Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 191405
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1005 AM EDT FRI SEP 19 2014

.SYNOPSIS...HIGH PRESSURE CENTERED NORTHEAST OF THE GREAT LAKES WILL
EXTEND DOWN THROUGH VIRGINIA AND THE CAROLINAS THROUGH THE WEEKEND.
A COLD FRONT WILL APPROACH FROM THE NORTHWEST SUNDAY... THEN MOVE
SOUTHEAST THROUGH THE REGION SUNDAY NIGHT THROUGH EARLY MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 10 AM FRIDAY...

A FEW SPRINKLES REMAIN OF WHAT WAS A DECENT AREA OF MODERATE TO
HEAVY RAIN SHOWERS ACROSS THE WESTERN/SOUTHWEST PIEDMONT EARLIER
THIS MORNING...FOCUSED ALONG A LOW-LEVEL MOISTURE CONFLUENCE ZONE
SITUATED ALONG THE SOUTHERN FLANKS OF THE BUILDING SURFACE HIGH AND
SELY ATLANTIC MOISTURE RETURN FLOW.

THIS BEST BOUNDARY LAYER MOISTURE CONVERGENCE WILL GRADUALLY SHIFT
SOUTH AND EAST OF THE AREA THROUGH THE REMAINDER OF THE DAY AS THE
SURFACE HIGH WEDGES MORE PROMINENTLY SOUTHWARD INTO CENTRAL
NC...RESULTING IN MORE OF A EASTERLY/NORTHEASTERLY LOW-LEVEL FEED.
AS SUCH...IT APPEARS THAT THE BEST RAIN CHANCES ARE BEHIND US...WITH
ONLY AN ISOLATED AFTERNOON SHOWER OR SPRINKLE POSSIBLE ACROSS THE
FAR WESTERN PIEDMONT OWING TO WEAK UPSLOPE FLOW.

LOW-LEVEL EASTERLY COMPONENT WILL RESULT IN A VERY SLOW DEMISE OF
THIS MORNINGS PERVASIVE CLOUD COVER. IF SKIES REMAIN BROKEN TO
OVERCAST...TEMPS WILL BE HELD DOWN IN THE MID-UPPER 70S. IF ENOUGH
BREAKS OCCUR...COULD SEE TEMPS WARM INTO THE UPPER 70S-LOWER 80S.
BELIEVE THE LATER SCENARIO WILL BE MORE PROBABLE ACROSS THE
EAST/NORTHEAST WHILE MORE CLOUDS THAN SUN SHOULD OCCUR ACROSS THE
SOUTH AND WEST. MAX TEMPS MOSTLY IN THE UPPER 70S TO AROUND 80 WITH
MID 70S IN THE NW PIEDMONT.

TONIGHT...EXPECT BULK OF CLOUDS TO DIMINISH WITH LOSS OF HEATING AND
EVENTUAL ADVECTION OF A DRIER LOW LEVEL AIR MASS. EXPECT A STEADY
EAST-NE WIND OVERNIGHT (5-10 MPH). THIS MIXING WILL PREVENT NEAR
SURFACE AIR MASS FROM REALIZING FULL COOLING POTENTIAL. MIN TEMPS
NEAR 60-LOWER 60S.


&&

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

SATURDAY...DRY AIR RIDGE WILL EXTEND SW-NE ACROSS CENTRAL NC
PROVIDING SUNNY-MOSTLY SUNNY SKIES TO START THE DAY. SHOULD SEE AN
INCREASE IN HIGH LEVEL CLOUDINESS FROM THE SOUTHEAST SATURDAY
AFTERNOON AS AN AREA OF LOW PRESSURE ORGANIZES OFF THE SE U.S.
COAST. NOT EXPECTING THESE CLOUDS TO HAVE MUCH EFFECT INITIALLY ON
TEMPS. LOW LEVEL THICKNESSES RANGE IN THE 1395-1402M
RANGE...SUPPORTIVE OF MAX TEMPS NEAR-LOWER 80S.

