-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 030605
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
105 AM EST TUE DEC 3 2013

.SYNOPSIS...LOW PRESSURE WILL GRADUALLY STRENGTHEN AS IT MOVES
NORTHEAST AWAY FROM NORTH CAROLINA OVERNIGHT. WEAK HIGH PRESSURE
WILL BUILD OVER THE AREA TUESDAY AND TUESDAY NIGHT...THEN SHIFT
OFFSHORE WEDNESDAY AS A WARM FRONT APPROACHES FROM THE SOUTH.

&&

.NEAR TERM /OVERNIGHT THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
AS OF 1020 PM MONDAY...

MAIN FORECAST CHALLENGE OVERNIGHT REVOLVES AROUND CLOUD COVERAGE AND
POTENTIAL FOR SPRINKLES OR LIGHT RAIN. ALSO...DEGREE OF CLOUDINESS
WILL PLAY A ROLE IN MIN TEMPS TONIGHT.

AREA OF LOW PRESSURE HAS MOVED NEWD AWAY FROM THE NORTHERN OUTER
BANKS.  FLOW IN THE WAKE OF THIS SYSTEM IS WEAK...SO NO TRUE CHANGE
IN AIR MASS BEING REALIZED. DEWPOINTS ACROSS THE NORTHERN 3-5
DEGREES WETTER THAN LAST NIGHT. CONVERSELY....DEWPOINTS ACROSS THE
SOUTHEAST 3-5 DEGREES DRIER.  THIS DIFFERENTIAL LIKELY ATTRIBUTED TO
A MID LEVEL DECK OF CLOUDS THAT HAS ENCROACHED UPON THE WESTERN  AND
NORTHERN PIEDMONT WHILE SKIES WERE MOSTLY CLEAR ACROSS THE SE. THIS
DECK OF MID LEVEL CLOUDS IN ADVANCE OF A WEAKENING UPPER LEVEL
SYSTEM CROSSING AL/GA. THIS SYSTEM WILL CONTINUE TO ADVECT MOISTURE
INTO CENTRAL NC...MAINLY ABOVE 5000FT. THIS WILL RESULT IN
THICKENING CLOUD COVERAGE MAINLY WEST OF I-95. THIS WILL YIELD MIN
TEMPS TONIGHT SEVERAL DEGREES WARMER THAN LAST NIGHT. MIN TEMPS
ACROSS THE WEST NEAR 40 DEGREES.

ACROSS THE EAST...AND ESPECIALLY THE SE...THE MAINLY CLEAR SKIES
THIS EVENING WILL GRADUALLY BECOME PARTLY CLOUDY TO OCCASIONALLY
CLOUDY AS CLOUDS INCREASE FROM THE WEST. HOWEVER, SKIES WILL REMAIN
CLEAR-PARTLY CLOUDY LONG ENOUGH TO ALLOW POCKETS OF FOG TO DEVELOP
(THOUGH VISIBILITIES SHOULD REMAIN ABOVE A MILE). THE LACK OF
SUBSTANTIAL CLOUD COVERAGE IN THE COASTAL PLAIN WILL RESULT IN
COOLER MIN TEMPS THAN IN THE WEST. MIN TEMPS MID 30S TO NEAR 40.

FINALLY...WHILE MID-UPPER LEVEL SYSTEM IN AL-GA CURRENTLY PRODUCING
PATCHES FO LIGHT RAIN ACROSS THAT REGION...AS SYSTEM GETS CLOSER TO
OUR AREA...WAA/LIFT PROJECTED TO BE WEAKER. THUS SHOULD SEE A
DECREASE IN RADAR ECHOES AS SYSTEM APPROACHED OUR REGION FROM THE
SW. HOWEVER...COULD SEE A FEW POCKETS OF SPRINKLES IN THE SOUTHERN
PIEDMONT BY DAYBREAK. -WSS

