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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 072031
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
330 PM EST SAT DEC 7 2013

.SYNOPSIS... 
-- Changed Discussion --
WARM AND MOIST AIR WILL RIDE ATOP ARCTIC HIGH PRESSURE
THAT WILL RIDGE THROUGH THE MIDDLE ATLANTIC AND CAROLINAS TONIGHT
AND SUNDAY. A WEAK COASTAL LOW WILL DEVELOP AND LIFT UP THE MIDDLE
ATLANTIC COAST SUNDAY NIGHT AND MONDAY...AND BE FOLLOWED BY ANOTHER
SLOW-MOVING FRONTAL ZONE THAT WILL DRIFT ACROSS OUR REGION MONDAY
NIGHT AND TUESDAY.
-- End Changed Discussion --

&&

.NEAR TERM /TONIGHT/...
-- Changed Discussion --
AS OF 245 PM SATURDAY...

TONIGHT: COLD AND DRY ADVECTION WILL CONTINUE AS 1042 MB ARCTIC HIGH
PRESSURE OVER THE UPPER MIDWEST BUILDS EASTWARD TO THE NORTHERN
MIDDLE ATLANTIC STATES AND SUBSEQUENTLY RIDGES SOUTHWARD EAST OF THE
APPALACHIANS - ALL IN A FAVORABLE POSITION FOR THE BEGINNING OF
STRONG COLD AIR DAMMING. AT THE SAME TIME...WARM AND MOIST AIR WILL
BE TRANSPORTED NORTH NORTHEASTWARD IN STRENGTHENING LOW LEVEL FLOW
FROM THE GOM...WHICH WILL CONSEQUENTLY CAUSE ISENTROPIC UPGLIDE TO
RAPIDLY INCREASE AND PROMOTE THE DEVELOPMENT OF RAIN FROM SOUTH TO
NORTH...WITH TEMPERATURES FALLING THROUGH THE 40S AND 30S...
OVERNIGHT. BY DAYBREAK...TEMPERATURES ACROSS THE NORTHERN PIEDMONT
WILL BE FLIRTING WITH THE FREEZING MARK...AS THE SUPPLY OF COLD AND
DRY AIR IN THE LOW LEVELS CONTINUES FROM THE PARENT HIGH...RESULTING
IN A TRANSITION TO FREEZING RAIN WITHIN A COUPLE HOURS EITHER SIDE
OF 7 AM. BOTH THE LIMITED DEPTH OF SATURATION (BELOW THE ICE
NUCLEATION LAYER) AND RAPIDLY WARMING TEMPERATURES ALOFT WILL
PRECLUDE ANY CONCERN FOR FROZEN PRECIPITATION...EXCEPT FOR PERHAPS A
NUISANCE MIX OF GRAUPEL/"SLEET" NEAR ONSET WHERE THE SATURATED LAYER
IS LOCALLY EXTENDED ABOVE MINUS 10 IN SHALLOW ELEVATED CONVECTION.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
-- Changed Discussion --
AS OF 320 PM SATURDAY...

FORECAST LARGELY ON TRACK...THOUGH WITH AN EMPHASIS TOWARD WARNING
CRITERIA ICE ACCRUAL ON A SCATTERED - NOT WIDESPREAD - BASIS.

SUNDAY AND SUNDAY NIGHT: THE DEEPER SATURATION THROUGH THE MIXED
PHASE LAYER AND ASSOCIATED RELATIVELY-UNIFORM STRATIFORM
PRECIPITATION SHIELD CHARACTERISTIC OF MANY WINTER STORMS IS NOT
EXPECTED TO MATERIALIZE OVER CENTRAL NC...AND WILL INSTEAD DEVELOP
OVER THE TN VALLEY AND SHEAR QUICKLY ACROSS THE OH VALLEY AND MIDDLE
ATLANTIC STATES WITH A PARENT DEAMPLIFYING SHORTWAVE MID-LEVEL
TROUGH (NORTH AND WEST OF CENTRAL NC). WARM RAIN PROCESSES DRIVEN BY
SHALLOW (BUT STRONG) ISENTROPIC LIFT - AMIDST A COMBINATION OF
SYMMETRIC AND SHALLOW ELEVATED UPRIGHT INSTABILITY - WILL INSTEAD
DOMINATE OVER CENTRAL NC...WHERE PRECIPITATION WILL BE MORE OF A
MIXED STRATIFORM/CONVECTIVE MODE...SUCH THAT NUMEROUS SHALLOW
CONVECTIVE ELEMENTS WILL OCCUR WITHIN MUCH LIGHTER OR DRIZZL"Y"
PRECIPITATION. THIS WILL SUPPORT THE HIGHEST PRECIPITATION AMOUNTS
OVER THE NW PIEDMONT - AROUND A THIRD OF AN INCH - AND LESSER
AMOUNTS OF AROUND A TENTH OR TWO OVER THE EASTERN SANDHILLS AND
SOUTHERN COASTAL PLAIN...BUT WITH A FOCUS TOWARD LESS UNIFORMITY AND
SMOOTH GRADIENTS OWING TO THE CONVECTIVE PRECIPITATION NATURE. IN
OTHER WORDS...PRECIPITATION AMOUNTS WILL VARY QUITE WILDLY OVER
SMALL DISTANCES...INCLUDING OVER SINGLE COUNTIES.

