Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 311430
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1025 AM EDT FRI OCT 31 2014

.SYNOPSIS...A POWERFUL STORM SYSTEM WILL AFFECT THE AREA TONIGHT
THROUGH SATURDAY NIGHT. LOW PRESSURE WILL DEVELOP OVER THE WESTERN
CAROLINAS THIS AFTERNOON... THEN TRACK EAST TOWARD THE COAST
TONIGHT. THIS COASTAL LOW WILL THEN RAPIDLY STRENGTHEN AND TURN
NORTHEASTWARD ALONG THE MID ATLANTIC COAST SATURDAY AND SATURDAY
NIGHT. COLD HIGH PRESSURE WILL BUILD IN FROM THE WEST SATURDAY NIGHT
THROUGH MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1025 AM FRIDAY...

REST OF TODAY: EARLIER FORECAST IS ON TRACK. A LARGE AREA OF
STRATOCU HAS HAMPERED THE TEMP RISE SOMEWHAT OVER THE NORTHWEST
PIEDMONT... BUT OTHERWISE ABUNDANT SUNSHINE AHEAD OF OUR INCOMING
STORM HAS ALLOWED TEMPS TO RISE THROUGH THE LOWER 50S SO FAR... ON
PACE TO REACH HIGHS IN THE LOW-MID 60S (EXCEPT FOR UPPER 50S TO NEAR
60 IN THE NW). THE COASTAL LOW JUST OFF THE OUTER BANKS AND ITS
ASSOCIATED PRECIP AND CLOUD SHIELD CONTINUES TO MOVE NE AWAY FROM
THE FORECAST AREA... AND SUBSIDING AND FAIRLY DRY AIR IN ITS
IMMEDIATE WAKE SHOULD YIELD SEVERAL HOURS OF SUNSHINE OVER MUCH OF
CENTRAL NC. THE NW PIEDMONT LOWER CLOUDINESS SHOULD PIVOT NE OUT OF
THE AREA... ALLOWING AT LEAST PARTIAL SUNSHINE... HOWEVER
ENCROACHING MID CLOUDS FROM THE W AND SW WILL LIMIT FULL HEATING
THERE. EXTRAPOLATION OF SCATTERED TO NUMEROUS SHOWERS NOW OVER ERN
KY/ERN TN INTO NE AL/NW GA BRINGS THIS ACTIVITY INTO OUR WRN CWA BY
MID TO LATE AFTERNOON... A FEW HOURS FASTER THAN THE LATEST HRRR
RUNS BUT VERY CLOSE TO OUR EXISTING FORECAST... SO LITTLE TO NO
CHANGE NEEDED THERE FOR NOW. -GIH


PREVIOUS DISCUSSION AS OF 330 AM:
RELATIVE CALM BEFORE THE STORM TODAY. A NARROW RIDGE OF 1018 MB HIGH
PRESSURE WAS ANALYZED AT 07Z OVER THE MIDDLE ATLANTIC AND WESTERN
CAROLINAS THIS MORNING...IN BETWEEN A DEVELOPING COASTAL LOW ALONG
THE OLD FRONTAL ZONE A FEW HUNDRED MILES OFF THE COAST OF THE
CAROLINAS AND A TRIO OF FLATTER WAVES OVER NORTHERN MS; WESTERN KY;
AND NORTHERN MI. ALOFT...THREE DISTINCT SHORTWAVE TROUGHS ARE
EVIDENT IN WV IMAGERY IN ASSOCIATION WITH THE SURFACE WAVES - ONE
OFF THE SE COAST...ANOTHER OVER THE MID-SOUTH...AND THE MOST POTENT
ONE OVER THE WESTERN GREAT LAKES.

