-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 161809
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
210 PM EDT SUN JUN 16 2013

.SYNOPSIS...
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HIGH PRESSURE WILL MOVE OFFSHORE THIS EVENING...AHEAD OF AN UPPER
LEVEL DISTURBANCE THAT MOVES THROUGH THE REGION OVERNIGHT AND
MONDAY. A COLD FRONT SLOWLY APPROACHES FROM THE NORTHWEST LATE
MONDAY AND MOVES ACROSS THE REGION LATE TUESDAY INTO WEDNESDAY
MORNING.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1150 AM SUNDAY...

THE UPPER RIDGE WILL CONTINUE TO FLATTEN TODAY AS SURFACE HIGH
PRESSURE CONTINUES TO MOVE OFF TO THE SOUTHEAST...AND THE GRADIENT
TIGHTENS BETWEEN THE RETREATING HIGH AND SURFACE TROUGHINESS
SHARPENING OVER THE WESTERN PART OF THE STATE. THE 12Z KGSO
SOUNDING...AS WELL AS THE SOUNDING FROM KMHX...SHOWED A DECENT CAP
REMAINING AROUND 700MB...WHILE THE KRNK SOUNDING INDICATED JUST
SLIGHTLY COOLER TEMPERATURES JUST ABOVE 700MB ALBEIT WITH A WEAK CAP
IN PLACE. THE RAP SOUNDINGS FORECAST THIS CAP ESSENTIALLY REMAINING
FOR THE REST OF THE DAY...VERY GRADUALLY DIMINISHING ESPECIALLY
TOWARD THE NORTHWEST PIEDMONT AS THE RIDGE FLATTENS...UPPER LEVELS
COOL...AND THE OVERALL MOISTURE OF THE AIR MASS INCREASES. THE RAP
FORECASTS 850MB SUBSIDENCE THROUGHOUT THE DAY...WITH ANY MODEST UVV
WITH APPROACHING MID-LEVEL SHORTWAVES HOLDING OFF UNTIL 00Z AND
AFTER. THE LATEST HRRR WRF IS DRY AS WELL...ALONG WITH QPF FROM THE
RAP. WILL CONTINUE WITH A DRY FORECAST TODAY...AND EXPECT PERIODS OF
MOSTLY MID- AND SOME HIGH-LEVEL CLOUDS TO RESULT IN A
PARTLY-TO-MOSTLY SUNNY LATE MORNING AND AFTERNOON. ALREADY THERE
HAVE BEEN A FEW WIND GUSTS IN THE TEENS KNOTS AND...BASED ON THE
LATEST RAP SOUNDINGS AND THE WINDS ALOFT ON THE KRAX 88D VAD WIND
PROFILE...INCREASED THE GUSTS A TRIFLE ESPECIALLY OUTSIDE OF
SOUTHEAST AREAS TO MORE AROUND 20KT. WHILE THE MAV MOS HAS SIMPLY
BEEN TOO WARM OF LATE...THE MET MOS IS CLOSER TODAY TO THE MAV AND
TO THE ONGOING FORECAST. LOWERED A DEGREE TOWARD KRWI BASED ON THE
LATEST TRENDS AND MOS...AND AS A RESULT OF SLIGHTLY COOLER
1000-850MB THICKNESSES COMPARED TO THE REST OF CENTRAL NORTH
CAROLINA. STILL...HIGHS 85 TO 90.

THE VERY LATEST GUIDANCE HAS BEEN A LITTLE MORE AGGRESSIVE WITH THE
POTENTIAL FOR AT LEAST LIGHT QPF MOVING IN A LITTLE MORE IN EARNEST
INTO NORTHERN AREAS OVERNIGHT...MAINLY AFTER 02Z OR SO. MID-LEVEL
COOLING AND OVERALL MOISTENING ON THE NAM IS EFFICIENT OVERNIGHT...
AND THE LATEST HRRR WRF SUGGESTS UPSTREAM PRECIPITATION CURRENTLY
OVER SOUTHERN ILLINOIS INTO KENTUCKY ABLE TO MAKE STEADY PROGRESS
EAST-SOUTHEAST INTO AT LEAST THE TRIAD AND TOWARD KTDF AS
MOISTENING...AND COOLING ALOFT...OCCUR. FOR THE LATE MORNING
UPDATE...RAISED POPS INTO CHANCE FOR THAT AREA. WILL NOTE THE LATEST
NAM MOS GUIDANCE IS INTO CATEGORICAL IN THE TRIAD FOR THE OVERNIGHT
HOURS...DIMINISHING BUT STILL HIGHER ELSEWHERE. AFTER A REVIEW OF
THE GFS...MAY NEED TO SHOW SOME FURTHER INCREASE FOR MANY PARTS OF
CENTRAL NORTH CAROLINA OVERNIGHT. OTHERWISE...CLOUDINESS...AGAIN
MAINLY MID AND UPPER...WILL BECOME PREVALENT TONIGHT AS THE
APPROACHING FRONT TRANSLATES INTO THE LEE TROUGH. MINS WILL BE MILD
AND SEASONABLE...UPPER 60S.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 315 AM SUNDAY...

