-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 221422
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1022 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/...
-- Changed Discussion --
AS OF 1015 AM WEDNESDAY...

QUIETER DAY TODAY AS CENTRAL NC SITS IN BETWEEN A SHORTWAVE SYSTEM
JUST OFF THE COAST AND A LARGER FRONTAL SYSTEM CURRENTLY STRETCHING
ACROSS THE MISSISSIPPI VALLEY THAT WILL CONTINUE TO PUSH EASTWARD
TODAY WITH THE PARENT LOW MOVING TOWARDS THE SOUTHERN GREAT LAKES.

FOR CENTRAL NC THE BIGGEST DIFFERENCE BETWEEN TODAY AND PREVIOUS
DAYS IS THE WEAKENING OF THE SHORTWAVE TROUGH AND THE PRESENCE OF
HIGH PRESSURE AT THE UPPER LEVELS OF THE ATMOSPHERE. IN ADDITION
PRECIPITABLE WATER VALUES HAVE RELAXED SOMEWHAT...NEAR 1.5 INCHES
WITH HIGHER VALUES SOUTH AND EAST AND DRIER CONDITIONS ACROSS THE
NORTHWESTERN PIEDMONT. CURRENT MVFR CEILINGS WILL GRADUALLY LIFT OUT
AND SET THE STAGE AGAIN FOR CUMULIFORM DEVELOPMENT LEADING TO
SHOWERS AND THUNDERSTORMS THIS AFTERNOON. COVERAGE OF STORMS SHOULD
BE LESS THAN PREVIOUS DAYS AND SURFACE BOUNDARIES WILL ONCE AGAIN BE
THE CATALYST. SEVERE PARAMETERS WILL ONCE AGAIN BE VERY WEAK
OUTSIDE OF THE INSTABILITY WITH SHEAR ONLY AT 10 KNOTS OR SO AND
WEAK LAPSE RATES NEAR 5.5 DEG/KM. ML CAPE VALUES ONLY PREDICTED TO
BE ABOUT 800 J/KG OR SO. THEREFORE NOT EXPECTING ANY SEVERE WX THIS
AFTERNOON BUT POP UP SHOWERS AND THUNDERSTORMS WILL STILL BE
POSSIBLE...ESPECIALLY NEAR SURFACE BOUNDARIES. HIGH TEMPERATURES
TODAY SHOULD BENEFIT FROM BETTER INSOLATION AFTER MVFR CEILINGS BURN
OFF. EXPECT MIDDLE 80S ACROSS THE CWA TODAY. THERE IS THE POTENTIAL
FOR MORE LOW STRATUS TONIGHT AFTER SUNSET WITH CEILINGS CLOSER TO
2000 FEET. LOWS IN THE MIDDLE 60S.
-- End Changed Discussion --

&&

.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...ELLIS
SHORT TERM...SEC
LONG TERM...SEC
AVIATION...WSS