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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 211819
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
219 PM EDT TUE MAY 21 2013

.SYNOPSIS...

AN UPPER LEVEL TROUGH WILL LINGER...BUT GRADUALLY WEAKEN OVER THE
CAROLINAS THROUGH WEDNESDAY. A COLD FRONT MOVES THROUGH THE REGION
THURSDAY...FOLLOWED BY COOL HIGH PRESSURE FOR MOST OF THE WEEKEND.
&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 218 PM TUESDAY...

UPPER AIR ANALYSIS FROM 12Z SHOWS THAT THE MAIN FEATURE ACROSS
CENTRAL NC TODAY IS A SHORTWAVE TROUGH VISIBLE FROM THE SURFACE UP
THROUGH 500 MB. THIS HAS BEEN REALIZED AT THE SURFACE THIS AFTERNOON
WITH A CONVERGENCE BOUNDARY THAT HAS BEEN THE PRIMARY CATALYST FOR
SHOWERS AND THUNDERSTORMS TO FORM ON JUST WEST OF THE 1-95 CORRIDOR.
ONE OR TWO STORMS HAVE BECOME STRONG AND APPROACHED THE LOWER
THRESHOLDS FOR SEVERE CRITERIA BUT REMAIN PRIMARILY HEAVY SHOWERS TO
THIS POINT. THIS BOUNDARY WILL TRAVEL OFF TO THE EAST AT A VERY SLOW
CLIP THIS AFTERNOON 20-30 KNOTS. A FEW MORE WEAKER BOUNDARIES TO THE
WEST WILL SLOWLY ROTATE AROUND THE SHORTWAVE TROUGH AXIS THIS
AFTERNOON...ALLOWING FOR NEW STORM DEVELOPMENT FURTHER TO THE WEST.
OTHER THAN THE SURFACE CONVERGENCE BOUNDARIES AND A FAIR AMOUNT OF
INSTABILITY...NOT TOO MUCH ELSE OUT THERE HELPING THE STORMS AT THIS
TIME. DCAPE IN THE EAST CONTINUES TO BE VERY LOW. LAPSE RATES ARE
MEDIOCRE AND SHEAR REMAINS VERY LOW. PRECIPITABLE WATER VALUES
CONTINUE TO BE CLOSE TO 1.75 INCHES AT THIS TIME MAKING HEAVY RAIN
AND LOCALIZED FLOODING THE PRIMARY THREAT THIS AFTERNOON.
TEMPERATURES ARE STILL ON TRACK TO MAX OUT IN THE MID 80S ACROSS THE
CWA. BACK TO THE WEST CONDITIONS ARE A BIT MORE FAVORABLE FOR SEVERE
STORMS WITH DAMAGING WINDS BUT THERE IS NOT AS BIG OF A FORCING
MECHANISM FOR STORM GENESIS AT THIS TIME SO COVERAGE SHOULD BE LESS
IN THE TRIAD. THAT BEING SAID BETTER HEATING AND INSTABILITY WILL
STILL MAKE STORMS POSSIBLE THIS AFTERNOON.

STORMS SHOULD BEGIN TO TAPER OFF AFTER SUNSET THIS EVENING.
DEWPOINTS WILL REMAIN IN THE MIDDLE 60S AND HELP TO INITIATE ANOTHER
ROUND OF LOW CEILINGS AND VISIBILITIES AFTER 3Z OR SO IN THE EAST
AND AFTER 6Z IN THE WEST. EXPECT LOWER CEILINGS AND VISIBILITIES TO
HANG AROUND UNTIL AFTER SUNRISE WEDNESDAY MORNING. LOWS TONIGHT IN
THE MIDDLE 60S.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 300 AM TUESDAY...

