Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 040256 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 955 PM EST TUE MAR 3 2015 .SYNOPSIS...HIGH PRESSURE AND ASSOCIATED COLD AIR DAMMING WILL REMAIN UNTIL A WARM FRONT RETREATS NORTH ACROSS CENTRAL NC ON WEDNESDAY. MEANWHILE...A STRONG COLD FRONT WILL APPROACH FROM THE NORTHWEST...THEN MOVE THROUGH THE AREA LATE WED NIGHT THROUGH EARLY THU. && .NEAR TERM /TONIGHT/...
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AS OF 955 PM TUESDAY... THE COOL AND STABLE COLD AIR DAMMING AIRMASS IS FIRMLY WEDGED IN ACROSS THE REGION...REACHING AS FAR SOUTH CENTRAL GEORGIA...WITH HIGH PRESSURE CENTERED OVER SOUTHEASTERN NC. IN THE ABSENCE OF AN EROSION MECHANISM AND WITH STRONG SOUTHWESTERLY FLOW ABOVE THE COLD DOME MAINTAINING THE STRONG STABILITY...THE AIRMASS IS LIKELY TO REMAIN UNCHANGED OVERNIGHT. 12Z MODELS WERE ALL TOO WARM AT 00Z...SOME BY AS MUCH AS 10 DEGREES OR MORE...AND MANY 18Z RUNS WERE ARE STILL TO WARM. THE NAM...AND SUBSEQUENTLY OUR LOCAL WRF- ARW...HAVE THE BEST HANDLE ON TEMPS...SO WILL LEAN HEAVILY ON THOSE. EXPECT THE WARM FRONT TO BEGIN TO MIX ITS WAY INLAND AFTER MIDNIGHT...THOUGH IT MAY NOT REACH THE I-95 CORRIDOR UNTIL AROUND 12Z AS TEMPS HOLD IN THE MID 30S TO AROUND 40. MEANWHILE...THE SETUP IS GOOD FOR DENSE FOG AFTER MIDNIGHT ONCE A FINAL SURGE OF DEEPER ISENTROPIC LIFT AND ASSOCIATED BATCH OF LIGHT RAIN DEPARTS THE NORTHERN COASTAL PLAIN. HOWEVER...A LIGHT SOUTHWEST WIND MAY CONTINUE OVERNIGHT GIVEN THAT THE HIGH IS CENTERED TO OUR SOUTHEAST...SO ITS UNCERTAIN HOW QUICKLY THE CURRENT LOW CEILINGS WILL SETTLE TO THE SURFACE. WILL HOLD OFF ON A DENSE FOG ADVISORY FOR NOW...BUT EXPECT THAT ONE WILL BE NEEDED AFTER MIDNIGHT AND MAY CONTINUE WELL INTO THE DAY ON WEDNESDAY.
