Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 230835
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
435 AM EDT TUE SEP 23 2014

.SYNOPSIS...A STALLED UPPER LEVEL LOW AND ATTENDANT COASTAL LOW
PRESSURE SYSTEM WILL LINGER OVER THE CAROLINAS THROUGH WEDNESDAY...
THEN TRACK OFFSHORE THE MID-ATLANTIC COAST WEDNESDAY NIGHT. HIGH
PRESSURE WILL EXTEND SOUTHWARD INTO THE REGION ON THURSDAY AND
FRIDAY.

&&

.NEAR TERM /TODAY AND TONIGHT/...
AS OF 200 AM TUESDAY...

OVERVIEW: A POTENT UPPER LEVEL LOW CENTERED OVER EAST-CENTRAL GA AT
06Z WILL TRACK INTO SC THIS MORNING...THEN STALL OUT OVER THE
CAROLINAS THROUGH TONIGHT. SHORTWAVE ENERGY ROTATING AROUND THE
UPPER LOW WILL AID IN CYCLOGENESIS IN VICINITY OF A COASTAL FRONT
SITUATED ALONG OR JUST OFFSHORE THE SOUTHEAST COAST TONIGHT AS HIGH
PRESSURE OVER THE MID-ATLANTIC EXTENDS SOUTHWARD THROUGH CENTRAL AND
WESTERN PORTIONS OF THE CAROLINAS.

PRECIPITATION: FORECAST UNCERTAINTY PERSISTS W/REGARD TO THE PRECISE
EVOLUTION OF THE CUT-OFF LOW OVER THE REGION...ESPECIALLY W/REGARD
TO THE TIMING/STRENGTH/LOCATION OF SHORTWAVE ENERGY ROTATING AROUND
THE LOW AND THE INFLUENCE OF CONVECTIVE PRECIPITATION EXPECTED TO
DEVELOP IN VICINITY OF THE COASTAL FRONT ALONG THE SOUTHEAST COAST
TODAY/TONIGHT. THE LATEST 00Z GFS/NAM GUIDANCE INDICATE A POTENTIAL
FOR ELEVATED CONVECTION UNDER THE COLD POOL ALOFT IN CENTRAL/WESTERN
NC TODAY...IN ADDITION TO A POTENTIAL FOR ELEVATED CONVECTION ON THE
COOL SIDE OF THE COASTAL FRONT IN THE SE COASTAL PLAIN...WITH THE
BEST CHANCE LATE TONIGHT IN THE COASTAL PLAIN AS THE COASTAL FRONT
SHARPENS AND EDGES CLOSER TO THE COAST IN ADVANCE OF A DEVELOPING
WAVE OF LOW PRESSURE. UNTIL ADDITIONAL GUIDANCE AND OBSERVATIONAL
DATA CAN BE ASSESSED...WILL INDICATE PRECIPITATION CHANCES AS
MENTIONED ABOVE.

TEMPS: CHALLENGING TEMPERATURE FORECAST. BROKEN TO OVERCAST MID-
LEVEL CEILINGS OVER THE BULK OF CENTRAL NC WILL INHIBIT INSOLATION
AND KEEP TEMPS COOLER THAN YESTERDAY...THOUGH EXACTLY HOW COOL WILL
HIGHLY DEPEND ON THE TIMING/LOCATION OF PRECIPITATION THAT DEVELOPS.
IF THE GFS SOLUTION VERIFIES...I.E. ELEVATED PRECIPITATION INLAND
OVER THE WESTERN PIEDMONT...TEMPS WOULD HAVE DIFFICULTY EXCEEDING
THE 50S TODAY. HOWEVER...IF THE NAM SOLUTION VERIFIES...I.E. NO
INLAND PRECIPITATION...TEMPS IN THE TRIAD WOULD RISE INTO THE UPPER
60S. AT THIS TIME WILL INDICATE HIGHS IN THE 60S OVER ALL OF CENTRAL
NC. EXPECT RELATIVELY LITTLE DIURNAL VARIATION IN TEMPS WITH LOWS
TONIGHT IN THE 50S TO LOWER 60S. -VINCENT

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 253 AM TUESDAY...

FORECAST UNCERTAINTY REMAINS ABOVE AVERAGE AS MODEL GUIDANCE
CONTINUES TO HAVE DIFFICULTY IN CAPTURING THE PRECISE EVOLUTION OF A
STALLED UPPER LEVEL LOW OVER THE SOUTHEAST CONUS...AND WITH
PRECIPITATION ALONG THE SOUTHEAST COAST. THE LATEST GUIDANCE IS
SIMILAR IN NATURE TO PREVIOUS GUIDANCE...SHOWING THE BEST POTENTIAL
FOR RAIN ALONG/EAST OF HWY 1 DURING THE DAY WEDNESDAY AS A WAVE OF
LOW PRESSURE ATTENDANT SHORTWAVE ENERGY ROTATING AROUND THE
DEAMPLIFYING UPPER LEVEL LOW TRACKS NORTHWARD ALONG A RETROGRADING
COASTAL FRONT. THE PRECISE TIMING/LOCATION OF SHORTWAVE ENERGY
ROTATING AROUND THE UPPER LOW AND ULTIMATELY THE PRECISE
TIMING/TRACK OF THE ATTENDANT WAVE OF LOW PRESSURE ALONG THE
RETROGRADING (WESTWARD/INLAND MOVING) COASTAL FRONT IS DIFFICULT TO
ASSESS...EVEN AT SHORT RANGE.

