918
FXUS62 KILM 181020
AFDILM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
620 AM EDT THU SEP 18 2025
SYNOPSIS
WARM AND DRY WEATHER WILL CONTINUE INTO THE WEEKEND AS HIGH
PRESSURE BUILDS IN. TEMPERATURES COOL TO NEAR NORMAL FROM SUNDAY
INTO NEXT WEEK WITH LOW RAIN CHANCES EACH DAY ASSOCIATED WITH A
COASTAL TROUGH.
NEAR TERM /THROUGH TONIGHT/
A NONDESCRIPT UPPER AIR PATTERN EXISTS BEHIND THE EAST COAST STORM
EARLIER THIS WEEK. AT THE SURFACE A WEAK TROUGH AXIS IS MOVING
SOUTHWARD ALONG THE COAST AND SHOULD END UP SOUTH OF GEORGETOWN, SC
BY SUNRISE. THERE WILL BE NO AIRMASS CHANGE BEHIND THIS TROUGH, BUT
LIGHT WINDS SHOULD ALLOW A CLASSIC SEABREEZE TO DEVELOP LATER TODAY
AS AIR TEMPERATURE DIFFERENCES REACH 12-15 DEGREES F ACROSS THE
BEACHES (UPPER 80S INLAND VS. MID 70S OFFSHORE.) THE SEABREEZE
SHOULD SHOW UP AT COASTAL PIERS AND AIRPORTS BY NOON AND THEN PUSH A
GOOD 40-50 MILES INLAND BY SUNSET.
ENOUGH LOW LEVEL MOISTURE SHOULD EXIST TODAY TO FUEL A DECK OF
SCATTERED TO OCCASIONALLY BROKEN CUMULUS CLOUDS THIS AFTERNOON. GFS
AND NAM FORECAST SOUNDINGS SHOW THERE SHOULD BE ENOUGH DEPTH OF
INSTABILITY TO ALLOW SOME OF THESE CUMULUS TO GROW INTO SHOWERS,
ESPECIALLY ALONG THE SOUTH CAROLINA PORTION OF THE SEABREEZE WHERE
DEWPOINTS WILL BE A FEW DEGREES HIGHER THAN IN NORTH CAROLINA.
GFS/NAM/ECMWF MOS AND NBM POPS ARE ALL 10 PERCENT OR LESS SO I'LL
KEEP THE FORECAST DRY - BUT WITH THE UNDERSTANDING 1 IN 10 LOCATIONS
IN EASTERN SOUTH CAROLINA WILL GET A SHOWER TODAY. FORECAST HIGHS
RANGE FROM THE LOWER 80S ON THE BEACHES TO THE UPPER 80S WEST OF
INTERSTATE 95.
LIGHT WINDS WILL CONTINUE TONIGHT WITH THE SEABREEZE BRINGING A
LAYER OF SHALLOW ATLANTIC MOISTURE BACK ONSHORE. THIS COULD LEAD TO
AREAS OF FOG DEVELOPING OVERNIGHT. LOWS SHOULD REACH THE MID 60S IN
MOST LOCATIONS.
SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/
ON FRIDAY, WEAK MID-LEVEL TROUGHING OVER THE AREA COUPLED WITH WEAK
SURFACE HIGH PRESSURE NEARLY OVERHEAD WILL RESULT IN PLENTY OF DRY
AIR AND SUBSIDENCE ALOFT, YIELDING A SUNNY AND DRY MORNING, GIVING
WAY TO SCATTERED FLAT STRATOCUMULUS IN THE MIDDAY TO AFTERNOON. THE
WEAK SURFACE PRESSURE PATTERN AND SUBSEQUENTLY WEAK AND CHAOTIC
WINDS ABOVE THE GROUND WILL RESULT IN VARIABLE WIND SPEEDS AND
DIRECTIONS, DRIVEN BY DIURNAL CIRCULATIONS WHICH DEPEND ON
DIFFERENTIAL HEATING BETWEEN LAND SURFACE TYPES (E.G., LAND VS.
WATER OR FOREST VS. FARM FIELDS). WITH HIGH TEMPS IN THE MID-UPPER
80S INLAND AND WATER TEMPS IN THE MIDDLE 70S, EXPECT A HEALTHY SEA
BREEZE TO DEVELOP AND PUSH INLAND, BRINGING SOUTHEAST WINDS BEHIND
IT.
