Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 011912 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 310 PM EDT MON JUN 1 2015 .SYNOPSIS...A MID LEVEL LOW PRESSURE TROUGH AND SURFACE COLD FRONT OVER THE TENNESSEE VALLEY WILL MOVE SLOWLY EASTWARD THEN STALL OVER THE CAROLINAS THROUGH THE WORK WEEK... BRINGING UNSETTLED WEATHER. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1045 AM MONDAY... QUICK UPDATE TO ACCOUNT FOR MORNING OBSERVATIONAL DATA AND SOME OF THE LATEST CONVECTION ALLOWING MODEL GUIDANCE. LATEST VISIBLE SATELLITE IMAGERY SHOWS MAINLY SUNNY SKIES ACROSS ALL OF CENTRAL NC OUTSIDE OF THE TRIAD WHERE A FEW SHOWERS HAVE SKIRTED BY THIS MORNING. WATER VAPOR IMAGERY SHOWS A PLUME OF GULF AND CARIBBEAN MOISTURE STREAMING INTO THE SOUTHERN APPALACHIANS AND DEEP SOUTH. CONVECTION ALLOWING GUIDANCE SUGGESTS THAT ISOLATED CONVECTION ACROSS THE WESTERN PIEDMONT WILL SLOWLY INCREASE IN COVERAGE DURING THE AFTERNOON AND MOVE SLOWLY NORTHEAST AS THE WHOLE AREA TRENDS EASTWARD TOWARD EVENING. CONVECTIVE COVERAGE ACROSS THE COASTAL PLAIN SHOULD BE VERY LIMITED TODAY. PREVIOUS FORECAST HAD A GOOD HANDLE ON THE COVERAGE AND TIMING OF THE POPS...WE ADDED SOME DETAIL USING A BLEND OF THE CAMS THROUGH TONIGHT. SPC HAS CENTRAL NC IN THE MARGINAL RISK FOR TODAY AND TONIGHT. WHILE INSTABILITY INCREASES DURING THE DAY WITH MLCAPE VALUES RANGING UP TO 500-1000 J/KG...BULK SHEAR VALUES WILL ONLY RANGE BETWEEN 10-15KTS...PERHAPS SLIGHTLY MORE NEAR THE VA BORDER SO ORGANIZED CONVECTION IS NOT LIKELY. LOCALLY HEAVY RAIN IS POSSIBLE AND GIVEN SLOW STORM MOTION...AMOUNTS COULD BE EXCESSIVE IN AN ISOLATED SPOT OR TWO. THE KGSO RAOB HAD A LOW-LEVEL THICKNESS VALUE OF 1404M WHICH WAS 8M WARMER THAN YESTERDAY AT THIS TIME. GIVEN A GOOD DEAL OF SUNSHINE THIS MORNING...HAVE ADJUSTED TEMPS UPWARD A DEGREE OR SO WITH HIGHS RANGING IN THE 86 TO 91 RANGE. -BLAES TONIGHT...BULK OF SCATTERED CONVECTION WILL DISSIPATE WITHIN A COUPLE HOURS OF SUNSET. HOWEVER...PERSISTENT LOW LEVEL SLY FLOW AND WEAK PERTURBATIONS ALOFT SUGGEST A FEW RANDOM SHOWERS POSSIBLE AT ANYTIME...MAINLY OVER THE PIEDMONT. OVERNIGHT TEMPS IN THE MID-UPPER 60S. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 320 AM MONDAY... UPEPR LEVEL LOW OVER THE TN VALLEY WILL DRIFT SLOWLY EAST. THE CIRCULATION AROUND THIS FEATURE ALONG WITH THE MID-UPPER LEVEL RIDGE OFFSHORE WILL MAINTAIN A DEEP SLY FLOW OVER CENTRAL NC. PRECIP WATER VALUES PROJECTED TO BE AS HIGH AS 1.8-1.9 INCHES IN OUR VICINITY BY TUESDAY AFTERNOON. THIS VERY MOIST AIR MASS COUPLED WITH A SERIES OF VORTICITY MAXIMA ALOFT AND THE APPROACH OF A SFC COLD FRONT TIED TO THE NORTHERN STREAM S/W WHICH WILL CROSS NEW ENGLAND-MID ATLANTIC TUESDAY AND TUESDAY NIGHT WILL INCREASE THE THREAT FOR SCATTERED/NUMEROUS SHOWERS AND STORMS OVER MUCH OF CENTRAL NC...ESPECIALLY TUESDAY AFTERNOON AND TUESDAY NIGHT. THE DEEP SOUTHERLY FLOW SUGGEST THE POTENTIAL FOR POSSIBLE TRAINING OF CONVECTION AS THE STEERING FLOW IS CONSIDERED WEAK (LESS THAN 20KTS). SINCE