-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 051154
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
650 AM EST WED MAR 5 2014

.SYNOPSIS...HIGH PRESSURE OVER THE MIDATLANTIC WILL WEAKEN TODAY. A
BACKDOOR COLD FRONT WILL DROP SOUTHWARD THROUGH NORTH CAROLINA
TONIGHT... BRINGING CHILLY TEMPERATURES BACK FOR THURSDAY. LOW
PRESSURE WILL STRENGTHEN OVER THE NORTHERN GULF THURSDAY AND MOVE
NORTHEAST ALONG THE CAROLINA COAST... BRINGING WIDESPREAD
PRECIPITATION TO THE REGION FROM LATE THURSDAY AFTERNOON THROUGH
FRIDAY.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
AS OF 220 AM WEDNESDAY...

PRECIP CHANCES WILL PERSIST TODAY IN THE SOUTHEAST CWA... BUT
AMOUNTS LOOK LIGHT AND INCONSEQUENTIAL. THE LATEST SURFACE MAP SHOWS
A WEAK RESIDUAL HIGH PRESSURE AREA EXTENDING FROM NC NE OVER THE
DELMARVA PENINSULA... RESULTING IN LIGHT NORTH AND NE SURFACE WINDS.
LOW LEVEL MOISTURE CIRCULATING AROUND LOW PRESSURE JUST OFF THE
OUTER BANKS IS GENERATING WIDESPREAD CLOUDS OVER THE ERN HALF OF THE
CWA... WHICH MODELS INDICATE WILL SLOWLY DEPART WEST TO EAST THROUGH
THE DAY. A BAND OF LIGHT PRECIP CURRENTLY STRETCHES FROM CENTRAL GA
ACROSS UPSTATE/CENTRAL SC INTO SOUTH CENTRAL NC... AND HAS BEEN
SPREADING SLOWLY NE IN THE LAST SEVERAL HOURS. THIS APPEARS TO BE
LARGELY SUPPORTED BY UPPER DIVERGENCE IN THE RIGHT ENTRANCE REGION
OF THE 150+ KT JET FROM WV OUT OVER THE NW ATLANTIC. THE LATEST
MODEL RUNS ALL GENERALLY SHOW THIS LIGHT PRECIP SPREADING
NORTHEASTWARD ACROSS THE SE CWA TODAY BUT CONTINUE TO DIFFER AS TO
THE QPF AND NORTHWARD EXTENT. BASED ON THE CURRENT LARGE DEW POINT
DEPRESSION (AROUND 15 DEG)... RAP MODEL TRENDS... AND FORECAST
SOUNDINGS SHOWING A LACK OF SATURATION BELOW 800 MB EVEN AT FAY...
BELIEVE THIS WILL BE A VERY LIGHT EVENT WITH MEASURABLE AMOUNTS
CONFINED TO AREAS ALONG/SE OF ROCKINGHAM-FORT BRAGG-GOLDSBORO. WILL
KEEP POPS HERE IN THE 20-40% RANGE... HIGHEST IN SRN SAMPSON CO.
CURRENT SURFACE WET BULB TEMPS ALONG THE PATH OF THIS LIGHT PRECIP
ARE BELOW FREEZING... BUT THESE ARE FORECAST TO RISE ABOVE 32F BY
LATE MORNING. WILL START PRECIP OUT AS LIGHT RAIN OR FREEZING
RAIN... CHANGING TO JUST LIGHT RAIN. EXPECT ANY ACCRUAL TO BE
MINIMAL GIVEN THE LACK OF A SOURCE OF DRY AIR TO OFFSET THE EFFECTS
OF THE LATENT HEAT RELEASE... PLUS COVERAGE AND DURATION OF NON-RAIN
PRECIP IS NOT EXPECTED TO BE GREAT ENOUGH TO WARRANT ANY SORT OF
CONCERN FOR TRAVEL PROBLEMS. HIGHS FROM 45 SOUTHEAST TO 53 IN THE
FAR WRN TRIAD REGION. THE HIGH-ROOTED LIFT WILL EXIT BY LATER THIS
AFTERNOON... SO WILL END PRECIP CHANCES BY THIS TIME... WITH SKIES
TRENDING TO FAIR/PARTLY CLOUDY. A BACKDOOR FRONT NOW STRETCHING JUST
SOUTH OF THE GREAT LAKES WILL PUSH SOUTHWARD INTO AND THROUGH NC
TONIGHT... WITH THE MAIN CONSEQUENCE BEING AN INCREASE IN NORTHEAST
SURFACE WINDS AS THE 1040 MB CENTRAL PRESSURE ARCTIC HIGH SHIFTS ESE
TO A POSITION OVER THE ST LAWRENCE VALLEY WHILE NOSING SOUTHWARD
INTO NC. EXPECT FAIR TO PARTLY CLOUDY SKIES OVERNIGHT WITH LOWS FROM
28-30 NORTH TO 33-35 SOUTHEAST. -GIH

