National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 191943
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
343 PM EDT WED JUN 19 2013

.SYNOPSIS...
-- Changed Discussion --
AS COLD FRONT SAGS FARTHER SOUTH THROUGH THIS EVENING...THE RISK
OF RAIN WILL SLOWLY END FROM NORTH TO SOUTH. THIS FRONT WILL
LINGER NEAR OR JUST SOUTH OF COASTAL NORTH CAROLINA AS HIGH
PRESSURE NOSES IN FROM THE NORTH PUSHING SOME DRIER AIR IN THROUGH
THURSDAY. THE LINGERING FRONT WILL NUDGE BACK TO THE NORTH FRIDAY
INTO THIS WEEKEND INCREASING CLOUDS AND CHANCE OF SHOWERS MAINLY
ACROSS THE COASTAL CAROLINAS.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 300 PM WEDNESDAY...THE SURFACE COLD FRONT HAS PUSHED MUCH
FARTHER SOUTH THAN I HAD INITIALLY EXPECTED AND HAS NOW CROSSED THE
SANTEE RIVER INTO NORTHERN CHARLESTON COUNTY SC. THIS HAS TAKEN
VIRTUALLY ALL THE SURFACE BASED INSTABILITY SOUTH OF THE SANTEE
RIVER WITH THE HEAVIER THUNDERSTORM ACTIVITY CONFINED DOWN THERE.
LIGHTER STRATIFORM RAIN BLOWING NORTHEAST FROM THE STORMS IS
SPREADING ACROSS PARTS OF WILLIAMSBURG AND GEORGETOWN COUNTIES AND
MAY PUSH UP THE COAST TO MYRTLE BEACH AND EVEN BALD HEAD ISLAND BY
EARLY EVENING. RAINFALL AMOUNTS WITHIN THIS RAIN SHOULD AVERAGE ONLY
A COUPLE HUNDREDTHS OF AN INCH...MUCH LIGHTER THAN BEING EXPERIENCED
SOUTH OF GEORGETOWN.

MODELS ARE STRUGGLING TO FIND THE ACTUAL POSITION OF THE SURFACE
COLD FRONT. OF THE 10 MODELS I LOOK AT...ONLY THREE OF THEM SHOW
THE CORRECT FRONTAL POSITION: THE HRRR...ECMWF AND CANADIAN. THE
THREE OF THESE MODELS SHOW THE FRONT REMAINING SOUTH OF GEORGETOWN
THROUGH THE NIGHT...ALTHOUGH THEY ALSO SHOW THE REDEVELOPMENT OF
THUNDERSTORMS ALONG AND JUST NORTH OF THE SURFACE FRONTAL POSITION
AROUND MIDNIGHT. NOCTURNAL REDEVELOPMENT OF CONVECTION IS CERTAINLY
SOMETHING WE SEE DURING THE SUMMER PARTICULARLY IN A VERY MOIST
AIRMASS LIKE WE HAVE HERE...SO AFTER RAMPING POPS DOWN THIS EVENING
I WILL SHOW A TREND TOWARD HIGHER POPS...30-40 PERCENT IN THE
GEORGETOWN VICINITY OVERNIGHT.

LOWS TONIGHT SHOULD RANGE FROM 65-70...WARMEST ALONG THE SC COAST
AND COOLER IN THE ELIZABETHTOWN/LUMBERTON AREA.
-- End Changed Discussion --

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
-- Changed Discussion --
AS OF 300 PM WEDNESDAY...LATEST MODEL RUNS HEDGING TOWARD A
CLOUDIER AND WETTER FORECAST FOR THE COASTAL AREAS AS FRONT
LINGERS NEAR OR JUST SOUTH OF AREA THROUGH THE PERIOD AND THEN
MOVES BACK NORTH AND WEST. ALTHOUGH HIGH PRESSURE TRIES TO BUILD DOWN
FROM THE NORTH...IT LOOKS LIKE THE RIDGE TO THE SOUTH WILL END UP
PUSHING THE DIFFUSE BOUNDARY AND ASSOCIATED MOISTURE BACK NORTH.
THE HIGH PRESSURE TO THE NORTH WILL CONTINUE TO NOSE DOWN INTO THE
INLAND PORTIONS OF THE CAROLINAS BUT THERE WILL BE A TIGHT
GRADIENT BETWEEN THE TWO AIR MASSES...SLIGHTLY COOLER AND MUCH
DRIER TO THE NORTHWEST AND MUCH WETTER TO THE SOUTHEAST. THE BIG
QUESTION IS WHERE WILL THIS DIVIDING LINE END UP. PREVIOUS MODEL
RUNS KEPT OUR AREA IN THE DRIER AIR BUT LATEST RUNS ARE TRENDING
TO A WETTER FORECAST...MAINLY ALONG THE COAST. PCP WATER VALUES
WILL BE AS LOW AS ONE INCH BASICALLY WEST OF I95 AND UP TO 1.75
INCHES OR GREATER OVER NORTHEAST SOUTH CAROLINA COAST.