TUESDAY AND TUESDAY NIGHT: THE OFFSHORE SURFACE LOW AND UPPER LEVEL
TROUGH WILL CONTINUE TO MOVE NE AWAY FROM THE NC COAST TUESDAY...
WITH THE UPPER LEVEL RIDGE AND SURFACE HIGH PRESSURE BUILDING INTO
THE AREA. ALTHOUGH THE EXTENT TO WHICH WE WARM TUESDAY WILL DEPEND
ON HOW FAST THE CLOUDS MOVE IN...THERE SHOULD BE SUFFICIENT WARM
ADVECTION...AND THE INCREASE IN LOW-LEVEL THICKNESSES WOULD INDICATE
AN INCREASE IN HIGH TEMPS OF 2-6 DEGREES...GREATEST WHERE CLOUDS
INHIBITED HIGHS TODAY...UPPER 50S TO MID 60S EXPECTED. THE SOUTHWEST
FLOW WILL ADVECT WARM MOIST AIR INTO CENTRAL NC FROM THE GULF AND
WITH DESCENT ISENTROPIC LIFT...EXPECT AND INCREASE IN CLOUDS ALONG
WITH THE SLIGHT CHANCE FOR SOME LIGHT RAIN ACROSS THE WEST TUESDAY
NIGHT. A WARM FRONT TO THE SOUTH MIGRATES NORTHWARD TUESDAY NIGHT AS
THE SURFACE HIGH IS PUSHED OFFSHORE. GIVEN THE ALREADY MOIST BOUNDARY
LAYER AND INCREASING DEWPOINTS...THERE IS A GOOD CHANCE FOR FOG/LOW
STRATUS TO DEVELOP EARLY WEDNESDAY MORNING. WITH THE CONTINUED WARM
ADVECTION AND INCREASING CLOUD COVER OVERNIGHT...LOWS WILL BE MUCH
HIGHER THAN MONDAY MORNING...GENERALLY IN THE MID 40S. -KC
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 245 PM MONDAY...

WSW FLOW ALOFT ON THE WESTERN PERIPHERY OF AN UPPER LEVEL RIDGE
BUILDING ALONG/JUST OFFSHORE THE EAST COAST WILL GIVE WAY TO
STRENGTHENING SW FLOW ALOFT ACROSS THE CAROLINAS BY FRIDAY AS AN
UPPER LEVEL TROUGH DEEPENS OVER THE ROCKIES/CENTRAL CONUS. IN THE
LOWER LEVELS...A PERSISTENT SOUTHERLY RETURN FLOW /WARM ADVECTION
REGIME/ WILL PREVAIL ON THE WESTERN PERIPHERY OF OFFSHORE HIGH
PRESSURE...WITH INCREASING MOISTURE ACROSS THE CAROLINAS IN THE WED-
FRI TIME FRAME. DESPITE INCREASING CLOUD COVER DOWNSTREAM OF PRECIP
EXPECTED TO DEVELOP ALONG A STRENGTHENING FRONTAL ZONE OVER THE
LOWER MS RIVER VALLEY AND TN/OH VALLEY ON THU/FRI...THERE IS HIGH
CONFIDENCE THAT STRONG WARM ADVECTION WILL RESULT IN A WARMING TREND
EACH DAY...WITH TEMPS IN THE LOWER/MID 70S (ESP. EAST OF HWY 1) BY
FRIDAY.

CONFIDENCE IN PRECIPITATION CHANCES REMAINS LOWER THAN AVERAGE. THE
LATEST MODEL GUIDANCE SUGGESTS A CHANCE OF LIGHT RAIN WED MORNING
THROUGH EARLY WED AFTERNOON IN ASSOC/W INCREASING MOISTURE AND THE
INITIAL SURGE OF STRONG LOW/MID-LEVEL WARM ADVECTION...THOUGH
PRECISE COVERAGE AND TIMING REMAIN DIFFICULT TO ASCERTAIN AT THIS
RANGE. DUE TO INCREASED CLOUD COVER AND A CHANCE OF RAIN...HIGH
TEMPS ON WED COULD RANGE FROM THE UPPER 50S TO UPPER 60S. EXPECT
LITTLE CHANCE FOR PRECIPITATION WED NIGHT THROUGH THE DAYTIME HOURS
ON FRIDAY GIVEN VERY LITTLE FORCING (ASIDE FROM TRANSIENT SMALL
AMPLITUDE WAVES IN SW FLOW ALOFT) AS THE AFOREMENTIONED FRONTAL ZONE
SLOWLY APPROACHES THE MOUNTAINS FROM THE WEST. WILL INDICATE LARGELY
DRY CONDITIONS WED NIGHT THROUGH FRIDAY. HIGHS WILL PRIMARILY DEPEND
ON CLOUD COVER THU/FRI...RANGING FROM THE MID/UPPER 60S NW (MORE
CLOUD COVER) TO LOWER 70S SE ON THU...AND UPPER 60S NW TO MID 70S SE
ON FRI. -VINCENT

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 345 PM MONDAY...

