AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
745 AM EDT WED MAY 22 2013

.SYNOPSIS...
BERMUDA HIGH PRESSURE WILL EXTEND INTO THE MIDDLE ATLANTIC TODAY. A 
SURFACE PRESSURE TROUGH WILL DEVELOP IN THE LEE OF THE APPALACHIANS 
THURSDAY...FOLLOWED BY THE PASSAGE OF A COLD FRONT THURSDAY NIGHT. 

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 315 AM WEDNESDAY...

THE MID LEVEL TROUGH THAT HAS PROMOTED NUMEROUS TO WIDESPREAD 
DOWNPOURS IN RECENT DAYS IS NO LONGER DISCERNIBLE IN REGIONAL VWP 
DATA. BERMUDA HIGH PRESSURE WILL CONSEQUENTLY BRIEFLY EXERT THE 
DOMINANT INFLUENCE TO WEATHER CONDITIONS OVER CENTRAL NC TODAY...SO 
CONVECTIVE COVERAGE SHOULD BE MUCH LESS THAN PREVIOUS DAYS...AND 
FOCUSED BY THE SEA BREEZE AND OTHER SMALLER SCALE/LOWER 
PREDICTABILITY DIFFERENTIAL HEATING OR REMNANT OUTFLOW BOUNDARIES.   
A BLANKET 20-30 PERCENT POP IS ACCORDINGLY WARRANTED...WITH RELATIVE 
HIGHEST CHANCES ASSOCIATED WITH THE SEA BREEZE OVER THE COASTAL 
PLAIN AND EASTERN SANDHILLS AND PIEDMONT. DESPITE WHAT SOME OF THE 
NWP GUIDANCE WOULD SUGGEST...IT SEEMS IMPROBABLE THAT ANY 
MOUNTAIN-INDUCED CONVECTION WOULD AFFECT THE WESTERN 
PIEDMONT...OWING TO SOUTH TO SOUTH SOUTHWESTERLY STEERING FLOW THAT 
WOULD HOLD STORM MOTIONS/PROPAGATION WEST OF THE YADKIN RIVER. HIGHS 
SIMILAR TO THOSE OF TUESDAY...GENERALLY IN THE MIDDLE 80S. 

HEIGHT FALLS IN ASSOCIATION WITH THE COMPLEX TROUGH ALOFT 
APPROACHING FROM THE CENTRAL CONUS...ON THE ORDER OF 20-30 METERS AT 
H5...WILL SPREAD EASTWARD ACROSS CENTRAL NC TONIGHT. WHILE THESE 
HEIGHT FALLS ARE APT TO SUPPORT A BAND OF PRE-FRONTAL SHOWERS AND 
STORMS FROM THE TN VALLEY TO THE APPALACHIANS BY THIS EVENING...IT 
SEEMS PROBABLE THAT THIS CONVECTION WILL WEAKEN CONSIDERABLY AS IT 
EMERGES INTO AN INCREASINGLY STABLE...NOCTURNALLY-COOLED BOUNDARY 
LAYER IN THE LEE OF THE MOUNTAINS - A SOLUTION DEPICTED WELL BY THE 
00Z SPC NMM. AS SUCH...WILL INDICATE A HIGH CHANCE OF MAINLY 
LEFT-OVER SHOWERS INTO THE SOUTHERN AND WESTERN PIEDMONT AFTER 11 
PM...TAPERING TO SLIGHT CHANCE RANGE AROUND THE TRIANGLE AREA...TO 
DRY ROUGHLY EAST OF I-95. A CONTINUED VERY MOIST AIR MASS WILL 
RESULT IN ADDITIONAL LOW STRATUS DEVELOPMENT THROUGH THU MORNING... 
WITH PERSISTENCE LOWS IN THE MIDDLE 60S. 

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
AS OF 308 AM WEDNESDAY... 