THE LATEST SUITE OF NWP GUIDANCE IS SLIGHTLY FARTHER SOUTH WITH THE
SHARPLY AMPLIFYING SHORTWAVE TROUGH AND ASSOCIATED CLOSED LOW
EVOLUTION THROUGH THE CAROLINAS...AND THE ACCOMPANYING PRIMARY
SURFACE LOW FORECAST TO CROSS THE CAROLINAS TONIGHT. THE STRONGEST
LOW LEVEL CAA AND ALREADY-ONLY MARGINAL OPPORTUNITY FOR ANY WET
FLAKES HAS CONSEQUENTLY SHIFTED SOUTH TO THE SOUTHERN NC PIEDMONT.
THE RELATIVE HIGHEST CHANCES OF RAIN...AND PRECIPITATION
AMOUNTS...WILL ALSO ACCORDINGLY BE FOCUSED IN AN ARC FROM WESTERN NC
TO NORTHERN SC TO EASTERN NC...AS THE SURFACE LOW AND DEFORMATION
ZONE EVOLVE IN A REGION OF STRONG ASCENT FUELED BY BOTH THE
"DYNAMICS" ALOFT AND STRONG LOW-MID LEVEL FGEN.

THE WEAK LEAD SURFACE WAVES OVER NORTHERN MS AND WESTERN KY ARE
FORECAST TO CONTINUE EAST...BENEATH THE PARENT SHORTWAVE
TROUGH...AND MERGE INTO A SINGLE LOW IN THE LEE OF THE APPALACHIANS
THIS AFTERNOON. THIS LEE LOW WILL THEN REMAIN RELATIVELY STATIONARY
AS THE STRONGEST HEIGHT FALLS ACCOMPANYING THE POTENT SHORTWAVE
AMPLIFYING SHARPLY SSE FROM THE WESTERN GREAT LAKES TO THE SOUTHERN
APPALACHIANS ALLOWS THE TRAILING SURFACE LOW OVER NORTHERN MI AND
ASSOCIATED PRESSURE FALLS TO CATCH UP TO AND "CAPTURE" THE LEAD LEE
LOW...WITH THE THEN MERGED SURFACE LOW FORECAST TO MOVE DUE EAST
INVOF THE SC/NC BORDER TONIGHT.

SHALLOW CONVECTION...INCLUDING SPORADIC LIGHTNING IN AN ENVIRONMENT
CHARACTERIZED BY MUCAPE OF UP TO A FEW HUNDRED J/KG...WILL EASE EAST
FROM THE SC UPSTATE AND NC FOOTHILLS...INTO THE NC SOUTHERN AND
WESTERN PIEDMONT ROUGHLY BETWEEN 7-10 PM. THESE SHOWERS AND ISOLATED
STORMS WILL MAKE ONLY SLOW EASTWARD PROGRESS ACROSS THOSE AREAS
THROUGH MIDNIGHT...BEFORE THE CHARACTER OF THE PRECIPITATION ASSUMES
AN INCREASINGLY STRATIFORM PRECIPITATION SHIELD WITH EMBEDDED
SHALLOW CONVECTIVE ELEMENTS LINGERING OWING TO STRONG MID LEVEL CAA
ATOP A WARM/MOIST TONGUE WRAPPED CYCLONICALLY BENEATH THE COLD POOL
ALOFT...AROUND THE DEVELOPING LOW LEVEL CYCLONE. RAIN...WITH
ASSOCIATED AMOUNTS BETWEEN ONE HALF AND ONE INCH...WILL CONSEQUENTLY
GRADUALLY PIVOT ACROSS THE SANDHILLS AND CENTRAL PIEDMONT THROUGH
DAYBREAK...WITH MUCH OF THE COASTAL PLAIN AND FAR NE PIEDMONT LIKELY
TO EXPERIENCE ONLY OCCASIONAL LIGHT RAIN AND AMOUNTS LESS THAN A
TENTH OF AN INCH. FORECAST PARTIAL THICKNESS VALUES HOLD IN THE
INDETERMINATE RANGE THROUGHOUT CENTRAL NC FROM EVEN THE COLDEST
EC/NAM GUIDANCE...AND BUFR SOUNDINGS EVEN IN THE SOUTHERN AND
WESTERN PIEDMONT LIKEWISE MAINTAIN A COUPLE OF THOUSAND FT ABOVE
FREEZING BOUNDARY LAYER.  LOWS GENERALLY IN THE UPPER 30S TO MIDDLE
40S FROM WEST TO EAST...AFTER HIGHS TODAY IN THE UPPER 50S TO MIDDLE
60S. -MWS

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
AS OF 350 AM FRIDAY...

