Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 020531
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
131 AM EDT SAT AUG 2 2014

.SYNOPSIS...
A TROUGH WILL REMAIN STALLED NEAR THE COAST THROUGH THE WEEKEND.
THIS WILL BRING A HEIGHTENED RISK FOR FLOODING AS WIDESPREAD SHOWERS
AND THUNDERSTORMS PLAGUE THE AREA FOR MUCH OF THE WEEKEND. THE
AIRMASS WILL ONLY SLOWLY DRY OUT DURING THE MIDDLE AND LATER
PORTIONS OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 1:30 AM SATURDAY...NO CHANGES TO THE FORECAST WITH THE
LATEST UPDATE. PREVIOUS DISCUSSIONS FOLLOW:

A COUPLE OF NOTABLE CHANGES TO THE FORECAST OVERNIGHT. WITH THE
FRONT NOW DROPPING SOUTHEASTWARD SLOWLY TOWARD THE COAST...THE
COOL WEDGE AIRMASS ACROSS WESTERN AND CENTRAL NORTH CAROLINA WILL
BEGIN TO MOVE INTO THE I-95 CORRIDOR SHORTLY. I HAVE SHAVED A
COUPLE DEGREES OFF FORECAST LOW TEMPS AT DARLINGTON...
FLORENCE...DILLON AND LUMBERTON AS THIS COOLER AIR SLIPS
SOUTHWARD. ALSO...SYNOPTIC MODELS AND THE LATEST FEW HRRR RUNS ARE
SHOWING THE DEVELOPING MASS OF MARINE CONVECTION SOUTH AND
SOUTHEAST OF CAPE FEAR SHOULD MOVE TOWARD SOUTHPORT AND WILMINGTON
OVER THE NEXT 3-4 HOURS. I HAVE BUMPED POPS UP TO 70-80 PERCENT IN
THIS AREA...WHILE TRIMMING THEM BACK INTO THE 30-50 PERCENT RANGE
ACROSS THE PEE DEE REGION WHERE THE LIGHTER SHOWERS CURRENTLY
OBSERVED ON RADAR MAY NOT LAST MUCH LONGER. PREVIOUS DISCUSSION
FROM 730 PM FOLLOWS...

THE COASTAL TROUGH/WARM FRONT MADE PRETTY GOOD INLAND PROGRESS
EARLIER TODAY...REACHING THE INTERSTATE 95 CORRIDOR FROM LUMBERTON
DOWN THROUGH FLORENCE. THE BOUNDARY IS STALLING AND IS EXPECTED TO
DROP BACK TOWARD THE SOUTH CAROLINA COAST LATE TONIGHT...WITH AT
LEAST SOME POTENTIAL IT COULD REACH MYRTLE BEACH BEFORE DAYBREAK.
FOCUSED CONVERGENCE ALONG THE FRONT HAS LED TO A LINE OF SHOWERS AND
EMBEDDED T-STORMS FROM BLADEN COUNTY THROUGH MARION...FLORENCE TO
NEAR ORANGEBURG SC. AN EASTWARD ADVANCING UPPER DISTURBANCE NEAR THE
SAVANNAH RIVER SHOULD HELP NUDGE THE FRONT AND A COLLOCATED DEEP
MOISTURE CHANNEL EASTWARD TONIGHT...REACHING THE COAST LATE.

CHANGES WITH THIS UPDATE WERE FAIRLY MINOR...WITH TWEAKS TO WIND
DIRECTIONS AND HOURLY POPS/WX MOST SIGNIFICANT. PREVIOUS DISCUSSION
FROM 300 PM FOLLOWS...

