Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 160305
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1105 PM EDT MON SEP 15 2014

.SYNOPSIS...A COLD FRONT APPROACHING THE REGION FROM THE WEST
TONIGHT WILL TRACK SLOWLY SOUTHWARD THROUGH THE CAROLINAS TUESDAY
INTO TUESDAY NIGHT. THE FRONT WILL GRADUALLY MOVE OFFSHORE THE
SOUTHEAST COAST ON WEDNESDAY AND THURSDAY AS HIGH PRESSURE
STRENGTHENS OVER THE GREAT LAKES AND EXTENDS SOUTHWARD THROUGH THE
MID ATLANTIC.

&&

.NEAR TERM /OVERNIGHT/...
AS OF 1045 PM MONDAY...

OVERVIEW: CENTRAL NC IS SITUATED ON THE NORTHEAST PERIPHERY OF A
GULF COAST RIDGE...AT THE SOUTHERN FRINGE OF THE WESTERLIES IN BROAD
CYCLONIC FLOW ALOFT. 02Z WV IMAGERY AND RAP DATA INDICATED SMALL
AMPLITUDE SHORTWAVE ENERGY OVER EASTERN TN AND FAR SOUTHWESTERN NC.

PRECIPITATION: COMPACT DPVA IN THE PRESENCE OF LOW-LEVEL MOISTENING/
WARM ADVECTION AND RESULTING DESTABILIZATION ALLOWED CONVECTION TO
BLOSSOM OVER THE MOUNTAINS/FOOTHILLS BETWEEN 21-00Z. THIS ACTIVITY
HAS PERSISTED AND PROGRESSED EASTWARD TO THE YADKIN RIVER BY 03Z AND
APPEARS TO BE EITHER 1) ELEVATED OR 2) HIGH-BASED WITH CONVECTIVE
CEILINGS AT 7-10 KFT AND OBSERVATION SITES REPORTING SPRINKLES/LIGHT
RAIN WITH 7-10SM VISBYS AS PRECIP FALLS THROUGH A DRY MID-LEVEL
AIRMASS (AS SEEN ON THE 00Z GSO SOUNDING). THIS ACTIVITY WILL TRACK
EAST TOWARD THE HWY 1 CORRIDOR THROUGH 06Z IN ASSOC/W THE
APPROACHING SHORTWAVE...THOUGH IT WILL ENCOUNTER AN INCREASINGLY
UNFAVORABLE THERMODYNAMIC ENVIRONMENT AND THUS APPEARS LIKELY TO
WEAKEN WITH EASTWARD PROGRESSION. WILL INDICATE A SLIGHT TO LOW
CHANCE OF SHOWERS/SPRINKLES THROUGH 06Z WEST OF I-95...WITH THE BEST
CHANCE IN THE WESTERN PIEDMONT. -VINCENT

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 300 PM MONDAY...

FOR TUE/TUE NIGHT: THE WEAK SURFACE TROUGH WILL BE IN PLACE OVER ERN
NC TUE MORNING... AND WILL EXTEND A SLIGHT CHANCE OF SHOWERS IN THE
SOUTHEAST INTO TUE TO REFLECT THE TROUGH`S PRESENCE AND THE
DEPARTING MID LEVEL WAVE. WITH SUBSEQUENT NORTHWESTERLY DOWNSLOPE
925-850 MB FLOW... WE SHOULD THEN BE FAIRLY DRY FOR SEVERAL HOURS...
UNTIL THE NEXT MID LEVEL VORTICITY MAX AND ACCOMPANYING STRONGER
SURFACE COLD FRONT APPROACH FROM THE NW BY EARLY-MID AFTERNOON.
SURFACE-925 MB LOW PRESSURE ALONG THIS FRONT WILL APPROACH FROM THE
NW AND BECOME BETTER DEFINED AS IT CROSSES THE MOUNTAINS INTO THE
PIEDMONT OF NC DURING THE AFTERNOON. MODELS SHOW A POCKET OF 6+ C/KM
MID LEVEL LAPSE RATES CROSSING SRN NC LATE TUE ALONG WITH NEGATIVE
LI VALUES. MUCAPE SHOULD PEAK AT JUST 750-1500 J/KG FOCUSED ON THE
SOUTHEAST... AND DEEP LAYER SHEAR IS MARGINAL AT ABOUT 20-25 KTS...
BUT THESE NUMBERS COMBINED WITH LOW LEVEL MASS CONVERGENCE SHOULD
STILL SUPPORT SCATTERED SHOWERS AND ISOLATED STORMS LATE TUE
AFTERNOON THROUGH TUE NIGHT. CONFIDENCE IN THE COVERAGE AND
PLACEMENT IS NOT GREAT HOWEVER... AS THERE IS LITTLE AGREEMENT IN
QPF AND POPS AMONG THE NAM/GFS/ECMWF. BUT GENERALLY EXPECT THE BEST
COVERAGE TO BE IN THE SOUTHEAST CWA... WHERE MOISTURE TRANSPORT AND
INSTABILITY WILL BE BEST... FROM LATE AFTERNOON THROUGH THE
EVENING... TAPERING DOWN TO ISOLATED SHOWERS OVERNIGHT. THICKNESSES
ADJUSTED FOR CLOUDS AND POSSIBLE SHOWERS LATE SUPPORT HIGHS FROM 82
TO 86. LOWS 60-65 TUE NIGHT AS COOLER AND DRIER AIR STARTS TO FILTER
IN POST-FRONT FROM THE NNW. -GIH