OVER FRIDAY NIGHT, A POWERFUL MID-UPPER TROUGH PIVOTING INTO
SOUTHEASTERN CANADA AND AN ASSOCIATED STRONG SURFACE HIGH PRESSURE
AREA BEHIND IT WILL SEND A COLD FRONT SOUTHWARD, REACHING THE AREA
AS THE TROUGH PULLS AWAY ON SATURDAY. THUS, EXPECT THE BOUNDARY TO
STALL OVER OR NEAR THE AREA WITH LITTLE TO NO NOTICEABLE DIFFERENCE
IN AIRMASS. MEANWHILE, THE HIGH PRESSURE CENTER WILL SLIDE EASTWARD
AND OFF THE NEW ENGLAND COAST EARLY ON SUNDAY AND CONTINUE TO MOVE
AWAY AS ANOTHER TROUGH PUSHES EAST.
THIS FRONT AND THE RATHER STRONG HIGH BEHIND IT WILL RESULT IN A
COOL AIR DAMMING WEDGE WITH A TIGHTENING PRESSURE GRADIENT RESULTING
IN BREEZY EAST TO NORTHEAST WINDS FROM SATURDAY ONWARD, ESPECIALLY
AS A COASTAL TROUGH TAKES SHAPE. WITH NO NOTABLE LIFTING MECHANISMS
ALOFT, THESE BREEZY CONDITIONS SHOULD BE THE PREDOMINANT IMPACT ON
SENSIBLE WEATHER, WITH ONLY A SLIGHT CHANCE FOR OFFSHORE SHOWERS TO
REACH THE COAST AS DRY AIR AND SUBSIDENCE ALOFT WILL OTHERWISE
CONTINUE TO KEEP RAIN LARGELY AT BAY. LOW-LEVEL MOISTURE COMING OFF
THE OCEAN AND CONVERGENCE INTO THE COASTAL TROUGH SHOULD ALSO RESULT
IN GREATER CLOUD COVER NEAR THE COAST, WITH THESE CLOUDS THINNING AS
ONE GOES INLAND.
TEMPERATURES OVER THE WEEKEND SHOULD END UP WITHIN A FEW DEGREES OF
SEASONABLE LEVELS, WITH MID-UPPER 80S ON SATURDAY AND LOW-MID 80S ON
SUNDAY WHILE OVERNIGHT LOWS FALL MAINLY INTO THE MIDDLE 60S BOTH
NIGHTS, EXCEPT UPPER 60S TO AROUND 70F AT THE BEACHES.
LONG TERM /MONDAY THROUGH WEDNESDAY/
THE COOL AIR DAMMING WEDGE SHOULD STILL BE IN PLACE ON MONDAY, WITH
THE SUPPORTING HIGH PRESSURE CENTER BECOMING INCREASINGLY ELONGATED
AND WEAKENING WITH TIME. THE STALLED FRONT SHOULD ALSO BE NEAR THE
COAST, KEEPING ELEVATED EAST TO NORTHEAST WINDS AND LOW CLOUDS IN
PLACE. HEREAFTER, AN APPROACHING MID-LEVEL TROUGH SHOULD LEAD TO
UNSETTLED WEATHER FOR TUESDAY AND WEDNESDAY, BUT HOW THE GUIDANCE
TOOLS HANDLE THE BREAKDOWN OF THE HIGH AND EVOLUTION OF THE TROUGH
DIFFERS CONSIDERABLY, LEADING TO A VERY LOW CONFIDENCE FORECAST
AFTER MONDAY. HOW TEMPERATURES RESPOND WILL OF COURSE DEPEND ON
CLOUD COVER AND ANY PRECIP, SO WHILE NEAR-NORMAL TEMPS ARE FORECAST
NOW, THESE MAY CHANGE ONCE THE FUTURE OUTCOME OF THIS TROUGH BECOMES
CLEARER.
AVIATION /12Z THURSDAY THROUGH MONDAY/
THERE IS HIGH CONFIDENCE THAT VFR CONDITIONS WILL PREDOMINATE THROUGH
06Z TONIGHT. THE ONLY POSSIBLE EXCEPTIONS ARE:
- A LOW POTENTIAL FOR MVFR CEILINGS AT KILM THROUGH 15Z AS A
LOW CLOUD DECK MOVES SOUTH ACROSS EASTERN NC.
