Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 010246
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1046 PM EDT MON AUG 31 2015

.SYNOPSIS...
LOW PRESSURE ALONG THE NORTH CAROLINA COAST SHOULD MOVE NORTHEAST
AND AWAY FROM THE AREA TONIGHT. A LINGERING TROUGH WILL REMAIN
ACROSS THE EASTERN CAROLINAS TUESDAY. HIGH PRESSURE WILL BUILD
INTO THE AREA FROM THE NORTH FRIDAY NIGHT AND THROUGH THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
AS OF 1030 PM MONDAY...INLAND SHOWERS HAVE DISSIPATED BUT ISOLATED
ACTIVITY CONTINUES OFFSHORE...MOVING EASTWARD. BASED ON SURFACE
WIND DIRECTIONS AT BUOYS AND MESONET SITES THE LOW APPEARS TO
HAVE MOVED TO A POSITION 10-15 MILES EAST OF TOPSAIL ISLAND. THE
LATEST RUC MODEL ISN`T BAD AND WAS BLENDED INTO OUR WIND GRIDDED
DATASET FOR THE REMAINDER OF THE NIGHT.

LOW CLOUDS HAVE DEVELOPED A FEW HOURS MORE QUICKLY THAN
ANTICIPATED. CLOUDINESS CURRENTLY EXTENDING FROM ELIZABETHTOWN
TO WHITEVILLE SHOULD GRADUALLY EXPAND AFTER MIDNIGHT TO COVER
MOST OF SE NORTH CAROLINA AND SOME PARTS OF NE SOUTH CAROLINA AS
WELL. DISCUSSION FROM 730 PM FOLLOWS...

THE DEEP TROPICAL MOISTURE CHANNEL IS FINALLY BEGINNING TO SHIFT
OFFSHORE. WATER VAPOR IMAGERY SHOWS THE LEADING/EASTERN EDGE OF
THE DRY AIR NOW ON THE NORTH CAROLINA COAST. LOCALLY HEAVY RAIN
CONTINUES TO FALL HOWEVER AS SURFACE LOW PRESSURE AND ITS
ASSOCIATED MAXIMUM IN LOW-LEVEL CONVERGENCE IS CENTERED JUST EAST
OF CAPE FEAR. THE 12/18Z MODELS WERE QUITE POOR WITH THE ACCURACY
OF THE POSITION OF THIS LOW. OF ALL THE MODELS AVAILABLE TO US
ONLY THE 12Z WRF-NMM AND 12Z WRF-ARW SHOWED THE LOW IN THE PROPER
POSITION AT 21Z. THESE TWO MODELS ARE THE BASIS FOR THE UPDATED
FORECAST THIS EVENING.

THE LOW SHOULD MOVE NORTHEASTWARD THIS EVENING AND AWAY FROM
SOUTHEASTERN NORTH CAROLINA. RAINFALL SHOULD SLOWLY TAPER OFF OVER
THE NEXT 2-3 HOURS...LINGERING FOR COASTAL PENDER COUNTY AND THE
ADJACENT OCEAN WATERS THE LONGEST. AN ADDITIONAL ONE-HALF INCH TO
ONE INCH OF RAIN COULD POTENTIALLY FALL FROM WRIGHTSVILLE BEACH
TO TOPSAIL ISLAND OVER THE NEXT FEW HOURS.

ONCE THE PRECIP CLEARS THE COAST...CLEAR SKIES ADVANCING IN FROM
THE WEST SHOULD OVERSPREAD MOST OF THE AREA. HOWEVER...MODELS ARE
INDICATING WRAP-AROUND MOISTURE WILL RE-ENTER THE PICTURE FROM THE
NORTH...SPREADING A DECK OF LOW STRATUS INTO AT LEAST
SOUTHEASTERN NORTH CAROLINA AFTER MIDNIGHT. WHERE THESE LOW CLOUDS
DO NOT REACH...BETTER RADIATIONAL COOLING CONDITIONS WILL
INTERSECT WITH LINGERING SURFACE MOISTURE AND WE CAN EXPECT AREAS
OF FOG TO DEVELOP. MOS GUIDANCE IS INDICATING THIS FOG COULD
BECOME LOCALLY DENSE...PARTICULARLY ACROSS SOUTH CAROLINA`S PEE
DEE REGION.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
AS OF 300 PM MONDAY...PROGRESSIVE PATTERN THROUGH THE PERIOD. A
TROUGH OF LOW PRESSURE WILL BE ALIGNED RIGHT ALONG THE COAST TUE.
A MID-LEVEL VORTICITY MAXIMA ASSOCIATED WITH FORMER TROPICAL
STORM ERIKA WILL BE MOVING UP THE SOUTHEAST COAST. THIS FEATURE
WILL BE APPROACHING THE FORECAST AREA TUE NIGHT AND IS EXPECTED TO
MOVE OFF THE CAROLINA COAST DURING THE DAY WED. A RIDGE BUILDING
ACROSS THE MIDDLE OF THE COUNTRY NEAR THE END OF THE PERIOD WILL
ALLOW A NW FLOW TO DEVELOP ACROSS THE CAROLINAS. A WEAK SHORTWAVE
EMBEDDED IN THE FLOW IS FORECAST TO APPROACH LATE WED NIGHT.

