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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 181746
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
145 PM EDT SAT MAY 18 2013

.SYNOPSIS...
 
-- Changed Discussion --
A STALLED SURFACE FRONT WILL LIFT NORTH OF THE AREA LATE
TONIGHT/EARLY SUNDAY. MEANWHILE...AN UPPER LEVEL TROUGH WILL TRACK
SLOWLY EAST ACROSS THE CAROLINAS THROUGH EARLY NEXT WEEK.
-- End Changed Discussion --

&&

.NEAR TERM /TODAY AND TONIGHT/...
AS OF 940 AM SATURDAY...

A BAGGY MID-LEVEL TROUGH EXTENDING FROM CENTRAL ILLINOIS
SOUTHEASTWARD INTO THE SOUTHERN APPALACHIANS WILL MOVE VERY SLOWLY
EASTWARD OVER THE NEXT 60-72 HOURS...MOVING OVERHEAD ON SUNDAY
BEFORE FINALLY SLIDING OFFSHORE LATE MONDAY.  IN THE LOWER
LEVELS...A WEAK SURFACE FRONT WILL SAG SOUTHWARD ACROSS THE
NORTHERN HALF OF THE STATE TODAY....AND WILL LIFT NORTHWARD INTO
SOUTHEAST VA AND THE DELMARVA LATE TONIGHT/EARLY SUNDAY. PWATS WILL
STEADILY RISE THROUGH THE WEEKEND DUE TO THE PROLONGED SOUTHERLY
MOISTURE FEED ALONG AND AHEAD OF THE TROUGH...WITH A POOL OF
1.6-1.8" PWATS (2 STANDARD DEVIATIONS ABOVE NORMAL)BECOMING CENTERED
OVER THE CAROLINAS.

THERE WILL NOT BE A SHORTAGE OF FORCING MECHANISMS TODAY WITH
THE INTERACTION OF BOTH SYNOPTIC AND MESOSCALE FEATURES MAKING
FOR AN ACTIVE/UNSETTLED WEATHER DAY. THE STALLED FRONTAL BOUNDARY
COUPLED WITH SUPPORT FROM INDIVIDUAL S/W DISTURBANCES EMBEDDED IN
THE SLOW EASTWARD MOVING MID-LEVEL TROUGH WILL RESULT IN PERIODS
OF SHOWERS AND THUNDERSTORMS ...DIURNALLY ENHANCED AND AIDED BY
SEVERAL MESOSCALE BOUNDARIES PRESENT ACROSS THE REGION THIS
MORNING...INCLUDING OUTFLOWS FROM LAST NIGHT`S CONVECTION... THE
REMNANTS OF YESTERDAY`S SEABREEZE...AND EXPECTATIONS OF ANOTHER
ROBUST SEABREEZE THIS AFTERNOON.

THE BEST DIURNAL DESTABILIZATION IS EXPECTED EAST OF HWY 1 WHERE
LESS CLOUD COVER AND BETTER LOW-LEVEL MOISTURE ARE ANTICIPATED.
EXPECT MLCAPE VALUES AS HIGH AS 1000-1200 J/KG. HOWEVER WEAK SHEAR
OF 20KTS OF LESS SUGGESTS DISORGANIZED/PULSE STORMS THAT WILL
QUICKLY WEAKEN BY THE EVENING AS THE BOUNDARY LAYER STABILIZES.
INSTEAD...THE PRIMARY THREAT COULD BE FROM LOCALLY HEAVY
RAINFALL...WITH AS MUCH AS 2 INCHES POSSIBLE ESPECIALLY INVOF OF THE
STALLED FRONTAL ZONE WHICH WOULD BE CONDUCIVE FOR TRAINING OF STORMS.

TEMPERATURES...WILL DEPEND PRIMARILY ON CLOUD COVER AND PRECIP.
HIGHS RANGING FROM THE MID 80S E/SE (HIGHEST EAST OF HWY 1/SOUTH OF
HWY 64) TO UPPER 70S AND LOWER 80S IN THE FAR W/NW PIEDMONT WHERE
CLOUD COVER WILL BE MORE PERVASIVE. LOWS GENERALLY IN THE MID 60S.

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
AS OF 315 AM SATURDAY...

THE ADDITIONAL SHORTWAVE ENERGY APPROACHING THE APPALACHIANS LATE
TONIGHT WILL PROGRESS INTO CENTRAL NC SUNDAY AFTERNOON INTO SUNDAY
NIGHT...SLOWLY DEAMPLIFYING ALONG THE WAY. A MOIST LOW-LEVEL
SOUTHERLY RETURN FLOW WILL PERSIST...WITH AN OVERALL MOIST COLUMN IN
PLACE GIVEN PLENTIFUL MID/UPPER LEVEL MOISTURE ALONG AND AHEAD OF
THE DISTURBANCE APPROACHING TODAY/TONIGHT AND THE SECONDARY
DISTURBANCE SUN/SUN NIGHT. AS A RESULT...EXPECT MORE WIDESPREAD
CLOUD COVER AND LESS DIURNAL DESTABILIZATION THAN TODAY WITH MLCAPE
VALUES NO HIGHER THAN 500-1000 J/KG. HOWEVER...GIVEN DEEP MOISTURE
AND UPPER LEVEL FORCING OVER THE REGION IN THE FORM OF WEAK DPVA...
EXPECT GREATER CONVECTIVE COVERAGE THAN TODAY...AND WILL INDICATE
PRECIP CHANCES RANGING FROM 70-80% WEST/NW TO 50% FAR EAST/SE WHERE
THE RELATIVE BETTER UPPER LEVEL FORCING ASSOC/W THE SECONDARY
SHORTWAVE SHOULD LAG SOMEWHAT BEHIND PEAK HEATING IN ADDITION TO
WEAKENING WITH TIME. THE BEST OVERALL PRECIP CHANCES ARE EXPECTED
DURING THE MID/LATE AFTERNOON THROUGH EARLY EVENING...WITH A GENERAL
DECREASE IN COVERAGE SUN NIGHT IN ASSOC/W NOCTURNAL STABILIZATION...
THOUGH PRECIP CHANCES WILL REMAIN HIGHER THAN AVERAGE (40-50%) GIVEN
A CONTINUED MOIST AIRMASS IN THE PRESENCE OF WEAK/SLOW MOVING
SHORTWAVE ENERGY ALOFT. EXPECT COOLER HIGHS THAN TODAY...RANGING
FROM THE UPPER 70S IN THE N/NW PIEDMONT TO LOWER 80S SE COASTAL
PLAIN. ONCE AGAIN...DO NOT ANTICIPATE A SEVERE THREAT GIVEN VERY
WEAK DEEP-LAYER SHEAR AND LOW DCAPE. -VINCENT

