Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 240336
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1036 PM EST SUN NOV 23 2014

.SYNOPSIS...A WARM FRONT WILL MOVE UP ALONG THE COAST THIS
EVENING AS LOW PRESSURE TRACKS ALONG THE BOUNDARY. A PRE-
FRONTAL TROUGH WILL MOVE EAST THROUGH THE REGION OVERNIGHT
ENDING THE HEAVIEST RAIN. A COLD FRONT WILL SWEEP EASTWARD
THROUGH THE REGION MONDAY NIGHT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 810 PM SUNDAY...

...THREAT OF SEVERE WEATHER WILL REMAIN AT OR VERY NEAR THE
COAST...

THE WATER VAPOR SATELLITE DATA INDICATED THE MID LEVEL LOW PRESSURE
WAS TRACKING NE THROUGH CENTRAL TN INTO KY THIS EVENING. THE MID
LEVEL FRONT WAS SURGING EASTWARD TOWARD OUR REGION ACCOMPANIED BY A
FINAL LINE OF SHOWERS AND SCATTERED THUNDERSTORMS.

THE STRONGEST LIFT ASSOCIATED WITH THIS SYSTEM WILL BE AFFECTING OUR
AREA FOR THE NEXT 3-6 HOURS WITH SEVERAL BANDS OF RAINFALL (WITH ONE
FINAL BAND WITH ISOLATED THUNDERSTORMS POSSIBLE) AS THE MID LEVEL
FRONT PASSES. THERE WERE TWO VERY IMPORTANT LOW LEVEL FEATURES
PRESENT. BOTH WILL ACT TO LIMIT SEVERE POTENTIAL FOR OUR REGION.
1)...THE EXPECTED IN-SITU DAMMING EVENT OVER THE FOOTHILLS AND
WESTERN PIEDMONT WHERE SURFACE WINDS HAVE BACKED TO THE NORTHEAST
AND NORTH AS THE DIABATIC PROCESS TOOK OVER. NOTE THE STRONG CAD
SIGNATURE EXTENDS THE ENTIRE LENGTH OF THE BLUE RIDGE EASTERN SLOPES
AND PIEDMONT FROM VIRGINIA THROUGH NORTH CAROLINA... NW SOUTH
CAROLINA AND NORTHEAST GEORGIA. TEMPERATURES WERE IN THE 40S ALL THE
WAY TO GAINESVILLE GEORGIA (JUST NE OF ATL) WITH A LOW LEVEL NE
FLOW. THE CAD BOUNDARY WAS LOCATED SOUTH OF GSP TO STATESVILLE...
THROUGH THE TRIAD...AND INTO SOUTHERN VA. WINDS EAST OF THE BOUNDARY
BECOME SE...AND GUSTY TO 20 MPH. TEMPS WERE IN THE MID 50S FROM GSP
TO CLT TO RDU AND RWI.

THE SECOND...BUT EVEN MORE IMPORTANT BOUNDARY (THE MAIN WARM FRONT)
WAS LOCATED FROM SE GEORGIA NORTHEAST ALONG THE CENTRAL SC COAST...
THEN OFFSHORE OF SC. IT APPEARS THAT A MESOSCALE LOW PRESSURE WAS
LOCATED SE OF AUGUSTA AND THIS IS EXPECTED TO MOVE NE TOWARD OR NEAR
WILMINGTON AROUND MIDNIGHT. THE ASSOCIATED WARM SECTOR SHOULD
APPROACH THE FAR SE PART OF NC...BUT THE WIDESPREAD RAIN OVER OUR
REGION SHOULD CONTINUE TO PREVENT THE MAIN WARM FRONT FROM SURGING
DEEP INTO THE MORE STABLE DOME OVER THE COASTAL PLAIN.