THERE WILL BE A GOOD AMOUNT OF DRY AIR MOVING ACROSS THE AREA AND
THIS IN AND OF ITSELF WILL BE GOOD REASON TO KEEP THE POPS IN
SLIGHT CHANCE/CHANCE CATEGORY. WILL SHOW HIGHEST POPS ALONG THE
COAST AHEAD OF AFOREMENTIONED MID-LEVEL VORTICITY...LATE TUE
NIGHT AND WED MORNING. HOWEVER...IT MAY END UP THAT MOST OF THE
PRECIPITATION AND CERTAINLY THE HEAVIEST OF THE SHOWER AND
THUNDERSTORM ACTIVITY...WILL BE OFFSHORE. WILL ALSO TRY TO
CAPTURE THE SLIGHT UPTICK IN THE POTENTIAL FOR CONVECTION WED
NIGHT WITH THE MID-LEVEL SHORTWAVE.

TEMPERATURES WILL RETURN TO SLIGHTLY ABOVE SEASONABLE LEVELS FOR
EARLY SEPTEMBER.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 300 PM MONDAY...THURSDAY SHOULD BE THE FIRST FULL DAY WHERE THE
AREA IS NO LONGER DEALING WITH ANY REMNANTS OF ERIKA. PW DROPS TO
ABOUT 1.6 INCHES ACROSS MUCH OF THE AREA BUT THERE WILL BE A MID
LEVEL DISTURBANCE MOVING THROUGH IN NORTHWEST FLOW. GFS NOW SHOWS A
VERY WEAK ATTENDANT SURFACE FEATURE AND SO FEEL THAT THE LOW END
SCATTERED (30 POPS) THAT WE HAVE IN THE FORECAST IS JUST FINE. QPF
PROSPECTS WILL BE LOW DUE TO THE LOWER AVAILABLE MOISTURE AND WEAK
FORCING. ANOTHER MID LEVEL FEATURE CROSSES ON FRIDAY BUT IN MORE OF
WESTERLY RATHER THAN NORTHWESTERLY SOURCE WHICH MAY FAVOR BETTER
RAIN CHANCES DUE TO DEEPER MOISTURE AT LEAST ACCORDING TO ECMWF. GFS
HAS MORE OF A REPEAT OF THURSDAY. LARGE UPPER RIDGE BUILDS OVER THE
EASTERN U.S. AND MID-ATLANTIC OVER THE WEEKEND WITH ITS CENTER
WELL TO OUR NORTH. THE SAME WILL HOLD TRUE AT THE SURFACE. THIS
WILL BRING A DEEP EASTERLY FLOW TO THE AREA THAT OFTEN LEADS TO
TROPICAL BLUE SKIES LADEN WITH TOWERING CU AND ALSO A FEW STRAY
SHOWERS MAINLY ALONG THE COAST.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AS OF 00Z...A MIXTURE OF VFR/MVFR/IFR ON TAP TONIGHT THROUGH THE
EARLY MORNING HOURS ON TUESDAY AS AREAS OF FOG AND LOW CIGS DEVELOP.
CONDITIONS IMPROVE TO VFR LATE TUESDAY MORNING AND CONTINUE THROUGH
THE END OF THE VALID TAF PERIOD.

SHOWERS CONTINUE TO MOVE THROUGH PORTIONS OF THE FORECAST AREA THIS
EVENING...CURRENTLY AFFECTING KILM...AS SEEN BY LATEST RADAR
IMAGERY. EXPECT THIS ACTIVITY TO TAPER OFF OVER THE NEXT COUPLE OF
HOURS AND FOR SKIES TO GRADUALLY CLEAR...AS ALREADY SEEN INLAND ON
SATELLITE IMAGERY. OTHER THAN INTERMITTENTLY LINGERING FEW/SCT MID
CLOUDS INTO THE OVERNIGHT HOURS...MAINLY CLEAR SKIES AND LIGHT WINDS
WILL NOT LAST LONG AS SOME GUIDANCE SUGGESTS MOISTURE RETURN
OVERNIGHT. AS A RESULT...ANTICIPATE STRATUS AND FOG DEVELOPMENT
OVERNIGHT TO CREATE MVFR/IFR CONDITIONS. CONFIDENCE REMAINS LOW
REGARDING WHICH FEATURE WILL PREVAIL...THUS HAVE KEPT A MIXTURE IN
GOING FORECAST ATTM. ON TUESDAY...CONDITIONS WILL IMPROVE TO VFR
WITH LIGHT WINDS BECOMING SOUTHEAST AOB 10 KTS IN THE AFTERNOON.
CANNOT ENTIRELY RULE OUT AN ISOLATED SHRA/TSRA IN THE AFTERNOON
HOURS.