WEDNESDAY AND WEDNESDAY NIGHT...WESTERLY FLOW ALOFT WILL INDUCE
PROGRESSIVE TOP DOWN DRYING THROUGH WEDNESDAY NIGHT...LESSENING THE
DEPTH OF MOISTURE...WHILE NORTHEAST LOW LEVEL FLOW MAINTAINS
MOISTURE THROUGH ABOUT 5KFT THROUGH THURSDAY MORNING. A SHORT WAVE
WILL BE MOVING ACROSS THE SOUTHERN PERIPHERY OF THE AREA ON
WEDNESDAY...ACCOMPANIED BY AN H85 WAVE THAT WILL ENHANCE LIFT VIA
CONVERGENCE AND WEAK ISENTROPIC LIFT AT THE TOP OF THE MOISTURE
COLUMN. HENCE WILL MAINTAIN A CHANCE POP FOR SHOWERS ACROSS THE
SOUTH AND A SLIGHT CHANCE ACROSS THE NORTH THROUGH WEDNESDAY...
DIMINISHING TO A LINGERING SLIGHT CHANCE IN THE EAST INTO THURSDAY.
COOL AIR ADVECTION WILL COMMENCE LATE DAY AS THE SHORT WAVE PASSES
AND WITH THE DAMPNESS AND CHANCE OF SHOWERS...HIGHS WEDNESDAY WILL
RANGE FROM 75 TO 80...WITH SOME LOWER 70S POSSIBLE ACROSS THE
NORTHEAST WHERE COOL AIR WILL ARRIVE A LITTLE SOONER. LOWS WEDNESDAY
NIGHT WILL BE MAINLY IN THE UPPER 50S. -MLM

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 245 PM MONDAY...

A LONG WAVE TROF SETS UP ACROSS THE EASTERN CONUS BY LATE WEEK...
CONCURRENT WITH STRONG HIGH PRESSURE BUILDING INTO EASTERN CANADA
AND DOWN THE EAST COAST ON FRIDAY WITH THE RESULTING DAMMING
SCENARIO LINGERING THROUGH THE WEEKEND. LOW AMPLITUDE MID LEVEL
RIDGING SHOULD INHIBIT PRECIP CHANCES THROUGH THE WEEKEND...WHILE
THE PROLONGED EAST TO NORTHEAST LOW LEVEL FLOW OFF THE ATLANTIC WILL
SUPPRESSES HIGH TEMPS INTO THE LOW AND MID 70S THROUGH SATURDAY.

A STRONG TROF MOVING ACROSS THE MIDWEST WILL NUDGE THE SURFACE HIGH
FURTHER OFFSHORE. THE WEAKENED FLOW WILL ALLOW THE AIRMASS TO
MODERATE ON SUNDAY...WITH HIGHS MOSTLY IN THE UPPER 70S. FLOW VEERS
TO SOUTHWEST BY MONDAY AHEAD OF THE UPPER TROF AND SURFACE
FRONT...WITH INCREASING MOISTURE IN THE RESULTING RETURN FLOW AND A
CHANCE OF SHOWERS BY LATE DAY MONDAY. HIGHS MONDAY WILL BE WITHIN A
DEGREE OR TWO OF 80. MORNING LOWS THROUGH THE PERIOD WILL BE MOSTLY
FROM 55 TO 60 DEGREES. -MLM

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AS OF 750 PM MONDAY...

24 HOUR TAF PERIOD: MVFR CONDITIONS HAVE HELD ON AT MOST LOCATIONS
THIS EVENING AND WILL CONTINUE TO DO SO OVERNIGHT TONIGHT WITH THE
POSSIBILITY OF IFR/LIFR CEILINGS DURING THE OVERNIGHT HOURS AND JUST
BEFORE SUNRISE. WINDS WILL BE LIGHT AND VARIABLE OVERNIGHT AS A WEAK
SHORTWAVE CROSSES THE AREA FROM THE WEST. A FEW SPRINKLES CANT BE
RULED OUT..ESPECIALLY IN THE TRIAD. CONDITIONS SHOULD GRADUALLY
IMPROVE TO VFR AS MOISTURE DECREASES ON TUESDAY WITH SOME CLOUDS IN
THE 3-5 KFT LAYER. THERE WILL BE A SLIGHT CHANCE FOR RAIN OR
ISOLATED THUNDER IN THE SOUTH AND EAST LATE TUESDAY AFTERNOON INTO
THE EVENING HOURS.

LONG TERM: A GENERALLY DRIER PERIOD WILL ROUND OUT THE END OF THE
WEEK WITH SLIGHT CHANCES FOR SOME AFTERNOON SHOWERS WEDNESDAY BUT
GENERALLY VFR CONDITIONS PREVAILING.

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...VINCENT
SHORT TERM...HARTFIELD/MLM
LONG TERM...MLM
AVIATION...ELLIS



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