Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 251017
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
617 AM EDT MON AUG 25 2014

.SYNOPSIS...SURFACE HIGH PRESSURE CENTERED OVER THE MID-ATLANTIC
WILL EXTEND SOUTHWARD INTO THE CAROLINAS THROUGH MID-WEEK.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 225 AM MONDAY...

TODAY AND TONIGHT: SURFACE HIGH PRESSURE CONTINUES TO EXTEND INTO
CENTRAL NC THIS MORNING FROM THE MID-ATLANTIC REGION... WHILE MID
LEVEL RIDGING BUILDS EAST FROM THE OZARKS INTO THE OHIO VALLEY AND
NORTHEAST U.S. MID LEVEL HEIGHTS ARE FORECAST TO INCREASE ACROSS
CENTRAL NC AS THE RIDGE AXIS SLOWLY SINKS SOUTHWARD TODAY. THIS WILL
RESULT IN AN ABUNDANCES OF MID LEVEL DRY AIR ACROSS CENTRAL NC FOR
THE NEXT SEVERAL DAYS. HOWEVER... WITH A GENERAL NORTHEAST TO EAST-
NORTHEASTERLY LOW LEVEL FLOW PERIODS OF MOISTURE ARE EXPECTED TO
ADVECT INTO THE REGION FROM TIME TO TIME. OUTSIDE OF SOME HIGH
CIRRUS THIS MORNING... SKIES ARE LARGELY CLEAR/MOSTLY CLEAR AS A
POCKET OF DRIER LOW LEVEL AIR HAS FILTER INTO THE AREA... HELPING TO
SCOUR OUT THE LINGERING LOW LEVEL CLOUDS ACROSS THE AREA. HOWEVER...
LOW LEVEL MOISTURE AT AROUND 850 MB IS EXPECTED TO INCREASE AGAIN
LATE THIS MORNING INTO THE AFTERNOON... YIELDING AT LEAST SOME
PARTLY SUNNY TO MOSTLY CLOUDY CONDITIONS ACROSS THE COASTAL PLAIN
AND SANDHILLS... PERHAPS A FAR WEST AS THE TRIANGLE. GIVEN THE STOUT
SUBSIDENCE INVERSION LOCATED AT AROUND 850-775 MB EXPECT THE CLOUD
COVER WILL SPREAD OUT BENEATH THE INVERSION... POSSIBLY RESULTING IN
A PERIOD OF MOSTLY CLOUDY SKIES. THUS...  WILL GO WITH HIGHS ONLY
RANGING FROM 81 TO 84 ACROSS THE AREA... BELOW NORMAL (ALSO...
AFTERNOON LOW LEVEL THICKNESS VALUES ARE EXPECTED TO RUN ABOUT 20
METERS BELOW NORMAL).

WE MAY SEE SOME LINGERING MOISTURE TRAPPED BELOW THE SUBSIDENCES
INVERSION ACROSS PORTIONS OF THE AREA THIS EVENING. HOWEVER... LOW
LEVEL FLOW IS FORECAST TO BACK TO MORE OF A NORTH-NORTHEASTERLY
DIRECTION AND ALLOW FOR SOME DRIER AIR TO AGAIN BEGIN WORKING INTO
THE AREA LATE TONIGHT. THUS... WILL SHOW SKIES BECOMING MOSTLY CLEAR
EVERYWHERE BY EARLY TUESDAY MORNING. LOWS TUESDAY MORNING ARE
EXPECTED TO GENERALLY BE IN THE UPPER 50S TO LOWER 60S AGAIN.

TUESDAY: MOSTLY SUNNY SKIES ARE EXPECTED FOR TUESDAY WITH LOW LEVEL
FLOW CONTINUING TO BE MORE NORTH-NORTHEASTERLY. THIS SHOULD YIELD A
BIT WARMER TEMPS. AFTERNOON LOW LEVEL THICKNESS VALUES ARE EXPECTED
TO REBOUND BY SOME 5 TO 10 METERS. THIS COMBINED WITH MORE SUN
SHOULD ALLOW FOR AFTERNOON HIGH TEMPS IN THE MID TO UPPER 80S (83-
87).

&&

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

TRANQUIL WEATHER PATTERN THIS PERIOD AS CENTRAL NC WEATHER WILL BE
INFLUENCED BY AN AREA OF HIGH PRESSURE AT THE SURFACE AND ALOFT. THE
PRESENCE OF WEATHER SYSTEM WILL MAINTAIN A RELATIVELY DRY AIR MASS
OVER OUR REGION...LEADING TO ABUNDANT SUNSHINE DURING THE DAY AND
CLEAR SKIES AT NIGHT. THE AIR MASS WILL MODIFY WITH TIME. LOW LEVEL
THICKNESSES AVERAGE ABOUT 10M ABOVE NORMAL WEDNESDAY AND 15-20M
ABOVE NORMAL BY THURSDAY. THIS YIELDS MAX TEMPS WELL INTO THE 80S TO
AROUND 90 WEDNESDAY AND UPPER 80S TO LOWER 90S THURSDAY.

A BACKDOOR COLD FRONT ASSOCIATED WITH A S/W CROSSING NEW ENGLAND
WILL MAKE A RUN FOR OUR NORTHERN COUNTIES LATE THURSDAY. LIFT ALONG
THIS BOUNDARY IS WEAK AND UPPER LEVEL SUPPORT IS SIMILARLY WEAK. AT
THIS TIME PLAN TO LIMIT POPS TO SLIGHT CHANCE AND CONFINED TO THE
FAR NORTHERN COUNTIES.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 315 AM MONDAY...