LOOKS LIKE OUR BEST CHC FOR DRIER NICER WEATHER WILL BE ON THURS
BEFORE BOUNDARY MAKES ITS PUSH NORTH. FOR NOW WILL KEEP ANY CHC OF
PCP JUST ALONG THE COAST AND PRIMARILY OVER COASTAL SOUTH
CAROLINA...BUT MAY END UP BEING A GOOD DEAL OF CLOUDS OVER MUCH OF
THE AREA EXCEPT INLAND COUNTIES...MAINLY WEST OF I95 WHERE DRIER
AND SUNNIER WEATHER SHOULD BE. BASICALLY ANY SHIFT IN THIS
BOUNDARY WILL CHANGE FORECAST QUITE A BIT AND THEREFORE MUCH
UNCERTAINTY EXISTS FOR FORECAST ACROSS THE COASTAL COUNTIES.

PCP ALONG THE COAST...CLOUDS AND NORTHEAST FLOW WILL KEEP TEMPS
BELOW NORMAL. TEMPS SHOULD REMAIN CLOSER TO 80 ALONG THE COAST TO
MID 80S INLAND. OVERNIGHT LOWS SHOULD BE IN THE MID 60S.
-- End Changed Discussion --

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
AS OF 300 PM WEDNESDAY...SOME UNCERTAINTY REMAINS IN THE
EXTENDED...BUT GUIDANCE IN DECENT AGREEMENT FOR THE MOST PART IN A
DEVELOPING TYPICAL SUMMERTIME PATTERN...WITH RIDGING AT 500MB AND A
BERMUDA HIGH SITTING OFFSHORE. DURING NEXT WEEK...HIGH PRESSURE
OFFSHORE WILL COMBINE WITH BUILDING 1000-500MB THICKNESSES TO CREATE
A WARMING TREND...WITH TEMPS RISING TO ABOVE NORMAL..AND WIDESPREAD
90S ARE LIKELY EARLY NEXT WEEK. AT THE SAME TIME...THIS PATTERN
TYPICALLY SUPPORTS SCATTERED AFTN CONVECTION...AND NEXT WEEK SHOULD
BE NO DIFFERENT. WITHOUT ANY MEANINGFUL CAP...AND PWATS RISING TO
NEAR TWO INCHES...HAVE CHC/SCHC CONVECTION EACH AFTN...WANING
NOCTURNALLY.

THE BIGGEST QUESTION MARK IN THE EXTENDED THEN IS THE FIRST PORTION
OF THE PERIOD. COLD FRONT OFFSHORE WILL BE WEAKENING...AND AS HIGH
PRESSURE BUILDS WELL EAST...SYNOPTIC RETURN FLOW WILL PUSH THIS
BOUNDARY BACK TOWARDS THE COAST DURING SATURDAY...LIFTING NORTH OF
THE AREA ON SUNDAY. QUESTION MARKS REMAIN AS TO HOW STRONG THIS
BOUNDARY WILL BE...HOW MUCH MOISTURE WILL STILL BE ASSOCIATED WITH
IT...AND WHETHER A LOW PRESSURE WILL DEVELOP ALONG IT. ATTM WILL
CONTINUE TO SUPPORT THE ECMWF WHICH HAS BEEN THE MOST
CONSISTENT...BUT MAY BE A BIT DRY...AND WILL NOT INCLUDE ANY MENTION
OF LOW PRESSURE DEVELOPMENT...BUT WILL SUPPORT CHC POP SAT INTO SUN
AS THE TROUGH PUSHES ONSHORE. TEMPS WILL BE HINDERED DURING THE WKND
BY CLOUDS AND PRECIP...AND EXPECT LOW/MID 80S SAT BEFORE WARMING AS
SOME COLUMN DRYING OCCURS ON SUNDAY.
-- End Changed Discussion --

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AS OF 18Z...PERIODS OF MVFR/IFR WITH SCATTERED SHOWERS AND
THUNDERSTORMS EXPECTED TO CONTINUE THROUGH THE EVENING HOURS.
MVFR/IFR DUE TO LOWERED CIGS/AREAS OF FOG OVERNIGHT INTO THE EARLY
MORNING HOURS ON THURSDAY. OTHERWISE EXPECT VFR.

ANTICIPATE TEMPO/INTERMITTENT PERIODS OF MVFR/IFR CIGS TO CONTINUE
THIS AFTN...ESPECIALLY ALONG THE COAST...AS SHOWERS AND ISOLATED
THUNDERSTORMS CONTINUED NEAR A COLD FRONT LOCATED BETWEEN MYR AND
CHS. THIS EVENING ACTIVITY WILL TAPER OFF WITH A FEW SHOWERS STILL
POSSIBLE ALONG THE COAST. ANTICIPATE LATE NIGHT STRATUS WILL CREATE
MVFR/IFR CONDITIONS...WITH AREAS OF FOG POSSIBLE ALONG THE COAST
OVERNIGHT. INTO THE MORNING HOURS CONDITIONS WILL BE SLOW TO IMPROVE
BUT ANTICIPATE VFR DEVELOPING BY NOON LOCAL TIME WITH NORTHEAST
WINDS AOB 12 KTS...WITH POSSIBLE HIGHER GUSTS.

