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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 220706
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
306 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 945 PM TUESDAY...

THE PESKY WEAK MID-LEVEL IMPULSE THAT HAS TAKEN 3 DAYS TO CROSS THE
STATE AND LARGELY RESPONSIBLE FOR THE UNSETTLED/STORMY WEATHER
DURING THE SAME TIME...IS FINALLY IN THE PROCESS OF PUSHING OUT TO
SEA. THIS WILL SPELL FOR DRIER CONDITIONS TONIGHT THAN THAT OF THE
PAST FEW NIGHTS. WITH THAT SAID...THE NORTHERN/NORTHWESTERN PIEDMONT
COULD STILL SEE SOME ISOLATED CONVECTION OVER THE NEXT COUPLE OF
HOURS AS BAND OF COLD POOL DRIVEN CONVECTION CROSSES THE MOUNTAINS
AND MOVES NORTHEAST INTO THE VIRGINIAS.

WITH THE PLUME OF HIGH 1.5-1.7" PWAT STILL IN PLACE OVER THE
REGION...LOW CEILINGS AND FOG ARE APT TO DEVELOP AFTER MIDNIGHT.
LOWS TONIGHT IN THE MIDDLE TO UPPER 60S.

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 218 PM TUESDAY...

ON WEDNESDAY CENTRAL NORTH CAROLINA WILL BE BETWEEN THE EXITING
SHORTWAVE SYSTEM THAT HAS BROUGHT US ALL OF THE RAIN OVER THE LAST
SEVERAL DAYS AND THE APPROACHING FRONTAL SYSTEM WITH THE PARENT LOW
PRESSURE SYSTEM CROSSING THE WESTERN GREAT LAKES. IT SHOULD BE THE
DRIEST DAY OF THE WEEK SO FAR BUT THERE WILL STILL BE PLENTY OF LOW
LEVEL MOISTURE CONVERGENCE BETWEEN RETURN FLOW FROM THE SURFACE HIGH
OFF OF THE ATLANTIC COAST AND SOUTHWESTERLY FLOW AHEAD OF THE
FRONTAL SYSTEM TO THE WEST. PRECIPITABLE WATERS WILL ONLY BE
SLIGHTLY LESS THAN TODAY ABOUT 1.6 INCHES OR SO IN THE EAST. SEVERE
PARAMETERS OUTSIDE OF INSTABILITY ARE ONCE AGAIN LACKING...VERY
SIMILAR TO THE ENVIRONMENT SEEN OVER THE LAST SEVERAL DAYS. A BIT
MORE RIDGING AND SUBSIDENCE IN THE MID TO UPPER LEVELS SHOULD KEEP
US A LITTLE DRIER THAN EARLIER IN THE WEEK BUT STILL EXPECT SOME
CONVECTIVE DEVELOPMENT BY LATE AFTERNOON. HEAVY RAIN WILL ONCE AGAIN
BE THE PRIMARY THREAT. WITH SOUTHERLY FLOW AND GREATER INSOLATION
ACROSS MUCH OF THE AREA...EXPECT HIGH TEMPERATURES AGAIN IN THE MID
80S OVER MUCH OF THE CWA. DEWPOINTS WILL REMAIN HIGH AGAIN ON
WEDNESDAY NIGHT KEEPING THE THREAT FOR LOW STRATUS AND FOG AROUND
FOR ONE MORE NIGHT AS LOWS APPROACH THE DEWPOINTS...MIDDLE TO UPPER
60S.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --
AS OF 305 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.

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.
-- End Changed Discussion --

&&

.AVIATION /06Z WEDNESDAY THROUGH SATURDAY/...
-- Changed Discussion --
AS OF 240 AM WEDNESDAY...

A CONTINUED VERY MOIST AIR MASS WILL RESULT IN A HIGH CHANCE OF
LIFR-IFR CEILINGS THIS MORNING. THESE CEILINGS WILL LIFT AND SCATTER
TO VFR WITH HEATING THROUGH MIDDAY. HEATING OF THE MOIST AIR MASS
WILL ALSO CAUSE WIDELY SCATTERED SHOWERS AND STORMS TO DEVELOP THIS
AFTERNOON...BUT WITH LESSER COVERAGE VERSUS PREVIOUS DAYS OWING TO
THE WEAKENING AND DEPARTURE OF A LIFT-INDUCING TROUGH THAT RESIDED
OVER THE AREA DURING RECENT DAYS. UNTIL A COLD FRONT SWEEPS
ACROSS CENTRAL NC THU NIGHT...THE CONTINUED VERY MOIST REGIME WILL
PROMOTE ADDITIONAL LOW STRATUS DEVELOPMENT TONIGHT...AND A CONTINUED
THREAT OF MAINLY AFTERNOON SHOWERS AND STORMS. VFR CONDITIONS WILL
OTHERWISE PREVAIL IN CANADIAN HIGH PRESSURE THROUGH THE WEEKEND.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...MWS
NEAR TERM...CBL
SHORT TERM...ELLIS
LONG TERM...SEC
AVIATION...MWS