-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 130809
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
307 AM EST FRI DEC 13 2013

.SYNOPSIS...HIGH PRESSURE WILL EXTEND ACROSS THE REGION THIS MORNING
THEN DRIFT OFFSHORE THIS AFTERNOON. A LOW PRESSURE SYSTEM WILL
DEVELOP OVER THE DEEP SOUTH TONIGHT... THEN TRACK NORTHEAST OVER THE
CAROLINAS AND MID ATLANTIC REGION THIS WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 AM FRIDAY...

TODAY...SURFACE HIGH OVER TEH AREA EARLY THIS MORNING WILL SCOOT
EASTWARD AND LIE OFFSHORE LATER TODAY. RETURN SW FLOW WILL FUNNEL
WARMER AIR INTO THE REGION. THIS REFLECTED IN LOW LEVEL THICKNESSES
RECOVERING INTO THE 1312-16M RANGE...ABOUT 20M HIGHER THAN THURSDAY
BUT STILL 15M BELOW NORMAL FOR MID DECEMBER. EXPECT TEMPS TO REBOUND
QUICKLY FROM EARLY MORNING TEMPS IN THE LOW-MID 20S...REACHING THE
MID-UPPER 40S BY NOON ..AND 50-55 FOR AFTERNOON MAX TEMPS. EXPECT TO
SEE AN INCREASE IN HIGH LEVEL CLOUDS THIS AFTERNOON BUT APPEARS THAT
THESE HIGH CLOUDS WILL NOT THICKEN IN TIME TO HAVE AN EFFECT ON MAX
TEMPS.

TONIGHT...HIGH CLOUDS WILL CONTINUE TO THICKEN AS A S/W IN THE
SOUTHERN STREAM MOVES EAST ACROSS THE SOUTHERN PLAINS-LOWER MS
VALLEY. MODEL GUIDANCE IN GOOD AGREEMENT IN DELAYING ARRIVAL OF
PRECIP UNTIL CLOSE TO DAYBREAK SO HAVE DELAYED ARRIVAL OF SLIGHT
CHANCE POPS A FEW HOURS FROM PREVIOUS FORECAST. THIS DELAYED ARRIVAL
ALSO SUGGEST THAT THE THREAT FOR FREEZING RAIN/FREEZING DRIZZLE ON
ITS ONSET IN THE WESTERN PIEDMONT ARE NOT AS MUCH AS A CONCERN AS
EARLIER IN THE WEEK BUT STILL NEEDS TO BE MONITORED A SFC WET BULB
TEMPS HOVER NEAR FREEZING ACROSS THE NW PIEDMONT UNTIL SHORTLY AFTER
DAYBREAK. MIN TEMPS GENERALLY IN THE MID 30S...AND LIKELY REALIZED
AROUND MIDNIGHT AS THICKENING CLOUD COVER OVERNIGHT SHOULD AID TO
STABILIZE TEMPS.

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
AS OF 300 PM THURSDAY...

A LEAD SHORTWAVE OVER THE SOUTHERN PLAINS FRIDAY NIGHT WILL SHEAR
AND LIFT NORTHEAST TOWARD THE OHIO VALLEY REGION ON SATURDAY...WITH
A PAIR OF NORTHERN AND SOUTHERN STREAM SHORTWAVES ON ITS HEELS ON
SUNDAY.  THE BULK OF THE PRECIP ASSOCIATED WITH THE LEAD WAVE WILL
OVERSPREAD THE AREA FROM THE SOUTHWEST BETWEEN 12Z AND 18Z SATURDAY
AS ISENTROPIC LIFT INCREASES IN CONJUNCTION WITH AN 850MB WARM FRONT
AND 40-50KT LOW LEVEL JET.  ANTECEDENT DRY AIR DEPOSITED BY HIGH
PRESSURE ON FRIDAY...WHICH WILL INITIALLY BE CHARACTERIZED BY
DEWPOINTS IN THE TEENS AND SINGLE DIGITS...SHOULD BE RAPIDLY
OVERWHELMED BY MOISTURE ADVECTION WITH THE PARENT HIGH EAST OF NC.
STILL...THERE IS A SMALL CHANCE THAT AN EARLY ARRIVAL OF PRECIP MAY
CAUSE  TO PUSH SURFACE TEMPS DOWN TO AROUND 32F IN THE NORTHWEST AND
NORTHERN PIEDMONT FOR A COUPLE OF HOURS. NO SIGNIFICANT IMPACTS ARE
EXPECTED.  THIS WILL LEAD TO A WEAK IN-SITU CAD AND A CHILL DAY IN
THE 30S AND 40S FOR MOST OF THE CWA BEFORE A WARM FRONT SURGES NORTH
INTO AT LEAST THE SOUTHEASTERN CWA BY SATURDAY EVENING.  WILL SHOW A
CLIMATOLOGICAL CAD-LIKE TEMP DISTRIBUTION WITH THE GRADIENT BETWEEN
30S AND 50S OVER THE SANDHILLS AND SOUTHERN COASTAL PLAIN.