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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 300 PM TUESDAY... WEDNESDAY: INSOLATION FROM THE HIGHER SOLAR SUN ANGLE AND BL MIXING VIA STRONG 40-45KT H8 SOUTHWEST FLOW WILL SCOUR OUT ANY LINGERING SHALLOW WEDGE AIRMASS WITH CENTRAL NC FIRMLY IN THE WARM SECTOR...SOUTH OF THE COLD FRONT SETTLING INTO THE TN VALLEY. GUIDANCE OVERCAST LOW CLOUDS WILL BECOME SCT/BKN BY AFTERNOON...WITH BREEZY SOUTHWESTERLY WINDS DEVELOPING AS THE BL WARMS AND DEEPENS. SUSTAINED WINDS OF 15 TO 20KTS WITH GUSTS AS HIGH AS 30-35KTS ARE EXPECTED AS TEMPERATURES RISE INTO THE UPPER 60S NW TO MID 70S ACROSS THE SOUTH. ONCE THE WEDGE MIXES OUT...FORCING LOOKS LARGELY ABSENT UNTIL THE ARRIVAL OF THE BACK-DOOR COLD FRONT INTO THE AREA BETWEEN 06 TO 12Z WITH VERY LITTLE DESTABILIZATION INDICATED...SO EXPECT MOSTLY DRY CONDITIONS WEDNESDAY AFTERNOON. WEDNESDAY NIGHT: A STRONG COLD FRONT WILL DROP SOUTH INTO THE AREA IN BACK-DOOR FASHION DURING THE PREDAWN HOURS. AS A WAVE DEVELOPS ALONG THE FRONT...ANA-FRONTAL PRECIP WILL SPREAD SOUTH INTO THE AREA. THERE IS STILL SOME MINOR TIMING ISSUES WITH THE TIMING OF THE FRONT AND PRECIP INTO THE NORTHERN AREAS...WITH THE NAM BEING A BIT SLOWER THAN THE GFS AND EC...BUT EXPECT CATEGORICAL POPS BY DAYBREAK FROM HIGHWAY 64 NORTH...MAKING FOR A MESSY MORNING COMMUTE FOR THE TRIAD AND TRIANGLE. EXPECT QUITE A SHARP NORTH-SOUTH CONTRAST IN TEMPERATURES...RANGING FROM LOWER 40S TO LOWER 60S. && .LONG TERM /THURSDAY THROUGH TUESDAY/... AS OF 300 PM TUESDAY... THURSDAY AND THURSDAY NIGHT: BY 12Z ON THURSDAY...PRECIPIATION ASSOCIATED WITH THE APPROACHING COLD FRONT WILL HAVE WORKED INTO NORTHERN SECTIONS OF THE CWA. AT THIS TIME ALL MODELS ARE HINTING AT THE FORMATION OF A SMALL MESO-LOW FORMING OVER UPSTATE SOUTH CAROLINA. THIS COULD ACT TO TEMPORARILY INCREASE PRECIPITATION OVER CENTRAL NC DURING THE DAYTIME HOURS AS FLOW BECOMES MORE SOUTHEASTERLY AND LOW LEVEL CONVERGENCE INCREASES. THIS FEATURE WILL QUICKLY ADVECT AWAY BY THURSDAY NIGHT. THE MAIN COLD FRONT HOWEVER WILL LINGER OVER THE AREA WITH A SOUTHWEST TO NORTHEAST ORIENTATION AS THE UPPER LEVEL TROUGH REALLY LAGS BACK OVER THE CENTRAL PLAINS ON THURSDAY AND THE REAL DRIVING FORCE PUSHING IT THROUGH WILL BE A SURFACE HIGH BACK ACROSS THE TENNESSEE VALLEY. THE EXTREMELY WARM TEMPERATURES FROM WEDNESDAY WILL QUICKLY COME CRASHING BACK TO REALITY AS TEMPERATURES DROP THROUGH THE DAY IN THE NORTH AND ONLY RISE BRIEFLY IN THE SOUTH BEFORE THE FRONT PASSES AND TEMPERATURES EVENTUALLY DROP BACK BELOW FREEZING THURSDAY NIGHT. THE COLD AIRMASS WILL BE CHASING THE PRECIPITATION AND AT LEAST IN SECTION NORTH OF HIGHWAY 64 THERE IS A GOOD CHANCE FOR A WINTRY MIX OF PRECIPITATION AT THE END OF THE EVENT THURSDAY NIGHT. PRIMARY TIMING WOULD BE BETWEEN 00Z AND 06Z WITH SLEET THE