UPPER LEVEL TROUGH WILL MOVE EASTWARD FROM THE MIDWEST ON
THURSDAY...WHICH WILL PUT THE AREA IN DEEP SOUTH TO SOUTHWESTERLY
FLOW DURING THE DAY. WITH MOISTURE IN PLACE AND SUFFICIENT
INSTABILITY... WITH MLCAPE VALUES OF 500 TO 1000 J/KG...
THUNDERSTORMS WILL DEVELOP DURING THE DAY. BULK SHEAR VALUES NEAR 25
KTS WILL SUPPORT THE DEVELOPMENT OF SOME MULTICELL CLUSTERS... AND
FEW STRONGER STORMS WITH GUSTY WINDS ARE POSSIBLE. NO WIDESPREAD
SEVERE WEATHER IS EXPECTED... AS THE BEST UPPER LEVEL FORCING
REMAINS NORTH OF THE AREA. HIGHS IN THE LOW TO MID 80S... LOWS IN
THE MID 60S.

THE ASSOCIATED COLD FRONT WILL PROGRESS INTO WESTERN NORTH CAROLINA
THURSDAY EVENING... REACHING THE COAST BY ABOUT 12Z FRIDAY. MIDLEVEL
DRYING WILL SPREAD ACROSS THE AREA FRIDAY... ENDING PRECIPITATION
AND DECREASING CLOUD COVER THROUGH THE DAY FROM WEST TO EAST. COLD
ADVECTION WILL TEMPER HIGHS... WHICH WILL BE IN THE MID 70S TO LOW
80S. COOLER LOWS IN THE MID 50S.

THE TROUGH MOVES OFF THE COAST EARLY SATURDAY... WITH AN UPPER LEVEL
RIDGE ACROSS THE MIDDLE OF THE COUNTRY AND THE SURFACE HIGH
POSITIONED WEST OF THE AREA... PUTTING THE REGION IN A NORTHWEST
FLOW REGIME THROUGH THE WEEKEND... AND KEEPING TEMPERATURES
SEVERAL DEGREES BELOW NORMAL THROUGH MONDAY... WITH HIGHS IN THE
UPPER 70S TO NEAR 80.. AND LOWS IN THE MID TO UPPER 50S.

&&

.AVIATION /18Z TUESDAY THROUGH SATURDAY/...
AS OF 115 PM TUESDAY...

24 HOUR TAF PERIOD:

SHOWERS AND THUNDERSTORMS BEGINNING TO POP UP THIS AFTERNOON ALONG A
BOUNDARY FROM LOUISBURG TO FAYETTEVILLE. THIS BOUNDARY AND
ASSOCIATED SHOWERS AND THUNDERSTORMS WILL SLOWLY MOVE EAST THIS
AFTERNOON. KRWI AND KFAY ARE THE TWO TERMINALS MOST AT RISK FOR
THUNDERSTORM ACTIVITY THIS AFTERNOON. WINDS WILL CONTINUE TO BE
SOUTH SOUTHWESTERLY AT 5-10 KNOTS AND SHOULD STAY THAT WAY THROUGH
THIS EVENING. OVERNIGHT EXPECT IFR/LIFR CEILINGS ONCE AGAIN AND MVFR
VISIBILITIES. THESE WILL BE QUICKER TO DEVELOP IN THE EAST...SOME
TIME AFTER 4Z AND WILL HOLD OFF TILL AFTER 6Z IN THE WEST. ONCE
CONDITIONS DETERIORATE THEY WILL MOST LIKELY REMAIN SUB-VFR THROUGH
SUNRISE. AFTER SUNRISE EXPECT A DRIER DAY TOMORROW WITH VFR CEILINGS
PREDOMINATE. WINDS WILL BE A BIT GUSTIER WEDNESDAY AFTERNOON...10
SUSTAINED GUSTING TO 15-20 KNOTS. SOME DIURNAL CONVECTION IS AGAIN
POSSIBLE WEDNESDAY BUT COVERAGE IS NOT EXPECTED TO BE AS LARGE.

LONG TERM: SUB VFR CONDITIONS ARE POSSIBLE AGAIN WEDNESDAY AND
THURSDAY AS SHOWERS AND THUNDERSTORMS WILL CONTINUE OUT AHEAD OF AN
APPROACHING FRONTAL SYSTEM THAT WILL MOVE THROUGH THE AREA LATE
THURSDAY INTO EARLY FRIDAY. VFR CONDITIONS SHOULD RETURN FOR FRIDAY.


&&

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

&&

$$

SYNOPSIS...DJF
NEAR TERM...ELLIS
SHORT TERM...ELLIS
LONG TERM...SEC
AVIATION...ELLIS