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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 031822
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
115 PM EST TUE MAR 3 2015

.SYNOPSIS...HIGH PRESSURE OVER THE REGION WILL SHIFT OFFSHORE THIS
AFTERNOON AS A LOW PRESSURE SYSTEM TRACKS NORTHEAST FROM THE CENTRAL
PLAINS INTO THE GREAT LAKES. A WARM FRONT WILL LIFT NORTHWARD
THROUGH THE REGION LATE TONIGHT AND EARLY WEDNESDAY. THE NEXT COLD
FRONT WILL APPROACH FROM THE NORTHWEST WEDNESDAY NIGHT...TRACKING
THROUGH THE CAROLINAS ON THURSDAY.

&&

.NEAR TERM /TODAY AND TONIGHT/...
-- Changed Discussion --
AS OF 1030 AM TUESDAY...

OVERVIEW: A 1030MB SURFACE HIGH CENTERED OVER THE MID-ATLANTIC
STATES THIS MORNING WILL SHIFT OFFSHORE THIS AFTERNOON. WELL
DOWNSTREAM OF THE SURFACE LOW MOVING EAST-NORTHEASTWARD INTO THE
LOWER GREAT LAKES...BROAD REGION OF LOW AND MID-LEVEL WARM ADVECTION
ATOP THE RESIDUAL SHALLOW WEDGE OF COOL/DRY AIR NEAR THE SFC WILL
SUPPORT COLD AIR DAMMING ACROSS THE CAROLINAS TODAY. THE WEDGE OF
COOL DRY AIR WILL THEN RETREAT NORTHWARD OVERNIGHT AS A WARM FRONT
LIFTS NORTHWARD THROUGH THE AREA.

TODAY:
LITTLE IF ANY UPPER LEVEL FORCING WILL BE PRESENT AS RIDGING
OVER THE GULF OF MEXICO BUILDS NORTHWARD OVER THE SOUTHEAST. AS A
RESULT...PRECIP CHANCES WILL BE VERY LIGHT...WITH INTERMITTENT
PERIODS OF LIGHT RAIN/DRIZZLE EXPECTED ACROSS THE AREA THROUGHOUT
THE DAY. IN FACT THE LATEST HRRR...SHOWS VERY LITTLE COVERAGE ACROSS
THE AREA THROUGH THE AFTERNOON.

DAYTIME HIGHS WILL ULTIMATELY DEPEND ON THE EXTENT/COVERAGE OF
PRECIP. WITHOUT DECENT COVERAGE OF PRECIP ACROSS THE AREA AND THE
BENEFITS OF ASSOCIATED EVAP COOLING...TEMPERATURES ARE
EXPECTED TO RANGE FROM MID/UPPER 30S NORTH TO LOWER/MID 40S
SOUTHEAST.

TONIGHT: LOW CONFIDENCE WITH TEMPERATURES OVERNIGHT...WRT TO WARM
FRONT LIFTING NORTHWARD INTO CENTRAL NC AND THE WESTERN/INLAND
EXTENT OF CAD EROSION OVERNIGHT. GIVEN THE LACK OF A WELL DEFINED
UPSTREAM CYCLONE...ONE WOULD TYPICALLY BE SKEPTICAL OF SIGNIFICANT
CAD EROSION DURING THE OVERNIGHT HOURS AS DEPICTED BY THE GFS WHICH
BLOWS AWAY THE DAMMING REGIME EVEN INTO THE HEART OF THE WEDGE
ACROSS THE NW PIEDMONT. HOWEVER...GIVEN THE POTENTIAL LACK OF
SIGNIFICANT PRECIP TO HELP LOCK IN THE WEDGE...THE GFS SCENARIO
REMAINS PLAUSIBLE. IN CONTRAST...THE HIGHER RESOLUTION NAM...WHICH
TYPICALLY HANDLES CAD EVOLUTION BETTER ACROSS THE CAROLINAS...KEEPS
THE WEDGE IN PLACE WITH TEMPS NEARLY STEADY AND GRADUALLY/MARGINALLY
INCREASE BY SUNRISE...PARTICULARLY NORTH OF HWY 64. WILL ERR TOWARDS
THE COOLER GUIDANCE...BUT THERE REMAINS HIGH BUST POTENTIAL. WARM
AIR LIFTING ATOP THE SHALLOW COOL AIR WILL SUPPORT AN ENHANCED
POTENTIAL FOR THE DEVELOPMENT OF DENSE FOG OVERNIGHT.
-- End Changed Discussion --


&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 400 AM TUESDAY...