SATURDAY NIGHT...THICKER VEIL OF HIGH CLOUDS ANTICIPATED OVER MAINLY
THE EAST HALF OF THE FORECAST AREA AS THE LOW PRESSURE SYSTEM MOVES
NORTH-NORTHEAST OFFSHORE OF THE CAROLINA COAST. LATEST GFS SUGGEST
POTENTIAL FOR LIGHT PRECIP AS FAR EAST AS I-95 CORRIDOR BY EARLY
EVENING BUT THIS CURRENTLY APPEARS OVERDONE. PRESENCE OF HIGH LEVEL
CLOUDS SHOULD MAINTAIN MILD OVERNIGHT TEMPS IN THE EAST WITH COOLER
MIN TEMPS EXPECTED IN THE WEST WHERE SKIES WILL BE NO WORSE THAN
PARTLY CLOUDY. MIN TEMPS UPPER 50S WEST TO MID 60S SE.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 345 AM FRIDAY...

SPLIT STREAM FLOW WILL UNDERGO AMPLIFICATION THROUGH THE
WEEKEND...AND RESULT IN A LEAD SOUTHERN STREAM TROUGH AND ASSOCIATED
SFC FRONTAL WAVE LIFTING UP THE SOUTHEAST COAST...WHILE A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES CARVE A TROUGH AND PROPEL A SFC
COLD FRONT ACROSS THE MIDDLE ATLANTIC AND NORTHEAST STATES SUN-MON.
GUIDANCE IS THEN IN RELATIVELY GOOD AGREEMENT REGARDING THE
SEPARATION AND RETREAT OF THE NORTHERN STREAM THAT LEAVES BEHIND MID-
UPPER TROUGHINESS INVOF THE SOUTHEAST US COAST...WHILE THE AMPLIFIED
RIDGING INITIALLY OVER WESTERN NOAM BUILDS...IN PROGRESS FLOW
ALOFT...EASTWARD ACROSS THE GREAT LAKES/MID ATLANTIC/NORTHEAST.

SUN: VERY WARM...AND DRY. AN APPALACHIAN-LEE SFC TROUGH WILL
DEVELOP...BETWEEN THE AFOREMENTIONED NORTHERN STREAM SFC COLD FRONT
APPROACHING FROM THE WEST AND THE OFFSHORE PASSING FRONTAL WAVE (A
BAROCLINIC ONE WHICH MAY ACQUIRE SUB-TROPICAL CHARACTERISTICS AT
BEST OWING TO THE STRONGLY SHEARED AND DEEP LAYER BAROCLINIC
ENVIRONMENT IN WHICH IT WILL EVOLVE). UNDER MOSTLY SUNNY
SKIES...FULL SUN TEMPERATURES WITH LOW LEVEL THICKNESS VALUES IN THE
NEIGHBORHOOD OF 1415 METERS SUPPORT HIGHS SOLIDLY IN THE MIDDLE 80S.

SUN NIGHT-MON: NWP GUIDANCE HAS CONTINUED TO HASTEN THE FRONTAL
PROGRESSION THROUGH THE EASTERN CONUS SUCH THAT FROPA IN CENTRAL NC
WILL LIKELY OCCUR LATE SUN NIGHT-EARLY MON PER A CONSENSUS OF THE
00Z NWP DATA. A FEW LINGERING SHOWERS FROM UPSTREAM CONVECTION...AND
ALONG THE FRONTAL MOIST AXIS...MAY DRIFT INTO THE PIEDMONT SUN
NIGHT...BUT DIURNAL TIMING AND GREATLY LIMITED GULF MOISTURE RETURN
SUGGESTS COVERAGE SHOULD BE WIDELY SCATTERED AT BEST...BEFORE
DIMINISHING WITH TIME OVERNIGHT AND EASTWARD EXTENT. THE FASTER
FRONTAL PROGRESSION ALSO FAVORS THE FRONT BEING SE OF CENTRAL NC BY
LATE MORNING...WHICH SHOULD ENSURE ANY ASSOCIATED REDEVELOPMENT OF
CONVECTION SHOULD OCCUR IN COASTAL AREAS. LOW LEVEL DRY AIR
ADVECTION WILL BE MORE PRONOUNCED THAN COLD AIR ADVECTION MON...SO
TEMPERATURES ARE APT TO REMAIN RELATIVELY WARM...IN THE UPPER 70S TO
LOWER 80S.