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 310 AM WEDNESDAY...

...A WINTRY MIX POSSIBLE...MAINLY OVER THE WESTERN PIEDMONT THURSDAY
NIGHT...

WEST COAST RIDGING WILL ALLOW A SHORTWAVE MOVING FROM THE ROCKIES
TOWARD THE SOUTHEAST US TO AMPLIFY OVER THE SOUTHEAST ON THURSDAY.
CYCLOGENESIS IS EXPECTED OVER THE EASTERN GOMEX BY THURSDAY
AFTERNOON...WITH A MILLER-A TYPE SURFACE LOW TRACK ALONG THE
CAROLINA COAST FRIDAY.  UPPER DIFLUENCE AHEAD OF THE TROUGH WILL
OVERSPREAD THE REGION DURING THE THE DAY ON THURSDAY...THOUGH MODELS
KEEP DEEPER MOISTURE AND PRECIP JUST TO OUR SOUTH THROUGH
MIDDAY...REACHING THE SOUTHERN CWA BY MID-LATE AFTERNOON.
MEANWHILE...A CANADIAN SURFACE HIGH IS EXPECTED TO EXTEND DOWN THE
EASTERN SEABOARD INTO THE CAROLINAS.  WHILE THE HIGH IS
PROGRESSIVE...THE HIGH DOES SHIFT INTO A FAVORABLE POSITION OVER NEW
ENGLAND LATE THURSDAY AND THURSDAY NIGHT.  AS THE HIGH NOSES INTO
THE AREA...DEWPOINTS ARE FORECAST TO DROP INTO THE MID 20S IN THE
WESTERN PIEDMONT AND THE WETBULB FREEZING LINE PUSHES SOUTH TO THE
NC/SC BORDER.  DURING THIS TIME...PARTIAL THICKNESSES ARE FORECAST
TO HOVER NEAR 1300/1550...WHICH SUGGESTS THERE MAY BE A FEW HOURS
OVERNIGHT WHERE A RAIN/SNOW MIX TRANSITIONING TO FREEZING RAIN WILL
BE POSSIBLE.  FORECAST SOUNDINGS SUPPORT THIS...WITH A WARM NOSE AS
FAR WEST ARE THE TRIAD AND MORE PROMINENT THAN IN PAST MODEL RUNS.
WE EXPECT TO LOSE THE SUPPLY OF COLD AIR BY FRIDAY MORNING AS THE
HIGH SHIFTS EAST... AND FORECAST SOUNDINGS SHOW JUST ENOUGH RISE IN
SURFACE TEMPS TO MITIGATE ADDITIONAL ICING.

ONE OF THE BIGGER UNCERTAINTIES IS IN QPF.  THE SURFACE LOW
TRACK...WHICH THE GFS AND ECMWF AGREE FAIRLY WELL ON BEING EAST OF
CHARLESTON FRIDAY MORNING...AND STRONGEST WARM ADVECTION/LOW-LEVEL
CONVERGENCE KEEP MOST OF THE PRECIP FOCUSED OVER EASTERN NC.
HOWEVER...MODELS HINT AT SOME MID-LEVEL FGEN BACK TO THE
WEST...WHERE MODELS HAVE VARIED TREMENDOUSLY WITH QPF FROM RUN TO
RUN...WITH THE LAST FEW RUNS OF THE ECMWF GOING FROM AROUND AN INCH
OVER WESTERN NC TO NEARLY NOTHING...BACK TO AN INCH AGAIN ON THE
MOST RECENT RUN.