EXTENDED OUTLOOK...PREDOMINATELY VFR WITH BRIEF MORNING FOG AND
ISOLATED/SCATTERED AFTERNOON CONVECTION.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 PM MONDAY...OBSERVATIONS SUGGEST THE LOW IS CURRENTLY
LOCATED 10-15 MILES EAST OF TOPSAIL ISLAND AND MOVING NORTHEASTWARD.
ISOLATED SHOWERS CONTINUE ACROSS THE NC COASTAL WATERS BUT SHOULD
END OVER THE NEXT FEW HOURS. A BELT OF STRONGER SOUTH-SOUTHWEST
WINDS OFFSHORE AHEAD OF THE LOW HAS BUILT SEA HEIGHTS AT THE
FRYING PAN SHOALS BUOY TO 5 FEET...WITH BUOYS CLOSE TO THE COAST
STILL REPORTING 3-4 FEET. DISCUSSION FROM 730 PM FOLLOWS...

USING RADAR IMAGERY AND SURFACE OBSERVATIONS LOW PRESSURE IS
CENTERED JUST EAST OF CAPE FEAR AT 7 PM. OF ALL THE MODELS
AVAILABLE TO US THE TWO THAT SEEM TO HAVE THE BEST HANDLE ON THE
CURRENT POSITION AND MOVEMENT OF THIS FEATURE ARE THE 12Z WRF-NMM
AND 12Z WRF-ARW. THESE MODELS ARE THE BASIS FOR THIS EVENING
UPDATE. OFFSHORE WINDS SHOULD GRADUALLY DIMINISH THROUGH THE NIGHT
SOUTH OF CAPE FEAR...BUT NORTH OF CAPE FEAR WE`VE GOT A FEW MORE
HOURS OF INTERESTING WEATHER AS SWIRLING WINDS UP TO 20 KNOTS AND
WIDESPREAD SHOWERS WITH HEAVY RAINFALL WILL CONTINUE. SEAS HAVE
BUILT TO A SOLID 4 FEET NEAR AND NORTH OF CAPE FEAR AND THERE
SHOULD BE SOME 5-FOOTERS DEVELOPING SHORTLY ACCORDING TO OUR LOCAL
WAVE MODEL USING UPDATED WIND FORECASTS. AN EXERCISE CAUTION
HEADLINE HAS BEEN HOISTED NORTH OF CAPE FEAR. AFTER MIDNIGHT SEAS
SHOULD SUBSIDE THROUGHOUT THE REGION TO 2-3 FEET.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 300 PM MONDAY...A SLACK PRESSURE GRADIENT IS EXPECTED TO BE
IN PLACE THROUGH THE PERIOD AND THIS SHOULD KEEP WIND SPEEDS TO
10 KT OR LESS. SW TO S WINDS DURING THE AFTERNOON AND EVE BOTH
DAYS SHOULD BECOME MORE OFFSHORE OVERNIGHT AND DURING THE MORNING
DUE TO A LAND BREEZE MOVING OFFSHORE. SEAS WILL BE MAINLY 2
FT...BUT UP TO 3 FT TUE. A WEAK 8 TO 10 SECOND SE SWELL WILL
PERSIST.

LONG TERM /THURSDAY THROUGH SATURDAY/...
AS OF 300 PM MONDAY...WIND SPEEDS WILL BE CAPPED AT JUST 10 KNOTS
THROUGH MOST OF IF NOT THE ENTIRE PERIOD. IT MAY STRUGGLE THURSDAY
AND FRIDAY TO FIND AN ESTABLISHED DIRECTION HOWEVER THOUGH NORTH AND
EAST COMPONENTS WILL TEND TO BE FAVORED. THIS WILL BE FORTIFIED
FRIDAY NIGHT INTO SATURDAY AS A STRONGER HIGH GETS ESTABLISHED
ACROSS NORTHEASTERN U.S. BETWEEN THE LENGTHENING SPATIAL AND
TEMPORAL FETCH ON SATURDAY THE WAVE FORECAST MAY RISE FROM 2 TO 2-3
FT.

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...TRA
SHORT TERM...RJD
LONG TERM...MBB
AVIATION...SRP


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