Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 281435
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1035 AM EDT THU AUG 28 2014

.SYNOPSIS...A BACK DOOR COLD FRONT WILL TRACK SOUTHWARD FROM
VIRGINIA INTO NORTH CAROLINA THROUGH TONIGHT...THEN STALL OUT
ACROSS THE REGION THROUGH FRIDAY NIGHT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1035 AM THURSDAY...

UPPER AIR ANALYSES FROM 12Z TODAY SHOW HIGH PRESSURE CENTERED OVER
THE MISSISSIPPI RIVER VALLEY WITH THE RIDGE AXIS SANDWICHED BETWEEN
A LOW OVER NE AND A LOW WELL TO THE NE OF NEW ENGLAND. THE H85 FRONT
EXTENDS FROM APPROX NYC WSW THROUGH OH AND INTO IA. EXPECT THE HIGH
TO DRIFT EAST TODAY...WITH THE RIDGE DAMPENING AND THE FRONT SLOWLY
SLIDING SOUTH TOWARD THE NC/VA BORDER. A WEAK DISTURBANCE AT H5
TRAVERSING THE RIDGE OVER VA ALONG THE FRONT MAY HELP GENERATE SOME
ISOLATED SHOWER ACTIVITY LATER THE AFT AND EVE. AT THE SURFACE...THE
BACKDOOR COLD FRONT WILL APPROACH THE AREA THROUGH THIS EVENING...
STALLING AROUND THE NC/VA BORDER OVERNIGHT. AS LOW-MID LEVEL
MOISTURE IS ADVECTED IN AHEAD OF THE FRONT WILL SEE DEWPOINTS
INCREASE ACROSS THE NORTH AND PW`S INCREASING FROM ABOUT 1.50" TO
1.75" THIS EVENING. THE FORECAST INSTABILITY DIFFERS BETWEEN THE NAM
AND GFS...WITH THE NAM FORECASTING MLCAPE OF 1000-1500 J/KG WHILE
THE GFS ONLY HAS AROUND 500 J/KG. MOST OF THE HI-RES CONVECTION
ALLOWING MODELS ARE GENERATING SOME SHOWERS AROUND 21Z THIS
AFTERNOON...MAINLY ACROSS THE NORTHERN HALF OF THE REGION...DRIFTING
SOUTH THROUGH THE EVENING. WILL CONTINUE TO INDICATE THE CHANCE FOR
CONVECTION LATER TODAY AND TONIGHT...BUT COVERAGE IS NOT EXPECTED TO
BE GREAT. HIGHS TODAY IN THE LOW TO MID 90S EXPECTED...WITH LOWS
TONIGHT AROUND 70 DEGREES.

&&

.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
AS OF 315 AM THURSDAY...

RIDGING ALOFT WILL PRECLUDE MUCH IN THE WAY OF UPPER LEVEL FORCING
FRI/FRI NIGHT...HOWEVER...THE FRONTAL ZONE STALLING OVER THE REGION
WILL INTRODUCE A LARGE DEGREE OF UNCERTAINTY WITH REGARD TO
TEMPERATURES AND PRECIP CHANCES...INCLUDING A POTENTIAL FOR WEAK
HYBRID CAD AND ELEVATED CONVECTION. AT THIS TIME WILL MAKE LITTLE
CHANGE TO THE PREVIOUS FORECAST...THOUGH ADDITIONAL MODIFICATIONS
MAY BE NEEDED PER FURTHER MODEL/DATA ANALYSIS THIS MORNING. THE MOST
LIKELY CHANGES WOULD BE A DROP IN HIGH TEMPS ACROSS THE N/NW
PIEDMONT AND AT LEAST A LOW CHANCE (20%) OF CONVECTION IN MOST
LOCATIONS...POSSIBLY EVEN FRI NIGHT WHEN FCST SOUNDINGS SUGGEST A
WEAK NOCTURNAL WARM ADVECTION REGIME IN THE PRESENCE OF PLENTIFUL
LOW-LEVEL MOISTURE AND ELEVATED INSTABILITY. -VINCENT

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 255 AM THURSDAY...