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 245 AM SATURDAY...

THE UNSETTLED PERIOD IS EXPECTED TO CONTINUE INTO THE UPCOMING WEEK.
THE AFOREMENTIONED MID/UPPER TROUGH IS FORECAST TO LINGER OVER OUR
REGION MONDAY INTO MONDAY NIGHT. SHOWERS AND THUNDERSTORMS ARE
EXPECTED AGAIN MONDAY... ESPECIALLY DURING THE AFTERNOON AND EVENING
HOURS. LOCALLY HEAVY RAIN SHOULD CONTINUE TO BE A THREAT WITH
LOCALLY 1+ INCHES LIKELY. THE HIGHEST POP SHOULD GRADUALLY SHIFT
EASTWARD WITH TIME... WITH THE HIGHEST POP MONDAY AFTERNOON AND
EVENING LIKELY TO BE IN THE CENTRAL AND EASTERN ZONES. HIGHS SHOULD
REACH NEAR 80... BUT CONVECTION WILL PUT A LID ON TEMPS BY EARLY
AFTERNOON.

BY TUESDAY AND WEDNESDAY... A SUBTROPICAL RIDGE WILL TRY TO BUILD
WESTWARD FROM THE WESTERN ATLANTIC AS THE MID/UPPER TROUGH WEAKENS.
IT APPEARS THAT SOME DRYING WILL GRADUALLY WORK INTO OUR REGION IN
THE MID AND UPPER LEVELS. HOWEVER... IT APPEARS THAT THERE WILL BE
PLENTY OF LOW LEVEL MOISTURE TO WORK WITH (DEW POINTS WELL INTO THE
60S) TO SUPPORT WIDELY SCATTERED TO SCATTERED DIURNALLY DRIVEN
SHOWERS AND THUNDERSTORMS BOTH DAYS. HOWEVER... A PRONOUNCED
REDUCTION IN COVERAGE OF CONVECTION IS EXPECTED BOTH DAYS WHEN
COMPARED TO SUNDAY AND MONDAY. HIGHS WILL REBOUND BACK INTO THE MID
80S (UPPER 80S SANDHILLS). LOWS WILL BE WARM AND HUMID... 65-70.

THURSDAY AND FRIDAY... AN INCREASE IN SHOWERS AND THUNDERSTORMS IS
EXPECTED AGAIN AS ANOTHER MID/UPPER TROUGH APPROACHES FROM THE WEST.
HOWEVER... THE MAIN COLD FRONT IS PROJECTED TO REMAIN WEST OF THE
APPALACHIANS UNTIL SATURDAY WHEN IT MAY MAKE A RUN AT CENTRAL NC.
THEREFORE... WE WILL CONTINUE TO SHOW A GRADUAL INCREASE IN
DIURNALLY DRIVEN CONVECTION THURSDAY INTO SATURDAY... KEEPING POP IN
THE "CHANCE" CATEGORY. LOWS WILL CONTINUE WARM AND HUMID (65-70).
HIGHS IN THE 80S ARE EXPECTED... WITH SOME MINIMAL COOLING SATURDAY
BACK INTO THE UPPER 70S TO MID 80S.

&&

.AVIATION /18Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
AS OF 145 PM SATURDAY...

24-HR TAF PERIOD:

AREA OF IFR TO LIFR CEILINGS AT KINT INVOF OF THE STALLED FRONTAL
ZONE SHOULD LIFT TO VFR BETWEEN 18 TO 20Z. OTHERWISE...OUTSIDE OF
CONVECTION...ANTICIPATE PREDOMINATELY VFR CONDITIONS. SCATTERED
SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS THE AREA THIS
AFTERNOON. CONDITIONS ARE EXPECTED TO DETERIORATE AFTER MIDNIGHT AS
CEILINGS LOWER TO MVFR TO IFR IN LINGERING SHOWERS.

LOOKING AHEAD:
A SLOW MOVING UPPER LEVEL TROUGH MOVING THROUGH THE REGION WILL
RESULT IN UNSETTLED CONDITIONS WITH NUMEROUS TO WIDESPREAD SHOWERS
AND STORMS SUNDAY THROUGH MONDAY. DRIER CONDITIONS BY TUESDAY WITH
MOSTLY DIURNAL RAIN CHANCES WITH THE THREAT OF MORNING
FOG/STRATUS.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...CBL
NEAR TERM...CBL/VINCENT
SHORT TERM...VINCENT
LONG TERM...BADGETT
AVIATION...CBL