BACKDOOR COLD FRONT PROJECTED TO DRIFT INTO CENTRAL NC THURSDAY
NIGHT AND STALL. UPPER LEVEL HEIGHTS SLOWLY BUILD IN THE WAKE OF THE
DEPARTING S/W OFF THE NEW ENGLAND COAST AND AS T.C. CRISTOBAL MOVES
NORTH-NE BETWEEN THE NC COAST AND BERMUDA. THE MODEST SUBSIDENCE
INVERSION IN THE MID LEVELS MAY BE ENOUGH TO CAP OFF THE ATMOSPHERE
FOR MOST OF OUR FORECAST AREA. HOWEVER...STRONG HEATING COUPLED WITH
AVAILABLE (THOUGH MARGINAL) MOISTURE TO TRIGGER ISOLATED CONVECTION
FRIDAY AFTERNOON AND AGAIN SATURDAY AFTERNOON. MODEL GUIDANCE HINTS
THAT THE BETTER PROBABILITY OF THIS OCCURRING WILL BE OVER THE NE
PIEDMONT-NORTHERN COASTAL PLAIN ALONG AND BEHIND THE STALLED SFC
BOUNDARY.

LOW LEVEL THICKNESSES WILL CONTINUE TO AVERAGE 10-12M ABOVE
NORMAL...SUPPORTIVE OF MAX TEMPS 2-3 DEGREES ABOVE NORMAL FOR LATE
AUGUST. MAX TEMPS FRIDAY-SATURDAY SHOULD REMAIN WELL INTO THE 80S TO
THE LOWER 90S. SFC DEWPOINTS WILL INCREASE AS SFC BOUNDARY WILL AID
TO POOL LOW LEVEL MOISTURE. THUS IT WILL FEEL MORE HUMID AS WE GET
TO THE END OF THE WEEK.

APPEARS THAT BY SUNDAY...CENTRAL NC WILL BEGIN TO BE INFLUENCED BY
AN APPROACHING MID LEVEL TROUGH AND ACCOMPANYING SFC BOUNDARY. WHILE
MOISTURE ADVECTION WEAK-MODEST...ENOUGH INSTABILITY WILL EXIST
COUPLED WITH AFTERNOON HEATING TO INCREASE CONVECTIVE COVERAGE TO
SCATTERED...MAINLY IN THE PIEDMONT. IF THE MID-UPPER LEVEL RIDGE
HOLDS ON...THE BETTER CONVECTIVE CHANCES MAY BE DELAYED UNTIL
MONDAY/LABOR DAY.

&&

.AVIATION /12Z MONDAY THROUGH THURSDAY/...
AS OF 615 AM MONDAY...

24-HR TAF PERIOD: VFR CONDITIONS AND A STEADY NORTHEAST BREEZE
SHOULD PREVAIL THROUGH THE TAF PERIOD AS DRY SURFACE HIGH PRESSURE
OVER THE MID-ATLANTIC EXTENDS SOUTHWARD INTO THE CAROLINAS.
HOWEVER... THE GENERAL NORTHEASTERLY LOW LEVEL FLOW WILL ALLOW FOR
PERIODS OF MOISTURE TO FILTER INTO THE AREA AT TIMES. THIS COUPLED
WITH DAYTIME HEATING WILL ALLOW FOR THE DEVELOPMENT OF SOME CIGS
LATE MORNING INTO THE EARLY AFTERNOON... PRIMARILY ACROSS THE EASTERN
HALF OF CENTRAL NC... KFAY AND KRWI... POSSIBLY KRDU. EXPECT ANY
CIGS THAT DEVELOP TO BE IN THE VFR RANGE THOUGH... 3500 FT TO AROUND
4500 FT. SOME OF THIS CLOUD COVER COULD LINGER AFTER SUNSET FOR A
FEW HOURS AS THE MOISTURE WILL BE TRAPPED UNDER THE SUBSIDENCE
INVERSION. REGARDLESS... EXPECT VFR CONDITIONS THROUGHOUT THE TAF
PERIOD.... WITH A NORTHEASTERLY BREEZE... STRONGEST DURING THE
DAYTIME... 10 TO 15 MPH SUSTAINED... WITH AGAIN EVEN A FEW GUSTS TO
AROUND 20 MPH FROM TIME TO TIME (BEST CHANCE OF GUSTS AT KRWI AND
KFAY).

OUTLOOK: VFR CONDITIONS SHOULD PREVAIL THROUGH MID-WEEK AS SURFACE
HIGH PRESSURE OVER THE MID-ATLANTIC CONTINUES TO EXTEND SOUTHWARD
INTO THE CAROLINAS AND TROPICAL CYCLONE CRISTOBAL MAINTAINS A
HEALTHY DISTANCE OFFSHORE THE SOUTHEAST COAST AS IT TRACKS NORTH OF
THE BAHAMAS. SOME POTENTIAL (ALBEIT LOW) FOR CONVECTION WILL BE
POSSIBLE BY THE END OF THE WEEK (THU/FRI) IN ASSOC/W NW FLOW ALOFT
DOWNSTREAM OF AN APPROACHING UPPER LEVEL RIDGE.

&&

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

&&

$$

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


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