WIDESPREAD RAIN WILL CONTINUE TO PIVOT EAST ACROSS THE SOUTHERN AND
EASTERN RAH CWFA...WHILE THE NORTHERN PIEDMONT REMAINS IN A RELATIVE
MINIMUM OF MORE SCATTERED IN NATURE "INSTABILITY SHOWERS"...AND THE
MOUNTAIN SHADOW/DOWNSLOPE FLOW ERODES THE RAIN AND CLOUDS OVER THE
WESTERN PIEDMONT. NORTHERLY WINDS WILL GRADUALLY RAMP UP SAT...FIRST
OVER THE WESTERN PIEDMONT AS THE MIXED LAYER DEEPENS WITH DOWNSLOPE
FLOW...THEN OVER THE COASTAL PLAIN AND NE PIEDMONT OWING TO A
TIGHTENING PRESSURE GRADIENT AROUND WHAT WILL BECOME A RAPIDLY
DEEPENING PRIMARY COASTAL LOW OFF THE NC COAST. WINDS OF 15-25 MPH
WITH GUSTS BETWEEN 30-35 MPH ARE LIKELY IN BOTH AREAS...WITH
SLIGHTLY WEAKER WINDS OVER THE TRIANGLE. WINDS WILL VEER TO NW SAT
NIGHT...BUT CONTINUE IN THE 15-25 MPH RANGE WITH GUSTS OF 30-35 MPH
OVER EASTERN SECTIONS...AND GRADUALLY LESSENING WINDS TO THE WEST.
IF A WIND ADVISORY WERE TRULY NEEDED...IT WOULD LIKELY BE FOR THE
LATE SAT-SAT NIGHT TIME FRAME OVER THE EASTERN THIRD OF THE CWFA.
NEAR STEADY...TO SLOWLY RISING TEMPERATURES WITH PARTIAL CLEARING IN
THE WESTERN PIEDMONT SAT...THEN CAA-DRIVEN LOWS IN THE 30S SAT
NIGHT.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 314 AM FRIDAY...

STRONG COASTAL STORM WILL BE MOVING NORTHEASTWARD OFF THE COAST...
WITH A STRONG 1032 MB HIGH BUILDING IN TO THE OHIO VALLEY. GUSTY
WINDS WILL STILL BE POSSIBLE UNTIL THE PRESSURE GRADIENT RELAXES
LATE IN THE DAY SUNDAY AS THE HIGH BEGINS TO MOVE INTO THE AREA.
SKIES WILL BE CLEAR ON SUNDAY... WITH DRY NORTHWESTERLY FLOW. THE
HIGH WILL MOVE OVER THE AREA SUNDAY NIGHT... SETTING THE STAGE FOR
EXCELLENT RADIATIONAL COOLING... AND LIKELY FROST/FREEZE CONDITIONS
MONDAY MORNING. MOSTLY SUNNY CONDITIONS WILL CONTINUE THROUGH
MONDAY... WITH HIGHS NEAR 60. HIGH PRESSURE WILL MOVE OFF THE EAST
COAST ON TUESDAY... AND TEMPERATURES WILL CONTINUE TO MODERATE INTO
THE 60S AS FLOW BECOMES SOUTHWESTERLY.

