Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 010526
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
126 AM EDT FRI AUG 1 2014

.SYNOPSIS...
A COASTAL FRONT JUST OFFSHORE WILL PUSH INLAND ON FRIDAY...THEN
SHOULD STALL OVER THE AREA DURING THE WEEKEND. THIS WILL BRING
GOOD RAIN CHANCES...WITH PERIODS OF HEAVY RAINFALL POSSIBLE FRIDAY
THROUGH MONDAY. MORE SEASONABLE WEATHER WILL DEVELOP THE MIDDLE OF
NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 1:30 AM FRIDAY...SCATTERED SHOWERS WITH A FEW EMBEDDED
THUNDERSTORMS ONGOING ACROSS THE FORECAST AREA. MOISTURE TAP SEEMS
TO BE GRADUALLY SHIFTING EASTWARDS. FORECAST UPDATED ACCORDINGLY.
PREVIOUS DISCUSSION FOLLOWS:

SEVERAL THINGS HAVE TRANSPIRED (OR IS IT CONSPIRED?) OVER THE FEW
HOURS TO CHANGE THE FORECAST PRETTY DRAMATICALLY. A MOIST CONVEYOR
ORIGINATING FROM THE EDGE OF THE GULF STREAM OFF THE SOUTH
CAROLINA COAST IS FEEDING INTO GEORGETOWN COUNTY AND HAS ITS EYES
FIXED ON THE I-95 CORRIDOR/PEE DEE REGION FOR THE NEXT FEW HOURS.
JUST GIVEN THE OBSERVED TRAJECTORY ON RADAR THIS MOISTURE IS
ENCOUNTERING RATHER SIGNIFICANT ISENTROPIC ASCENT AS IT MOVES UP
INTO THE IN-SITU COLD DOME IN PLACE ACROSS THE CENTRAL CAROLINAS.

EVEN THOUGH THE 00Z CHS SOUNDING SHOWED DRY AIR ABOVE 700 MB AND A
PRECIPITABLE WATER VALUE OF ONLY 1.55 INCHES...AMSU + SSM/I BLENDED
TOTAL PRECIPITABLE WATER SATELLITE DATA HAD A RELATIVE MAXIMUM
ACROSS THE SANTEE RIVER INTO THE PEE DEE REGION OF 1.9 INCHES. THIS
IS CO-LOCATED WITH THE HEAVY RAINFALL BAND OBSERVED ON RADAR. I HAVE
INCREASED AREAL AVERAGE RAINFALL FORECASTS TO AROUND 0.75 INCHES
ACROSS FLORENCE AND MARION NORTHWARD INTO DILLON AND BENNETTSVILLE
OVERNIGHT...WITH THE EXPECTATION THAT ISOLATED AREAS WILL SEE 2 TO
2.5 INCHES. THE HAZARDOUS WEATHER OUTLOOK HAS BEEN UPDATED WITH THE
POTENTIAL FOR MINOR FLOODING OVERNIGHT AS WELL. OBVIOUSLY FORECAST
POPS ACROSS THIS CORRIDOR ARE 100 PERCENT.

THE HRRR IS TOO FAR WEST WITH THE CURRENT CONVECTIVE ACTIVITY...BUT
SHOWS THAT ONCE THIS HEAVY RAIN MOVES NORTHWARD INTO CENTRAL NORTH
CAROLINA THE NEXT WAVE OF CONVECTION MAY DEVELOP OVER THE COASTAL
WATERS OFF THE SC COAST MOVING NORTHWARD INTO COASTAL SE NORTH
CAROLINA AROUND OR SHORTLY AFTER DAYBREAK.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY NIGHT/...
AS OF 230 PM THURSDAY...PERIOD CONTINUES TO LOOK UNSETTLED WITH
INCREASING DEEP MOISTURE AND DEVELOPING LOW LEVEL CONVERGENCE. MID
LEVEL TROUGH HANGING OVER THE EASTERN CONUS THE PAST SEVERAL DAYS
STARTS TO WEAKEN AND SHIFT WEST AS 5H RIDGE OVER THE WESTERN
ATLANTIC EXPANDS. MEANWHILE AT THE SURFACE WESTERN ATLANTIC HIGH
WILL EXTEND WEST...PUSHING FRONT STALLED OFF THE COAST INTO THE
REGION. DEEP SOUTHWEST FLOW...TAPPING GULF MOISTURE...COMBINED
WITH LOW LEVEL SOUTHEAST FLOW...TAPPING ATLANTIC MOISTURE...WILL
PUSH PRECIPITABLE WATER VALUES TO AND ABOVE 2 INCHES FOR MUCH OF
THE PERIOD. DIVERGENT FLOW ALOFT AND LOW LEVEL CONVERGENCE ALONG
THE QUASI-STATIONARY BOUNDARY IN A MODERATELY UNSTABLE ENVIRONMENT
SHOULD PRODUCE PLENTY OF SHOWERS AND THUNDERSTORMS. NOT
ANTICIPATING ANY WIDESPREAD STRONG TO SEVERE STORMS BUT GIVEN THE
TIME OF YEAR CANNOT RULE OUT AN ISOLATED STRONGER STORM. ALTHOUGH
THERE IS LIKELY TO BE A DIURNAL INCREASE IN ACTIVITY PRECIP
CHANCES WILL REMAIN ELEVATED OVERNIGHT GIVEN FAVORABLE CONDITIONS.

