Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 160221
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1021 PM EDT MON SEP 15 2014

.SYNOPSIS...
A COLD FRONT WILL PUSH OFFSHORE EARLY TUESDAY MORNING. HIGH PRESSURE
WILL RIDGE DOWN INTO THE CAROLINAS FROM THE NORTH BEHIND THIS
FRONT...PROVIDING FALL-LIKE WEATHER FOR THE REMAINDER OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 PM MONDAY...THE NCEP PARALLEL VERSION OF THE HRRR HAS AN
EXCELLENT HANDLE ON OBSERVED RADAR ECHOES AND EVEN HAS PICKED UP ON
THE MESOSCALE LANDBREEZE WINDS OBSERVED NEAR THE BEACHES THIS
EVENING. BASED ON ITS EXCELLENT HANDLING OF ACTIVITY SO FAR I HAVE
BLENDED ITS 23Z RUN INTO MOST SENSIBLE FORECAST GRIDS OVERNIGHT. THE
BEST POTENTIAL FOR MEASURABLE RAIN OVERNIGHT WILL EXIST FOR THE NEXT
FEW HOURS NEAR THE SANTEE RIVER AND ALONG THE SOUTH CAROLINA COAST.
THIS ACTIVITY WILL PROBABLY THIN OUT AFTER MIDNIGHT...BUT AS THE 500
MB TROUGH APPROACHES OUR LONGITUDE LATE TONIGHT SHOWER COVERAGE MAY
INCREASE AGAIN ACROSS SOUTHEAST NORTH CAROLINA AND THE SC COAST. NO
CHANGES ARE NEEDED TO FORECAST LOWS WHICH RANGE FROM THE UPPER 60S
INLAND TO AROUND 70 AT THE BEACHES. PREVIOUS DISCUSSION FROM 730 PM
FOLLOWS...

ONLY TWO CHANGES HAVE BEEN MADE TO THE FORECAST WITH THIS EARLY
EVENING UPDATE. FORECAST LOW TEMPERATURES HAVE BEEN RAISED BY
SEVERAL DEGREES BASED ON THE EXPECTATION CLOUD COVER WILL IMPEDE
RADIATIONAL COOLING OVERNIGHT. INCREASING LOW-LEVEL WINDS WILL ALSO
HELP TO KEEP THE BOUNDARY LAYER MIXED WITH ONLY A WEAK NOCTURNAL
INVERSION EXPECTED. RADAR SHOWS AN AREA OF RAIN WITH EMBEDDED
THUNDERSTORMS CROSSING THE SANTEE RIVER HEADING TOWARD GEORGETOWN.
POPS HAVE BEEN RAISED SUBSTANTIALLY ACROSS GEORGETOWN COUNTY FOR THE
NEXT COUPLE OF HOURS...BUT LATEST MODELS SHOW PRECIP CHANCES FOR THE
REMAINDER OF THE FORECAST AREA ARE QUITE LOW OVERNIGHT. PREVIOUS
DISCUSSION FROM 300 PM FOLLOWS...

THICK CLOUDS HAVE KEPT AFTERNOON TEMPS BELOW NORMAL. THESE CLOUDS
ARE EXPECTED TO HANG ON THROUGH THE NIGHT GIVEN PLENTIFUL LOW LEVEL
MOISTURE WITH CEILINGS LOWERING AS THE COLUMN COOLS AND STABILIZES.
A WEAK MID-LEVEL SHORTWAVE AND SURFACE REFLECTION WILL REACH THE
EASTERN CAROLINAS FROM THE WEST OVERNIGHT. THESE FEATURES MAY
PROVIDE JUST ENOUGH CONVERGENCE TO GENERATE ISOLATED TO SCATTERED
SHOWERS AND THUS WILL HAVE TO KEEP SMALL POPS IN THE FORECAST
THROUGH SUNRISE TUE. WE DO NOT EXPECT ANY OF THE PRECIPITATION TO BE
HEAVY GIVEN THE DIMINISHING DEPTH OF DEEPER MOISTURE AND THE LACK OF
INSTABILITY.