TROUGH REMAINS STALLED ALONG THE COAST WHILE DEEP GULF MOISTURE
CONTINUES TO SPREAD NORTHEAST. ALONG WITH LOW LEVEL CONVERGENCE
ASSOCIATED WITH THE BOUNDARY...WEAK DIVERGENCE ALOFT CONTINUES. THIS
COUPLED WITH MODERATE INSTABILITY...CAPE IS 1000-1500 J/KG...HAS
BEEN PRODUCING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE AREA.
EXPECT ACTIVITY TO CONTINUE AND INCREASE IN COVERAGE FOR THE
REMAINDER OF THE AFTERNOON. LOSS OF DIURNAL HEATING SHOULD BRING
ABOUT A DECREASE IN COVERAGE BUT DO NOT THINK ACTIVITY WILL
COMPLETELY DISAPPEAR THIS EVENING.

TROUGH WILL REMAIN STALLED ALONG OR JUST INLAND OF THE COAST WITH
PRECIPITABLE WATER VALUES HANGING AROUND 2 INCHES OVERNIGHT.
ADDITIONALLY THERE APPEARS TO BE A WEAK DEFORMATION ZONE EAST OF THE
AREA. THIS FEATURE WILL SLOWLY DRIFT WEST THIS EVENING AND OVERNIGHT
AS THE MID LEVEL WESTERN ATLANTIC RIDGE EXPANDS. BASED ON THIS HAVE
HELD ONTO LIKELY POP ALONG THE COAST ALL NIGHT BUT DROP INLAND AREAS
TO HIGH CHANCE AROUND MID NIGHT. MID LEVEL PATTERN AND LACK OF
SURFACE LOW IN EASTERN TX SUGGESTS THE TROUGH WILL REMAIN STALLED
ALONG THE COAST THROUGH THE END OF THE PERIOD AND THIS IS WHERE THE
HIGHEST QPF SHOULD BE FOUND.

CLOUD COVER AND MOISTURE ALONG WITH BOUNDARY LAYER WINDS WILL KEEP
LOWS NEAR TO ABOVE CLIMO. WEST OF THE BOUNDARY LOWS WILL BE CLOSE TO
CLIMO...AROUND 70. ON THE EAST SIDE OF THE BOUNDARY MODEST ONSHORE
FLOW WILL KEEP TEMPERATURES IN THE MID 70S.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY NIGHT/...
AS OF 300 PM FRIDAY...A FLOOD WATCH IS IN EFFECT THROUGH SUNDAY. A
COASTAL TROUGH WILL REMAIN POSITIONED ALONG THE CAROLINA COAST
THIS PERIOD. WHILE SOME OF THE MODELS ARE INDICATING THE TROUGH
WILL VERY SLOWLY MOVE INLAND...THE MID-LEVEL FLOW SUGGESTS
OTHERWISE. AN EXTREMELY DEEP S/SW FLOW WILL REMAIN LOCKED IN PLACE
ALONG WITH A MOIST COLUMN THROUGH A VERY DEEP LAYER. THE PERSISTENT
UPPER DIFFLUENCE WITHIN THE ENTRANCE REGION OF JET STREAK ACROSS
THE NORTHEAST AND THE LOW LEVEL CONVERGENCE ALONG THE TROUGH WILL
PROVIDE THE NECESSARY LIFT FOR A LARGE SCALE...SIGNIFICANT
RAINFALL EVENT. WE ARE EXPECTING TOTAL RAINFALL AMOUNTS TO AVERAGE
2 TO 4 INCHES WITH UPWARDS OF 4 AND 5 INCHES ALONG COASTAL CAPE
FEAR. HOWEVER...HIGHER AMOUNTS ARE POSSIBLE AND GIVEN THE GROUND
IS WET FROM A VERY WET JULY...WE FEEL THE RISK FOR SIGNIFICANT
FLOODING IS HIGH ENOUGH TO WARRANT A FLOOD WATCH.