FRI NIGHT THROUGH SAT: DESPITE BEING 120+ HOURS OUT...FORECAST
CONFIDENCE REMAINS HIGH THAT A STRONG COLD FRONT WILL PROGRESS
THROUGH CENTRAL NC FRIDAY NIGHT AND SATURDAY MORNING...THOUGH THE
PRECISE TIMING IS STILL DIFFICULT TO ASCERTAIN THIS FAR OUT IN THE
FCST AND WILL HIGHLY AFFECT BOTH LOW TEMPS FRI NIGHT AND HIGHS ON
SAT. PRECIP AMOUNTS ALONG AND BEHIND THE COLD FRONT APPEAR GENERALLY
ON THE LOWER END OF THE SPECTRUM. WITHOUT MUCH IN THE WAY OF UPPER
LEVEL FORCING AND UNIDIRECTIONAL SW FLOW ALOFT...FORCING WILL
PRIMARILY BE CONFINED TO LOW-LEVEL CONVERGENCE ALONG THE SFC FRONT
AND WARM ADVECTION OVER/BEHIND THE SURFACE FRONT PROGRESSING E/SE
THROUGH THE CAROLINAS...WITH THE 925-850 MB TROUGH LAGGING BEHIND.
WILL MAINTAIN PRECIP CHANCES ~60% LATE FRI NIGHT THROUGH EARLY SAT
AFTERNOON. THEREAFTER...PRECIP CHANCES MAY LARGELY END SAT AFT/EVE
ASIDE FROM A POTENTIAL FOR PATCHY DRIZZLE. TEMPS WILL FALL FROM THE
60S LATE FRI EVENING TO THE 40S FROM NW-SE SATURDAY MORNING THROUGH
EARLY SAT AFTERNOON...LIKELY CONTINUING TO FALL MID/LATE SAT
AFTERNOON AS STRONG/COLD HIGH PRESSURE OVER THE UPPER MIDWEST
PROGRESSES EAST INTO THE GREAT LAKES RESULTING IN FURTHER PRESSURE
RISES /COLD ADVECTION/ LATE SAT INTO SAT NIGHT...WITH A PRONOUNCED
SFC RIDGE AXIS EXTENDING SOUTHWARD INTO THE CAROLINAS.

