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000
FXUS62 KRAH 051141
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
640 AM EST THU DEC 5 2013

.SYNOPSIS...
A WARM AND MOIST SOUTHERLY FLOW WILL PERSIST THROUGH
FRIDAY...RESULTING IN ABOVE NORMAL TEMPERATURES. A COLD FRONT WILL
MOVE IN FROM THE NORTH EARLY SATURDAY BRINGING MUCH COLDER
TEMPERATURES AND OCCASIONAL RAIN THIS WEEKEND.

&&

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

SWLY FEED OF WARM MOIST AIR BETWEEN SFC HIGH PRESSURE OVER THE
WESTERN ATLANTIC AND A SLOW MOVING/QUASI-STATIONARY ARCTIC FRONT
OVER THE OHIO/TN VALLEY WILL STRENGTHEN OVER THE AREA TODAY AND
TONIGHT. PWATS WILL INCREASE FROM 1.0" THIS MORNING TO 1.5" BY THE
AFTERNOON WITH BOUNDARY LAYER DEW POINTS RISING INTO THE LOWER 60S.
WEAK ISENTROPIC LIFT AIDED BY WEAK S/W IMPULSES EMBEDDED IN THE SWLY
FLOW ALOFT MAY RESULT IN A BRIEF PASSING SHOWER/SPRINKLES.
OTHERWISE... PRETTY MUCH A TEMPERATURE FORECAST TODAY...MADE
DIFFICULT BY WHAT WILL LIKELY BE A BROKEN/OVERCAST DAY FEATURING
MULTIPLE LAYERS OF CLOUDS...THE MOST DISCONCERTING BEING THE
LEFTOVER FOG/STRATUS THAT BUFR SOUNDINGS SUGGEST MAY NEVER SCOUR OUT
ACROSS THE WESTERN PIEDMONT. HIGHS IN THE MID/UPPER 60S NW TO
LOWER/MID 70S SE.  MILD OVERNIGHT LOWS IN THE LOWER 60S.

&&

.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
AS OF 300 AM THURSDAY...

DOWNSTREAM OF THE LONG WAVE POSITIVE-TILT TROUGH OVER THE
WESTERN/SOUTHWEST US...AFOREMENTIONED ARCTIC COLD FRONT SAGGING
SOUTHWARD ACROSS THE MID-ATLANTIC AND INTO THE SOUTHERN APPALACHIANS
WILL BECOME PARALLEL TO THE DEEPENING SWLY FLOW ALOFT. FRONT WILL BE
VERY SLOW TO CROSS THE MOUNTAINS ON FRIDAY...LEAVING CENTRAL NC IN
THE WARM SECTOR FRIDAY AFTERNOON/EVENING. THE ANA-FRONTAL STRUCTURE
OF THE FRONT WILL ALSO RESULT IN CONTINUED MOSTLY DRY CONDITIONS FOR
CENTRAL THROUGH FRIDAY AFTERNOON WITH INCREASING POPS FROM NW TO SE
FRIDAY EVENING...ESPECIALLY AFTER MIDNIGHT AS FRONT FINALLY PUSHES
SOUTHEAST INTO THE AREA...FORECAST TO BISECT THE AREA BY DAYBREAK
SATURDAY. WEAK INSTABILITY 200-300 J/KG DEVELOPS IN THE EAST FRIDAY
AFTERNOON...BUT IS ERASED BY NOCTURNAL COOLING/STABILIZATION WELL
BEFORE THE FRONT ARRIVES. THUS...WILL KEEP IT ALL SHOWERS WITH NO
MENTION OF THUNDER.

HIGHS FRIDAY IN THE WARM SECTOR WILL APPROACH RECORD
TERRITORY...RANGING FROM LOWER/MID 70S NW TO UPPER 70S/NEAR 80S
SOUTHEAST. MIN TEMPS FRIDAY NIGHT/SATURDAY MORNING WILL DEPEND ON
TIMING/LOCATION OF THE FRONT BISECTING THE AREA. EITHER WAY EXPECT A
LARGE NW-SE SPREAD IN MORNING LOWS RANGING FROM MID 40S NW TO UPPER
50S/NEAR 60 SE.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 250 AM THURSDAY...

