AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
340 AM EDT WED SEP 17 2014

.SYNOPSIS...A COLD FRONT WILL TRACK SOUTHEAST THROUGH THE CAROLINAS 
THIS MORNING. COOL HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE 
NORTH THIS AFTERNOON AND PERSIST THROUGH THE REMAINDER OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/... 
AS OF 340 AM WEDNESDAY...

TODAY...SURFACE COLD FRONT CURRENTLY DRIFTING SOUTH ACROSS CENTRAL 
NC (AT 07Z FRONT WAS FAIRLY ALIGNED WITH HIGHWAY 64) AND SHOULD BE 
DRAPED ACROSS THE SANDHILLS AND SOUTHERN COASTAL PLAIN THIS 
MORNING...DRIFTING INTO NORTHERN SC-SE NC THIS AFTERNOON. A MID-
UPPER LEVEL VORTICITY MAXIMUM CROSSING SC EARLY THIS MORNING WILL 
MAINTAIN A THREAT FOR SHOWERS AND AN ISOLATED STORM FOR THE FAR 
SOUTHERN SECTIONS OF OUR FORECAST AREA THROUGH 12Z. 

LATER THIS MORNING...THE COOL MOIST STABLE AIR MASS BEHIND THE FRONT 
SHOULD RESULT IN A WEAK DAMMING EVENT. AS IS TYPICAL WITH THIS SET-
UP...SHOULD SEE WIDESPREAD LOW CLOUDS AND PATCHES OF LIGHT RAIN OR 
DRIZZLE AS A SERIES OF UPPER LEVEL DISTURBANCES PASS OVERHEAD. THE 
EXTENSIVE CLOUDS AND SPOTTY LIGHT PRECIP SHOULD HOLD TEMPS IN THE 
LOW-MID 70S ACROSS THE PIEDMONT. GFS APPEARS TOO OPTIMISTIC IN ITS 
DEPICTION OF SCATTERING THE LOW CLOUDS INTO A SCATTER-BROKEN 
STRATOCU DECK THIS AFTERNOON. IF THE GFS IS MORE CORRECT...THEN 
EXPECT SCATTERED SHOWERS RATHER THAN LIGHT RAIN ACROSS THE PIEDMONT 
ALONG WITH WARMER TEMPS. CURRENTLY...PLAN TO HAVE MAX TEMPS RANGE 
FROM THE LOWER 70S NW TO THE LOWER 80S FAR SOUTH-SE.

SLIGHT TO MODERATE INSTABILITY ACROSS THE SANDHILLS AND SOUTHERN 
COASTAL PLAIN SUGGEST A THREAT FOR SCATTERED CONVECTION THIS 
AFTERNOON. GFS DEPICTS BULK SHEAR OF 30KTS...SUGGESTING SOME 
ORGANIZATION TO THE CONVECTION...MAINLY IN THE FORM OF A BROKEN 
LINE. MAY SEE A STRONG WIND GUSTS WITH CELLS THAT HAVE SUSTAINED 
UPDRAFTS DUE TO PRECIP LOADING BUT MAJORITY OF SHOWERS AND STORMS 
WILL BE BELOW SEVERE LIMITS. FORCING THAT NOT ALL THAT IMPRESSIVE SO 
PLAN TO CAP POPS AT 30-40 PERCENT.

TONIGHT...EXPECT WEAK CAD AIR MASS TO PERSIST OVER MOST OF THE 
PIEDMONT WITH PATCHES OF DRIZZLE OR FOG AND LOW CLOUDS. BULK OF 
CONVECTION IN THE SE WILL DIMINISH WITH LOSS OF HEATING AND LACK OF 
SUPPORT ALOFT. MAY SEE A SLIGHT UPSURGE IN LIGHT PRECIP TOWARD 
MORNING AS MOST OF THE MODELS DEPICT A MINOR S/W APPROACHING FROM 
THE WEST. MIN TEMPS GENERALLY 60-65.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/... 
AS OF 340 AM WEDNESDAY...

