Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 231456 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 950 AM EST SUN NOV 23 2014 .SYNOPSIS...A WARM FRONT WILL APPROACH THE REGION FROM THE SOUTH THIS MORNING...THEN SURGE NORTHWARD THROUGH THE CAROLINAS AND MID- ATLANTIC LATE TODAY INTO TONIGHT AS A LOW PRESSURE SYSTEM TRACKS NORTHEAST FROM THE LOWER MIDWEST TO THE GREAT LAKES. AN ASSOCIATED COLD FRONT WILL SWEEP EASTWARD THROUGH THE CAROLINAS MONDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 950 AM SUNDAY... HIGH PRESSURE OFFSHORE STILL EXTENDS ACROSS CENTRAL NC THIS MORNING...WITH STRENGTHENING SOUTHWESTERLY FLOW ALOFT AHEAD OF A LONGWAVE TROUGH OVER THE WEST-CENTRAL US. A VIGOROUS SHORTWAVE CURRENTLY OVER THE ARKLATEX REGION WILL BECOME NEGATIVELY TILTED THIS MORNING AND LIFT NORTHEAST TOWARD THE GREAT LAKES REGION. OUT OF AHEAD OF THIS WAVE...MOISTURE IS ON THE INCREAS OVER NC AND THE FIRST ROUND OF RAIN IS CURRENTLY MOVING THROUGH THE SOUTHERN PIEDMONT. RAINFALL AMOUNTS HAVE BEEN VERY LIGHT THUS FAR...LESS THAN A TENTH OF AN INCH...AS THE PRECIP ENCOUNTERS DEWPOINTS IN THE UPPER 20S TO LOWER 30S. A SLIGHTLY HEAVIER BAND ASSOCIATED WITH A REGION OF MID-LEVEL FGEN OVER SC WILL SPREAD IN THROUGH MIDDAY. AN IN-SITU CAD AIRMASS WILL DEVELOP AS THIS RAIN SPREADS NORTH THIS MORNING THROUGH EARLY AFTERNOON...WITH AREAS TO THE NORTHEAST LIKELY TO SEE A LITTLE BETTER WARMING PRIOR TO THE ONSET OF PRECIP BY 18Z. HAVE MADE SOME MINOR ADJUSTMENTS TO TEMPS TO REFLECT THE CURRENT RADAR TRENDS AND EXPECTED EXPANSION OF PRECIP. THERE MAY BE BIT OF A LULL IN RAIN AFTER 18Z...BEFORE A BETTER SURGE OF 295-300K ISENTROPIC LIFT ARRIVES ACROSS THE PIEDMONT AROUND 21Z. REGIONAL OBS SHOW THE SFC AND 850MB WARM FRONT STILL WELL TO OUR SOUTH OVER SOUTHERN AL/GA...SO INSTABILITY WILL BE ABSENT DURING THE DAY...WITH THE SMALL SEVERE THREAT TO EVOLVE LATER THIS EVENING. -BLS TONIGHT... THE 850 MB FRONT IS EXPECTED TO SURGE INTO AND ACROSS THE AREA THIS EVENING... WITH 850 MB SOUTHERLY WINDS OF AROUND 50 TO 70 KTS. AS THE SFC-850 MB WARM FRONT MOVES THROUGH THE AREA EXPECT WE COULD SEE A FEW ISOLATED EMBEDDED STORMS... WITH EVEN THE THREAT OF AN ISOLATED TORNADO ACROSS OUR FAR SOUTHEAST (SAMPSON/WAYNE... MAYBE CUMBERLAND AND WILSON AND EDGECOMBE) AS LOW LEVEL AND DEEP LAYER SHEAR WILL BE STRONG... WITH LARGE CYCLONIC LOOPING HODOGRAPHS... BUT INSTABILITY WILL BE MINIMAL TO NIL (BEST CHANCE OF SURFACE BASED INSTABILITY ACROSS OUR FAR SE/E). SPC DAY ONE OUTLOOK CLIPS OUR FAR EAST/SOUTHEAST WITH THE MARGINAL AREA... AND ONLY EXTREME SOUTHERN SAMPSON WITH THE SLIGHT RISK AREA. THE SMALL WINDOW FOR AN ISOLATED SEVERE STORM ACROSS OUR FAR EAST/SOUTHEAST WOULD BE FROM AROUND 00Z TO 04/05Z... WITH THE MAIN THREATS OF AN ISOLATED TORNADO AND/OR DAMAGING WIND GUST. MID LEVEL DRY AIR IS THEN