GUIDANCE HAS BEEN IN PRETTY GOOD AGREEMENT REGARDING THE FRONTAL
PASSAGE LATE FRIDAY NIGHT AND EARLY SATURDAY...SURGING FROM NORTH TO
SOUTH TO THE NC/SC BORDER BY 12-15Z SATURDAY MORNING. THE FRONT WILL
BE ACCOMPANIED BY MOSTLY ANAFRONTAL PRECIP AS THE FRONT SURGES SOUTH
BENEATH THE SOUTHWESTERLY FLOW JUST ABOVE THE SURFACE.  A CHILLY
NORTHERLY WIND WILL ALSO DEVELOP BEHIND THE FRONT AS HIGH PRESSURE
OVER THE MIDWEST EXTENDS ACROSS THE CENTRAL APPALACHIANS. A LULL IN
PRECIP...OR DIMINISHING TREND IN PRECIP RATES IS POSSIBLE SATURDAY
AFTERNOON/EVENING...MAINLY ACROSS THE NORTHERN CWA...BEFORE THE LOW-
LEVEL FLOW BEGINS TO ACCELERATES ONCE AGAIN AHEAD OF ANOTHER WAVE
EJECTING OUT OF THE SOUTHERN PLAINS.  THE BEST PERIOD OF ISENTROPIC
ACCENT AND WIDESPREAD PRECIP SHOULD COME SATURDAY NIGHT INTO SUNDAY.
AT THE SAME TIME..AN ARCTIC HIGH IS FORECAST TO BUILD ACROSS THE
GREAT LAKES TO THE NORTHEAST US AND SUPPLY A SECONDARY SURGE OF COLD
AIR FROM THE NORTH. THE POSITION AND STRENGTH OF THE HIGH (1036MB)
ARE FAVORABLE CLASSIC CAD...BUT THE HIGH WILL BE PROGRESSIVE AND
RETREAT TO THE NORTHEAST ON SUNDAY AFTERNOON. THE PATTERN SUPPORTS
AT LEAST A BRIEF PERIOD OF MIXED PTYPE...MAINLY FREEZING RAIN IN THE
NORTHWEST PIEDMONT...THOUGH MODELS KEEP THE WETBULB FREEZING LINE
JUST OUTSIDE OF THE NORTHWEST PIEDMONT. THIS WILL NEED TO BE
MONITORED WITH SUBSEQUENT MODEL RUNS.  ONCE THE RAIN AND COLD AIR
DAMMING SET IN ON SATURDAY...TEMPS WILL LIKELY REMAIN RELATIVELY
UNCHANGED THROUGH SUNDAY...WITH MID 30S TO LOWER 40S ACROSS THE CWA.

FOR MONDAY AND TUESDAY... A SURFACE LOW ASSOCIATED WITH THE
SHORTWAVE MENTIONED ABOVE IS PROGGED TO LIFT TOWARD THE GREAT LAKES
MONDAY...PUTTING CENTRAL NC BACK IN THE WARM SECTOR.  WILL SHOW A
MINIMUM IN POPS ON MONDAY AS THE FOCUS OF FORCING SHIFTS BACK WEST
OF THE MOUNTAINS BEFORE THE COLD FRONT SWEEPS ACROSS THE CWA MONDAY
NIGHT AND EARLY TUESDAY. AHEAD OF THE FRONT... 850MB TEMPS ARE
PROGGED TO RISE BACK ABOVE 10C ON MONDAY AFTERNOON...BUT GUIDANCE IS
LIKELY TOO HIGH REGARDING SURFACE TEMPS GIVEN THE PRECEDING COLD AIR
DAMMING AIRMASS...SO WILL STICK WITH COOLER READINGS IN THE LOWER
50S TO MID 60S.

BEHIND THE FRONT...ANOTHER STRONG HIGH PRESSURE IS FORECAST TO BUILD
ACROSS THE MIDWEST TOWARD THE MID-ATLANTIC STATES...AND GUIDANCE
SHOWS ANOTHER ROUND OF BELOW NORMAL TEMPS BY MIDWEEK.


&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/
... AS OF 640 AM THURSDAY...

WIDESPREAD IFR TO LIFR CONDITIONS ARE EXPECTED TO IMPACT MOST IF NOT
ALL OF THE TAF SITES THROUGH AT LEAST 12Z-14Z.
THEREAFTER...CONDITIONS WILL IMPROVE SLOWLY... LIFTING TO VFR AT
KFAY...KRWI AND KRDU BETWEEN 15Z-18Z. ITS QUITE POSSIBLE THAT
WESTERN TERMINALS(KGSO AND KINT)COULD REMAIN SUB-VFR THROUGHOUT THE
TAF PERIOD.

LIGHT WINDS WILL BECOME SWLY AND WILL INCREASE TO 10-15KT DURING THE
AFTERNOON. LOW CIGS COULD REDEVELOP AGAIN TONIGHT/FRIDAY MORNING
WITH THE S-SW FLOW...ESPECIALLY IN THE WEST IN CLOSER PROXIMITY TO
THE DEEPER MOISTURE ATTENDANT TO THE QUASI-STATIONARY FRONT WEST OF
THE MOUNTAINS.

SUB-VFR CONDITIONS ARE LIKELY FRIDAY THROUGH THE WEEKEND AS A COLD
FRONT WILL SHIFT SOUTH THROUGH THE REGION BY 12Z SATURDAY. IFR TO
LIFR CIGS ALONG WITH LOW VSBYS WITH LIGHT RAIN AND FOG SHOULD
PREVAIL SATURDAY INTO SUNDAY. A NORTHERLY TO NORTHEAST FLOW AT 10-15
KT WILL PREVAIL SAT-SUN.

&&

.CLIMATE...
RECORD HIGH TEMPERATURES FOR DECEMBER 6TH:

GSO... 76 SET IN 1998
RDU... 80 SET IN 1998
FAY... 80 SET IN 1998

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR NCZ007>011-
021>028-038>043-073>078-083>086-088-089.

&&

$$

SYNOPSIS...BADGETT/NP
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...BLS
AVIATION...BADGETT/CBL
CLIMATE...