THURSDAY...MINOR S/W PROJECTED TO PASS ACROSS THE FORECAST AREA IN 
THE MORNING. WEAK SUBSIDENCE IN ITS WAKE IN THE AFTERNOON AND 
ADVECTION OF DRIER AIR WILL BEGIN EROSION OF RESIDUAL CAD AIR MASS 
IN THE PIEDMONT. HOWEVER...MODELS TYPICALLY ARE TOO AGGRESSIVE WITH 
THIS TRANSITION. FAVOR A SLOWER IMPROVEMENT TREND THAN ADVERTISED BY 
THE MODELS. THIS LEADS TO MAX TEMPS ON THE COOL SIDE OF GUIDANCE. IF 
EROSION IS EVEN SLOWER THAN EXPECTED...MAX TEMPS MAY BE AS MUCH A 3-
4 DEGREES TOO WARM IN THE PIEDMONT. CONVECTION THURSDAY AFTERNOON 
APPEARS LIMITED TO THE FAR EAST-SE SECTIONS. JUST WEAK INSTABILITY 
AND SHEAR PROJECTED SO EXPECT MAINLY ISOLATED SHOWERS IN THE 
COASTAL PLAIN/SANDHILLS. MAX TEMPS MID-UPPER 70S NORTH TO AROUND 80 
SOUTH.

THURSDAY NIGHT...EXPECT GRADUAL IMPROVEMENT IN SKY CONDITIONS. THIS 
MAY LEAD TO SOME PATCHY FOG BUT INTRUSION OF DRIER AIR NEAR THE 
SURFACE MAY LIMIT/INHIBIT FOG FORMATION. BEST CHANCE FOR FOG WILL 
LIKELY BE THE SE HALF. MIN TEMPS IN THE UPPER 50S NW TO THE LOWER 
60S SE.
&&

.LONG TERM /FRIDAY THROUGH TUESDAY/... 
AS OF 340 AM WEDNESDAY...

A PORTION OF THE LONGWAVE TROUGH INITIALLY ALONG THE EAST COAST WILL 
BE LEFT BEHIND...OFFSHORE THE SE US COAST THIS WKND...BUT THE 
OTHERWISE DEAMPLIFYING/LIFTING TROUGH WILL YIELD TO RISING HEIGHTS 
ALOFT OVER THE CAROLINAS...AS A FLAT MID LEVEL RIDGE RIDGE NOSES 
EASTWARD FROM THE SOUTHERN PLAINS AND LOWER MS VALLEY. THE RE-
ESTABLISHMENT AND AMPLIFICATION OF A WESTERN NOAM RIDGE WILL THEN 
RESULT IN DOWNSTREAM TROUGH AMPLIFICATION FROM SOUTH-CENTRAL CANADA 
TO THE EAST-CENTRAL US DAYS 5-7.  
 
BENEATH THE RISING HEIGHTS ALOFT...A CANADIAN-SOURCE SFC HIGH (AROUND 
1030 MB) WILL BUILD FROM CENTRAL CANADA TO THE CANADIAN MARITIMES 
AND RIDGE SOUTH/SOUTHWESTWARD THROUGH THE EASTERN STATES THROUGH THE 
FIRST HALF OF THE WEEKEND...BEFORE YIELDING - AMIDST FALLING HEIGHTS 
DOWNSTREAM OF THE AFOREMENTIONED REDEVELOPING TROUGH ALOFT HEADED 
FOR THE EAST-CENTRAL US - TO APPALACHIAN-LEE SFC TROUGH DEVELOPMENT 
SUN...AND A PASSING COLD FRONT MON-MON NIGHT. 