THE CLOUDS...RAIN...AND LOWERED THICKNESSES WILL KEEP HIGHS BELOW
NORMAL FOR EARLY-AUGUST...BUT AT THE SAME TIME MAINTAIN NORMAL OR
SLIGHTLY ABOVE NORMAL LOWS. EXPECT HIGHS IN THE LOWER TO MID 80S
BOTH DAYS...AND LOWS IN THE LOWER TO MID 70S.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 300 PM FRIDAY...MID-LEVEL TROUGH AXIS WILL REMAIN WEST OF
THE AREA MONDAY AND TUESDAY...RESULTING IN A CONTINUED AMPLE
SUPPLY OF MOISTURE TO ENHANCE THE POTENTIAL FOR SHOWERS AND TSTMS.
SURFACE CONVERGENCE WILL BE PROVIDED BY THE STALLED FRONTAL
BOUNDARY WHICH WILL LINGER ALONG THE COAST AS WELL AS WEAK WAVES
OF LOW PRESSURE WHICH MODELS INDICATE MAY DEVELOP ALONG THE
BOUNDARY. EXPECT TEMPS WILL BE HELD IN CHECK BY CLOUD COVER
MONDAY...BUT LESS SO TUESDAY-WEDNESDAY. THE MID-LEVEL TROUGH AXIS
WILL SLOWLY TRANSITION EAST AND ALLOW SOME DRIER AIR TO FILTER IN
BY MIDWEEK...SO ALTHOUGH POPS WILL BE INCLUDED EACH DAY...TREND
WILL BE DOWNWARD. ANOTHER WEAK FRONTAL BOUNDARY WILL DROP INTO THE
AREA THURSDAY AND LINGER INTO FRIDAY...SO SLIGHT/LOW CHANCE POPS
WILL BE WARRANTED THOSE DAYS AS WELL.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
AS OF 06Z...LIGHT RAIN IS WINDING DOWN NEAR KFLO/KLBT. CIGS ARE IFR
AT THOSE TERMINALS AND EXPECTED TO REMAIN SO THROUGH 14-15Z...WITH A
GOOD CHANCE OF LIFR CIGS/IFR VSBYS BY 08Z. CONVECTION IS INCREASING
AT THE COASTAL TERMINALS...WITH SOME ISOLATED LIGHTNING STRIKES JUST
OFFSHORE MYR.

MODEL SOLUTIONS VARY WIDELY ON THE EVOLUTION OF THE FRONTAL BOUNDARY
NEAR KFLO/KLBT...THUS CONFIDENCE IS LOW. ATTM WILL SWING THE FRONT
BACK TOWARDS THE COAST WITH THE PASSAGE OF AN UPPER IMPULSE. THIS
SHOULD ALLOW FOR AN INCREASE IN CONVECTION AT THE COASTAL TERMINALS
EARLY THIS MORNING WITH ISOLATED THUNDER. IFR/LIFR CONDITIONS WILL
EVENTUALLY SPREAD EAST AND AFFECT THE COASTAL TERMINALS EXCEPT KILM
TOWARDS SUNRISE. HIGHEST CONFIDENCE OF LIFR/IFR CIGS/VSBYS WILL BE
AT KFLO/KLBT.

LIFR/IFR CIGS IMPROVE TO MVFR BY MID MORNING. SHRA/TSRA RE-DEVELOP
BY LATE MORNING...WITH BEST POTENTIAL FOR VCTS ALONG THE BOUNDARY
NEAR THE COASTAL TERMINALS.

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

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1:30 AM SATURDAY...NO CHANGES TO THE FORECAST WITH THE
LATEST UPDATE. PREVIOUS DISCUSSIONS FOLLOW:

ONLY MINOR CHANGES ARE NEEDED TO WIND AND SEA FORECASTS THROUGH
DAYBREAK. RADAR SHOWS DEVELOPING SHOWERS AND THUNDERSTORMS...MOST
NUMEROUS ACROSS THE OFFSHORE WATERS SOUTHEAST OF CAPE FEAR. THESE
SHOWERS AND STORMS ARE ANTICIPATED TO BECOME MORE NUMEROUS OVER
THE NEXT FEW HOURS AS THEY MOVE TOWARD LAND. PREVIOUS DISCUSSION
FROM 730 PM FOLLOWS...

