Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 240007 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 806 PM EDT WED JUL 23 2014 .SYNOPSIS...A COLD FRONT WILL MOVE THROUGH THE OHIO VALLEY OVERNIGHT...AND GRADUALLY MOVE SOUTHEAST THROUGH MUCH OF THE REGION THURSDAY AND THURSDAY NIGHT. THE FRONT STALLS AND WEAKENS NEAR THE SOUTH CAROLINA BORDER FRIDAY. WEAK HIGH PRESSURE WILL BE LOCATED NORTH OF THE FRONT FRIDAY INTO EARLY SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 315 PM WEDNESDAY... TEMPS WERE HAMPERED EARLY IN AREAS ACROSS THE SOUTH WHERE SHOWERS WERE A LITTLE MORE WIDESPREAD DURING THE VERY EARLY AFTERNOON...BUT WILL SHOW SOME REBOUND AS THE CLOUDS SCATTER OUT. THE ISOLATED TO WIDELY SCATTERED CONVECTION LINGERING THIS AFTERNOON WILL WANE QUICKLY WITH LOSS OF ISOLATION...AND WILL BE TRIMMING POPS TO SLIGHT CHANCE WITH SKIES BECOMING MOSTLY CLEAR THROUGH MIDNIGHT. EXPECT INCREASING CLOUDS AFTER MIDNIGHT IN THE WEST WHERE MOISTURE IN THE LIGHT SOUTHWEST FLOW WILL BE POOLING IN THE COOLING AIRMASS ALONG THE SURFACE TROF. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... AS OF 315 PM WEDNESDAY... THE COLD FRONT WILL REACH THE MOUNTAINS TOWARDS SUNRISE...WITH SHOWERS AND THUNDERSTORMS SPREADING INTO THE WESTERN PIEDMONT BY MID MORNING... AND ACROSS THE REMAINDER OF THE AREA THROUGH AFTERNOON. THE FRONT WILL BE MOVING ACROSS THE AREA IN A FAVORABLE DIURNAL TIME FRAME CONCURRENT WITH BETTER SUPPORT FROM ALOFT AS MID AND UPPER FLOW STRENGTHENS WITH THE ASSOCIATED UPPER TROF PIVOTING ACROSS THE AREA. UPPER DIFFLUENCE IS ESPECIALLY IMPRESSIVE...AS WE WILL BE UNDER THE FAVORABLE ENTRANCE OF AN 80-90KT JET LIFTING OUT OF THE TROF. MID LEVEL LAPSE RATES WILL BE PRETTY WEAK...GENERALLY <5.5K...WITH INSTABILITY RANGING FROM ~1K JOULES WEST WHERE HIGHS WILL BE HAMPERED BY CLOUD COVERAGE...TO >1.5K EAST. RISK OF SEVERE IS NOT IMPRESSIVE...WITH UNIDIRECTIONAL DEEP SHEAR OF 25KTS... BUT THE CHANCE OF TRAINING STORMS WILL PRODUCE A FLOOD THREAT...ESPECIALLY IN THE EAST AS THE FRONT WILL BE SLOWING BY LATE AFTERNOON. WILL HAVE LIKELY POPS IN THE WEST BY 15Z...SPREADING TO THE REMAINDER OF THE AREA BY 18Z. HIGHS WILL RANGE FROM MID 80S NORTHWEST TO 90-92 IN THE SOUTHEAST. THE UPPER TROF WILL BE BLOCKED BY HIGH PRESSURE OFFSHORE...AND THE COLD FRONT WILL CORRESPONDINGLY SLOW AND THEN STALL AS IT REACHES THE COAST FRIDAY MORNING. AS SUCH...POPS WILL FALL OFF TO SLIGHT CHANCE WEST OF I95 BY MIDNIGHT...WITH LINGERING CHANCES IN THE EAST THROUGH MORNING. MODEST FLOW OF COOLER AND DRIER AIR INTO THE NORTHWEST WILL PRODUCE OVERNIGHT MINS IN THE MID 60S...WITH MINS OVER THE EAST STILL IN THE LOW 70S. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... AS OF 235 PM WEDNESDAY... NWP GUIDANCE IS RELATIVELY CONSISTENT IN BRINGING THE SURFACE COLD FRONT TO THE COASTAL PLAIN OF THE CAROLINAS BY 12 UTC FRIDAY AS THE UPPER LEVEL TROUGH AXIS CROSSES THE APPALACHIANS. THE UPPER LEVEL TROUGH AXIS MAKES LIMITED PROGRESS EAST ON FRIDAY AS THE NEXT SHORTWAVE TROUGH OVER THE OH VALLEY EARLY FRIDAY SPLITS WITH ONE PIECE OF ENERGY MOVING EAST INTO THE NORTHEAST AND THE OTHER DROPS TOWARD THE SAVANNAH RIVER VALLEY. THE FRONT DRIFTS SOUTH AND BRIEFLY STALLS BEFORE MOVING NORTH INTO THE MID ATLANTIC AS A WARM FRONT SATURDAY. DEEP MOISTURE DECREASES ON FRIDAY COMPARED TO THURSDAY WITH THE BULK OF THE MOISTURE CONFINED TO THE 925 TO 700 MB LAYER IN A REGION OF RELATIVELY STEEP LAPSE RATES. THIS PATTERN SUGGESTS THE BEST CONVECTIVE COVERAGE