HIGH TEMPERATURES WILL CONTINUE TO RUN BELOW CLIMO WITH CLOUD COVER
AND PRECIP KEEPING HIGHS IN THE LOW TO MID 80S. SOUTHERLY
FLOW...INCREASING MOISTURE...AND CLOUD COVER WILL KEEP LOWS NEAR TO
SLIGHTLY ABOVE CLIMO...LOW TO MID 70S.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 230 PM THURSDAY...ATYPICALLY WELL DEFINED (FOR THE TIME OF
YEAR) MID AND UPPER LEVEL TROUGHINESS TO OUR WEST ON SUNDAY.
DECAYING SURFACE BOUNDARY TO PROVIDE LOW LEVEL LIFT...WHICH WILL
THEN BE AIDED BY MID LEVEL PVA AND UPPER DIVERGENCE ASSOC WITH
RIGHT ENTRANCE OF UPPER JET STREAK ACROSS NORTHEAST AND MID
ATLANTIC. AND WHILE RAIN CHANCES SEEM TO WARRANT LIKELY POPS
MODELS ARE NOT SUGGESTIVE OF HIGH QPF AMOUNTS. THIS MAY BE DUE TO
IT BEING SUCH A CLOUDY DAY THAT VERY LITTLE INSTABILITY MANAGES TO
DEVELOP SAVE FOR PERHAPS ALONG THE IMMEDIATE COAST. THESE PLAYERS
ALL REMAIN NEARLY IN PLACE HEADING INTO MONDAY ALTHOUGH ALL OF
THEM WEAKEN. LOOKING FOR ANOTHER DAY OF HIGH POPS AND SUPPRESSED
AFTERNOON TEMPS. TUESDAY SHOULD BRING LOWER RAIN CHANCES BUT STILL
ONES THAT ARE HIGHER THAN NORMAL. THE UPPER JET CONTINUES TO
WEAKEN AND LIFT OUT TO THE NORTHEAST WHILE THE MID LEVEL TROUGH
WEAKENS...BUT ALSO SENDS ITS REMAINING VORT CENTER ACROSS THE
CAROLINAS. IN RESPONSE TO THIS THE GFS STRAIGHTENS THE PIEDMONT
TROUGH AT THE SURFACE. WE ALSO MAY SEE A BIT MORE SUNSHINE IN
CONTRAST TO THE EARLY PARTS OF THE PERIOD. TUESDAY MAY THUS BE A
DAY WHERE WE TRANSITION TO MORE SCATTERED AND DEEPER CONVECTION
ESP IF TEMPS START BOUNCING BACK TOWARDS CLIMO. WEDNESDAY AND
THURSDAY LOOK SEASONABLE WITH RESPECT TO BOTH TEMPERATURES AND
AREAL COVERAGE OF CONVECTION. MID LEVEL FLOW SHOULD BE OF A DRIER
WESTERLY DIRECTION WHILE SOME SEMBLANCE OF A PIEDMONT TROUGH
REMAINS.

&&

.AVIATION /05Z FRIDAY THROUGH TUESDAY/...
AS OF 06Z...SHOWERS WILL BE LIKELY THIS TAF VALID PERIOD AT ALL
TERMINALS. THUNDERSTORMS WILL BE POSSIBLE THIS MORNING NEAR THE
COASTAL TERMINALS...THEN RE-DEVELOP THIS AFTERNOON ACROSS MAINLY
INLAND LOCATIONS. TEMPO PERIODS OF MVFR CAN BE EXPECTED WITH THE
ACTIVITY. DUE TO THE QUICK MOVEMENT OF CELLS ONLY BRIEF PERIODS OF
IFR EXPECTED. WINDS WILL BE E-ESE AROUND 10KT...EXCEPT VRBL TO 20
KT NEAR CONVECTION. RADAR AND SATELLITE TRENDS SUGGEST THAT THE
COASTAL TERMINALS WILL BE MOST LIKELY TO EXPERIENCE SHRA/TEMPO
MVFR THROUGH SUNRISE. SHOWERS AT THE COASTAL TERMINALS SHOULD END
12-15Z. LIGHT RA SHOULD END OVER THE NEXT SEVERAL HOURS AT
KFLO/KLBT. MVFR CIGS/VSBYS SHOULD DEVELOP AFTERWARDS AT KFLO/KLBT
AND PERSIST THROUGH SUNRISE.