MONDAY AND MONDAY NIGHT...TRANSITION TO A BROAD LONGWAVE TROF WILL
BE UNDERWAY AND THE LINGERING LOW LEVEL TROFFING ALONG THE ATLANTIC
SEABOARD WILL PROMOTE AN INCREASINGLY MOIST AIRMASS. THICKNESSES ARE
RELATIVELY HIGH AND SIMILAR TO SUNDAY...WITH THE POTENTIAL FOR UPPER
80S. MOSTLY CLOUDY SKIES WILL HAMPER INSOLATION A BIT...MOSTLY MID
80S WEST TO UPPER 80S EAST. CHANCES OF SHOWERS WILL INCREASE MONDAY
AFTERNOON INTO MONDAY NIGHT IN INCREASINGLY DISTURBED FLOW...BUT ITS
DIFFICULT TO PICK OUT A PARTICULAR FEATURE DURING THIS TIME FRAME TO
FOCUS ACTIVITY...WILL CONTINUE CHANCE CATEGORY POPS FAVORING THE
WEST AND NORTH.

TUESDAY AND TUESDAY NIGHT: WITHIN A BROAD TROUGH ALOFT EAST OF THE
ROCKIES...A LOW AMPLITUDE SOUTHERN STREAM SHORTWAVE TROUGH...AND
PERHAPS A PRECEDING MCV FROM CONVECTION INITIATED AHEAD OF THIS WAVE
OVER THE CENTRAL PLAINS LATER TODAY AND TONIGHT...WILL MIGRATE
THROUGH THE BASE OF THE TROUGH/ACROSS THE CENTRAL APPALACHIANS AND
MIDDLE ATLANTIC REGION TUE. THESE FEATURES WILL BE FOLLOWED QUICKLY
BY AN ELONGATED BUT STRONGER NORTHERN STREAM WAVE IN NW FLOW FROM
THE UPPER MIDWEST TO THE CENTRAL APPALACHIANS TUE NIGHT.

IN THE LOW LEVELS...A PRE-FRONTAL TROUGH OVER VA/NC TUE WILL BE
OVERTAKEN BY A COLD FRONT ATTENDING THE AFOREMENTIONED NORTHERN
STREAM S/W TROUGH...AND THIS MERGED BOUNDARY WILL SETTLE SOUTHWARD
ACROSS CENTRAL NC TUE NIGHT. WITH A CONDITIONALLY UNSTABLE AND
UNCAPPED ENVIRONMENT PER BUFR SOUNDINGS...AND WITH FORECAST
PRECIPITABLE WATER VALUES APPROACHING TWO INCHES...THE WEAK (~20
METER/12 HR) HEIGHT FALLS ASSOCIATED WITH THE SERIES OF DISTURBANCES
ALOFT AND LOW LEVEL CONVERGENCE ALONG THE PRE-FRONTAL TROUGH/FRONT
WILL SUPPORT THE DEVELOPMENT OF NUMEROUS TO WIDESPREAD SHOWERS AND
STORMS TUE. THE SLOW SOUTHWARD PASSAGE OF THE SURFACE FRONT WILL END
THE THREAT OF CONVECTION FROM NORTH TO SOUTH TUE EVENING AND
OVERNIGHT...WITH JUST A LINGERING CHANCE OF A FEW SHOWERS ALONG THE
FAR SOUTHERN TIER BY WED MORNING.

WHILE WSW MEAN FLOW ALIGNED PARALLEL TO THE UNDERLYING SURFACE FRONT
SUGGESTS DOWNPOURS/ LOCALIZED FLOODING IN TRAINING STORMS ALONG THE
BOUNDARY MAY PROVIDE THE GREATEST IMPACT...INCREASING MID LEVEL
FLOW/BULK SHEAR TO AROUND 30 KTS MAY ALSO SUPPORT MULTI-CELL STORM
ORGANIZATION WITH PRECIPITATION-LOADED STRONG WET MICROBURST WIND
GUSTS. IN ADDITION...FORECAST MAXIMUM SRH AROUND 100 M2/S2 COULD BE
NEARLY DOUBLED LOCALLY INVOF OUTFLOW/BACKED SURFACE FLOW...WHICH
COULD SUPPORT BRIEF SUPERCELLULAR STRUCTURES...THOUGH SUCH A
SCENARIO WILL BE DEPENDENT ON MESO AND STORM SCALE INFLUENCES WITH
LIMITED PREDICTABILITY BEYOND A FEW HOURS. AS SUCH...WILL INCLUDE
ONLY A GENERIC ONE SENTENCE MENTION OF A STRONG TO SEVERE STORM IN
THE HWO FOR NOW FOR TUE. MOSTLY CLOUDY AND STORMY CONDITIONS WILL
SUPPORT HIGHS FROM THE UPPER 70S NW...TO LOWER TO MIDDLE 80S OVER
THE SOUTH...WITH LOWS MOSTLY IN THE UPPER 60S...TO AROUND 70 DEGREES
SOUTH.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 255 AM SUNDAY...