COLD FRONT WILL CROSS THE AREA... ENTERING THE STATE FROM THE WEST 
THURSDAY EVENING... AND WILL REACH THE COAST BY 12Z FRIDAY. 
THUNDERSTORMS WILL DEVELOP IN THE MOIST AIRMASS IN ADVANCE OF THE 
FRONT THURSDAY... AND MODEST INSTABILITY OF 500-1000 J/KG MLCAPE AND 
0-6 KM BULK SHEAR VALUES OF 25 KTS WILL SUPPORT A FEW MULTICELL 
CLUSTERS. BEST UPPER LEVEL FORCING REMAINS NORTH OF THE AREA... AND 
WITH THE STRONGEST LOW LEVEL FORCING ASSOCIATED WITH THE FRONT NOT 
MAKING IT THROUGH THE AREA UNTIL LATE THURSDAY... SEVERE POTENTIAL 
IS LOW. HIGHS LOW TO MID 80S... LOWS IN THE 60S.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 305 AM WEDNESDAY... 

BEHIND THE FRONT... NORTHWESTERLY FLOW WILL USHER IN A MUCH DRIER 
AIRMASS... AND PRECIPITATION WILL END FROM WEST TO EAST EARLY 
FRIDAY. TEMPERATURES WILL BE SEVERAL DEGREES BELOW NORMAL THROUGH 
THE WEEKEND... WITH HIGHS IN THE 70S. COOLEST LOWS FRIDAY NIGHT... 
IN THE UPPER 40S TO LOW 50S... THEN LOW TO MID 50S SATURDAY NIGHT. 

MOISTURE WILL INCREASE AGAIN ON MONDAY AS THE FLOW BECOMES MORE 
SOUTHERLY... WITH PWAT VALUES AGAIN CLIMBING TO NEAR 1.5 INCHES. 
GUIDANCE INDICATES A WARM FRONT WILL BE IN THE VICINITY OF THE 
MIDATLANTIC MONDAY EVENING INTO TUESDAY... AND TEMPERATURES TUESDAY 
WILL REBOUND TO NEAR NORMAL... UPPER 70S TO LOW 80S. DEPENDING ON 
THE LOCATION OF THE FRONT... ISENTROPICALLY DRIVEN SHOWERS ARE 
POSSIBLE... AND WILL CONTINUE WITH SLIGHT CHANCE POPS.
    
&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 745 AM WEDNESDAY...

WIDESPREAD MVFR CEILINGS EARLY THIS MORNING WILL GIVE WAY TO A 
SCATTERED-BROKEN VFR CLOUD BASES BY 10-11 AM. AS THE AIR MASS HEATS 
UP THIS AFTERNOON AND BECOMES SLIGHTLY UNSTABLE...SCATTERED 
CONVECTION WILL DEVELOP...ESPECIALLY AFTER 2 PM. THE SHOWERS AND 
THUNDERSTORMS MAY BE A LITTLE MORE CONCENTRATED NEAR AND EAST OF 
KFAY...AND NEAR AND WEST OF KINT AND KGSO. EXPECT MVFR CEILINGS AND 
VISIBILITY IN VICINITY OF THE CONVECTION. THE BULK OF THE SHOWERS 
AND STORMS WILL DIMINISH AFTER 8 PM.

MVFR CEILINGS DUE TO STRATUS WILL DEVELOP LATE TONIGHT AND PERSIST 
INTO EARLY THURSDAY MORNING. A COLD FRONT CURRENTLY ACROSS THE OH 
AND TN VALLEYS WILL CONTINUE TO DRIFT EAST AND SHOULD CROSS CENTRAL 
NC LATE THURSDAY AND THURSDAY EVENING. AHEAD OF THE FRONT...NUMEROUS 
SHOWERS AND SCATTERED THUNDERSTORMS AND ASSOCIATED MVFR/IFR 
CONDITIONS WILL OCCUR. THE HIGHEST CONCENTRATION OF SHOWERS AND 
STORMS WILL OCCUR IN THE AFTERNOON THROUGH THE EVENING HOURS WITH 
CONVECTION DIMINISHING AFTER MIDNIGHT.

CANADIAN HIGH PRESSURE WILL BUILD INTO OUR AREA FROM THE NW FRIDAY 
IN THE WAKE OF THE DEPARTING SYSTEM. THIS WEATHER SYSTEM WILL ADVECT 
DRIER AND MORE STABLE AIR INTO THE CAROLINAS...RESULTING IN A 
PROLONGED PERIOD OF VFR CONDITIONS THAT SHOULD LAST THROUGH SUNDAY.

&&

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

&&

$$

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