EXTENDED OUTLOOK...SHRA/TSRA LIKELY WITH PERIODS OF MVFR
CONDITIONS THROUGH MON AS A FRONT STALLS AND FINALLY DISSIPATES
OVER THE EASTERN CAROLINAS. A CHANCE OF SHOWERS CONTINUES ON TUE.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1:30 PM FRIDAY...NO CHANGES TO THE FORECAST WITH THE LATEST
UPDATE. PREVIOUS DISCUSSION FOLLOWS:

THE PINCHED PRESSURE GRADIENT ALONG THE WEST SIDE OF THE COASTAL
TROUGH/WARM FRONT OFFSHORE HAS PUSHED WIND SPEEDS TO 20 KNOTS WITH
GUSTS AS HIGH AS 24 KNOTS ALONG THE HORRY COUNTY SC COAST EARLIER.
THIS IS STRONGER THAN ANY MODEL INDICATED...AND THIS MOST-RECENT
FORECAST UPDATE IS BASED MORE ON CURRENT OBSERVATIONS THAN ANY
COMPUTER MODEL. EAST WINDS AROUND 20 KNOTS SHOULD BEGIN TO
DIMINISH AROUND 2-3 AM AS THE FRONT GETS A LITTLE CLOSER TO THE
COAST AND THE BAGGIER PRESSURE GRADIENT SURROUNDING THE BOUNDARY
ARRIVES. SEAS HAVE RESPONDED TO THE HIGHER WIND SPEEDS WITH 5 FEET
SHOWING UP AT THE NEARSHORE WRIGHTSVILLE BEACH CORMP BUOY. THIS IS
A FULL 3 FEET HIGHER THAN FORECASTS JUST SIX HOURS AGO AND SHOWS
HOW QUICKLY CONDITIONS HAVE DETERIORATED HERE. AN EXERCISE CAUTION
HEADLINE HAS BEEN ADDED TO THE FORECAST THROUGH 3 AM FOR ALL
WATERS.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 230 PM THURSDAY...PERIOD WILL BE DOMINATED BY SOUTHEAST
FLOW AS FRONT STALLED OFFSHORE MOVES TO THE COAST FRI THEN PUSHES
ONSHORE SAT. GRADIENT WILL BE WEAK FOR MUCH OF THE PERIOD WITH THE
ONLY POSSIBLE EXCEPTION DURING FRI NIGHT WHEN GRADIENT SHARPENS AS
BOUNDARY BECOMES A LITTLE MORE DEFINED. SPEEDS FRI NIGHT MAY TOUCH
15 KT BUT OTHERWISE SPEEDS WILL BE ON THE LOWER END OF THE 10 TO
15 KT RANGE. SEAS 2 TO 3 FT EARLY IN THE PERIOD INCREASE TO A
SOLID 3 FT GIVEN THE PROLONGED SOUTHEAST WINDS AND DEVELOPMENT OF
EAST-SOUTHEAST WIND WAVE.

LONG TERM /SUNDAY THROUGH TUESDAY/...
AS OF 230 PM THURSDAY...LIGHT SOUTHERLY WINDS ON SUNDAY WITH
FRONTAL BOUNDARY JUST INLAND OF THE COAST. WIND CHOP WILL BE
COINCIDENT WITH 11 SECOND SOUTHEASTERLY SWELL. THE WEAKENING
BOUNDARY WILL MOVE FURTHER INLAND FOR THE REMAINDER OF THE PERIOD
AND THE WEST ATLANTIC HIGH POKES A BIT WESTWARD FURTHER INTO THE
CAROLINAS. THIS COULD LEAD TO AN OCCASIONAL INCREASE IN FLOW BY A
FEW KNOTS AND ALSO A SLIGHT VEER FROM S TO SW.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.

&&

$$

SYNOPSIS...III
NEAR TERM...REK/TRA/SGL
SHORT TERM...III
LONG TERM...MBB
AVIATION...MRR
MARINE...REK/TRA/III/MBB/SGL




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