WEDNESDAY THROUGH SATURDAY: BELOW AVERAGE TEMPERATURES - IN THE
UPPER 70S TO LOWER-MIDDLE 80S - IN WEAK POST-FRONTAL HIGH PRESSURE
AND ASSOCIATED GENERALLY EAST TO ENE LOW LEVEL FLOW...WILL THEN
PREVAIL THROUGH THE END OF THE WEEK. HOWEVER...THE SURFACE FRONT
WILL LIKELY LINGER OVER SC THROUGH THU GIVEN CONTINUED FRONT-
PARALLEL FLOW ALOFT IN THE BASE OF BROAD EASTERN CONUS TROUGH. WILL
ACCORDINGLY MAINTAIN A SLIGHT CHANCE OF A SHOWER OR STORM OVER THE
FAR SOUTHERN SANDHILLS AND COASTAL PLAIN...IN CLOSEST PROXIMITY TO
THIS FRONT AND HIGHER BL MOISTURE...AND ALSO TOWARD THE YADKIN RIVER
WHERE A FEW WEAKENING SHOWERS/STORMS MAY DRIFT AFTER INITIATION AND
PROPAGATION FROM THE EASTERN SLOPES. A WARMER SOUTHEASTERLY...TO
SOUTHERLY RETURN FLOW BY SATURDAY...WILL RESULT IN RISING
TEMPERATURES TO AROUND THE 30-YEAR AVERAGE...AND HUMIDITY
LEVELS...BY THE WEEKEND. A RISK OF A FEW LATE AFTERNOON PULSE
SHOWERS OR STORMS WILL CONSEQUENTLY INCREASE TO NEAR CLIMATOLOGICAL
PROBABILITIES...AROUND 20 PERCENT OR SO...BY SAT.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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AS OF 210 PM SUNDAY...

SOMEWHAT CHALLENGING TAF FORECAST...DEPENDENT ON HOW MUCH
PRECIPITATION IS ABLE TO MAKE IT SOUTHEAST INTO THE SLIGHTLY MORE
CAPPED AIR MASS. OVERNIGHT...EXPECT A HIGH PROBABILITY OF VFR
CONDITIONS...WITH A CHANCE OF A PERIOD OF MVFR CONDITIONS IN
SCATTERED SHOWERS. THE CHANCES FOR AREAS OF MVFR CONDITIONS IMPROVE
LATE TONIGHT AND MONDAY...IN AT LEAST SCATTERED AREAS OF SHOWERS AND
WIDELY SCATTERED THUNDERSTORMS. SREF PROBABILITIES OF IFR CONDITIONS
ARE CURRENTLY LOW AND WILL SHOW CENTRAL NORTH CAROLINA TAF SITES
ONLY GETTING AS LOW AS MVFR DURING THE 18Z VALID TAF PERIOD.
MODESTLY GUSTY SOUTHWEST SURFACE WINDS THIS AFTERNOON WILL DIMINISH
TO MAINLY 5 TO 10KT OVERNIGHT...HOWEVER...DURING THE OVERNIGHT
PERIOD WINDS WITHIN 3K FEET OF THE SURFACE SHOULD INCREASE TO 25 TO
30KT...WITH WINDS AT THAT LEVEL DIMINISHING TOWARD 12Z MONDAY.
BEYOND THE 18Z VALID TAF PERIOD...GOOD PROBABILITY OF PERIODS OF
SUB-VFR CONDITIONS MONDAY AFTERNOON THROUGH TUESDAY IN LOW CLOUDS
AND SCATTERED-TO-NUMEROUS SHOWERS AND THUNDERSTORMS. CONDITIONS
BECOME PRIMARILY VFR WEDNESDAY THROUGH FRIDAY...OUTSIDE OF ANY
REMAINING ISOLATED SHOWERS AND THUNDERSTORMS.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...KMC/DJF
NEAR TERM...DJF/MLM
SHORT TERM...MLM/MWS
LONG TERM...MWS
AVIATION...DJF