Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 310028 RRA
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
828 PM EDT WED JUL 30 2014

.SYNOPSIS...DRY HIGH PRESSURE WILL WEAKEN AND MODIFY THROUGH FRIDAY
AS ATLANTIC MOISTURE GRADUALLY RETURNS TO THE REGION. A MORE
UNSETTLED PATTERN WILL DEVELOP OVER THE WEEKEND AS AN UPPER LEVEL
TROUGH APPROACHES FROM THE WEST AND AN ASSOCIATED COASTAL FRONT
MOVES INLAND ACROSS THE CENTRAL CAROLINAS.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 245 PM WEDNESDAY...

SHOWERS STARTING TO BREAK OUT MAINLY ALONG THE HIGHWAY 1 CORRIDOR
HIGHLIGHTED ON THE VISIBLE SATELLITE IMAGERY BY A MORE ENHANCED
CUMULUS FIELD. THIS WAS CAPTURED WELL ON HIGH RESOLUTION
MODELS...PARTICULARLY THE LATEST RUN OF THE HI-RES WRF NMM. THIS
SOLUTIONS CONTINUES SHOWERS THROUGH THE EVENING BUT DOES NOT ENHANCE
ACTIVITY MUCH. THEREFORE WILL KEEP SLIGHT CHANCE OF SHOWERS AND
INTRODUCE ISOLATED THUNDER IN THE FORECAST...AS ALTHOUGH MOISTURE
APPEARS VERY SHALLOW AT THIS TIME...SPC SURFACE ANALYSIS SUGGESTS
500 J/KG OF MIXED LAYER CAPE OVER CENTRAL NC AND A SMALL AREA OF 25-
30 KT EFFECTIVE SHEAR IN THE KFAY AREA. CLOUD COVER HAS LIMITED HIGH
TEMPERATURES...ESPECIALLY IN THE NORTH AND WEST AND WILL LIKELY TOP
OUT IN THE UPPER 70S NW TO LOW TO MID 80S IN THE EXTREME SOUTH.
EXPECT TO HAVE CLOUD COVER AND POSSIBLY A LINGERING SHOWER RUN INTO
THE OVERNIGHT HOURS WHICH SHOULD HELP LIMIT FOG/LOW STRATUS BUT A
BRIEF PERIOD OF BOTH WILL BE POSSIBLE AT KRDU...KFAY...AND KRWI JUST
BEFORE SUNRISE. THE INCREASE IN CLOUD COVER SHOULD HELP KEEP LOW
TEMPERATURES UP A COUPLE DEGREES FROM LAST NIGHTS LOWS...MAINLY LOW
TO MID 60S ACROSS THE AREA FROM NW TO SE.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
AS OF 245 PM WEDNESDAY...

THE UPPER LEVEL TROUGH WILL REMAIN DRAPED ACROSS THE EASTERN CONUS
ON THURSDAY. AT THE LOW LEVELS SOUTHERLY FLOW WILL BEGIN TO RETURN
TO THE AREA...INCREASING MOISTURE IN THE SOUTHWESTERN CWA VIA RETURN
FLOW. THIS PROCESS WILL TAKE A WHILE TO GET GOING HOWEVER AND MOST
OF THE MORNING/EARLY AFTERNOON SHOULD REMAIN DRY WITH INCREASING
CLOUD COVER FROM THE SOUTHWEST DURING THE DAY. AFTER 18Z...THE
CHANCES FOR SHOWERS AND POTENTIALLY A THUNDERSTORM WILL INCREASE
WITH MOST MODEL SIMULATIONS PRODUCING QPF BY 00Z FRIDAY AS
PRECIPITABLE WATER VALUES BEGIN TO CLIMB TOWARDS TWO INCHES.
INSTABILITY WILL BE VERY LIMITED THURSDAY AFTERNOON AND EVENING
ALTHOUGH ABOUT 40 KTS OF BULK SHEAR WILL BE AVAILABLE. ANY
SHOWERS/STORMS THAT DO COMMENCE THURSDAY AFTERNOON WILL HAVE A
CHANCE OF CONTINUING THROUGH THE OVERNIGHT HOURS AS SOME ELEVATED
INSTABILITY MAY BE PRESENT IN THE FORM OF A VORT MAX MOVING THROUGH
ON THE EASTERN SIDE OF THE UPPER TROUGH FROM SOUTHWEST TO NORTHEAST.
WITH INCREASE CLOUDS FROM THE SOUTHWEST...MAX TEMPS MAY BE HIGHEST
IN THE NORTHEAST ON THURSDAY WITH TEMPS IN THE MID TO UPPER 80S AND
ONLY LOWER 80S IN THE WEST AND SOUTHWEST. OVERNIGHT LOWS THURSDAY
NIGHT WILL MODERATE INTO THE UPPER 60S.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
AS OF 315 PM WEDNESDAY...

