT AS THE ATMOSPHERE OVER CENTRAL NC BECOMES INCREASINGLY MOIST AND UNSTABLE. A SERIES OF UPPER LEVEL DISTURBANCE WILL TRAVERSE THE REGION THROUGH MONDAY...CAUSING SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS. IN ADDITION...THERE WILL BE AN INCREASED PROBABILITY FOR PROLONGED MVFR-IFR CEILINGS.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...32 SHORT TERM...ELLIS LONG TERM...BLAES AVIATION...WSS

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