TUE-THU: ANOTHER STRONG CANADIAN HIGH WILL EXPAND AND STRENGTHEN
ACROSS MUCH OF THE CENTRAL AND EASTERN CONUS IN THE WAKE OF THE
PASSING COLD FRONT...WHICH GUIDANCE SUGGESTS WILL CLEAR ALL BUT
PERHAPS SOUTHERN FL BY MID NEXT WEEK. DRY AIR RIDGING IN CENTRAL NC
WILL RESULT FROM THE PARENT HIGH CENTER OVER THE NORTHEAST...WHICH
SHOULD RESULT IN DRY AND MILD CONDITIONS WITH TEMPERATURES IN THE
MIDDLE 70S TO AROUND 80 DEGREES BOTH TUE-WED. SINCE THE SFC HIGH
CENTER WILL BE SO WELL REMOVED FROM CENTRAL NC/OVER THE NE
CONUS...THE ASSOCIATED MSLP GRADIENT WILL LIKELY MAINTAIN ENOUGH
STIRRING OF THE SFC WINDS OVERNIGHT TO KEEP LOWS FROM DIPPING INTO
THE 40S ON MORE THAN AN ISOLATED BASIS OVER THE NORTHERN
PIEDMONT...WITH LOWS OTHERWISE IN THE 50S. BY THU...THE LOW LEVEL
FLOW AROUND THE HIGH IS FORECAST TO ASSUME A MORE NE TO ENE
COMPONENT...WHICH WOULD SERVE TO DIRECT MOISTURE/CLOUDINESS WESTWARD
INTO CENTRAL NC WED NIGHT-THU. IN ADDITION...THE PAST COUPLE OF
GUIDANCE RUNS HAVE BEEN HINTING AT THE POTENTIAL FOR ADDITIONAL SFC
WAVE DEVELOPMENT INVOF THE SOUTHEAST COAST BY THU...WHICH WOULD
ENHANCE BOTH CLOUD COVER AND RAIN CHANCES...PARTICULARLY OVER THE
EASTERN CAROLINAS...BY THU.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
AS OF 10 AM FRIDAY...

HIGH PRESSURE WILL BUILD INTO CENTRAL NC FROM THE NORTH. THE
CIRCULATION AROUND THIS HIGH WILL RESULT IN AN LOW LEVEL EASTERLY
FLOW ACROSS NC. THIS FETCH OFF THE ATLANTIC WILL SPREAD LOW LEVEL
MOISTURE INTO OUR REGION. THIS WILL CAUSE A CLOUD DECK WITH BASES
4500-6000FT WITH OVERCAST CONDITIONS HIGHLY PROBABLE OVER THE
PIEDMONT...AND SCATTER-BROKEN SKY CONDITIONS IN THE SANDHILLS AND
COASTAL PLAIN.  AS THE HIGH STRENGTHENS FURTHER INTO CENTRAL NC LATE
TONIGHT INTO SATURDAY...DRIER AIR WILL INFILTRATE THE REGION...
DIMINISHING THE CLOUD COVERAGE.

A DEVELOPING AREA OF LOW PRESSURE OFFSHORE WILL SPREAD A VEIL OF
HIGH CLOUDS ACROSS THE EAST HALF OF NC LATE SATURDAY THROUGH EARLY
SUNDAY. A COLD FRONT WILL APPROACH FROM THE NW SUNDAY AND CROSS
CENTRAL NC SUNDAY NIGHT THROUGH EARLY MONDAY. A PERIOD OF MVFR
CEILINGS MAY OCCUR WITH THE FRONT. VFR CONDITIONS WILL RETURN MONDAY
INTO TUESDAY AS HIGH PRESSURE AND ASSOCIATED DRIER AIR MASS BUILDS
INTO OUR AREA.

&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...CBL/WSS
SHORT TERM...WSS
LONG TERM...MWS
AVIATION...WSS


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