NORTHERN STREAM SHORTWAVE ENERGY WILL MOVE ALONG THE CANADIAN
BORDER... AND THE ASSOCIATED WEAK COLD FRONT WILL ENTER THE AREA
LATE THURSDAY/EARLY FRIDAY. THE STRONGEST FORCING WILL REMAIN NORTH
AND MOISTURE LOOKS TO BE LIMITED... AND MODEL QPF IS CONSEQUENTLY
NEAR 0 ACROSS THE AREA. WILL KEEP POPS TO SLIGHT CHANCE AT THIS
TIME... BUT IF THE CURRENT TREND FOR A DRY FRONTAL PASSAGE
CONTINUES... EVEN THIS MAY BE OVERDONE.

&&

.CLIMATE...

RECORD LO-MAX TEMPERATURES FOR NOVEMBER 1ST

        LO-MAX

RDU     50/1925
GSO     45/1925
FAY     48/1988

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
AS OF 755 AM FRIDAY...

A SMALL PATCH OF MVFR STRATOCUMULUS DEVELOPED OVERNIGHT AND SWEPT
QUICKLY WESTWARD INTO THE TRIAD. NO NWP GUIDANCE HAS HANDLED THIS
MOIST LAYER WELL (OR AT ALL). IT APPEARS THE CLOUDS ARE BANKING UP
AGAINST THE MOUNTAINS...AND SATELLITE TRENDS SUGGEST THE ASSOCIATED
CEILINGS MAY LINGER FOR A FEW HOURS AT KINT...WHILE REMAIN MORE
SCATTERED IN NATURE AT KGSO. VFR CONDITIONS SHOULD OTHERWISE AND
ELSEWHERE PREVAIL FOR THE REMAINDER OF THE DAY...AS WE AWAIT THE
APPROACH OF A PAIR OF STRONG DISTURBANCES ALOFT...WHICH WILL CAUSE
MULTI-LAYERED CLOUDINESS - AROUND 5 K FT AND 15 K FT - TO INCREASE
THIS AFTERNOON. THE ASSOCIATED FORCING FOR ASCENT/LIFT...IN
CONJUNCTION WITH THE DEVELOPMENT OF WEAK INSTABILITY...WILL CAUSE A
BAND OF SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TO DEVELOP OVER
THE UPSTATE OF SC AND EDGE SLOWLY NE ACROSS TRIAD TERMINALS THIS
EVENING. THE SHOWERS WILL MARK THE BEGINNING OF MVFR TO IFR
CONDITIONS AND PERIODS OF RAIN SHOWERS THAT ARE EXPECTED TO PERSIST
THROUGH EARLY SAT. THE AREA OF SHOWERS...AND SUB-VFR
CONDITIONS...WILL EDGE ONLY SLOWLY EAST ACROSS CENTRAL NC LATE
TONIGHT AND EARLY SAT...AS THE STRONGEST LIFT PIVOTS TO THE WEST AND
SOUTH OF CENTRAL NC.

OUTLOOK: PERIODS OF SHOWERS AND AN ISOLATED THUNDERSTORM WILL
CONTINUE THROUGH SAT AFTERNOON...AS A POCKET OF COLD TEMPERATURES/
STEEP LAPSE RATES ALOFT...ASSOCIATED WITH THE AFOREMENTIONED STRONG
DISTURBANCES...PIVOT EAST ACROSS CENTRAL NC. IN ADDITION...NORTH TO
NORTHWESTERLY SURFACE WINDS WILL BECOME BLUSTERY IN THE 15-20 KT
RANGE WITH GUSTS UP TO 30 KTS LATE SAT AND SAT NIGHT...AS COASTAL
LOW PRESSURE RAPIDLY INTENSIFIES OFF THE NC AND VA COAST.

&&

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

&&

$$

SYNOPSIS...MWS/HARTFIELD
NEAR TERM...HARTFIELD/MWS
SHORT TERM...MWS
LONG TERM...SEC
CLIMATE...CBL
AVIATION...MWS



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