SATURDAY NIGHT THROUGH MONDAY: AN UPPER LEVEL TROUGH DIGGING INTO
THE 4-CORNERS REGION SAT IS PROGGED TO TRACK EAST INTO THE CENTRAL
PLAINS SAT NIGHT...AFFECTING THE LOW-LEVEL HEIGHT PATTERN
(BACKING/STRENGTHENING LOW-LEVEL FLOW) OVER THE SOUTHEAST CONUS AND
ENHANCING WARM ADVECTION /ISENTROPIC LIFT/ ATOP THE STRONG SFC RIDGE
AXIS /CAD WEDGE/ OVER THE CAROLINAS. AS A RESULT...AFTER A BRIEF
LULL SAT AFT/EVE LIGHT RAIN COULD RE-DEVELOP FROM SOUTH-NORTH SAT
NIGHT. LOWS SAT NIGHT WILL HIGHLY DEPEND ON THE PRECISE NATURE OF
THE COLD/DRY AIRMASS ADVECTING INTO THE REGION AND ANY POTENTIAL
EVAP COOLING ASSOC/W PRECIPITATION THAT MAY RE-DEVELOP...AND IT IS
POSSIBLE THAT PTYPE ISSUES (I.E. FZRA) COULD BE AN ISSUE IN THE NW
PIEDMONT. HOWEVER...AT THIS RANGE CONFIDENCE IS TOO LOW W/REGARD TO
THE SPECIFICS AND WILL MENTION ALL RAIN WITH LOWS IN THE MID 30S
(NW) TO UPPER 30S (SE). THE UPPER LEVEL WAVE IS EXPECTED TO
DEAMPLIFY AS IT TRACKS INTO THE TN VALLEY AND MID-ATLANTIC SUN AND
SUN NIGHT. EXPECT OVERCAST SKIES/RAIN AND NEAR STEADY TEMPS IN THE
30S TO PERHAPS 40S IN FAR SE COASTAL PLAIN ON SUNDAY IN ASSOC/W A
STRONG CAD WEDGE AND EVOLVING WEAK MILLER-B CYCLONE. FROM A PATTERN
RECOGNITION STANDPOINT...BASED ON THE LATEST GUIDANCE...FZRA AND
SOME POTENTIAL FOR ICE ACCUMULATION CANNOT BE RULED OUT IN THE NW
PIEDMONT ON SUNDAY...DEPENDING ON THE PRECISE NATURE/TIMING OF THE
AIRMASS ADVECTING INTO THE REGION FROM THE NORTH AND THE EVOLUTION
OF THE AFOREMENTIONED MILLER-B CYCLONE. DUE TO SIGNIFICANT
UNCERTAINTY AT THIS RANGE...WILL MENTION ONLY RAIN IN THE OFFICIAL
FORECAST. PRECIPITATION WILL END FROM W-E SUN NIGHT IN ASSOC/W A
COLD FRONTAL PASSAGE FROM THE WEST AS THE PRIMARY SFC CYCLONE
CONSOLIDATES ALONG THE MID-ATLANTIC COAST AND TRACKS NE AWAY FROM
THE REGION. -VINCENT

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
AS OF 100 AM TUESDAY...

SUB-VFR CONDITIONS ARE EXPECTED TO DEVELOP AT CENTRAL NC TAF SITES
DURING THIS 24 HR PERIOD... BUT THE TIMING AND HAZARDS WILL DIFFER
AT EACH LOCATION. AT INT/GSO... VFR CONDITIONS WILL PERSIST UNTIL
AROUND 17Z WHEN CIGS ARE LIKELY TO DROP TO MVFR AS THE WARM FRONTAL
ZONE APPROACHES FROM THE SW. MVFR CIGS/VSBY SHOULD DOMINATE AT
INT/GSO THROUGH 06Z WED. AT FAY... CIGS WILL STAY VFR THIS MORNING
BUT MVFR VSBYS IN FOG ARE EXPECTED 06Z-13Z WITH BRIEF IFR VSBYS
POSSIBLE. CIGS SHOULD DROP TO MVFR AFTER 18Z... THEN IMPROVE BACK UP
TO VFR AFTER 23Z. AT RDU/RWI... BRIEF MVFR VSBYS IN FOG ARE POSSIBLE
THROUGH 13Z THIS MORNING BUT OTHERWISE VFR CONDITIONS SHOULD STILL
DOMINATE THROUGH MIDDAY. CIGS MAY DROP TO MVFR AFTER 19Z BEFORE
RISING BACK TO VFR AFTER 23Z. WINDS WILL STAY LIGHT/VARIABLE THIS
MORNING THEN BECOME PREDOMINANTLY FROM THE SW OR SOUTH UNDER 8 KTS.

LOOKING BEYOND 06Z WED... SUB-VFR CONDITIONS ARE EXPECTED TO
DOMINATE AT ALL SITES FOR WED INTO THU WITH LOW CIGS AND SOME MAINLY
NIGHTTIME/MORNING FOG WITHIN A MOIST FLOW FROM THE SW. THESE POOR
AVIATION CONDITIONS MAY LAST THROUGH FRI INTO SAT AS WELL AS A COLD
FRONT MOVES SLOWLY INTO THE AREA FROM THE WNW... BRINGING INCREASING
RAIN CHANCES. -GIH
-- End Changed Discussion --

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...WSS/KC
SHORT TERM...VINCENT
LONG TERM...VINCENT
AVIATION...HARTFIELD