FORECAST TO SURGE INTO OUR AREA... AS WARM FRONT LIFTS NORTH AND NORTHWEST OF OUR AREA. THUS... EXPECT TEMPS WILL RISE THIS EVENING INTO THE EARLY MORNING HOURS... THEN BECOMING STEADY. THUS... LOW TEMPS FOR THE OVERNIGHT PERIOD WILL ACROSS AT THE START OF THE OVERNIGHT. EXPECT TEMPS TO WARM INTO THE 60S AREAWIDE ACROSS THE AREA BY 12Z MONDAY. -BSD && .SHORT TERM /MONDAY AND MONDAY NIGHT/... AS OF 325 AM SUNDAY... ...WARM AND WINDY CONDITIONS ON MONDAY... MONDAY AND MONDAY NIGHT: DRYING AND SUBSIDENCE ALOFT IN THE WAKE OF THE EARLY MORNING MID/UPPER TROUGH PASSAGE TO THE NORTH WILL HELP TO MIX OUT LINGERING LOW CLOUDS AND FOG MONDAY MORNING. AS SFC TEMPS WARM MONDAY AFTERNOON AND LOW-LEVEL CONVERGENCE INCREASES WITH THE APPROACH OF THE FRONT...THERE IS A CHANCE FOR SOME CONVECTIVE RE- DEVELOPMENT OVER THE COASTAL PLAIN-EASTERN PIEDMONT MONDAY AFTERNOON IN AN AXIS OF LOWER TO MIDDLE 60S SURFACE DEWPOINTS. OTHERWISE...THE HEADLINES MONDAY WILL BE THE WARM TEMPERATURES AND STRONG WINDS LATE MORNING AND THROUGH THE AFTERNOON. SOUNDINGS OVER THE PAST COUPLE OF DAYS HAVE STEADILY TRENDED TOWARDS A DEEPER MIXED LAYER...TAPPING INTO THE STRONG WINDS ALOFT...WITH LATEST SOUNDINGS INDICATING 35- 40KTS RIGHT OFF THE DECK AND 45 TO 50KTS AT THE TOP OF THE MIXED LAYER. A WIND ADVISORY FOR MONDAY AFTERNOON MAY BE NEEDED IN LATER FORECASTS FOR SUSTAINED WINDS OF 20 TO 25 MPH...WITH GUSTS BETWEEN 35 AND 45 MPH. ADDITIONALLY...DOWNWARD MOMENTUM TRANSFER OF THESE STRONG WINDS WITH ANY CONVECTION THAT DEVELOPS MONDAY AFTERNOON COULD RESULT IN THUNDERSTORM WIND DAMAGE. HIGHS IN THE LOWER 70S NW TO MID/UPPER 70S SE. COLD AND DRY ADVECTION BEHIND THE COLD FRONTAL PASSAGE MONDAY EVENING/NIGHT WILL SUPPORT LOWS IN THE LOWER 40S NW TO LOWER 50S EAST. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 325 AM SUNDAY... TUESDAY THROUGH WEDNESDAY: A VIGOROUS SOUTHERN STREAM TROUGH EMBEDDED AT THE BASE OF THE POSITIVELY LONG WAVE TROUGH WILL TRAVERSE THE GULF COAST REGION ON TUESDAY AND THEN ACROSS THE SOUTHEAST AND MID-ATLANTIC WEDNESDAY-WEDNESDAY NIGHT. APPROACH OF THE SOUTHERN STREAM TROUGH WILL SPAWN SFC CYCLOGENESIS ALONG THE STALLED BAROCLINIC FRONTAL ZONE OFF THE SOUTHEAST COAST LATE TUESDAY- TUESDAY NIGHT AND WILL TRACK NORTH ALONG THE NC COAST ON WEDNESDAY AND UP THE MID-ATLANTIC AND INTO SOUTHERN NEW ENGLAND WEDNESDAY NIGHT. DURING THE MEANTIME...A TRANSITORY 1027 MB SURFACE HIGH PRESSURE WILL BUILD EASTWARD INTO THE MIDDLE ATLANTIC STATES TUE NIGHT. AFTER A DRY START TO THE DAY ON TUESDAY...RAIN CHANCES WILL RETURN TUESDAY EVENING/NIGHT AND INTO THE DAY ON WEDNESDAY AS WESTERN EDGE OF DEEPER MOISTURE AXIS ATTENDANT TO OFFSHORE FRONTAL ZONE RETREATS INLAND WITH DEEP LAYER FORCING OWING TO STRONG DPVA AND UPPER LEVEL DIVERGENCE WITHIN THE RIGHT ENTRANCE REGION OF A 140-150KT JETSTREAK. THE CANADIAN