QUALITATIVELY...EXPECT BROKEN TO OVERCAST CLOUD COVER EVERYWHERE AND
AN INCREASING CHANCE OF RAIN FROM THE TRIANGLE EASTWARD TO THE COAST
WITH TEMPS STRUGGLING TO EXCEED THE 60S. PRECIPITATION CHANCES
SHOULD DECREASE FROM SW-NE WED NIGHT AS THE LINGERING UPPER LEVEL
LOW BECOMES PROGRESSIVE IN RESPONSE TO STRENGTHENING SOUTHWESTERLY
FLOW ALOFT IN ADVANCE OF SHORTWAVE ENERGY TRACKING EASTWARD FROM THE
CENTRAL PLAINS INTO THE WESTERN OH VALLEY...THOUGH THIS FEATURE
ITSELF IS EMBEDDED IN WEAK STEERING FLOW AND EXPECTED TO CUT-OFF
OVER THE CENTRAL MS RIVER VALLEY WED NIGHT/THU...INTRODUCING MORE
UNCERTAINTY THAN WOULD OTHERWISE BE THE CASE. ONCE AGAIN...EXPECT
LITTLE DIURNAL VARIATION IN TEMPS WITH LOWS IN THE 50S/60S.

WIND: THE MSLP/HEIGHT GRADIENT WILL TIGHTEN OVER CENTRAL NC
WEDNESDAY...BETWEEN STRONG HIGH PRESSURE TO THE NORTH AND A
DEVELOPING LOW PRESSURE SYSTEM ALONG THE CAROLINA COAST...AND FCST
SOUNDINGS SUGGEST LOW-LEVEL NORTHEAST FLOW AS STRONG AS 30-40 KT.
SHALLOW MIXING ASSOCIATED WITH LOW-LEVEL COLD ADVECTION WILL BE
ENHANCED BY PRECIPITATION /EVAP COOLING/ ON WED...ESP IN THE SE
COASTAL PLAIN WHERE A TIGHTER MSLP GRADIENT WILL BE JUXTAPOSED WITH
HEAVIER PRECIPITATION. WITH THE ABOVE IN MIND...AREAS SOUTH AND EAST
OF THE TRIANGLE COULD SEE A PERIOD OF BREEZY NORTHEAST WINDS GUSTING
AS HIGH AS 30-40 MPH DURING THE DAY WED. KEEP IN MIND THAT THIS
WOULD BE A WORST-CASE SCENARIO AND THAT WIND OF THIS MAGNITUDE WOULD
FALL SHORT OF WIND ADVISORY CRITERIA...THOUGH PERHAPS CAPABLE OF A
FEW DOWNED TREES IN THE PRESENCE OF HEAVY PRECIPITATION. -VINCENT

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 330 AM TUESDAY...

SOME DRYING MAY BEGIN SOONER THAN PREVIOUSLY EXPECTED AS THE MID/UPPER LOW
AND ASSOCIATED SURFACE TROUGH SHOULD BE QUICKER TO EXIT. AT LEAST SOME RESIDUAL
CLOUDINESS IS EXPECTED THURSDAY AS THE SURFACE WAVE MOVES SLOWLY UP THE MID-
ATLANTIC COAST... WITH CLEARING IN THE LEE OF THE MOUNTAINS SPREADING SE DURING
THE DAY.

THE NEXT CHANCE OF RAIN SHOULD COME EARLY NEXT WEEK. HOWEVER... MODELS CONTINUE
TO SHOW PLENTY OF DISAGREEMENT.

ALL IN ALL... TEMPERATURES SHOULD TURN MILDER LATE WEEK AS THE CLOUDS DEPART.
HOWEVER... THE PROLONGED NE FLOW COURTESY OF HIGH PRESSURE TO OUR NE WILL KEEP
READINGS IN CHECK.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AS OF 200 AM TUESDAY...

24-HR TAF PERIOD: EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE TAF
PERIOD WITH CEILINGS GENERALLY NO LOWER THAN 5-8 KFT AND A NORTHEAST
BREEZE AT 5-10 KT...EXCEPT 10-15 KT AT THE FAY TERMINAL LATER TODAY
INTO TONIGHT AS THE MSLP GRADIENT TIGHTENS ALONG THE SOUTHEAST
COAST. ANY CHANCE FOR SUB-VFR CONDITIONS SHOULD BE CONFINED TO THE
FAY/RWI TERMINALS AT THE END OF THE TAF PERIOD WHEN PRECIPITATION
AND MVFR CEILINGS MAY SPREAD INLAND IN ADVANCE OF A WAVE OF LOW
PRESSURE TRACKING NE ALONG THE FRONTAL ZONE STALLED IN VICINITY OF
THE SE COAST.

LOOKING AHEAD: SUB-VFR CONDITIONS ASSOC/W RAIN WILL BE POSSIBLE AT
THE RDU/FAY/RWI TERMINALS ON WEDNESDAY AS THE AFOREMENTIONED WAVE OF
LOW PRESSURE TRACKS NORTHWARD ALONG THE MID-ATLANTIC COAST...THOUGH
UNCERTAINTY PERSISTS WITH REGARD TO HOW FAR WEST PRECIPITATION WILL
DEVELOP AND THE RELATIVE BEST CHANCE FOR SUB-VFR CONDITIONS WILL BE
AT THE FAY/RWI TERMINALS. OTHERWISE...EXPECT VFR CONDITIONS TO
PREVAIL THROUGH THE REMAINDER OF THE WEEK AS HIGH PRESSURE EXTENDS
INTO THE CAROLINAS FROM THE NORTH. -VINCENT

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...VINCENT
SHORT TERM...VINCENT
LONG TERM...PWB
AVIATION...VINCENT


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