REGARDING TEMPERATURES...THE ARCTIC HIGH WILL BECOME INCREASINGLY
ESTABLISHED EAST OF THE APPALACHIANS DURING THE DAY SUNDAY...SO
TEMPERATURES WILL HOVER IN THE LOWER 30S THROUGHOUT THE DAY AND
EVENING. ELSEWHERE...TEMPERATURES WILL CREEP THROUGH THE 30S...TO
NEAR 40 DEGREES TOWARD KFAY TO KCTZ AND KGSB. WITH TEMPERATURES
NEAR/BELOW FREEZING OVER THE NW PIEDMONT...MOST OF THE
AFOREMENTIONED PRECIPITATION WILL LIKELY FALL IN THE FORM OF
FREEZING RAIN OVER THE WARNING AREA...WITH A 5-8 HOUR PERIOD OF FZRA
AND CONSEQUENT LIGHTER ACCRUAL OF A GLAZE TO AROUND A TENTH OF AN
INCH...IN THE ADVISORY AREA. THE GREATEST IMPACTS ARE STILL EXPECTED
TO OCCUR ON ELEVATED SURFACES (ESPECIALLY TREES AND POWER LINES).

THE PRECIPITATION WILL TAPER TO DRIZZLE...AND FREEZING DRIZZLE OR
LIGHT FREEZING RAIN OVER THE NW PIEDMONT...AS THE LLJ AND ASSOCIATED
ISENTROPIC LIFT WELL NORTH OF OUR REGION SUN EVE AND NIGHT.
TEMPERATURES WILL HOLD STEADY OR INCH SLIGHTLY UPWARD ESPECIALLY
LATE...AS THE ARCTIC RIDGE SHIFTS OFFSHORE.

MON AND MON NIGHT: THOUGH THE CENTER OF THE SURFACE HIGH WILL BE
WELL OFFSHORE THE NE COAST BY MON...THE RESIDUAL WEDGE AIR MASS WILL
NOT BE FULLY ERADICATED BEFORE A COLD/OCCLUDED FRONT PASSES FROM THE
WEST MON EVE. WITH LOW OVERCAST AND EVEN A LITTLE DRIZZLE LINGERING
THROUGH THE DAY OVER THE PIEDMONT...AND AFTERNOON SCATTERING OVER
THE COASTAL PLAIN...TEMPERATURES WILL VARY SIGNIFICANTLY FROM THE
40S OVER THE NW PIEDMONT TO 60S IN THE COASTAL PLAIN. WILL RETAIN A
CHANCE OF ELEVATED SHOWERS AREA-WIDE...IN ADDITION TO THE OCCASIONAL
DRIZZLE OVER THE PIEDMONT. SHOWERS MAY BECOME BRIEFLY NUMEROUS ALONG
AND BEHIND THE AFOREMENTIONED FRONT FORECAST TO SLOWLY CROSS OUR
REGION THROUGH EARLY TUESDAY...WITH LOWS IN THE 40S...TO LOWER 50S
OVER THE SANDHILLS AND SOUTHERN-CENTRAL COASTAL PLAIN.
-- End Changed Discussion --

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 304 PM SATURDAY...

SHORTWAVE OVER THE SOUTHERN PLAINS ON LATE MONDAY WILL LIFT
NORTHEASTWARD THROUGH THE DAY TUESDAY. ANOTHER COLD FRONT WILL MOVE
ACROSS THE AREA ON TUESDAY... BRINGING ANOTHER ROUND OF RAIN. 12Z
GFS DEVELOPS A FRONTAL WAVE OVER THE CAROLINAS... WITH RESULTANT
PRECIP CHANCES LINGERING THROUGH WED. THE ECMWF CONTINUES TO SHOW A
QUICK FRONTAL PASSAGE TUESDAY. WILL SIDE WITH A SOMEWHAT SLOWER
PASSAGE GIVEN THE SIMILARITIES TO THE CURRENT PATTERN... AND EXTEND
CHANCE POPS THROUGH 06Z... TAPERING TO SLIGHT CHANCE WED MORNING.

BELOW NORMAL TEMPERATURES WILL REMAIN THROUGH THE END OF THE WEEK AS
AN AREA OF HIGH PRESSURE... ORIGINATING FROM CANADA... BUILDS IN
FROM THE NORTHWEST. HIGHS IN THE 40S... LOWS IN THE 20S TO NEAR 30.
THERE IS THE POTENTIAL FOR A SOUTHERN STREAM WAVE TO IMPACT THE AREA
SATURDAY.

&&

.AVIATION /18Z SATURDAY THROUGH WEDNESDAY/...
AS OF 102 PM SATURDAY...

A COLD FRONT HAS MOVED THROUGH THE AREA... CURRENTLY VFR CONDITIONS
AT KGSO AND KINT... WITH MVFR TO IFR CONDITIONS FURTHER EAST...
CLOSER TO THE CURRENT POSITION OF THE FRONT. CONDITIONS WILL BECOME
IFR/LIFR WITH LIGHT RAIN TONIGHT AS A COLD AIR DAMMING REGIME SETS
UP OVER THE AREA. PERIODS OF FREEZING RAIN WILL OCCUR AT KGSO AND
KINT BEGINNING EARLY SUNDAY MORNING... AND LASTING THROUGH THE DAY.
LIGHT RAIN IS EXPECTED THROUGH THE DAY AT KFAY...KRWI...AND KRDU...
WITH THE POSSIBILITY OF A PERIOD OF FREEZING RAIN AT KRDU FROM 15Z-
19Z.

SUB-VFR CONDITIONS ARE LIKELY WITH PERIODS OF LIGHT RAIN THROUGH
TUESDAY. IMPROVING CONDITIONS ON WEDNESDAY AS HIGH PRESSURE BUILDS
IN.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
FREEZING RAIN ADVISORY FROM 4 AM TO 7 PM EST SUNDAY FOR
NCZ008>010-024-025-038>040.
ICE STORM WARNING FROM 4 AM SUNDAY TO MIDNIGHT EST SUNDAY NIGHT
FOR NCZ007-021>023.

&&

$$

SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...MWS
LONG TERM...SEC
AVIATION...SEC