IF THE WARM FRONT HAS NOT PROGRESSED THROUGH THE BULK OF CENTRAL NC
BY SUNRISE WED...IT SHOULD DO SO SHORTLY THEREAFTER AS THE
INCREASINGLY SHALLOW CAD WEDGE DISSIPATES VIA INCREASING
INSOLATION/MIXING AND STRENGTHENING SOUTHWEST FLOW. INITIALLY
OVERCAST SKIES WILL BECOME SCT/BKN BY AFTERNOON...WITH A BREEZY
SOUTHWEST WIND. THE GFS SUGGESTS DEEP/MORE VIGOROUS MIXING AND A
POTENTIAL FOR GUSTS AS HIGH AS 30-40 KT...THOUGH THE NAM INDICATES
LESS MIXING AND GUSTS NO HIGHER THAN 20-25 KT. GIVEN LITTLE IN THE
WAY OF DIURNAL DESTABILIZATION....UNIDIRECTIONAL SW FLOW ALOFT WITH
FEW (IF ANY) SHORTWAVE DISTURBANCES...AND UNIDIRECTIONAL SW LOW-
LEVEL FLOW...EXPECT LARGELY DRY CONDITIONS OVER CENTRAL NC DURING
THE DAY. AN AMPLIFYING TROUGH DIGGING SE INTO THE CENTRAL MS RIVER
VALLEY WED EVE/NIGHT WILL RESULT IN CYCLOGENESIS ALONG A SLOW MOVING
FRONTAL ZONE PROGRESSING INTO THE AREA WED NIGHT...THOUGH THE BULK
OF PRECIPITATION IS EXPECTED TO BE ANAFRONTAL...OCCURRING AFTER
SUNRISE. RAIN CHANCES WILL BE RELATIVELY HIGHEST NEAR THE VA BORDER
AND IN THE NW PIEDMONT /TRIAD/. -VINCENT

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 400 AM TUESDAY...

THE LATEST MODELS ARE IN GOOD AGREEMENT IN BRING THE COLD FRONT
SOUTH THROUGH CENTRAL NORTH CAROLINA THURSDAY MORNING. A WAVE IS
EXPECTED TO FORM ALONG THE FRONT OVER UPSTATE SC... WHICH IN TURN
HELPS TO HOLD UP THE COLD FRONT FOR SEVERAL HOURS FROM REACHING THE
SOUTHERN ZONES. THE STRONGEST CAA SHOULD ALSO LAG THE FRONTAL
PASSAGE BY SEVERAL HOURS IT APPEARS. THIS SUPPORTS THE CONTINUATION
OF OUR CURRENT PREDOMINATELY RAIN FORECAST FOR THURSDAY WITH LIMITED
POTENTIAL FOR WINTERY MIX NEAR THE END OF THE EVENT BETWEEN 18Z AND
23Z OR SO THURSDAY AFTERNOON FOR THE NORTHERN PIEDMONT AND NORTHERN
COASTAL PLAIN.

P-TYPE NOMOGRAMS SUPPORT SOME MIX WITH OR CHANGE TO FREEZING RAIN
THEN EVEN A BRIEF PERIOD OF LIGHT SNOW/SLEET AT THE VERY VERY END OF
THE EVENT...ACROSS THE FAR NORTHERN PIEDMONT DURING THE MID TO LATE
AFTERNOON. FORECAST WET BULB TEMPERATURES DEPENDING ON THE MODEL OF
CHOICE WITH SOME MODEL VARIABILITY ALSO TARGET THE NORTHERN ZONES
FOR THIS POTENTIAL CHANGEOVER (ESPECIALLY NORTH OF A LINE EXTENDING
FROM DAVIDSON TO RANDOLPH TO WAKE TO WARREN COUNTIES. PRECIPITATION
SHOULD END QUICKLY BETWEEN 21Z-00Z...LIMITING THE WINDOW OF
OPPORTUNITY FOR ICE TO BECOME A SIGNIFICANT WEATHER HAZARD. TO THE
SOUTH...ALL RAIN IS EXPECTED WITH THE SLOWER TO COOL TEMPERATURES
THERE.