HAS STARTED TO CONVERGE TOWARDS THE WETTER GFS AND EC SOLUTIONS..WHILE THE NAM IS AN OUTLIER...KEEPING IT DRY WITH THE FRONTAL ZONE AND LOW PRESSURE WAVE FARTHER OFFSHORE. IT LOOKS TO BE A COLD RAIN FOR MOST OF CENTRAL NC WITH TEMPERATURES IN THE UPPER 30S AND LOWER 40S...WITH PARTIAL THICKNESSES SUGGESTING THE POTENTIAL FOR A LITTLE WET SNOW MIXING IN WITH THE RAIN OVER THE NW PIEDMONT. GIVEN THE MARGINALLY COLD THERMODYNAMIC PROFILES OWING TO THE TRANSITORY AND WEAK PARENT HIGH AND AND FREEZING LEVELS AROUND 1000 FT OVER THE PIEDMONT...NO ACCUMULATIONS ARE EXPECTED. FOR NOW WILL KEEP IT ALL RAIN ACROSS THE AREA. THURSDAY THROUGH SATURDAY: MEDIUM RANGE GUIDANCE HAS TRENDED SIGNIFICANTLY LESS AMPLIFIED WITH THE UPPER AIR PATTERN OVER THE CONUS. A MILDER/MORE MODIFIED HIGH PRESSURE OVER THE SOUTHEAST STATES AND POSSIBLY MORE IN THE WAY OF ZONAL FLOW ALOFT COULD KEEP CENTRAL NC ON THE SOUTHERN PERIPHERY OF THE ARCTIC AIRMASS TO THE NORTH. EXPECT DRY CONDITIONS WITH BELOW NORMAL TEMPERATURES...BUT JUST HOW FAR BELOW NORMAL WILL NEED TO BE RE-EVALUATED OVER THE NEXT COUPLE OF DAYS. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... AS OF 655 AM SUNDAY... LIGHT RAIN IS SLOWLY SPREADING NORTHWARD INTO CENTRAL NC THIS MORNING. HOWEVER... CIGS ARE EXPECTED TO SLOWLY LOWER THIS MORNING... GENERALLY REMAINING VFR THROUGH MID MORNING... OUTSIDE OF A BRIEF PERIOD OF MVFR CIGS AT KGSO/KINT. EXPECT THE RAIN WILL BECOME WIDESPREAD BY AFTERNOON... WITH SUB-VFR CIGS EXPECTED ACROSS ALL OF CENTRAL NC AS A LOW PRESSURE SYSTEM APPROACHES FROM THE SOUTHWEST. CIGS/VSBYS WILL GRADUALLY FALL INTO THE IFR/LIFR RANGE THROUGH THE AFTERNOON HOURS...AS PRECIP OVERSPREADS THE AREA FROM SOUTH TO NORTH. LLWS WILL ALSO BE POSSIBLE (ESPECIALLY AT KGSO/KINT) AS LOW LEVEL FLOW ATOP AN INITIAL COOL STABLE AIRMASS AT THE SURFACE INCREASINGS TO AROUND 50-55 KTS AT AROUND 2 KFT OUT OF THE SOUTH. HAVE LIMITED WS TO KGSO/KINT/KRDU AS ANY LOW LEVEL WIND SHEAR SHOULD END AS THE WARM FRONT MOVES THROUGH THE AREA... ALLOWING SURFACE WINDS TO BEGIN TO BECOME MORE SOUTHERLY AND INCREASE IN SPEED (10-15 KTS... WITH SOME GUSTS OF UP TO 17-20 KTS). OUTLOOK...CONDITIONS WILL IMPROVE SOME ON MONDAY AS DRIER AIR ALOFT MOVES IN FROM THE WEST...THOUGH LOW CEILINGS MAY LINGER AT EASTERN TERMINALS. THERE MAY ALSO BE SOME GUSTY SOUTHWESTERLY WINDS (GUSTS UP TO 35-40 MPH) MONDAY AFTERNOON AHEAD OF A COLD FRONT. BEYOND MONDAY..ANOTHER SYSTEM WILL IMPACT THE REGION BY MIDWEEK...THOUGH THERE IS SOME UNCERTAINTY AS TO HOW MUCH OF THE AREA WILL BE IMPACTED BY PRECIPITATION AND ADVERSE AVIATION CONDITIONS AS A SURFACE LOW MOVES ALONG THE EAST COAST. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BSD/VINCENT NEAR TERM...BSD/BLS SHORT TERM...CBL LONG TERM...CBL AVIATION...BSD/KRD

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