LATER IN THE DAY...MODELS HAVE BEEN INDICATING THE DEVELOPMENT OF A
SURFACE WAVE/TRIPLE POINT LOW TO OUR SOUTHWEST....THOUGH TRENDS HAVE
BEEN WEAKER OVER THE PAST COUPLE OF DAYS.  STILL...THE WARM SECTOR
IS PROGGED TO MAKE A MODEST PUSH INTO THE WEAK CAD
AIRMASS...REACHING THE US 1 CORRIDOR ON THE NAM AND ECMWF. WITHIN
THE WARM SECTOR...THERE THERE DOESNT APPEAR TO BE ENOUGH TIME FOR
SUFFICIENTLY HIGHER DEWPOINT AIR TO PUSH NORTHWARD AND CAUSE
DESTABILIZATION OF MORE THAN JUST A COUPLE HUNDRED J/KG OF NEAR
SURFACE BASED CAPE AT BEST ACROSS THE FAR SOUTHEAST CWA BEFORE WINDS
VEER TO SOUTHWESTERLY SATURDAY EVENING.  BASED ON FORECAST
SOUNDINGS...THERE IS JUST A NARROW WINDOW CENTERED AROUND 00Z SUNDAY
WHERE SHEAR AND WEAK INSTABILITY PHASE TOGETHER...AND WHILE MID-
LEVEL LAPSE RATES ARE MARGINAL AT AROUND 6C PER ECMWF...THE CHANCE
OF THUNDER APPEARS RATHER SMALL AND CONFINED TO THE -
FAYETTEVILLE-GOLDSBORO STRETCH.

WILL SHOW CATEGORICAL POPS ACROSS THE WEST SATURDAY MORNING
TRANSITIONING EAST THROUGH SATURDAY NIGHT AS THE DRY SLOT SPREADS IN
FROM THE WEST AND THE SURFACE WAVE BEGINS TO DEEPEN AND LIFT OFF TO
THE NORTHEAST. THE FOCUS OF HIGHER QPF SHOULD REMAIN TO OUR SOUTH
AND RANGE FROM FROM HALF AN INCH IN THE WEST TO AROUND AN INCH IN
THE EAST. LOWS 37-47 SATURDAY NIGHT.
-- End Changed Discussion --


&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
AS OF 305 AM FRIDAY...

SUNDAY AND SUNDAY NIGHT: STRENGTHENING SURFACE LOW PRESSURE WILL
LIFT OFF TO THE NORTHEAST ON SUNDAY AS MID LEVEL DRY AIR SURGES INTO
THE REGION. THIS WILL LEAD TO A DRYING CONDITIONS... WITH MOSTLY TO
PARTLY SUNNY SKIES AT LEAST RETURNING BY SUNDAY AFTERNOON. THUS...
WITH IMPROVING CONDITIONS ON SUNDAY AND DOWNSLOPE FLOW WILL RAISE
HIGH TEMPS BY A COUPLE OF DEGREES AND END ALL POPS BY MID MORNING AT
THE LATEST. THIS YIELDS HIGH TEMPS RANGING FROM AROUND 50 NW TO MID
50S SOUTH AND EAST. SOME STATISTICAL GUIDANCE ALONG WITH THE IN
HOUSE LOW LEVEL THICKNESS SCHEME IS SHOWING HIGH TEMPS APPROACHING
THE UPPER 50S TO AROUND 60 FOR SUNDAY ACROSS THE SOUTHEAST.
HOWEVER... MODEL SOUNDINGS ARE SHOWING A RATHER SHALLOW MIXED LAYER
ACROSS OUR SOUTHEAST/SOUTH... ALONG WITH POSSIBLY SOME LINGERIN LOW
LEVEL MOISTURE. THUS... WILL LIMIT/CAP HIGHS FOR SUNDAY IN THE MID
50S.

SURFACE HIGH PRESSURE WILL BE BUILDING INTO THE AREA FROM THE GULF
COAST STATES ON SUNDAY NIGHT. THUS... WILL RAISE LOWS TEMPS FROM THE
PREVIOUS FORECAST A BIT... SHOWING LOWS AROUND FREEZING WITH CLEAR
SKIES.

