Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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648 FXUS62 KRAH 301750 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 150 PM EDT SAT APR 30 2016 .SYNOPSIS... A STATIONARY FRONT --WITH COOL AND CLOUDY CONDITIONS TO THE NORTH...AND MUCH WARMER ONES TO THE SOUTH-- WILL REMAIN OVER SOUTHERN AND SOUTHWESTERN NC TODAY. THE FRONT AND ASSOCIATED FOLLOWING WARMER TEMPERATURES WILL RETREAT NORTH ACROSS THE MIDDLE ATLANTIC STATES LATE TONIGHT AND ESPECIALLY SUNDAY. WARM SOUTHWESTERLY FLOW WILL THEN RESULT THROUGH MONDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1050 AM SATURDAY... MAIN FORECAST CHALLENGE FOR THIS AFTERNOON CENTERS ON TEMPERATURES. LOW LEVEL ELY FLOW HAS ADVECTED A COOL MOIST STABLE AIR MASS INTO CENTRAL NC WITH LOW CLOUDS CURRENTLY COVERING THE AREA. 12Z UPPER AIR ANALYSIS DEPICTS A S/W RIDGE OVER THE REGION. SUBSIDENCE ASSOCIATED WITH THIS FEATURE WILL TRAP/CONFINE THE LOW LEVEL MOISTURE SO ANY EROSION WILL BE LIMITED TO THE FAR SOUTHERN-SW SECTIONS OF OUR CWA. THIS...IN TURN WILL YIELD A WIDE VARIANCE IN MAX TEMPS...POTENTIALLY RANGING FROM THE LOW-MID 60S ACROSS THE NORTHERN PIEDMONT TO THE MID 70S ACROSS THE FAR SOUTH. IF PARTIAL SUN DEVELOPS SOONER THAN EXPECTED OVER THE SOUTHERN PIEDMONT...TEMPS MAY BE ABLE TO REACH 80. ASIDE FROM A STRAY PATCH OF DRIZZLE...MOST OF CENTRAL NC CAN EXPECT DRY CONDITIONS THROUGH MID-LATE AFTERNOON. AFTER 18Z...AND MORE SO AFTER 20Z...COULD SEE SCATTERED SHOWERS/ISOLATED T-STORMS MOVE INTO OUR FAR WESTERN-SW COUNTIES IN VICINITY OF A STALLED BOUNDARY WHICH IS PROJECTED TO RETREAT NWD AS A WARM FRONT TONIGHT. EFFECTIVE BULK SHEAR PRETTY ANEMIC ACROSS THIS REGION AND ATMOSPHERE PROJECTED TO ONLY BECOME SLIGHTLY UNSTABLE THIS AFTERNOON. THUS...POTENTIAL FOR A STRONG/SEVERE STORMS ALONG A SOUTH OF A LEXINGTON TO LAURINBURG LINE CURRENTLY LOOKING PRETTY SLIM. WILL CONTINUE TO MONITOR. -WSS TONIGHT: NOCTURNAL COOLING OF THE ALREADY STABLE SURFACE LAYER WILL CAUSE LOW CLOUD BASES TO FURTHER LOWER/RE-DEVELOP WHERE ANY BREAKS MAY OCCUR ALONG THE EDGES THIS AFTERNOON. THE REMAINS OF UPSTREAM CONVECTION...AND AN ASSOCIATED MID-LEVEL DISTURBANCE...WILL MOVE INTO THE WESTERN HALF OF THE RAN FORECAST AREA LATE THIS EVENING- EARLY TONIGHT...BUT CONTINUED DOWNSTREAM RIDGING AND STATIC STABILITY OVER THE EASTERN PART OF THE STATE WILL LIMIT THE EASTWARD PROGRESS. AS SUCH...SHOWERS WILL BE LIKELY OVER THE WESTERN PIEDMONT...SOME POSSIBLY ACCOMPANIED BY A FEW RUMBLES OF THUNDER LATE OWING TO MIXING/BOUNDARY LAYER DESTABILIZATION...WITH JUST A SLIGHT CHANCE OF SHOWERS IN THE I-95 CORRIDOR AND POINTS EAST. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 350 AM SATURDAY... A PORTION OF THE COMPLEX UPPER LOW OVER THE WESTERN US WILL EJECT EASTWARD AND RACE ACROSS LOWER GREAT LAKES ON SUNDAY...SHUNTING THE SHORTWAVE RIDGE OVER THE SOUTHEAST US OFFSHORE. MEANWHILE...THE FRONTAL ZONE LINGERING OVER CENTRAL NC TODAY WILL RETREAT NORTHWARD IN TO THE MID-ATLANTIC REGION. ONGOING OVER SHOWERS OVER WESTERN NC...OWING TO SOUTHEASTERLY LOW-LEVEL FLOW AND WEAK HEIGHT FALLS ALOFT...WILL LIKELY BLEED INTO THE WESTERN PIEDMONT SUNDAY MORNING...THOUGH WITHOUT BETTER SUPPORT ALOFT THE COVERAGE OF SHOWERS AND STORMS IS A LITTLE UNCERTAIN WITH EASTWARD EXTENT SUNDAY AFTERNOON. NAM/GFS FORECAST SOUNDINGS SHOW MODEST STEEPENING OF MID- LEVEL LAPSE RATES AND MLCAPE POSSIBLY REACHING 1000-1500 J/KG CAPE AMIDST PW OF 1.25-1.50". CAPE GENERALLY APPEARS TO BE HIGHER IN THE WEST..THOUGH THE DEGREE OF SURFACE HEATING IS UNCERTAIN GIVEN THE AFOREMENTIONED