EVEN WITH THE PERIODS OF SHOWERS...ELEVATED THUNDERSTORMS WILL
ACCOMPANY THE BANDS OF CONVECTION FOR THE REMAINDER OF THE EVENING
BEFORE ENDING FROM THE SW LATE EVENING OVER THE SW PIEDMONT. SHOWERS
AND ELEVATED STORMS WILL GRADUALLY END IN THE EAST OVERNIGHT.

ANY SEVERE THREAT SHOULD REMAIN OUTSIDE OF EVEN OUR FAR SE COUNTIES
WITH THIS EVENT...LIMITED TO THE IMMEDIATE COASTAL COUNTIES FROM
WILMINGTON TO MOREHEAD CITY.

IT APPEARS THAT THE IN-SITU DAMMING WILL LINGER OVERNIGHT IN THE NW
AND NORTH PIEDMONT...AND IT WILL BE INTERESTING TO SEE IF THE WEDGE
BOUNDARY ACTUALLY COMES BACK EAST WITH THE MAIN BAND OF CONVECTION
ACROSS THE PIEDMONT. THIS FAVORS LOWS HOLDING STEADY IN THE NW...
AND THE RISING TEMPS IN THE CENTRAL AND NE ZONES SHOULD BE HALTED
BY THE PASSAGE OF THE PRE-FRONTAL TROUGH AND POSSIBLY THE EASTWARD
MOVING WEDGE BOUNDARY.

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
AS OF 305 PM SUNDAY...

...WARM AND WINDY CONDITIONS ON MONDAY...

THE MID/UPPER LEVELS WILL CONTINUE TO DRY ON MONDAY...WHILE LOW-
LEVEL MOISTURE LINGERS WITH THE TRAILING COLD FRONT STILL WEST OF
THE MOUNTAINS.  WITH SOME BREAKS IN CLOUD COVER AND NO AIRMASS
CHANGE...TEMPS ARE EXPECTED TO RISE INTO THE LOW 70S WEST TO MID AND
EVEN UPPER 70S EAST (STILL A COUPLE DEGREES SHORT OF RECORDS).
MIXING DEPTH IN NAM AND GFS FORECAST SOUNDINGS VARIES BY AS MUCH AS
2000 FT...ESPECIALLY IN THE EAST.  WIND FIELDS WILL STILL BE QUITE
STRONG...WITH UP TO 50KT IN THE LOWEST 3000FT. HOW MUCH OF THAT WILL
BE MIXED DOWN TO THE SURFACE IS A LITTLE UNCERTAIN...BUT AT A
MINIMUM IT APPEARS GUSTS TO AROUND 30KT WILL BE POSSIBLE.
CONFIDENCE IN WIDESPREAD HIGHER GUSTS IS TOO LOW AT THE MOMENT AND
WIND ADVISORY CRITERIA APPEARS OUT OF REACH.  WILL CONTINUE MENTION
IN THE HWO.  WITH DEWPOINTS STILL ELEVATED IN THE COASTAL
PLAIN..SOME WEAK INSTABILITY SHOULD DEVELOP.  HOWEVER... THERE IS NO
REAL SIGNIFICANT TRIGGER FOR ASCENT...SO WILL JUST MAINTAIN A SLIGHT
CHANCE IN THE EAST.

THE COLD FRONT WILL CROSS THE AREA MONDAY NIGHT.  THE GFS IS A BIT
QUICKER THAN THE NAM/ECMWF..BUT ALL MODELS HAVE THE COLD FRONT EAST
OF THE AREA BY 12Z TUESDAY.  LOWS IN THE LOWER 40S WEST TO LOWER 50S
EAST.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
AS OF 335 PM SUNDAY...