EXTENDED OUTLOOK...VFR THURSDAY THROUGH SATURDAY. SLIGHT CHANCE OF
SHOWERS ON SUNDAY.

&&

.MARINE...
-- Changed Discussion --
NEAR TERM /THROUGH TONIGHT/...
AS OF 300 WEDNESDAY...DEFYING ALL EXPECTATIONS...THE FRONT HAS
CONTINUED TO PUSH FARTHER SOUTH AND IS NOW IN NORTHERN CHARLESTON
COUNTY ABOUT 5-10 MILES SOUTH OF THE SANTEE RIVER. OF 10 MODELS I
HAVE ACCESS TO...ONLY THREE HAVE ANY CLUE ABOUT THE CURRENT POSITION
OF THIS FRONT: THE HRRR...ECMWF AND CANADIAN. BLENDING THE OUTPUT OF
THESE THREE MODELS TOGETHER SHOWS THE FRONT SHOULD REMAIN SOUTH OF
OUR AREA OVERNIGHT WITH HIGH PRESSURE OVER THE EASTERN GREAT LAKES
BUILDING SOUTHWARD INTO THE MID-ATLANTIC REGION. THIS WILL TIGHTEN
THE PRESSURE GRADIENT LOCALLY PRODUCING A MODERATE NORTHEAST SURGE
OVERNIGHT. AT THIS TIME IT APPEARS WINDS AND SEAS WILL REMAIN JUST
BELOW THE CRITERIA NEEDED TO ADD AN "EXERCISE CAUTION" HEADLINE TO
THE FORECAST. THE ROUGHEST CONDITIONS ARE EXPECTED NORTH OF CAPE
FEAR. IN TERMS OF SHOWER AND THUNDERSTORM POTENTIAL...THE FRONT HAS
TAKEN MOST OF THE ATMOSPHERIC INSTABILITY SOUTH OF OUR REGION.
SHOWERS COULD REDEVELOP JUST NORTH OF THE FRONT MAINLY FROM MYRTLE
BEACH SOUTH TONIGHT.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 PM WEDNESDAY...HIGH PRESSURE WILL BUILD IN BEHIND FRONT
WHICH WILL SLOWLY SAG SOUTH INITIALLY AND THEN BACK NORTH BY
FRIDAY. THE PINCHED GRADIENT BETWEEN THE HIGH PRESSURE BUILDING
SOUTH AND STALLED FRONT OFF THE COAST WILL PRODUCE PERSISTENT
NORTHEAST WINDS AROUND 15 KT THURSDAY. THIS IN TURN WILL PRODUCE
SEAS IN THE 3 TO 5 FT RANGE MOST WATERS...BUT LOWER JUST SOUTH OF
CAPE FEAR WHICH REMAINS BLOCKED FROM NORTHEAST WINDS.

GRADIENT WILL RELAX A BIT LATE THURS INTO FRI WITH WINDS SUBSIDING
TO 10 TO 15 KTS THURS NIGHT AND CLOSER TO 10 KTS BY FRI. THIS WILL
ALLOW SEAS TO DROP DOWN TO 2 TO 4 FT. WINDS VEER AROUND AS
BOUNDARY LIFTS NORTH BECOMING MORE EAST TO SOUTHEAST THROUGH
FRIDAY ON EAST SIDE OF BOUNDARY. WINDS WILL REMAIN NORTHEAST 10
KTS OR LESS ON WEST SIDE OF LILNGERING FRONT AND MORE SOUTHERLY UP
TO 15 KTS ON EAST SIDE OF BOUNDARY WHICH MAY INTERSECT RIGHT
THROUGH OUR LOCAL WATERS ON FRIDAY.

LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 300 PM WEDNESDAY...LIGHT NE WINDS SATURDAY WILL GRADUALLY TURN
TO THE SE AS COASTAL TROUGH/REMNANT FRONT PUSHES WEST ONSHORE DURING
THE DAY. THIS IS IN RESPONSE TO A BERMUDA HIGH PRESSURE BUILDING
ACROSS THE WESTERN ATLANTIC OCEAN...WHICH WILL THEN CONTROL THE
SYNOPTIC ENVIRONMENT THROUGH THE REMAINDER OF THE
EXTENDED...CREATING SW WINDS AROUND 10 KTS OVER THE WATERS. WITH THE
GRADIENT REMAINING RELATIVELY WEAK...WIND WAVE CONTRIBUTION TO THE
SPECTRUM WILL BE ONLY MINIMAL...AND THE COMBINATION OF WIND WAVES
(NE ON SATURDAY...SE SUN/MON) AND A GROWING SE SWELL WILL CREATE 2-4
FT SEAS THROUGH THE PERIOD.
-- End Changed Discussion --

&&

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

&&

$$

NEAR TERM...TRA
SHORT TERM...RGZ
LONG TERM...JDW
AVIATION...TRA/SGL