THE WARM FRONT/COASTAL FRONT HAS MOVED INLAND THROUGH ELIZABETHTOWN
AND WHITEVILLE WITH SOUTH WINDS REPORTED AT ALL WEATHER OBS STATIONS
ALONG THE COAST. MODELS ARE SHOWING THE BOUNDARY MAY REVERSE COURSE
OVERNIGHT AND DROP BACK DOWN TOWARD THE COAST. MY LATEST FORECAST
BRINGS IT FAIRLY CLOSE TO MYRTLE BEACH AGAIN LATE TONIGHT. THE
PRESSURE GRADIENT IS AWFULLY "BAGGY" IN THE VICINITY OF THE FRONT
AND THIS SHOULD RESULT IN WIND SPEEDS DIMINISHING
OVERNIGHT...PARTICULARLY ALONG THE SOUTH CAROLINA COAST. WINDS OF
10-15 KNOTS SHOULD CONTINUE ALONG NORTH CAROLINA COAST MUCH OF THE
NIGHT. SEAS ARE CURRENTLY 3 FEET AT THE SUNSET BEACH BUOY...AND JUST
UNDER 4 FEET AT THE NEARSHORE WRIGHTSVILLE BEACH BUOY AND OFFSHORE
LEJEUNE BUOY...NECESSITATING ONLY A SLIGHT INCREASE IN WAVE
FORECASTS. PREVIOUS DISCUSSION FROM 300 PM FOLLOWS...

COASTAL TROUGH STALLED NEAR THE COAST KEEPS SOUTHEAST FLOW IN PLACE
OVER THE WATERS THROUGH THE END OF THE PERIOD. LITTLE CHANGE TO THE
GRADIENT IS EXPECTED AND WINDS WILL REMAIN IN THE 10 TO 15 KT RANGE.
PROLONGED ONSHORE FLOW WILL KEEP SEAS 3 TO 4 FT.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 300 PM FRIDAY...A COASTAL TROUGH WILL LIKELY NOT MOVE MUCH
THROUGH THE PERIOD AND WE EXPECT THE TROUGH WILL BE OVER THE AREA
OR JUST TO THE WEST THROUGH SUNDAY NIGHT. THE WIND DIRECTION ON THE
WEST SIDE OF THE TROUGH WILL BE MORE NORTHERLY WHILE WINDS ON THE
EAST SIDE WILL BE MORE SOUTHERLY. AT THIS TIME...EXPECT THE WIND
DIRECTION ACROSS THE WATERS WILL BE PREDOMINATELY FROM A S OR SE
DIRECTION. THE PROXIMITY OF THE TROUGH SHOULD KEEP WIND SPEEDS
FROM EXCEEDING 10 TO 15 KT. SEAS WILL BE 3 TO 4 FT WITH PERHAPS
SOME 5 FT SEAS DEVELOPING ACROSS THE OUTERMOST WATERS LATE IN THE
WEEKEND. A STILL RATHER WEAK 9 TO 11 SECOND SE SWELL WILL BE PRESENT.

LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 300 PM FRIDAY...SURFACE FLOW IS EXPECTED TO REMAIN
RELATIVELY LIGHT AS THE PRESSURE GRADIENT WILL REMAIN WEAK THROUGH
THE PERIOD. HOWEVER THERE IS UNCERTAINTY IN THE WIND DIRECTION
DURING THIS TIME AS A STALLED FRONTAL BOUNDARY WILL LINGER ALONG
THE COAST. A 3 TO PERHAPS 4 FOOT SWELL WITH 11 SECOND PERIOD WILL
BE POSSIBLE TUESDAY-WEDNESDAY FROM BERTHA...WHICH IS CURRENTLY
FORECAST TO BE MOVING NORTHWARD WELL OFF THE CAROLINA COAST AT
THAT TIME.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...FLOOD WATCH THROUGH SUNDAY EVENING FOR SCZ017-023-024-032-033-
     039-053>056.

NC...FLOOD WATCH THROUGH SUNDAY EVENING FOR NCZ087-096-099-105>110.

MARINE...NONE.

&&

$$

SYNOPSIS...RJD
NEAR TERM...REK/III
SHORT TERM...RJD
LONG TERM...III
AVIATION...REK/MRR
MARINE...REK/RJD/III



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