TUE-WED NIGHT: 1025 MB CONTINENTAL POLAR SURFACE HIGH PRESSURE WILL
BUILD EAST ACROSS THE MID MS AND TN VALLEYS TUE...THEN NORTHEASTWARD
INTO THE NORTHERN MIDDLE ATLANTIC STATES AND NEW ENGLAND TUE NIGHT
AND WED. MEANWHILE...THE APPROACH OF A COMPLEX POSITIVELY-TILTED
TROUGH ALOFT WILL INDUCE CYCLOGENESIS FROM THE CENTRAL GOM TO THE
SOUTHEAST US COAST LATE TUE AND TUE NIGHT...THEN UP SOUTHERN MIDDLE
ATLANTIC COAST ON WED. THE PREFERRED CLOSER TO THE COAST/MORE
WESTWARD SOLUTION FOR THE LOW TRACK FROM YESTERDAY HAS GAINED
INCREASING MODEL SUPPORT SINCE...WITH THE PAST TWO RUNS OF THE
CANADIAN NOW CLOSE ENOUGH TO THE COAST TO SPREAD PRECIPITATION
THROUGHOUT CENTRAL NC LATE TUE NIGHT THROUGH WED EVENING...LEAVING
THE NAM THE LONE WELL OFFSHORE/EASTERN OPERATIONAL OUTLIER.

WITH THE ABOVE FAVORED LOW TRACK IN MIND...THE RESULT WILL BE RAIN
DEVELOPING FROM THE SOUTH LATE TUE AND ESPECIALLY TUE NIGHT...WITH A
COLD RAIN AND TEMPERATURES FALLING INTO THE MIDDLE 30S TO AROUND 40
DEGREES...ON WED. THE TRACK OF THE COASTAL LOW AND PRESENCE OF THE
CP HIGH PRESSURE...WHICH ARE FORECAST TO MIGRATE IN TANDEM UP THE
EAST COAST...WILL PROVIDE A FAVORABLE PATTERN FOR SNOW ON THE NW
SIDE OF THE PRECIPITATION SHIELD. WHILE MOST OF THE SNOW EAST OF THE
APPALACHIANS WILL LIKELY NOT MATERIALIZE UNTIL THE SYSTEM MOVES
PARALLEL TO THE LARGER METRO AREAS IN THE I-95 CORRIDOR...FORECAST
PARTIAL THICKNESS VALUES SPEND TIME IN THE "WINTRY MIXTURE" TO
"MEASURABLE SNOW WITH RAIN" PORTION OF THE NOMOGRAM AS THE
PRECIPITATION BEGINS TO PULL AWAY DURING THE MIDDAY AND AFTERNOON
HOURS WED. GIVEN THE MARGINALLY COLD PARTIAL THICKNESS VALUES/
THERMODYNAMIC PROFILES...AND FREEZING LEVELS AROUND 1000 FT OVER THE
PIEDMONT PER GFS BUFR FORECAST SOUNDINGS...ANY SUCH SNOW WOULD
LIKELY BE DRIVEN BY SECONDARY FACTORS SUCH AS PRECIPITATION
RATES/MELTING...WHICH IS NOT UNCOMMON FOR EVENTS THAT FALL IN THE
ABOVE-REFERENCED PORTIONS OF THE NOMOGRAM.

WITH THE ABOVE FACTORS IN MIND...THERE IS A HIGH ENOUGH PROBABILITY
FOR WET SNOW TO AT LEAST OCCASIONALLY MIX IN TO WARRANT MENTION OF A
SLIGHT CHANCE TO CHANCE OF SNOW MAINLY NORTH OF HIGHWAY 64 IN THE
GRIDDED AND TEXT FORECAST. THE BREVITY AND INTERMITTENT NATURE OF
SNOW DURING OTHERWISE CHILLY RAIN...ABOVE FREEZING BOUNDARY LAYER
TEMPERATURES ( ALBEIT ONLY MARGINALLY)...RELATIVELY WARM SOIL
TEMPERATURES 9MOSTLY IN THE 50S TODAY)...AND WETNESS FROM THE RAIN
WILL ALL MAKE IT EXTREMELY DIFFICULT FOR ANY ACCUMULATION TO OCCUR.
NO TRAVEL IMPACTS ARE CONSEQUENTLY EXPECTED. TEMPERATURES
WILL...HOWEVER...DIP INTO THE UPPER 20S TO LOWER BEHIND THE SYSTEM
WED NIGHT...SO ANY MOISTURE ON THE ROADWAYS COULD RESULT IN PATCHY
BLACK ICE THROUGH EARLY THU MORNING.