THE BOTTOM LINE AT THIS POINT IS THAT WE ARE CONFIDENT THAT THE
WESTERN PIEDMONT HAS THE BEST CHANCE OF A WINTRY MIX...WITH LESSER
CHANCES CLOSER TO THE TRIANGLE AND POINTS EAST.  MODELS HAVE TRENDED
TOWARD A BETTER CHANCE OF FREEZING RAIN...BUT CONFIDENCE IN THE
PREDOMINATE PRECIP TYPE AND POSSIBLE ACCUMULATIONS IS STILL LOW
GIVEN SOME OF THE SMALL DIFFERENCES IN THE SURFACE/850MB LOW TRACK
AND WESTERN EXTENT/STRENGTHEN OF THE WARM NOSE.

CHILLY HIGHS IN THE 40S ON THURSDAY WILL BE SENSITIVE TO HOW QUICKLY
PRECIP SPREADS INTO THE AREA...WITH TEMPS THEN FALLING INTO THE 30S
THURSDAY NIGHT...HOVERING NEAR THE FREEZING MARK IN THE NORTHWEST
PIEDMONT WHERE THE POTENTIAL FOR ANY WINTRY PRECIP WOULD BE
GREATEST. GIVEN THAT MODELS ARE A LITTLE SLOWER WITH PRECIP EXITING
ON FRIDAY AND THE RESIDUAL COLD AIR DAMMING AIRMASS WILL HAVE TO BE
ERODED...HIGHS WILL LIKELY BE IN THE LOW TO MID 40S AGAIN. OW FRIDAY
NIGHT IN THE 30S.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 320 AM WEDNESDAY...

A FAIRLY UNEVENTFUL PERIOD WITH MOSTLY DRY WEATHER AND NO LARGE
DEVIATIONS FROM NORMAL TEMPS... BUT TURNING WARMER.

FOR SAT THROUGH SUN NIGHT: THE SHORTWAVE TROUGH WILL BE SHIFTING
OFFSHORE BY DAYBREAK SATURDAY AS THE SURFACE CYCLONE TRACKS NE WELL
OFF THE NE COAST. SURFACE HIGH PRESSURE IS EXPECTED TO BUILD OVER
THE SOUTHEAST STATES SAT/SAT NIGHT WITH DRY LOW-MID LEVEL AIR. A
WEAK PASSING DISTURBANCE COULD BRING A BATCH OF HIGH CLOUDS... BUT
OTHERWISE EXPECT MOSTLY SUNNY/MOSTLY CLEAR SKIES SAT/SAT NIGHT.
FORECAST THICKNESSES NEAR NORMAL AND MODIFYING SUPPORT TEMPS NEAR TO
SLIGHTLY ABOVE NORMAL. A NRN STREAM SHORTWAVE TROUGH CROSSING THE
NORTHEAST STATES SUNDAY WILL PUSH A LARGELY DRY COLD FRONT SOUTHWARD
TOWARD NC... ALTHOUGH THE GFS/ECMWF DIFFER ON THIS WAVE`S AMPLITUDE
WITH THE FASTER/WEAKER ECMWF KEEPING IT TO OUR NORTH THROUGH SUNDAY
WHILE THE SLOWER/STRONGER GFS PUSHES IT TO OUR SOUTH (RESULTING IN
COOLER TEMPS SUN/SUN NIGHT). SUCH DETAILS ARE UNRESOLVABLE AT THIS
RANGE SO WILL GO WITH A COMPROMISE... WITH SUNDAY TEMPS SIMILAR TO
SAT BUT A BIT COOLER SUN NIGHT AS COMPARED TO SAT NIGHT.