ANTECEDENT CONDITIONS ARE DRY...NOT ANTICIPATING ANY WIDESPREAD FLOODING ISSUES AT THIS TIME. HOWEVER...IF TRAINING OCCURS OVER URBANIZED AREAS...LOCALIZED NUISANCE FLOODING A DEFINITE POSSIBILITY. WILL HAVE POPS STARTING OUT IN THE CHANCE-SLIGHT CHANCE CATEGORIES IN THE MORNING...RAMPING UP TO LIKELY OVER THE NW PIEDMONT BY AFTERNOON....AND SOLID CHANCE OVER THE SE COUNTIES. BY TUESDAY EVENING...SURFACE FRONT WILL BE IN VICINITY OF THE VA BORDER AND EDGE SWD WITH TIME INTO OUR NORTHERN COUNTIES. THIS FEATURE INTERACTING WITH AVAILABLE MOISTURE AND SOME SUPPORT ALOFT WILL MAINTAIN SCATTERED TO NUMEROUS SHOWERS AND A FEW STORMS WELL INTO TUESDAY NIGHT. EXTENSIVE CLOUDINESS AND EXPECTED EARLIER COMMENCEMENT OF CONVECTION WILL RESULT IN HIGH TEMPS TUESDAY ONE-TWO CATEGORIES COOLER COMPARED TO TODAY. MAX TEMPS NEAR 80 NW TO THE MID 80S SOUTH AND EAST. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... AS OF 310 PM MONDAY... WET WEATHER WILL CONTINUE THROUGH WED. THE MID LEVEL LOW OVER ERN TN EARLY IN THE DAY WILL CONTINUE A VERY SLOW WOBBLE TO THE EAST DURING THE DAY... AS A LOBE OF VORTICITY ROTATES NORTHWARD THROUGH CENTRAL NC. PW VALUES WILL REMAIN ELEVATED (150-180% OF NORMAL) WITH A CONFLUENT LOW LEVEL ATLANTIC-SOURCE FLOW AND AT LEAST MODERATE UPPER DIVERGENCE AS WEAK JETLETS ROTATE ABOUT THE UPPER LOW. LATEST MODEL RUNS SHOW THE FRONT DROPPING INTO FAR NRN AND NW NC EARLY WED MORNING... WHICH SHOULD HELP FOCUS RAINFALL. MARGINAL INSTABILITY PERSISTS WITH PROJECTIONS OF 500-1000 J/KG OF MUCAPE MAINLY IN THE SW CWA. THE COMBO OF MOISTURE/LIFT/INSTABILITY SUPPORTS RETAINING LIKELY POPS (AND IF TRENDS CONTINUE THESE SHOULD GO UP TO CATEGORICAL IN LATER FORECASTS). RAIN TOTALS MAY BE LOCALLY HEAVY WITH POSSIBLE TRAINING CONVECTIVE ELEMENTS. ADJUSTMENT BY EARLIER SHIFTS OF TAKING WED MAX TEMPS DOWN ESPECIALLY N AND NW OF THE FRONT (NW CWA) LOOKS GOOD AND WILL STAY THAT COURSE... WITH HIGHS FROM THE LOWER 70S NW TO LOWER 80S SE... IN LINE WITH STATISTICAL GUIDANCE. THERE MAY BE A SLIGHT BIT OF DRYING (MARGINALLY LOWER PW AND A LULL IN DPVA) ROTATING ABOUT THE LOW AND WORKING INTO THE SW CWA WED NIGHT... BUT WITH PW STILL ABOVE NORMAL AND THE SURFACE WEDGE FRONTAL ZONE IN PLACE... WILL KEEP A CHANCE OF SHOWERS IN OVERNIGHT. LOWS 61-66 NW TO SE. MORE OF THE SAME THU WITH THE SYNOPTIC CONFIGURATION SIMILAR TO WED... EXCEPT THE MID LEVEL LOW TO OUR WEST WILL HAVE DRIFTED SLIGHTLY CLOSER... INTO FAR WRN NC. INSTABILITY MAY BE A TAD HIGHER (750-1500 J/KG AREAWIDE ON THE GFS) WITH SIMILAR WEAK DPVA... UPPER DIVERGENCE... PW 150-180% OF NORMAL... AND ONSHORE-DIRECTED LOW LEVEL FLOW FOCUSED ALONG THE FRONTAL ZONE. EXPECT ANOTHER ROUND OF NUMEROUS SHOWERS AND EMBEDDED STORMS... PEAKING IN THE AFTERNOON AND EVENING. THICKNESSES ARE EXPECTED TO BE 10 M BELOW NORMAL... AND FACTORING IN THE CLOUDS AND PRECIP... PREFER TO KEEP HIGHS BELOW NORMAL (MID 70S TO MID 80S)... AND EVEN THESE MAY BE TOO HIGH IN THE NW HALF OF THE CWA. WILL TREND PRECIP CHANCES DOWN BUT NOT OUT THU