Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 231056
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
655 AM EDT SAT AUG 23 2014

.SYNOPSIS...A COLD FRONT WILL MOVE SOUTH THROUGH THE STATE TONIGHT
INTO SUNDAY. HIGH PRESSURE WILL THEN BUILD SOUTH INTO THE REGION FOR
EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 315 AM SATURDAY...

TODAY AND TONIGHT: NORTHWEST TO NORTH-NORTHWEST MID LEVEL FLOW WILL
CONTINUE ACROSS CENTRAL NC THIS MORNING AND TODAY... YIELDING A
CONTINUED THREAT OF DISTURBANCES ALOFT TRACKING ACROSS CENTRAL NC.
MEANWHILE... A WEAK SURFACE TROUGH WILL SLIP TO THE SOUTH OF CENTRAL
NC THIS MORNING... YIELDING GENERALLY A LIGHT NORTHEAST TO NORTHERLY
SURFACE FLOW ACROSS THE AREA TODAY. HOWEVER... THE MAIN SURFACE
FRONT IS EXPECTED TO REMAIN TO THE NORTH OF THE AREA THROUGH AT
LEAST THIS AFTERNOON/EVENING. GIVEN ALL OF THIS... EXPECT MOSTLY
CLOUDY TO OVERCAST SKIES TODAY... WITH SCATTERED SHOWERS AND STORMS
TODAY (POSSIBLY NUMEROUS)... MOST DURING PEAK HEATING AIDED BY THE
APPROACHING SURFACE FRONT. THIS SHOULD HELP TO HOLD TEMPS DOWN SOME
FROM YESTERDAY FOR MOST LOCATIONS. THUS... WILL SHOW HIGH TEMPS
RANGING FROM THE MID 80S NE TO LOWER 90S SW. WRT A SEVERE THREAT
TODAY... GIVEN THE EXPECTED CLOUD COVER AND CONTINUED GENERAL 20-25
KTS OF DEEP LAYER SHEAR EXPECT ANY THREAT TO BE VERY ISOLATED. BOTH
THE GFS AND NAM SHOW THE BEST INSTABILITY ACROSS THE SOUTHWESTERN
HALF OF THE CWA (GENERALLY IN THE 1000-1500 J/KG RANGE... SURFACE
BASED)... AND THUS WOULD EXPECT THIS LOCATION TO BE MOST FAVORED FOR
A STRONG TO SEVERE STORM OR TWO. HOWEVER... GIVEN THE PROBABILITY IS
RATHER LOW WE ARE NOT EVEN OUTLOOKED IN THE DAY ONE CONVECTIVE
OUTLOOK FROM SPC. HEAVY RAIN WILL BE A THREAT WITH THE STRONGEST
CONVECTION AS PW`S ARE FORECAST TO REMAIN NEAR 2 INCHES.

MAIN AREA OF CONVECTION IS FORECAST TO BEGIN PUSHING TO THE SOUTH OF
THE AREA BY THIS EVENING... WHILE THE LOW LEVEL FRONTAL ZONE BEGINS
TO MOVE INTO THE AREA. THIS SHOULD YIELD A CONTINUED LOW END CHANCE
OF AT LEAST SOME SHOWERS THOUGH. WITH A LOW LEVEL EAST TO
NORTHEASTERLY FLOW TONIGHT... LOW STRATUS IS APT TO DEVELOP... WITH
PATCHY LIGHT DRIZZLE EVEN. THE MAIN PUSH OF THE COOLER AIR SHOULD
HOLD OFF UNTIL AFTER DAYBREAK SUNDAY. THUS... EXPECT LOW TEMPS WILL
BE IN THE UPPER 60S TO LOWER 70S.

SUNDAY: SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE AREA
ON SUNDAY... ALONG WITH DRIER AIR ALOFT. THIS WILL YIELD MUCH DRIER
CONDITIONS ON SUNDAY... WITH SKIES BECOMING PARTLY SUNNY BY
AFTERNOON. HIGH TEMPS WILL BE COOLER... AROUND 80 NORTHEAST TO MID
80S SOUTH/SOUTHWEST. CAN`T RULE OUT SOME LIGHT SHOWERS IN THE EAST
TO EAST-NORTHEASTERLY LOW LEVEL FLOW IN THE MORNING TO EARLY
AFTERNOON THOUGH.

&&

.SHORT TERM /SUNDAY NIGHT AND MONDAY/...
AS OF 306 AM SATURDAY...

SURFACE DRY AIR RIDGE EXTENDS SOUTHWARD INTO NC FROM A PARENT HIGH
POSITIONED OVER NORTHERN MID ATLANTIC. THIS SURFACE RIDGE SUPPORTED
ALOFT BY A BUILDING UPPER LEVEL RIDGE...STRETCHING FROM THE MID-
LOWER MS VALLEY NEWD INTO NEW ENGLAND. NELY LOW LEVEL FLOW WILL
ADVECT COOLER DRIER AIR INTO CENTRAL NC. THIS DRIER AIR WILL AID TO
DIMINISH ANY RESIDUAL STRATOCU.

LOW LEVEL THICKNESSES DROP TO VALUES 15-20M BELOW NORMAL FOR LATE
AUGUST. THIS YIELDS MAX TEMPS OF NEAR 80 ACROSS THE FAR NORTH-NW TO
LOW/MID 80S FAR SOUTH. MIN TEMPS SUNDAY NIGHT LOW-MD 60S.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 306 AM SATURDAY...

