Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 151859 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 255 PM EDT TUE APR 15 2014 .SYNOPSIS...A STRONG COLD FRONT WILL CROSS THE AREA THROUGH EARLY EVENING. UNUSUALLY CHILLY HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE NORTH LATE TONIGHT THROUGH THURSDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1010 AM TUESDAY... HAVE JUST UPDATED THE FORECAST TO ACCOUNT FOR THE CONVECTIVE LINE NOW EXITING THE ERN CWA. LATEST SURFACE ANALYSIS SHOWS THE FRONT NOW ALONG THE NC MOUNTAINS AND EXPECT A STEADY EASTWARD PROGRESS THIS AFTERNOON... PROPELLED BY THE DENSITY OF THE ANOMALOUSLY COLD INCOMING AIR MASS AS WELL AS THE MID LEVEL TROUGH MOVING EAST OF THE MS RIVER VALLEY. A FEW ROTATING ELEMENTS AND SHORT SEGMENTS WITH ENHANCED WIND GUSTS WERE OBSERVED WITH THIS PRIMARY LINE OF CONVECTION... AND AS THIS DEPARTS ALONG WITH THE BETTER INSTABILITY... WE SHOULD SEE A BRIEF LULL WITHIN THE REARWARD SUBSIDENCE ZONE. BUT ADDITIONAL CONVECTION NOW OVER S/E GA AND SC SHOULD SPREAD UP INTO THE S/E CWA IN THE NEXT SEVERAL HOURS... AND THIS EXTRAPOLATION IS SUPPORTED BY RAP/HRRR GUIDANCE. INSTABILITY IS NOT PROJECTED TO BE PARTICULARLY STRONG WITH THIS (AROUND 250 J/KG POTENTIALL APPROACHING 500 J/KG) BUT WILL LIKELY BE ACCOMPANIED BY AN UPTICK IN LOW LEVEL SHEAR NEAR/EAST OF WHAT THE SHORT RANGE MODELS INDICATE WILL BE A PREFRONTAL WEAK SURFACE LOW... AND IN FACT THE RAP FORECAST SOUNDINGS SHOW A PERIOD OF CURVED HODOGRAPHS EARLY THIS AFTERNOON. THIS MAY POSE OUR BEST CHANCE FOR AN ADDITIONAL SEVERE WEATHER THREAT... IN THE FORM OF DAMAGING WINDS WITHIN BOWING SEGMENTS AND AN ISOLATED WEAK TORNADO... LARGELY EAST OF I-95 AS THIS IS WHERE THE SREF SHOWS THE BEST COMBINATION OF (MODEST) INSTABILITY AND DEEP LAYER SHEAR AHEAD OF THE FRONT. THE THREAT OF ANY STRONG STORMS SHOULD BE OVER (TO OUR EAST) BY 00Z. IN ANY CASE... MOST PLACES SHOULD SEE AN ADDITIONAL PERIOD OF SHOWERS (IF NOT STORMS) FROM LATE MORNING THROUGH MID/LATE AFTERNOON EITHER WITH THE ACTIVITY TO OUR SOUTH OR ALONG AND JUST BEHIND THE COLD FRONT. PW VALUES WILL REMAIN WELL ABOVE NORMAL... WITH ABUNDANT MOISTURE WITH DEW POINTS HOLD IN THE 60S TO LOWER 70S. LIFT WILL BE AUGMENTED BY UPPER DIVERGENCE IN THE RIGHT REAR QUAD OF THE SRLY JET STREAK TO OUR NNW. SO... AFTER A SHORT LULL WILL TREND POPS BACK UP FOR THIS AFTERNOON. ADJUSTED HOURLY TEMPS TOWARD THE GLAMP AND HRRR RAPID- UPDATE GUIDANCE... TO INDICATE FALLING TEMPS IN THE WEST THIS AFTERNOON. THIS YIELDS HIGHS FROM THE MID 60S WEST TO UPPER 70S EAST. -GIH MINIMAL ADJUSTMENT NEEDED FOR LOWS IN STRONG CAA TONIGHT...INTO THE 30 TO 37 DEGREE RANGE...COOLEST WEST. THE FREEZE WATCH HAS BEEN CONSEQUENTLY BE UPGRADED TO A WARNING. -MWS && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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AS OF 255 PM TUESDAY... WED AND WED NIGHT: RISING HEIGHTS ALOFT/DNVA AND ASSOCIATED STRONG SUBSIDENCE WILL RESULT IN FURTHER DEEP LAYER DRYING (SUNSHINE) WED...FOLLOWED BY GENERALLY NEUTRAL VERTICAL MOTION...BUT WITH A STILL