ON FRIDAY WILL BE ACROSS THE FAR SOUTHEAST PIEDMONT AND ESPECIALLY THE COASTAL PLAIN AND EASTERN SANDHILLS FRIDAY AFTERNOON AND EVENING. POPS IN THE SLIGHT CHANCE TO LOW CHANCE RANGE SHOULD SUFFICE. HIGHS ON FRIDAY WILL RANGE IN THE MID TO UPPER 80S. PARTLY CLOUDY SKIES ARE EXPECTED FRIDAY NIGHT WITH LOWS IN THE MID 60S TO NEAR 70. SATURDAY WILL FEATURE PARTLY CLOUDY SKIES WITH THE BULK OF THE CONVECTION SUPPRESSED TOWARD THE COAST. THERE IS JUST A LIMITED THREAT OF PRECIPITATION IN CENTRAL NC WITH THE BEST CHANCE OF STORMS ON SATURDAY ACROSS THE EASTERN COASTAL PLAIN WITH ONLY SLIGHT CHANCE POPS WARRANTED. SATURDAY SHOULD FEATURE THE FAIRER WEATHER OF THE WEEKEND WITH VERY LIMITED PRECIPITATION COVERAGE AND NEAR SEASONABLE TEMPERATURES. TEMPERATURES WILL MODERATE A BIT ON SATURDAY WITH HIGHS IN THE 87 TO 92 RANGE. THE NEXT UPPER TROUGH APPROACHES FROM THE NORTHWEST ON SUNDAY WITH A COLD FRONT DROPPING ACROSS THE OH VALLEY. A LEE TROUGH AHEAD OF THE FRONT ACROSS THE PIEDMONT OF VA AND THE CAROLINAS IS EXPECTED TO BECOME CONVECTIVELY ACTIVE DURING THE AFTERNOON AND EVENING WITH SCATTERED CONVECTION. THE SOUTHERLY FLOW AHEAD OF THE UPPER TROUGH... COMBINED WITH DEEP MIXING WILL RESULT IN HIGHS IN THE LOWER 90S. THE UPPER TROUGH AXIS AND COLD FRONT WILL CROSS CENTRAL NC ON MONDAY WITH GOOD CONVECTIVE COVERAGE ANTICIPATED. WILL INCREASE POPS INTO THE HIGH CHANCE RANGE. WITH THE APPROACHING TROUGH...THE LOW AND MID LEVEL FLOW INCREASES WITH BULK SHEAR VALUES OF 30-40 KTS EXPECTED SUGGESTING SOME HIGH-BASED STORM ORGANIZATION IS POSSIBLE. SLIGHTLY COOLER TEMPERATURES ARE EXPECTED ON MONDAY WITH THE CLOUD COVER AND PRECIPITATION...HIGHS SHOULD RANGE IN THE 86 TO 91 RANGE WITH LOWS MONDAY MORNING IN THE 69 TO 74 RANGE. THE LARGE AMPLITUDE UPPER LEVEL TROUGH SLOWLY MOVES EAST ON TUESDAY WITH THE COLD FRONT PROGGED TO MOVE INTO THE COASTAL PLAIN MONDAY NIGHT AND SLOWLY PUSH TOWARD THE COAST ON TUESDAY. COOL HIGH PRESSURE BUILDS INTO THE REGION WITH ANY PRECIPITATION ON TUESDAY LIKELY CONFINED TO THE COASTAL PLAIN AND POINTS EAST. MAINLY DRY CONDITIONS ARE EXPECTED ON WEDNESDAY BUT IT IS WORTH NOTING THAT THE GFS/ECMWF BOTH INDICATE THE STALLED FRONT NEAR THE COAST MAY TRY TO WORK WEST. FOR NOW WILL INCLUDE A DRY FORECAST. THE MUCH COOLER AIR MASS WITH LOW LEVEL THICKNESS VALUES FALLING INTO THE 1375-1390M RANGE FOR TUESDAY AND WEDNESDAY MORNINGS. THIS WOULD SUPPORT LOWS IN THE 60S AND PERHAPS UPPER 50S IN THE TRIAD OR NEAR THE VA BORDER ON WEDNESDAY MORNING WITH HIGHS OF 79-86. -BLAES && .AVIATION /00Z THURSDAY THROUGH MONDAY/... AS OF 804 PM WEDNESDAY... REMAINING ISOLATED SHOWERS AND THUNDERSTORMS ARE DIMINISHING ACROSS THE REGION WITH THE LOSS OF HEATING. FOG IS POSSIBLE AT KRWI AND KFAY... AND MAY BRING A BRIEF PERIOD OF MVFR CONDITIONS NEAR SUNRISE. SHOWERS AND THUNDERSTORMS WILL BEGIN TO DEVELOP ACROSS THE AREA AFTER 15Z AHEAD OF AN APPROACHING COLD FRONT... WHICH WILL CROSS THE AREA DURING THE DAY AND APPROACH THE NC COAST BY 06Z FRIDAY. WINDS WILL BECOME NORTHWESTERLY BEHIND THE FRONT. THERE WILL BE LINGERING CONVECTION IN THE FAY AREA FRIDAY...OTHERWISE VFR CONDITIONS WILL PREVAIL THROUGH SATURDAY WHEN OUR NEXT FRONT WILL BE APPROACHING FROM THE WEST. THIS FRONT WILL PRODUCE INCREASING CHANCES FOR CONVECTION ON SUNDAY...BUT ESPECIALLY ON MONDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS..DJF NEAR TERM...MLM SHORT TERM...MLM LONG TERM...BLAES AVIATION...SEC/MLM

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