- A LOW POTENTIAL FOR AN ISOLATED SHOWER THIS AFTERNOON WITH
ASSOCIATED BRIEF VISIBILITY RESTRICTIONS.
AVIATION WEATHER ISSUES HAVE A BETTER POTENTIAL TO DEVELOP LATE
TONIGHT IN GROUND FOG. MVFR TO IFR CONDITIONS WILL HAVE A
MODERATE POTENTIAL TO BRING IMPACTS AFTER 08Z, ESPECIALLY AT
THE KFLO AIRPORT WHERE THE POTENTIAL FOR IMPACTS IS HIGH.
EXTENDED OUTLOOK...THERE IS MODERATE POTENTIAL FOR GROUND FOG WITH
MVFR TO IFR VISIBILITY AGAIN SATURDAY MORNINGS, MAINLY BETWEEN
06-12Z. ISOLATED SHOWERS AND THUNDERSTORMS MAY DEVELOP NEAR THE
COAST SUNDAY INTO MONDAY, BUT CONFIDENCE IS LOW.
MARINE
THROUGH TONIGHT...
A WEAK TROUGH IS PUSHING SOUTH ACROSS SOUTHEASTERN NORTH CAROLINA AT
THE TIME OF THIS WRITING AND SHOULD END UP SOUTH OF GEORGETOWN, SC
BY SUNRISE. IN ITS WAKE, LIGHT NORTH TO NORTHEAST WINDS WILL SPREAD
ACROSS THE COASTAL WATERS THIS MORNING.
INLAND AIR TEMPERATURES SHOULD SOAR THROUGH THE 80S THIS AFTERNOON,
CONTRASTING SHARPLY WITH AIR TEMPS OVER THE WATER IN THE 70S. THIS
WILL GENERATE A MODERATE SEABREEZE THAT WILL TURN NEARSHORE WIND
DIRECTIONS SOUTHEASTERLY THIS AFTERNOON WITH SPEEDS UP TO 10 KNOTS
EXPECTED. WINDS SHOULD REMAIN LIGHT AND SLOWLY TURN CLOCKWISE
TONIGHT AS A LANDBREEZE DEVELOPS. SEAS THROUGH TONIGHT SHOULD
AVERAGE ONLY 1-2 FEET IN A COMBINATION OF 9 SECOND EASTERLY SWELL
AND SMALL WIND WAVES.
FRIDAY THROUGH MONDAY... A WEAKLY-DEFINED PRESSURE PATTERN WILL LEAD
TO BENIGN MARINE CONDITIONS CONTINUING THROUGH FRIDAY NIGHT, WITH
VARIABLE WINDS LESS THAN 10 KTS DRIVEN PRIMARILY BY DIURNAL
CIRCULATIONS (E.G., SOUTHEAST WINDS DUE TO THE SEA BREEZE PUSHING
INLAND) AND A 1-2 FT EAST-SOUTHEASTERLY SWELL WITH A PERIOD
AROUND 8 SEC. HOWEVER, RATHER STRONG HIGH PRESSURE NORTH OF THE
AREA WILL SEND A COLD FRONT SOUTHWARD, WITH IT LIKELY STALLING
INLAND OF THE COAST ON SATURDAY. NEVERTHELESS, A COASTAL TROUGH
IS STILL EXPECTED TO DEVELOP OVER THE WATERS, LEADING TO A
TIGHTENING GRADIENT AND INCREASING EAST TO NORTHEAST WINDS AND
SWELLS FROM SATURDAY ONWARD. PEAK WINDS AND SEAS LOOK TO OCCUR
ON SUNDAY, WHEN MARGINAL SMALL CRAFT ADVISORY CONDITIONS MAY
OCCUR DUE TO WINDS FREQUENTLY GUSTING AROUND 25 KTS AND SEAS UP
TO 6 FT IN OUTER PORTIONS OF THE COASTAL WATERS. THE PATTERN
BEGINS TO BREAK DOWN ON MONDAY, WITH THE GRADIENT LOOSENING UP,
LEADING TO DECREASING WINDS AND SEAS.
ILM WATCHES/WARNINGS/ADVISORIES
NC...NONE.
SC...NONE.
MARINE...NONE.
SYNOPSIS...ILM
NEAR TERM...TRA
SHORT TERM...ABW
LONG TERM...ABW
AVIATION...TRA
MARINE...TRA/ABW
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