THU-SUN: BENEATH A BROAD TROUGH ALOFT FROM NORTH-CENTRAL CANADA TO
THE MIDDLE ATLANTIC COAST...A SERIES OF CLIPPER LOWS WILL TRACK
ACROSS THE OH VALLEY AND NORTHERN MIDDLE ATLANTIC STATES...WHICH
WOULD FAVOR THE RE-ESTABLISHMENT OF ARCTIC HIGH PRESSURE ACROSS THE
NORTHERN HALF OF THE CONUS EAST OF THE ROCKIES (JUST TO THE NORTH OF
NC)...THROUGH THE END OF THE WEEK. THE FRONTAL ZONE BETWEEN THE
ARCTIC AIR MASS TO THE NORTH AND A MILDER/MORE MODIFIED HIGH
PRESSURE SYSTEM OVER THE SOUTHEAST STATES WILL GRADUALLY RETREAT
NORTH AS THE FLOW ALOFT LOSES AMPLITUDE/RELAXES TOWARD THE END OF
THE FORECAST PERIOD. THE RESULTANT PATTERN OF RELAXING NW TO WNW
FLOW ALOFT WOULD RESULT IN A TRANSITION FROM DRY AND COOL CONDITIONS
TO DRY AND SEASONABLE ONES THROUGH THE FORECAST PERIOD.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 1030 PM SUNDAY...

24-HR TAF PERIOD: HEAVY SHOWERS ALONG/IN ADVANCE OF A WARM FRONT
SURGING NORTHWARD THROUGH THE REGION HAVE PROGRESSED EAST OF THE
INT/GSO TERMINALS AS OF 03Z...AND WILL EXIT THE RDU/FAY/RWI
TERMINALS BETWEEN 04-05Z. IFR/MVFR CEILINGS WILL PERSIST OVERNIGHT
THROUGH MONDAY MORNING...LIFTING/SCATTERING OUT TO VFR BY
EARLY MONDAY AFTERNOON (15-18Z). HOWEVER...A RENEWED POTENTIAL FOR
SHOWERS CANNOT BE RULED OUT AT EASTERN TERMINALS MON AFT INTO MON
NIGHT IN ASSOC/W A COLD FRONT APPROACHING FROM THE WEST. SOUTHERLY
WINDS SUSTAINED AT 15-20 MPH WITH GUSTS UP TO 30 MPH ARE EXPECTED
TONIGHT IN THE WAKE OF THE WARM FRONT. WINDS WILL VEER TO THE
SSW/SW AND INCREASE TO 20-25 MPH WITH GUSTS UP TO 40 MPH BY 15-18Z
MONDAY AND REMAIN WINDY THROUGH THE AFTERNOON. WINDS WILL WEAKEN TO
~10 KT WITH OCCASIONAL GUSTS UP TO 20 KT BY MONDAY EVENING.

LOOKING AHEAD: A BRIEF RESPITE FROM SUB-VFR CONDITIONS WILL BE
POSSIBLE MONDAY AFTERNOON INTO MONDAY NIGHT. HOWEVER...ADVERSE
AVIATION CONDITIONS ARE EXPECTED TO DEVELOP OVER THE ENTIRE AREA
TUE AND PERSIST THROUGH THE DAY WED AS A LOW PRESSURE SYSTEM
DEVELOPS/INTENSIFIES ALONG THE SOUTHEAST COAST. VFR CONDITIONS WILL
RETURN IN THE WAKE OF THE SFC LOW THU/THU NIGHT AS HIGH PRESSURE
BUILDS INTO THE REGION FROM THE WEST. -VINCENT

&&

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

&&

$$

SYNOPSIS...PWB
NEAR TERM...PWB
SHORT TERM...BLS
LONG TERM...MWS
AVIATION...VINCENT


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