MONDAY THROUGH THURSDAY: QUITE WEATHER IS EXPECTED FOR THE MEDIUM
RANGE PORTION OF THE FORECAST... WITH GENERALLY A WEAK L/W TROUGH
ACROSS THE EASTERN HALF OF THE COUNTRY. ANY S/W ENERGY WILL REMAIN
IN THE NORTHERN STREAM AND ONLY SEND A WEAK DRY COLD FRONT ACROSS
CENTRAL NC IN THE TUESDAY INTO TUESDAY NIGHT TIME FRAME. GIVEN THE
LACK OF MOISTURE WITH THIS SYSTEM WILL KEEP THE FORECAST DRY AND
ONLY SHOW A VERY MINOR INCREASE IN CLOUD COVER (MAINLY MID AND HIGH
CLOUDS). MODELS DIFFER THOUGH WITH HOW THEY HANDEL THE EVOLUTION OF
THE NEXT SIGNIFICANT SYSTEM EXPECTED TO MOVE INTO THE CENTRAL PART
OF THE COUNTRY BY THE END OF NEXT WEEK. WHILE WE DO NOT EXPECT ANY
PRECIP ON THURSDAY AT THIS TIME... THE GFS AND ECMWF DIFFER WRT THE
LOW LEVEL PATTERN. THE GFS IS MORE AGGRESSIVE IN BUILDING A 1038 MB
HIGH INTO THE AREA FROM THE NORTH... WHILE THE ECMWF DEPICTS A
WARMING SOUTHERLY RETURN FLOW FOR THE AREA... WITH THE MAIN FRONTAL
ZONE TO THE NORTH OF CENTRAL NC. FOR NOW WILL STICK CLOSE TO WPC AND
KEEP THE WARMER SOLUTION FOR US (ALTHOUGH NOT NEAR AS WARM AS THE
ECMWF IS DEPICTING AT THIS TIME)... WHICH IS IN AGREEMENT WITH THE
LATEST ECMWF. TEMPS DURING THE MEDIUM RANGE WILL START OFF SLIGHTLY
BELOW NORMAL AND TREND TO NEAR TO SLIGHTLY ABOVE NORMAL BY MID TO
LATE IN THE PERIOD (WITH THE POSSIBILITY OF WELL ABOVE NORMAL NEAR
THE END OF THE PERIOD IF THE LATEST ECMWF VERIFIES).
-- End Changed Discussion --

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
AS OF 1245 AM FRIDAY...

AN AREA OF HIGH PRESSURE OVER THE SE U.S. WILL CAUSE VFR CONDITIONS
ACROSS CENTRAL NC THROUGH THIS EVENING. LIGHT AND VARIABLE SURFACE
WINDS EARLY TODAY WILL BECOME SW BETWEEN 5-7KTS THIS AFTERNOON. A
VEIL OF HIGH CLOUDS WILL INCREASE AND THICKEN LATE TODAY AND THIS
EVENING.

VFR CONDITIONS TONIGHT WILL QUICKLY DETERIORATE SATURDAY MORNING
AFTER DAYBREAK AS AN AREA OF LOW PRESSURE OVER THE DEEP SOUTH
FUNNELS MOISTURE INTO THE CAROLINAS. THERE IS A HIGH LIKELIHOOD OF
IFR/LOW END MVFR CEILINGS DEVELOPING ACROSS CENTRAL NC PRIOR TO NOON
SATURDAY AND PERSISTING INTO SATURDAY NIGHT. RAIN WILL BECOME
WIDESPREAD AS WELL WITH MVFR/IFR VISIBILITIES DUE TO RAIN AND FOG
HIGHLY PROBABLE SATURDAY AFTERNOON INTO SATURDAY EVENING.

THE AREA OF LOW PRESSURE WILL CROSS AND LIFT NE ACROSS THE CAROLINAS
SATURDAY NIGHT. NW FLOW ON THE BACKSIDE OF THE DEPARTING LOW WILL
ADVECT DRIER AIR INTO CENTRAL NC...LEADING TO IMPROVING AVIATION
CONDITIONS SUNDAY MORNING. SFC WINDS WILL BECOME BLUSTERY WITH
SUSTAINED 10-15KTS AND GUSTS AROUND 25KTS FROM LATE SUNDAY MORNING
THROUGH THE AFTERNOON.

VFR CONDITIONS APPEAR LIKELY FOR MONDAY INTO TUESDAY AS HIGH
PRESSURE CENTERED OVER THE DEEP SOUTH WILL BE THE DOMINATE WEATHER
FEATURE FOR OUR REGION.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE

&&

$$

SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...SMITH
LONG TERM...BSD
AVIATION...WSS