MORNING PRECIP/CLOUD COVER. DEEP LAYER SHEAR IS MODEST...30-35KT ACROSS THE NORTH IN CLOSER TO PROXIMITY TO THE SHORTWAVE CROSSING THE GREAT LAKES AND STRONGER MID-LEVEL FLOW. THE MAIN LIMITATION FOR SEVERE WEATHER APPEARS TO BE A LACK OF A FOCUS...OUTSIDE IF A RIPPLE IN THE FLOW ALOFT. THUS..ITS HEARD TO HAVE MORE THAN CHANCE POPS AT THIS POINT...WITH LOW CONFIDENCE IN ANY SEVERE STORMS. HIGHS IN THE MID 70S NW TO AROUND 80 SE. THE NAM AND GFS INDICATE AT LEAST A CHANCE OF LINGERING SHOWERS INT HE COASTAL PLAIN SUNDAY NIGHT AS THE DEEP LAYER FLOW VEERS TO MORE WESTERLY AND DEEP MOISTURE SHIFTS EASTWARD. LOWS 61-68 WEST TO EAST. && .LONG TERM /MONDAY THROUGH FRIDAY/... AS OF 350 AM SATURDAY... DEEP LAYER FLOW WILL BECOME MORE WEST-SOUTHWESTERLY ON MONDAY AS DISTURBANCES CONTINUE TO TRACK FROM THE CENTRAL PLAINS TO THROUGH THE OH VALLEY. MID-LEVEL DRYING AND STRONGER BL MIXING WILL LIMIT INSTABILITY ACROSS THE NORTHERN/WESTERN PIEDMONT...FOCUSING SCATTERED SHOWERS AND STORMS TO SOUTHERN PIEDMONT AN COASTAL PLAIN. MONDAY AFTERNOON. HOWEVER...A COLD FRONT WILL APPROACH FROM THE NORTHWEST LATE MONDAY...OFFERING A BETTER FOCUS FOR CONVECTION MONDAY NIGHT AND INTO TUESDAY...DEPENDING ON HOW FAR SOUTH THE FRONT SETTLES. FORECAST CONFIDENCE THEN FALLS FOR THE MID TO LATE WEEK PERIOD AS RIDGE BUILDS OVER THE WESTERN US AND SHORTWAVES DROPPING SOUTH OUT OF CANADA RESULT INTO A DEEP TROUGH OVER THE EASTERN US. THE EVENTUAL AMPLITUDE OF THE TROUGH IS UNCERTAIN...BUT THE EC ENSEMBLE SUGGESTS 2-3 STD BELOW NORMAL OVER THE DEEP SOUTH AND THE OPERATIONAL GFS SETTLES AN UPPER LOW OVER THE CAROLINAS BY THE END OF THE WEEK. THIS PATTERN SUGGESTS PERIODS OF SHOWERS WILL CONTINUE TO BE POSSIBLE...WITH A SURFACE LOW LIKELY TO DEVELOP OFF THE SOUTHEAST COAST BY THURSDAY...AND DAILY HIGHS AT LEAST A COUPLE CATEGORIES BELOW NORMAL...IF NOT MORE. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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AS OF 150 PM SATURDAY... WIDESPREAD MVFR CONDITIONS DUE TO CEILINGS WILL PERSIST THROUGH 00Z WITH POCKETS OF IFR CEILINGS PROBABLE IN VICINITY OF THE TRIAD TERMINALS. NOW APPEARS THAT ANY SHOWERS/ISOLATED T-STORMS WILL BE CONFINED TO OUR FAR WESTERN-SW COUNTIES. A STRAY SHOWER MAY SKIRT CLOSE TO KINT BUT CONFIDENCE NOT HIGH ENOUGH TO MENTION IN THE TERMINAL FORECAST UNTIL LATER TONIGHT. CEILINGS WILL LIKELY LOWER LATER TONIGHT RESULTING IN WIDESPREAD IFR CEILINGS. ANY AREAS OF RAIN SHOULD BE CONFINED TO THE WESTERN-NW PIEDMONT THOUGH NOW APPEARS THAT PRECIP INTENSITY WILL BE RELATIVELY LIGHT. A WARM FRONT WILL DRIFT NWD ACROSS CENTRAL NC LATER TONIGHT THROUGH EARLY SUNDAY. WINDS WILL VEER QUICKLY FROM AN EAST-SE DIRECTION AT THE SFC TO A SSW FLOW A COUPLE THOUSAND FEET OFF THE SURFACE. THE LOW LEVEL JET WILL REACH SPEEDS OF 30-35KTS...POSSIBLY APPROACHING 40KTS IN VICINITY OF KINT/KGSO AFTER 09Z. THIS WILL NEED TO BE MONITORED FOR A POSSIBLE INCLUSION OF LLWS IN THE TAF. BREEZY SW SFC WINDS PROBABLE SUNDAY AFTERNOON THOUGH CEILINGS WILL IMPROVE TO THE LOW END OF VFR PARAMETERS. AFTERNOON HEATING OF THE MOIST AND SLIGHTLY UNSTABLE AIR MASS WILL TRIGGER SCATTERED SHOWERS AND A FEW STORMS SUNDAY AFTERNOON-EVENING. AN UNSETTLED WEATHER PATTERN MONDAY THROUGH THURSDAY IS EXPECTED TO RESULT IN VARIABLE AVIATION CONDITIONS. IT IS HIGHLY PROBABLE THAT PERIODS OF MVFR/IFR PARAMETERS WILL OCCUR DUE TO CEILINGS...IN ADDITION TO SCATTERED CONVECTION.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...WSS/26 SHORT TERM...22 LONG TERM...22 AVIATION...WSS

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