MONDAY NIGHT THROUGH THURSDAY...TRANQUIL WEATHER PATTERN WILL
CONTINUE. UPPER LEVEL RIDGE WILL REMAIN HIGHLY AMPLIFIED UNTIL LATE
WEDNESDAY INTO THURSDAY AT WHICH TIME A S/W IN THE NORTHERN STREAM
WILL BE EXITING THE NORTHERN PLAINS INTO THE GREAT LAKES. THE
APPROACH OF THIS SYSTEM WILL WEAKEN/SUPPRESS THE UPPER RIDGE
SOUTHWARD. ASSOCIATED SFC RIDGE WILL MAINTAIN A DRY WEATHER REGIME
WITH MODERATING TEMPERATURES THROUGH THURSDAY. MAX TEMPS TUESDAY
NEAR 80 NORTH TO LOWER 80S SOUTH WARM TO THE MID-UPPER 80S BY
THURSDAY. MIN TEMPS ALSO GRADUALLY MODIFY...FROM THE UPPER 50S-LOWER
60S TUESDAY MORNING TO THE MID 60S THURSDAY MORNING.

FORECAST CONFIDENCE WANES THURSDAY INTO FRIDAY AS GFS IS MUCH FASTER
WITH THE APPROACH OF THE NORTHERN STREAM S/W TOWARD THE EAST COAST
VERSUS THE SLOWER ECMWF. ALSO OF CONCERN IS THE EVENTUAL TRACK OF
THE TROPICAL SYSTEM THAT IS EXPECTED TO TRACK PARALLEL BUT OFFSHORE
OF THE SE U.S. COAST. LATEST MODEL GUIDANCE (MAINLY ECMWF) HAS
SHIFTED A LITTLE MORE TO THE WEST...WITH MAJOR TIMING DIFFERENCES
(ECMWF MUCH FASTER COMPARED TO THE GFS). WITH THE TROPICAL SYSTEM
OFFSHORE AND A TROUGH IN THE VICINITY OF THE GREAT LAKES/MID MS
VALLEY...WOULD EXPECT A NARROW RIDGE OVER THE CAROLINAS. UNTIL THE
DIFFERENCES ARE RESOLVED...FAVOR A WARM AND MAINLY DRY FORECAST FOR
THE END OF THE WORK WEEK. HAVE WARMED TEMPS INTO THE MID 80-AROUND
90 FOR MAX TEMPS FRIDAY WHILE DECREASED RAIN CHANCE TO SLIGHT CHANCE.

&&

.AVIATION /11Z SATURDAY THROUGH WEDNESDAY/...
AS OF 655 AM SATURDAY...

A FEW LIGHT ISOLATED TO LOCALLY SCATTERED SHOWERS CONTINUE TO MOVE
ACROSS NORTHEAST PORTIONS OF CENTRAL NC THIS MORNING... POSSIBLY
AFFECTING KRDU AND KRWI FOR THE NEXT COUPLE OF HOURS. HOWEVER...
CONDITIONS ARE GENERALLY EXPECTED TO REMAIN VFR WITH THESE SHOWERS.
GREATER CONVECTIVE COVERAGE IS EXPECTED LATER THIS MORNING INTO THE
AFTERNOON AS A SERIES OF UPPER LEVEL DISTURBANCES TRACK S/SSE ACROSS
THE CAROLINAS AND A BACK DOOR COLD FRONT/PRE-FRONTAL TROUGH
PROGRESSES TOWARDS CENTRAL NC FROM THE N/NE. THUS... WILL MENTION A
TEMPO GROUP FOR SHOWERS AND SUB-VFR CONDITIONS IN THE TAFS FOR THE
AFTERNOON. THUNDERSTORMS WILL BE POSSIBLE AS WELL... BUT WILL HOLD
OFF ADDING THUNDER UNTIL WE HAVE A HIGHER CONFIDENCE THAT A GIVEN
LOCATION WILL BE AFFECTED BY A THUNDERSTORM. THE STRONGEST STORMS
WILL HAVE THE POTENTIAL TO PRODUCE IFR/LIFR VISBYS AND STRONG WIND
GUSTS.

IFR TO POSSIBLY EVEN LIFR CEILINGS WILL BE POSSIBLE IN THE WAKE OF
THE BACKDOOR COLD FRONT TONIGHT THROUGH MID-DAY SUNDAY...THOUGH
COVERAGE AND DURATION REMAIN A BIT UNCERTAIN (HIGHEST CONFIDENCES OF
SUB-VFR CONDITIONS AT KGSO/KINT). AN UPPER LEVEL RIDGE CENTERED IN
VICINITY OF THE SOUTHERN APPALACHIANS SHOULD RESULT IN BETTER-THAN-
NORMAL CHANCES FOR VFR CONDITIONS MON-WED...THOUGH A PERSISTENT E/NE
LOW-LEVEL FLOW MAY ALLOW ADEQUATE MOISTURE FOR LOW-TOPPED SHOWER
ACTIVITY...ESP AT THE EASTERN TERMINALS (FAY/RWI).

&&

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

&&

$$

SYNOPSIS...BSD/PWB
NEAR TERM...BSD
SHORT TERM...WSS
LONG TERM...WSS
AVIATION...BSD/VINCENT



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