ALL IN ALL...A SIGNIFICANT WINTER WEATHER EVENT IS NOT EXPECTED AT
THIS TIME WITH THE PREDOMINATE P-TYPE EXPECTED TO BE RAIN. THE
CHANGEOVER WOULD OCCUR DURING THE AFTERNOON IN THE NORTH (IF AT
ALL)... AND THE WARM GROUND TEMPERATURES AND TIME OF DAY WOULD LIMIT
THE POTENTIAL TO MOSTLY ELEVATED SURFACES.

THURSDAY NIGHT...BREEZY AND COLDER CONDITIONS COULD LEAD TO A QUICK
FREEZE OF RESIDUAL WATER LEFT BEHIND WHICH MAY BECOME A WEATHER
HAZARD. OTHERWISE...SIMPLY CLEARING AND COLD WITH LOWS IN THE 20-25
RANGE.

FRIDAY IS EXPECTED TO BE MOSTLY SUNNY AND COLD WITH THE HEART OF THE
ARCTIC COLD EXPECTED OVER THE OHIO VALLEY AND NORTHERN MID ATLANTIC
STATES. WE WILL STILL BE A GOOD 20 DEGREES BELOW NORMAL WITH HIGHS
EXPECTED IN THE UPPER 30S TO LOWER 40S.

MODERATION WILL OCCUR IN THE TEMPERATURES OVER THE WEEKEND AS THE
HIGH SLIPS SOUTH AND A WESTERLY FLOW DEVELOPS. HIGHS SHOULD RAPIDLY
WARM INTO THE MID 40S TO LOWER 50S SATURDAY AND MID 50S TO LOWER 60S
SUNDAY. A DRIER PATTERN IS ALSO ANTICIPATED THROUGH THE WEEKEND.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
AS OF 122 PM TUESDAY...

24-HR TAF PERIOD: EXPECT WIDESPREAD MVFR CONDITIONS THIS
AFTERNOON...LOWERING TO IFR IN POCKETS OF LIGHT RAIN AND
DRIZZLE. CEILINGS WILL LOWER TO IFR/LIFR AFTER SUNSET...QUICKLY
FOLLOWED BY VISBYS FALLING TO LIFR/VLIFR WITH WIDESPREAD DENSE FOG
AS A WARM FRONT PROGRESSES NORTHWARD INTO THE COLD AIR DAMMING WEDGE
IN PLACE OVER CENTRAL NC AFTER 05-06Z. CEILINGS ARE EXPECTED TO
IMPROVE FROM SE TO NW AS STRONG SWLY FLOW HELPS TO LIFT AND
SCOUR OUT LINGERING WEDGE AIRMASS IN PLACE...POSSIBLY IMPROVING TO
VFR AT KFAY...KRWI AND KRDU...WHILE MVFR CEILINGS MAY PERSIST
AT KINT AND KGSO. BREEZY SOUTHWEST WINDS ARE EXPECTED TO DEVELOP BY
THE AFTERNOON AS TEMPERATURES START TO WARM INTO THE 60S AND
70S. SUSTAINED WINDS OF 15 TO 20KTS WITH GUSTS AS HIGH AS 30-35 KT
...DEPENDING ON CLOUD COVER/MIXING.


LOOKING AHEAD:  ADVERSE AVIATION CONDITIONS ARE EXPECTED TO RETURN
WEDNESDAY NIGHT AND WILL PERSIST THROUGH THURSDAY IN ASSOC/W A
STRONG COLD FRONTAL PASSAGE AND ATTENDANT ANA-FRONTAL PRECIP BAND
THROUGH THE THE AREA. PRECIPITATION COULD END AS A BRIEF PERIOD
OF SLEET AND FREEZING RAIN THURSDAY AFTERNOON AND EVENING.
VFR CONDITIONS ARE EXPECTED TO RETURN ON FRIDAY...AND SHOULD REMAIN
PREDOMINATELY VFR THROUGH THE WEEKEND.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...CBL/VINCENT
SHORT TERM...VINCENT
LONG TERM...BADGETT
AVIATION...CBL