Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 040745 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 245 AM EST WED MAR 4 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/... 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. && .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 /FRIDAY THROUGH TUESDAY/... AS OF 245 AM WEDNESDAY... FRI/FRI NIGHT: COLD ADVECTION ATTENDANT ~1040 MB ARCTIC HIGH PRESSURE BUILDING INTO THE CAROLINAS FROM THE N/NW DURING THE DAY WILL RESULT IN WELL...WELL BELOW NORMAL TEMPERATURES (AS MUCH AS 25- 30 DEGREES) ON FRIDAY...WITH THE LATEST 00Z GFS/ECMWF SUGGESTING HIGHS RANGING FROM THE UPPER 20S TO LOWER 30S IN THE NE COASTAL PLAIN TO LOW/MID 30S WEST/SW PIEDMONT. GIVEN CLEAR SKIES AND EARLY MARCH INSOLATION...WILL REDUCE HIGHS SEVERAL DEGREES FROM THE PRIOR FORECAST...REMAINING SEVERAL DEGREES ABOVE WHAT GUIDANCE ALONE WOULD SUGGEST. LOWS FRI NIGHT IN THE UPPER TEENS NORTHEAST TO LOW/MID 20S SOUTHWEST. SAT-SUN NIGHT: UNIDIRECTIONAL FLOW ALOFT /DRY CONDITIONS/ AND MOSTLY CLEAR SKIES ARE EXPECTED TO PREVAIL ACROSS THE REGION THROUGH THE WEEKEND...WITH NORTHERN STREAM SHORTWAVE ENERGY CONFINED TO THE GREAT LAKES /NEW ENGLAND/ AND SOUTHERN STREAM SHORTWAVE ENERGY CONFINED TO THE DESERT SW AND WESTERN GOMEX. EXPECT MODERATING TEMPS...THOUGH STILL BELOW NORMAL...WITH HIGHS GENERALLY IN THE 50S SAT/SUN AND LOWS RANGING FROM THE LOWER 30S SAT NIGHT TO MID/UPPER 30S SUN NIGHT WHEN MID/UPPER LEVEL CLOUD COVER IS PROGGED TO INCREASE AS SOUTHERN STREAM SHORTWAVE ENERGY...ATTENDANT WAA/FGEN...AND RESULTING PRECIPITATION PROGRESS EASTWARD ALONG THE GULF COAST. MON-TUE: GIVEN A SPLIT FLOW SYNOPTIC PATTERN...CONFIDENCE IN FORECAST DETAILS DECREASES DRAMATICALLY BY EARLY NEXT WEEK... PARTICULARLY WITH REGARD TO THE EVOLUTION OF SOUTHERN STREAM SHORTWAVE ENERGY PROGRESSING EAST ALONG THE GULF COAST. AT THIS TIME...WILL STEER THE FORECAST CLOSE TO CLIMATOLOGY. -VINCENT && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 1230 AM WEDNESDAY... LIFR CEILINGS WILL WORSEN THROUGH THE NIGHT AS VISIBILITIES LOWER AS WELL. 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. ANOTHER ISSUE AFTER THE LOW CIGS AND VSBYS LIFT WILL BE THE INCREASING SW WINDS AT 15-25KT WITH GUSTS TO 30KT BETWEEN 15Z-23Z. THEN A COLD FRONT AND ASSOCIATED AREA OF RAIN AND SUB-VFR CONDITIONS ARRIVE FROM THE NORTHWEST WED NIGHT...AND PERSIST THROUGH THU. A BRIEF MIX OF SLEET AND/OR FREEZING RAIN WILL BE POSSIBLE BEFORE PRECIPITATION ENDS LATE THU OR THU EVENING AT KGSO KINT AND KRDU. OUTLOOK FOR THURSDAY NIGHT INTO SATURDAY: VFR CONDITIONS UNDER HIGH PRESSURE. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...PWB NEAR TERM...CBL/BLS SHORT TERM...CBL LONG TERM...VINCENT AVIATION...PWB

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