THOUGH THE CANADIAN RIDGING WILL RESULT IN A RELATIVELY PROLONGED 
PERIOD OF EAST TO NORTHEAST LOW LEVEL FLOW THROUGH EARLY THIS 
WEEKEND...THE LATEST GUIDANCE SUGGESTS THE BRUNT OF THE ASSOCIATED 
COOLER AND DRIER AIR WILL HOLD OVER THE NORTHERN MIDDLE ATLANTIC AND 
NORTHEAST STATES. IN ADDITION...THE ORIENTATION OF THE LOW LEVEL 
RIDGE AXIS SHOULD ALSO DIRECT MARITIME MOISTURE/CLOUDS AROUND THE 
RIDGE...TO THE SOUTH OF CENTRAL NC. AS SUCH...SKIES ARE APT TO BE 
PARTLY TO MOSTLY SUNNY OVER CENTRAL NC...WITH TEMPERATURES ABOUT A 
CATEGORY WARMER THAN EARLIER ANTICIPATED...IN THE MIDDLE 70S TO 
AROUND 80 DEGREES FRI-SAT. WARMER YET AHEAD OF THE APPROACHING FRONT 
SUN-MON - LIKELY LOWER TO PERHAPS MIDDLE 80S...WITH JUST A SLIGHT 
CHANCE OF SHOWERS ATTENDING THE FRONT LATE MON...GIVEN A LIMITED 
GULF MOISTURE FEED. COOLER TUE...AND THOUGH THERE REMAINS SOME 
POTENTIAL FOR LINGERING LIGHT RAIN (ESPECIALLY EAST) PER THE 12Z 
EC...THE 00Z EC HAS TRENDED TOWARD THE MORE CONSISTENT AND FAVORED 
EC ENSEMBLE MEAN WITH A "CLEANER" FRONTAL PASSAGE AND DRIER SOLUTION 
FOR TUE.
&&

.AVIATION /06Z TUESDAY THROUGH SUNDAY/...
AS OF 155 AM WEDNESDAY...

VFR CONDITIONS REPORTED ACROSS MUCH OF CENTRAL NC AT 05Z WITH 
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS MOVING EAST-SE ALONG 
THE NC-SC BORDER. THESE SHOWERS AND STORMS WERE AHEAD OF A SURFACE 
COLD FRONT THAT WAS DRIFTING SOUTH ACROSS THE NORTHERN PIEDMONT AT 
05Z. THIS WEATHER FEATURE SHOULD BE CLOSE TO THE SC BORDER BY 
DAYBREAK THEN DRIFT FARTHER SOUTH LATER TODAY. LOW LEVEL NORTH-
NORTHEAST FLOW BEHIND THE FRONT WILL MAINTAIN A COOL MOIST STABLE 
AIR MASS. THIS WILL RESULT IN WIDESPREAD IFR/LIFR CEILINGS ACROSS 
MUCH OF THE PIEDMONT INCLUDING KINT/KGSO AND KRDU...ALONG WITH 
PATCHES OF LIGHT RAIN OR DRIZZLE. THE LOW CEILINGS SHOULD DEVELOP 
BETWEEN 08Z-12Z AND PERSIST ALL DAY AND INTO TONIGHT. MVFR CEILINGS 
ARE EXPECTED IN THE VICINITY OF KRWI. NEAR KFAY...A BRIEF PERIOD OF 
MVFR/IFR CEILINGS THIS MORNING MAY LIFT INTO THE HIGH END MVFR-LOW 
END VFR BY AFTERNOON WITH A  THREAT FOR SCATTERED SHOWERS...MAINLY 
TO THE EAST AND SOUTH.

THE ADVERSE AVIATION WEATHER CONDITIONS WILL PERSIST ACROSS MUCH OF 
CENTRAL NC TONIGHT INTO THURSDAY MORNING WITH LOW CEILINGS AND 
MVFR/IFR VISIBILITY DUE TO DRIZZLE OR FOG. A GRADUAL IMPROVEMENT IN 
AVIATION CONDITIONS EXPECTED BY THURSDAY AFTERNOON AS DRIER AIR 
BEGINS TO ARRIVE INTO THE LOWER LEVELS OF THE ATMOSPHERE. 

VFR CONDITIONS ARE EXPECTED TO OCCUR THURSDAY NIGHT THROUGH SUNDAY 
AS HIGH PRESSURE GAINS GREATER INFLUENCE ON OUR WEATHER.

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...MWS
AVIATION...WSS



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