FOR MON-TUE: TROUGHING IN THE SOUTHERN STREAM OVER NM/OK/TX INTO NRN
MEX OVER THE WEEKEND WILL DRIFT SLOWLY OUT OVER THE NW GULF EARLY IN
THE WEEK... WHILE THE LARGELY FLAT AND WNW MID LEVEL FLOW OVER MUCH
OF THE CONUS WILL KEEP OUR WEATHER RATHER TRANQUIL WITH ONLY WEAK
SURFACE TROUGHING AND A DRY DOWNSLOPE WESTERLY LOW LEVEL FLOW.
EXPECT FAIR TO PARTLY CLOUDY SKIES WITH TEMPS TRENDING ABOVE NORMAL
AS THICKNESSES RISE. GIH

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
AS OF 650 AM WEDNESDAY...

GOING FROM THE THE BEST TO WORST AVIATION CONDITIONS: FIRST... VFR
CONDITIONS WILL DOMINATE AT INT/GSO THROUGH THE NEXT 24 HOURS
(THROUGH TONIGHT). WEAK SURFACE HIGH PRESSURE COVERING THE
INTERIOR MIDATLANTIC REGION DOWN THROUGH NC WILL WEAKEN FURTHER
TODAY... AS A BACKDOOR COLD FRONT DROPS SOUTHWARD TOWARD NC LATE
TODAY... PUSHING SOUTH THIS EVENING. NEXT... AT RDU/RWI/FAY... WEAK
LOW PRESSURE OFF THE COAST AND RESULTING MOIST ATLANTIC INFLOW
BROUGHT MVFR CIGS (BUT VFR VSBYS) EARLY THIS MORNING. RDU HAS SINCE
RISEN TO VFR AT RDU... BUT AT RWI/FAY... MVFR CIGS ARE LIKELY TO
HOLD THROUGH 00Z... FOLLOWED BY A POSSIBILITY OF IMPROVEMENT TO VFR
TOWARD THE END OF THE TAF PERIOD AT RWI. AS AN UPPER LEVEL
DISTURBANCE CROSSES SE AND ERN NC TODAY... BRIEF VSBYS OF 5-6 SM IN
LIGHT RAIN ARE POSSIBLE BUT SHOULD NOT DOMINATE. WINDS WILL BE LIGHT
FROM THE NNE THROUGH MUCH OF TODAY... INCREASING TO AROUND 10-12 KTS
THIS EVENING BEHIND THE BACKDOOR FRONT AS IT DROPS SOUTHWARD... AND
TO 12-15 KTS TOWARD THE END OF THE TAF PERIOD LATE TONIGHT INTO
EARLY THU MORNING. WHILE LLWS CRITERIA ARE UNLIKELY TO BE MET
TONIGHT... AVIATION INTERESTS SHOULD BE PREPARED FOR A QUICK
INCREASE IN NE WINDS TO 25-30 KTS AT AROUND 1000-1500 FT AGL AFTER
FRONTAL PASSAGE LATER THIS EVENING.

LOOKING BEYOND 12Z TONIGHT... THERE IS A CHANCE OF IFR CIGS AT FAY
EARLY THU MORNING DUE TO THE ENHANCED ONSHORE FLOW BEHIND THE
FRONT... BUT IN GENERAL VFR CONDITIONS ARE EXPECTED THROUGH EARLY
THU AFTERNOON. A STORM SYSTEM WILL STRENGTHEN OVER THE NRN GULF THU
BEFORE TRACKING EAST THEN NE ALONG THE CAROLINA COAST... BRINGING
WIDESPREAD PRECIP (POTENTIALLY WINTRY) AND IFR/LIFR CONDITIONS TO
CENTRAL NC FROM 21Z THU THROUGH FRI EVENING. STRONG NE WINDS
(ESPECIALLY AT FAY/RWI) AND LLWS ARE LIKELY LATE THU THROUGH FRI DUE
TO THE COASTAL STORM. VFR CONDITIONS EXPECTED TO RETURN LATE FRI
NIGHT AND HOLD THROUGH SUN WITH HIGH PRESSURE BUILDING IN FROM THE
WEST WITH LIGHT WINDS. -GIH
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...SMITH
LONG TERM...HARTFIELD
AVIATION...HARTFIELD