NIGHT AS THE BY-NOW-WEAKENING UPPER LOW STARTS TO SHIFT OVERHEAD. LOWS IN THE MID 60S. COOLER-THAN-NORMAL WEATHER IS LIKELY TO EXTEND INTO FRI... BUT MODERATING SLOWLY AS WE GO THROUGH THE SAT-MON TIME FRAME. THE UPPER LOW WILL OPEN UP AND WEAKEN TO A BAGGY TROUGH WHILE CONTINUING AN EASTWARD DRIFT OFF THE MIDATLANTIC COAST... HOWEVER THIS TROUGH AXIS IN THE MEAN MAY LINGER OVER OUR AREA THROUGH MON... AS WEAK ENERGY MAY DROP IN FROM THE NW TO RELOAD THE TROUGH OVERHEAD. THE ECMWF IS MORE ROBUST WITH THIS... RESULTING IN ANOTHER CLOSED LOW OVER THE CAROLINAS SUN INTO MON... WHILE THE GFS IS MUCH LESS AMPLIFIED... FOCUSING INSTEAD ON STRONG NRN STREAM TROUGHING DEVELOPING OVER SOUTH CENTRAL CANADA INTO THE UPPER MIDWEST. THE GFS HAS BEEN SLIGHTLY MORE CONSISTENT BUT OTHERWISE THERE IS NO CLEAR INDICATION OF WHICH SOLUTION IS MORE LIKELY. THE FRONTAL ZONE SHOULD HOLD IN PLACE (WITH NOTHING TO MOVE IT OUT) YET CONTINUE TO SLOWLY WASH OUT WITH TIME... AND THE GFS KEEPS PW VALUES ABOVE NORMAL. SO WITH WEAK (BUT NON-ZERO) FORCING FOR ASCENT AND ABOVE NORMAL MOISTURE IN PLACE WITH LIMITED FOCUS... WE SHOULD SEE DAILY SHOWERS AND STORMS... NEAR OR JUST ABOVE CLIMATOLOGICAL COVERAGE. WILL HAVE TEMPS SLIGHTLY BELOW NORMAL FRI... RISING BACK TOWARD NORMAL BY MON. -GIH && .AVIATION /18Z MONDAY THROUGH SATURDAY/... AS OF 100 PM MONDAY... VFR CONDITIONS WILL PERSIST THROUGH AT LEAST 06Z TONIGHT AT ALL CENTRAL NC SITES. THERE IS A CHANCE OF SUB-VFR (LIKELY IFR/LIFR) CIGS BETWEEN 08Z AND 13Z TONIGHT/TUE MORNING AT RDU/RWI/FAY... ALTHOUGH CONFIDENCE IS LOWER THAN USUAL DUE TO LACK OF AGREEMENT AMONG THE MODELS REGARDING STRATUS FORMATION. ANY SUB-VFR CIGS WILL LIFT/MIX OUT TO VFR BY 15Z TUE. SCATTERED STORMS ARE MOST PROBABLY NEAR INT/GSO THIS AFTERNOON/EARLY EVENING (17Z-23Z)... TRENDING TOWARD RDU THIS EVENING (23Z-04Z)... WHICH MAY CAUSE A BRIEF DROP IN VSBYS TO MVFR/IFR AND IN CIGS TO MVFR... BUT THESE CONDITIONS WILL NOT BE PREVAILING. BETTER CHANCE OF SHOWERS/STORMS FORMING EARLIER TUE... TOWARD THE END OF THE TAF VALID PERIOD AT 15Z-18Z. WINDS GENERALLY LIGHT FROM SOUTH OR SW EXCEPT IN/NEAR STORMS. LOOKING BEYOND 18Z TUE: THE MORE NUMEROUS SHOWERS/STORMS TUE AFTERNOON AND INTO THE NIGHT WILL MEAN A BETTER CHANCE OF BRIEF SUB- VFR CIGS/VSBYS AT ALL SITES... HOWEVER OUTSIDE OF SHOWERS/STORMS WE SHOULD HAVE VFR CONDITIONS TUE. A COLD FRONT DROPPING IN FROM THE NORTH TUE NIGHT INTO EARLY WED WILL BRING A GOOD CHANCE OF IFR/LIFR STRATUS AFTER 06Z TUE NIGHT... WITH AT LEAST MVFR IF NOT IFR CONDITIONS LASTING THROUGH MUCH OF WED WITH NUMEROUS SHOWERS AND ISOLATED STORMS. IFR CONDITIONS LIKELY BOTH WED NIGHT AND THU NIGHT MAINLY AT INT/GSO/RDU/RWI... NEAR A LINGERING FRONTAL ZONE... RISING SLOWLY TO MVFR EACH MORNING. SLIGHTLY DRIER AIR IS EXPECTED BY SAT... SUGGESTING VFR CONDITIONS WILL AGAIN PREVAIL. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...BLAES/WSS SHORT TERM...WSS LONG TERM...HARTFIELD AVIATION...HARTFIELD

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