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000
FXUS62 KRAH 180648
AFDRAH

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

.SYNOPSIS...
AN UPPER LEVEL TROUGH WILL TRACK SLOWLY EAST ACROSS OUR REGION
THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1000 PM FRIDAY...

THE COLD FRONT THAT APPROACHED NORTHEASTERN NC EARLIER TODAY HAS
ESSENTIALLY STALLED...AND CENTRAL NC REMAINS IN THE WEAKLY UNSTABLE
AIRMASS SOUTH OF THE FRONT.  CONVECTION HAS BEEN PRIMARILY FOCUSED
NEAR A SURFACE TROUGH OVER THE WESTERN PIEDMONT THIS EVENING...AND
HAS DRIFTED NORTH TOWARD THE NC/VA BORDER OVER THE PAST COUPLE OF
HOURS.  ELSEWHERE...CONVECTION HAS BEEN VERY ISOLATED...WITH THE
STRONGEST CELL OVER EASTERN WAYNE NOW DRIFTING EAST SINCE BEING
UNDERCUT BY THE SEABREEZE.  DESPITE BETTER DEEP LAYER MOISTURE THIS
EVENING (PW UP TO 1.25")...THE BOUNDARY LAYER REMAINS FAIRLY
DRY...SO IT WILL TAKE QUITE A BIT OF LIFT/MOISTENING TO TAP INTO THE
WEAK ELEVATED INSTABILITY THAT SHOULD RESIDE ABOVE THE NOCTURNAL
INVERSION.  THE REMNANT VORTEX FROM CONVECTION OVER THE SOUTHERN US
THE PAST COUPLE OF DAYS WILL DRIFT EAST TOWARD NC OVERNIGHT...BUT
SHOULD FAR ENOUGH TO OUR WEST NOT TO HAVE SIGNIFICANT INFLUENCE
UNTIL SATURDAY.  AHEAD OF THE WAVE...LOW LEVEL FLOW WILL INCREASE
SLIGHTLY ACROSS WESTERN NC TONIGHT AND MAY PROVIDE ENOUGH WARM
ADVECTION TO AID ADDITIONAL ISOLATED SHOWERS/STORMS.  THIS IS
SUPPORTED BY A FEW CONVECTION ALLOWING MODELS...PRIMARILY TOWARD
09-12Z.  WILL KEEP A SLIGHT CHANCE IN OVERNIGHT WITH VARIOUS
OUTFLOW/SEABREEZE BOUNDARIES LINGERING...AND BRING IN A LOW END
CHANCE OVER THE WESTERN PIEDMONT BY 12Z.  SKIES WILL REMAIN MOSTLY
CLOUDY...THOUGH IF PARTIAL CLEARING OCCURS...IT WOULD MOST LIKELY
OVER EASTERN AREAS.  LOWS SHOULD SETTLE INTO THE MID 60S IN MOST
LOCATIONS..THOUGH SOME LOWER 60S MAY BE POSSIBLE IN THE EAST IF
CLEARING OCCURS.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
AS OF 255 PM FRIDAY...

THE TROUGH ALOFT GRADUALLY MOVES INTO CENTRAL NORTH CAROLINA
SATURDAY AND SATURDAY NIGHT. WHILE DIFFERENCES CONTINUE WITH THE
DETAILS IN THE GUIDANCE...INCLUDING VARIOUS WRF OUTPUT...ON A LARGE
SCALE...MEAN RH INCREASES TO A MAXIMUM DURING THE PERIOD LATE
SATURDAY AFTERNOON IN THE NORTHWEST PIEDMONT...AND TO ABOUT U.S. 1
OR SO SATURDAY NIGHT. THE BEST LIFT IS NORTHWEST CLOSER TO THE UPPER
TROUGH...850MB THETA-E IS GREATEST IN CONJUNCTION WITH THE MEAN
RELATIVE HUMIDITY...AND BY LATE SATURDAY AFTERNOON AND SATURDAY
NIGHT...THE 850MB FLOW FROM THE SOUTHWEST INCREASES TO AROUND 25KT
FOCUSED OVER AND NEAR THE WESTERN PIEDMONT. BUFR SOUNDINGS
ESPECIALLY FROM THE GFS SHOW GREATER MOISTURE AND INSTABILITY WEST
COMPARED TO EAST IN CENTRAL NORTH CAROLINA. AS A RESULT...INSTEAD OF
TRYING TO INTERPRET THE VARIETY OF WRF TRENDS...HAVE FOLLOWED A
PRECIPITATION FORECAST LEANING MORE TOWARD LARGE-SCALE FEATURES.
THIS RESULTS IN MOSTLY CHANCE POPS FOR SATURDAY...BECOMING LIKELY IN
THE IMMEDIATE TRIAD BY LATE IN THE DAY AND SPREADING LIKELY POPS TO
AROUND U.S. 1 BY OVERNIGHT SATURDAY CLOSER TO 850MB LOW PRESSURE.
THE LEAST CHANCES WILL BE TOWARD KGSB AND KCTZ...WHERE OVERALL
MOISTURE AND LIFT ARE LEAST...CLOSER ALSO TO THE 850MB RIDGE JUST
OFFSHORE. THE GFS HAS FAIRLY ROBUST PRECIPITATION AMOUNTS IN THE
TRIAD OVERNIGHT SATURDAY AND THIS WILL HAVE TO BE WATCHED...BUT FOR
NOW WILL FORECAST AVERAGE PRECIPITATION AMOUNTS THERE AROUND 0.75
INCH FROM LATE SATURDAY AFTERNOON THROUGH SATURDAY NIGHT. HIGHS
SATURDAY NEAR 80 NORTHWEST TO THE UPPER 80S SOUTHEAST...WITH
OVERNIGHT LOWS SATURDAY NIGHT IN THE MID 60S.

&&

.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. 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. 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 /06Z SATURDAY THROUGH WEDNESDAY/...
AS OF 145 AM SATURDAY...

24-HR TAF PERIOD:
A POTENTIAL FOR MVFR FOG WILL EXIST BETWEEN 08-12Z THIS MORNING...
PRIMARILY AT THE INT/GSO/RWI TERMINALS WHERE RECENT SHOWER ACTIVITY
HAS RESULTED IN RELATIVELY LOW TEMP/DPT SPREADS AS OF 05Z.
ELSEWHERE...SCT/BKN MID-LEVEL CLOUD COVER AND RELATIVELY HIGHER
TEMP/DPT SPREADS SHOULD PRECLUDE FOG FORMATION. OTHERWISE...
ANTICIPATE VFR CONDITIONS TO GENERALLY PREVAIL THROUGH MID
AFTERNOON. BY LATE AFTERNOON AND EVENING...EXPECT AN INCREASING
CHANCE FOR ISOLD TO SCT SHOWERS AND STORMS...ESP AT THE INT/GSO/
RDU/RWI TERMINALS...OR ALONG AND NORTH OF HWY 64.

LOOKING AHEAD:
A SLOW MOVING UPPER LEVEL DISTURBANCE APPROACHING THE REGION WILL
RESULT IN AN INCREASING CHANCE FOR SCATTERED TO WIDESPREAD SHOWERS/
STORMS AND ASSOCIATED SUB-VFR CONDITIONS SAT NIGHT THROUGH EARLY
NEXT WEEK...WITH THE BEST OVERALL CHANCE DURING THE AFTERNOON AND
EVENING HOURS EACH DAY. -VINCENT


&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...SMITH
SHORT TERM...DJF
LONG TERM...BADGETT
AVIATION...VINCENT