THE OVERALL PATTERN DURING THE LONG TERM PERIOD FEATURES AN EASTERN
CONUS TROUGH AND A WESTERN U.S. RIDGE WHICH WILL SUPPORT NEAR OR
COOLER THAN AVERAGE TEMPERATURES AND NEAR OR GREATER THAN NORMAL
THREAT OF PRECIPITATION.

THE BROAD EASTERN U.S. TROUGH SHARPENS ACROSS THE LOWER MISSISSIPPI
VALLEY ON FRIDAY AND A STRENGTHENING INVERTED TROUGH/COASTAL FRONT
DEVELOPS. AN INCREASINGLY MOIST ENVIRONMENT COMBINED WITH ISENTROPIC
LIFT WILL PROMOTE A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS FRIDAY
AFTERNOON AND EVENING THAT WILL LINGER BUT BECOME MORE SCATTERED
FRIDAY NIGHT.

THE UPPER TROUGH SHARPENS FURTHER OVER THE WEEKEND AS THE INVERTED
TROUGH MOVES INLAND AND DEEP MOISTURE OVERSPREADS THE REGION.
PRECIPITABLE WATER VALUES CLIMB TO AROUND OR JUST OVER 2 INCHES
WHICH IS 2 STANDARD DEVIATIONS ABOVE CLIMATOLOGY DURING THE WEEKEND.
THE AXIS OF GREATEST MOISTURE EXTENDING SOUTH-NORTHEAST ACROSS
CENTRAL NC. NWP GUIDANCE ADVERTISE MULTIPLE DISTURBANCES IN THE
SHARPENING UPPER TROUGH THAT WILL LIKELY ENHANCE PRECIPITATION
COVERAGE AND INTENSITY ALTHOUGH IT IS DIFFICULT TO PIN POINT THE
TIMING AND LOCATION AT THIS POINT. FOR NOW WILL INCLUDE LIKELY POPS
FOR SATURDAY AND VERY HIGH CHANCE POPS FOR SUNDAY WITH THE GREATEST
COVERAGE DURING THE AFTERNOON AND  EVENING HOURS.

BOTH THE GFS AND THE ECMWF SUGGEST A PORTION OF THE TROUGH WILL
BREAK OFF AND MOVE ACROSS THE NORTHEAST ON MONDAY AND OFFSHORE
TUESDAY WHILE A PORTION OF THE TOUGH LINGERS ACROSS THE LOWER
MISSISSIPPI VALLEY. THIS SHOULD RESULT IN A DECREASE IN CONVECTIVE
COVERAGE AND MORE TYPICAL CHANCES OF MAINLY AFTERNOON AND EVENING
THUNDERSTORMS. ANOTHER DISTURBANCE DROPS INTO HE TROUGH ON WEDNESDAY
BRING A COLD FRONT WITH IT THAT COULD ONCE AGAIN ENHANCE
PRECIPITATION CHANCES FOR THE MID WEEK.

HIGH TEMPS WILL GENERALLY RANGE IN THE UPPER 70S TO LOWER 80S ON
FRIDAY THROUGH SUNDAY AN THEN MODERATE SLIGHTLY INTO THE LOWER TO
MID 80S BY MID WEEK. MORNING LOWS WILL RANGE IN THE MID 60S TO NEAR
70 FOR MOST OF THE PERIOD. -BLAES

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
AS OF 815 PM WEDNESDAY...

24-HR TAF PERIOD: VFR CONDITIONS WILL PREVAIL THROUGH THE MAJORITY
OF THE TAF PERIOD. THE ONLY EXCEPTION WILL BE A SMALL POTENTIAL FOR
SUB-VFR FOG NEAR SUNRISE THU MORNING (09-12Z THU) AT THE FAY/RWI
TERMINALS...AND ISOLD/SCT CONVECTION THAT COULD AFFECT ANY TERMINAL
DURING THE AFTERNOON AND EVENING HOURS. WINDS WILL REMAIN LIGHT AND
VARIABLE AT 4-7 KNOTS IN MOST LOCATIONS.

LOOKING AHEAD: EXPECT AN INCREASING POTENTIAL FOR ADVERSE AVIATION
CONDITIONS ASSOCIATED WITH LOW CEILINGS AND SCATTERED TO WIDESPREAD
CONVECTION FRIDAY NIGHT THROUGH THE WEEKEND AS A COASTAL FRONT
RETROGRADES INLAND INTO CENTRAL PORTIONS OF THE STATE IN ADVANCE OF
AN UPPER LEVEL TROUGH APPROACHING FROM THE WEST. -VINCENT

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...ELLIS
SHORT TERM...ELLIS
LONG TERM...BLAES
AVIATION...VINCENT


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