STRONGLY CAPPED AND RESIDUALLY DRY REGIME OVER OUR REGION THROUGH WED NIGHT. BENEATH THE STRONG SUBSIDENCE ALOFT...SURFACE HIGH PRESSURE WILL CONSEQUENTLY BECOME UNSEASONABLY STRONG INTO THE 1040-1045 MB RANGE AS IT BUILDS FROM THE OH VALLEY TO NEW ENGLAND. COOL NORTHEASTERLY FLOW AND DRY ADIABATIC MIXING THROUGH 900 MB...WITH A COUPLE OF DEGREES ADDED TO ACCOUNT FOR A USUAL SLIGHT COOL BIAS WITH THIS TECHNIQUE LIKELY IN PART OWING TO A SUPER- ADIABATIC NEAR SURFACE LAYER...SUPPORTS HIGHS IN THE LOWER TO MIDDLE 50S. PROJECTED LOW LEVEL THICKNESS VALUES IN THE 1300-1310 METER RANGE AT 12Z THU...WITH OPTIMAL RADIATIONAL COOLING...WOULD SUPPORT MIDDLE 20S. HOWEVER...A PROJECTED 4-6 MB RISE IN MSL PRESSURE WITH THE STRENGTHENING HIGH WED NIGHT WILL LIKELY MAINTAIN A NORTHEASTERLY STIRRING FOR MOST AREAS OVERNIGHT...THOUGH WITH TYPICALLY COOLER/SHELTERED AREA LIKELY TO EXPERIENCE PERIODS OF CALM. IN ADDITION...MOISTURE ADVECTION IN NORTHEASTERLY FLOW BENEATH THE CAPPING INVERSION MAY RESULT IN SCT TO BKN LOW CLOUDS MAINLY IN THE COASTAL PLAIN LATE. AS SUCH...TEMPERATURES ARE APT TO DISPLAY A RELATIVELY LARGE RANGE...FROM 28-30 DEGREES IN RURAL WESTERN PIEDMONT LOCATIONS (IN CLOSEST PROXIMITY TO THE RIDGE AXIS) TO AROUND FREEZING IN URBAN AREAS FROM RDU WESTWARD TO THE TRIAD...TO 33-37 DEGREES IN THE COASTAL PLAIN AND EASTERN SANDHILLS. -MWS THURSDAY AND THURSDAY NIGHT... HIGH PRESSURE AND DRY AIRMASS WILL MEAN FAIR WEATHER FOR THURSDAY. HIGH CLOUDS WILL BE ON THE INCREASE LATE AS SW FLOW ALOFT INCREASES AHEAD OF THE SHORT WAVE CROSSING THE SOUTHERN PLAINS. WITH LOW LEVEL THICKNESSES REBOUNDING 30-40M FROM WEDNESDAY...LOOK FOR HIGHS IN THE MID 60S. STILL COOL THURSDAY NIGHT WITH LOWS 5-10 DEGREES BELOW NORMAL...RANGING FROM THE UPPER 30S TO LOWER 40S.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/...
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AS OF 255 PM TUESDAY... AT THE START OF FRIDAY...THE UPPER TROUGH WILL BE CROSSING THE MISSISSIPPI RIVER VALLEY. MEANWHILE...A SOUTHERN STREAM SHORTWAVE MOVING ACROSS THE NE GOMEX WILL MOVE TOWARD THE WESTERN ATLANTIC BY DAYS END. IN RESPONSE...SURFACE LOW PRESSURE WILL DEVELOP IN VICINITY OF THE GULF STREAM AND LIFT TO THE NE AS THE AFOREMENTIONED SHORT WAVE MOVES EAST. MEANWHILE...THE NORTHERN STREAM UPPER TROUGH AXIS WILL CROSS THE CAROLINAS BETWEEN 00-06Z SATURDAY. RIGHT NOW IT APPEARS THAT THESE SYSTEMS WILL HAVE LITTLE IMPACT ON OUR SENSIBLE WEATHER FRIDAY AND FRIDAY NIGHT...MAINLY BECAUSE...1) THE MOISTURE ASSOC WITH THE SYSTEM OFF THE COAST IS PROGGED TO REMAIN WELL TO OUR EAST...AND 2) THE NORTHERN TROUGH AXIS WILL MOVE ACROSS OUR AREA MOISTURE-STARVED...WITH THE BULK OF ITS MOISTURE REMAINING WELL TO OUR NORTH. THEN IN THE WAKE OF THE UPPER TROUGH AXIS AND SFC COLD FRONT PASSAGE SATURDAY MORNING...HIGH PRESSURE AND DRY AIRMASS WILL BUILD SOUTH ACROSS THE CAROLINAS AND PROVIDE FAIR AND SEASONABLE WEATHER FOR THE REST OF WEEKEND. UNSETTLED WEATHER MAY RETURN EARLY NEXT WEEK WITH A SHORT WAVE EMBEDDED IN THE NW FLOW MOVING ACROSS OUR AREA LATE MONDAY THROUGH MIDDAY TUESDAY.