MOST LIKELY FROZEN PRECIPITATION TYPE. NORTHEASTERN COUNTIES MAY ALSO SEE A BRIEF PERIOD OF FREEZING RAIN AT THE INITIAL TRANSITION AROUND 00Z BUT THEN ALSO CHANGING OVER TO SLEET. FORECAST SOUNDINGS SUPPORT THIS WITH A VERY WARM NOSE INITIALLY AS TEMPERATURES AT THE SURFACE DROP BELOW FREEZING AT THE SURFACE. THIS WARM NOSE WILL ERODE RATHER QUICKLY AND JUST BELOW THAT AN EQUALLY STRONG COLD NOSE DEVELOPS...SUGGESTING THAT ANY REMAINING PRECIPITATION WILL REFREEZE PRIOR TO HITTING THE SURFACE. THE GOOD NEWS IS THAT MOST SREF MEMBERS POINTING TO THE VAST MAJORITY OF PRECIPITATION ENDING PRIOR TO THE CHANGEOVER TO FREEZING P-TYPES. AS A RESULT NO ICE ACCUMULATION AND VERY LITTLE SLEET ACCUMULATION IS EXPECTED...ESPECIALLY WHEN FACTORING IN VERY WARM GROUND TEMPERATURES FROM WEDNESDAY. MOST PRECIPITATION SHOULD WORK ITS WAY OUT OF THE AREA AROUND OR JUST AFTER 6Z. FRIDAY THROUGH SUNDAY NIGHT: THE WEEKEND WILL FEATURE DRIER WEATHER WITH THE FRONTAL ZONE LOOMING JUST TO OUR SOUTH. A TRANSITORY SURFACE HIGH WILL CONTROL THE WEATHER PATTERN INITIALLY FOSTERING COLD TEMPERATURES ON THE EASTERN SIDE OF THE HIGH AND THEN MODERATING NICELY THROUGH THE WEEKEND. INITIALLY HIGHS IN THE UPPER 30S/LOW 40S ON FRIDAY RISING TO MID TO UPPER 50S BY THE END OF THE WEEKEND. LOWS SLIGHTLY BELOW FREEZING FRIDAY TO SLIGHTLY ABOVE ON SUNDAY NIGHT. MONDAY THROUGH TUESDAY: SOLUTIONS DIVERGE EARLY NEXT WEEK IN REGARDS TO THE STRENGTH OF THE UPPER LEVEL TROUGH AND A LOW PRESSURE SYSTEM COMING OUT OF THE GULF OF MEXICO THAT COULD AFFECT OUR AREA EARLY NEXT WEEK. TEMPERATURES LOOK WARM ENOUGH THAT ANY PRECIPITATION SHOULD BE LIQUID. HIGHS IN THE UPPER 50S TO LOW 60S. LOWS IN THE MID TO UPPER 30S. && .AVIATION /00Z TUESDAY THROUGH SUNDAY/... AS OF 750 PM TUESDAY... ALREADY LIFR CONDITIONS WITH RESPECT TO CEILINGS WILL WORSEN AS CEILINGS LOWER FURTHER...AND VISIBILITIES LIKEWISE TREND DOWN. IN FACT...AREAS OF DENSE FOG ARE LIKELY TO DEVELOP OVERNIGHT OR EARLY WED...AS WARM AND MOIST AIR IS FORCED ATOP A COLD...SATURATED...AND VERY STABLE LAYER OF AIR NEAR THE SURFACE. CONDITIONS WILL TRANSITION UP BRIEFLY THROUGH IFR-MVFR RANGE...BEFORE LIKELY SCATTERING OUT TO VFR ALTOGETHER...AS THE WARM FRONT AT THE SURFACE FINALLY MAKES INROADS ACROSS CENTRAL NC DURING THE MIDDAY-EARLY AFTERNOON HOURS AT EASTERN TAF SITES...TO MID-LATE AFTERNOON (IF AT ALL) AT KINT/KGSO...BEFORE A COLD FRONT AND ASSOCIATED TRAILING AREA OF RAIN AND SUB-VFR CONDITIONS ARRIVE FROM THE NORTHWEST WED NIGHT...AND PERSISTS THROUGH THU. A BRIEF MIX OF SLEET AND/OR FREEZING RAIN WILL BE POSSIBLE BEFORE PRECIPITATION ENDS LATE THU OR THU EVENING AT KRWI AND KRDU. OUTLOOK: VFR && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...RAH NEAR TERM...CBL/BLS SHORT TERM...CBL LONG TERM...ELLIS AVIATION...RAH

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