UPPER RIDGING IS EXPECTED TO RESIDE OVER THE SOUTHEASTERN STATES SAT-
MON... THEN BUILD WESTWARD INTO THE SOUTHERN PLAINS NEXT WEEK.
GUIDANCE WAS FASTER THIS RUN WITH THE HEIGHT FALLS AND THE ATTENDANT
SURFACE COLD FRONT NOW SLATED INTO THE REGION FROM THE NORTHWEST ON
WEDNESDAY AFTERNOON AND EVENING.

HIGHLIGHTS IN THE LONG TERM WILL BE INCREASING HEAT...HUMIDITY...
AND THE CHANCES OF SHOWERS AND THUNDERSTORMS. THIS PATTERN WILL
LIKELY LAST THROUGH MID-WEEK WHEN A COLD FRONT IS NOW SLATED TO
ARRIVE WED PM. THE FRONT SHOULD SETTLE SOUTH OF THE STATE THURSDAY
ALLOWING FOR COOLING FROM THE NE AGAIN THU-FRI.

UNTIL THEN... EXPECT PARTLY SUNNY TO PARTLY CLOUDY SKIES THIS
WEEKEND. A CHANCE OF PM THUNDERSTORMS ESPECIALLY BY SUNDAY. HIGHS
RETURN TO NEAR NORMAL (86-92) BOTH SAT-SUN. LOWS 65-70.

MON-WED... A CHANCE OF MAINLY AFTERNOON AND EVENING THUNDERSTORMS
EACH DAY... WITH THE BEST CHANCE EXPECTED WEDNESDAY. HIGHS 86-92.
LOWS IN THE UPPER 60S TO MID 70S.

TEMPS WILL COOL BACK INTO THE LOWER TO MID 80S BY THURSDAY WITH THE
NE FLOW LEVEL FLOW. ALSO... THE CHANCE OF THUNDERSTORMS WILL SHIFT
WITH THE FRONT INTO FAR SE NC AND SC.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
AS OF 715 AM THURSDAY...

24-HR TAF PERIOD: VFR CONDITIONS AND CALM OR LIGHT AND VARIABLE
WINDS WILL PREVAIL THROUGH THE MAJORITY OF THE TAF PERIOD. THE ONLY
POSSIBLE EXCEPTION WILL BE A POTENTIAL FOR ISOLD TO SCT CONVECTION
AT THE LEADING EDGE OF A BACKDOOR COLD FRONT MOVING SOUTH/SE INTO
THE REGION THIS AFT/EVE INTO TONIGHT...OR ROUGHLY FROM 21Z THIS AFT
THROUGH 06Z FRI MORNING...WITH THE BEST CHANCE FROM THE VA BORDER
SOUTH TO THE INT/GSO/RDU/RWI TERMINALS.

LOOKING AHEAD: THE FRONT WILL STALL AND SLOWLY BEGIN TO DISSIPATE
OVER THE REGION FRI/FRI NIGHT. CONFIDENCE REMAINS BELOW NORMAL IN
THIS PERIOD...AND IT IS POSSIBLE THAT VFR CONDITIONS PREVAIL
EVERYWHERE FRI/FRI NIGHT...OR THAT SUB-VFR CONDITIONS ASSOC/W LOW
CEILINGS AND ISOLD ELEVATED CONVECTION COULD BE PRESENT LATE FRI/FRI
NIGHT. OTHERWISE...CLIMATOLOGICAL CONDITIONS APPEAR LIKELY SAT
THROUGH EARLY NEXT WEEK...I.E. A POTENTIAL FOR ISOLD AFT/EVE
CONVECTION AND EARLY MORNING FOG/STRATUS. -VINCENT

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...KC
SHORT TERM...VINCENT
LONG TERM...PWB
AVIATION...VINCENT


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