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&& .AVIATION /18Z TUESDAY THROUGH SUNDAY/... AS OF 240 PM TUESDAY... ADVERSE AVIATION CONDITIONS WILL DOMINATE FOR THE NEXT 6-9 HOURS OR SO... FOLLOWED BY QUICK IMPROVEMENT TO VFR... BUT BRISK GUSTY WINDS WILL PERSIST. A COLD FRONT IS CURRENTLY MOVING THROUGH CENTRAL NC. PATCHY SHOWERS HAVE PRECEDED THIS FRONT ACROSS THE ENTIRE AREA IN RECENT HOURS... BUT ALONG AND JUST AHEAD OF THIS FRONT... A SOLID BAND OF HEAVY SHOWERS AND A FEW STORMS WILL SWEEP EASTWARD FROM NOW THROUGH ABOUT 03Z. CURRENT TAFS REFLECT THIS WITH A PERIOD OF IFR VSBYS AND MVFR TO IFR CIGS... AND STRONG GUSTY WINDS THROUGH LATE THIS AFTERNOON. WINDS WILL SHIFT SUDDENLY WITH FRONTAL PASSAGE... AS WINDS FROM THE SW SHIFT AROUND TO NW AND GUST UP TO 25-35 KTS... SO AVIATION INTERESTS SHOULD KEEP A CLOSE TAB ON THE FRONTAL POSITION IN THE NEXT SEVERAL HOURS. BETWEEN 02Z (WEST) AND 06Z (EAST)... CIGS ARE LIKELY TO RISE TO VFR WITH P6SM VSBYS AS SKIES CLEAR OUT. BRISK WINDS FROM NW WILL PERSIST THE REST OF TONIGHT... SUSTAINED NEAR 12- 18 KTS WITH A FEW GUSTS... THEN WILL SWING AROUND TO BE FROM THE NORTH AND EVENTUALLY NORTHEAST VERY LATE TONIGHT THROUGH WED MORNING... WITH VFR CONDITIONS LIKELY. LOOKING BEYOND 18Z WED... VFR CONDITIONS LIKELY THROUGH THU... ALTHOUGH THERE IS A CHANCE OF IFR CIGS WITH STRATUS AT FAY/RWI AS SURFACE WINDS SHIFT AROUND TO BE FROM THE SE AND BRING IN ATLANTIC LOW LEVEL MOISTURE. THIS CHANCE IS GREATER LATE THU NIGHT INTO FRI MORNING. A MID LEVEL TROUGH WILL MOVE THROUGH THE EASTERN US FRI THROUGH SAT... AND MAY BRING A PERIOD OF SUB-VFR CONDITIONS... BUT UNCERTAINTY IN THE DETAILS WITH THIS IS HIGH. -GIH && .CLIMATE... THE FOLLOWING ARE THE RECORD LOW TEMPERATURES FOR WED AND THU MORNING... AND THE RECORD LOW MAXIMUM TEMPERATURES FOR WED: WED 04/16 THU 04/17 LOW/YEAR LOW MAX/YEAR LOW/YEAR FAY: 28/1943 56/1950 31/1953 GSO: 25/1943 48/1929 29/1953 RDU: 28/1950 46/1890 29/1962 && .RAH WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR NCZ007>010- 021>026-038>041-073>077-083-084. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD/MWS SHORT TERM...MWS/KCP LONG TERM...NP AVIATION...HARTFIELD CLIMATE...MWS

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