A RATHER FLAT DIURNAL CURVE IS EXPECTED WITH NIGHTTIME VALUES ONLY
ABOUT 10 DEGREES BELOW THE HIGHS ACHIEVED THIS AFTERNOON. DESPITE
THE CLOUDS...WE ARE GENERALLY FORECASTING MINIMUMS TO BE NEAR OR
JUST BELOW THE COOLEST OF GUIDANCE.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 300 PM MONDAY...A LINGERING FRONT THAT WAS SOUTH OF AREA
WILL MOVE BACK INTO THE AREA. A MINOR PERTURBATION IN THE MID TO
UPPER LEVELS WILL MOVE THROUGH EARLY TUES HELPING TO ENHANCE
CONVECTION ALONG THE FRONT. LOOKS LIKE THE FRONT WILL CONTINUE TO
MOVE SLOWLY NORTHWARD THROUGH TUES AS A COLD FRONT MOVES DOWN FROM
THE NORTHWEST. A PRE FRONTAL TROUGH SHOULD MERGE WITH THIS SYSTEM
AND MODELS CONTINUE TO SHOW WEAK LOW PRESSURE DEVELOPING ALONG
THIS SYSTEM ALONG THE SC COAST THROUGH TUES NIGHT INTO WED BEFORE
AMPLIFYING MID TO UPPER TROUGH FINALLY PUSHES THE WHOLE SYSTEM OFF
SHORE. THE HIGHEST PCP WATER VALUES WILL CREEP BACK NORTH THROUGH
TUES MORNING REMAINING OVER EASTERN CAROLINAS BEFORE GETTING
PUSHED OFF SHORE. THEREFORE SHOULD SEE DECENT CONVECTIVE ACTIVITY
THROUGH AT LEAST EARLY TUES AS WAVE OF LOW PRESSURE DEVELOPS ALONG
LINGERING FRONT WHILE ANOTHER COLD FRONT MOVES IN FROM THE
NORTHWEST. PCP WATER VALUES UP ABOVE 2 INCHES ON TUES WILL
DECREASE SLOWLY TO 1.5 INCHES BY WED AND DOWN TO 1.3 INCHES BY
EARLY THURS MORNING AS MID TO UPPER TROUGH SHIFTS EAST WITH DEEPER
DRIER NW FLOW DEVELOPING. LOW LEVEL MOISTURE BELOW 5K FT WILL
PERSIST AND THEREFORE EXPECT PLENTY OF CLOUDS THROUGH MOST OF THE
PERIOD. SOME DRIER AIR DOES MAKE IT INTO AREA IN W-NW LOW LEVEL
FLOW IN THE LOW TO MID LEVELS BY TUES AFTN AND THEREFORE MAY SEE
SOME SUNSHINE ACROSS INLAND AREAS THROUGH THE DAY ON TUES. THE BEST
CHC OF HEAVIER SHWRS/TSTMS WILL EXIST ON TUES...BUT LINGERING
MOISTURE WILL KEEP CLOUDS AND SOME PCP IN THE AREA THROUGH WED.

TEMPERATURES MAY BE A BIT TRICKY ON TUES. SHOULD REACH INTO THE
MID 80S AS WINDS SHIFT SOUTH OVER PORTIONS OF THE AREA AND IN
PLACES THAT SEE SOME BRIGHTENING OF SKIES TUES AFTN. TEMPS WILL BE
LOWER ON WED AS COOLER AIR MAKES ITS WAY IN BEHIND FRONT. OVERNIGHT
LOWS WILL RUN ABOVE NORMAL WITH CLOUDS BLANKETING THE AREA MOST OF
THE TIME.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 300 PM MONDAY...MID LEVEL TROUGH OVER THE EAST COAST AT THE
START OF THE PERIOD WILL SHIFT NORTHEAST AS MID LEVEL RIDGE OVER
THE WESTERN GULF COAST EXPANDS EAST. DEVELOPMENT OF PROGRESSIVE
FLOW OVER NEW ENGLAND FRI WILL HELP PUSH SURFACE HIGH RIDGING DOWN
THE COAST THU/FRI OFF THE COAST FOR THE WEEKEND. THIS WILL BRING
AN END TO LOW CLOUDS...BELOW CLIMO TEMPERATURES...AND THE THREAT
OF PRECIP FOR SAT AND SUN.

WEAK MID LEVEL RIDGING OVER THE REGION COMBINED WITH ELONGATED
SURFACE HIGH OVER THE CENTRAL CAROLINAS WILL CLEAR SKIES AND BRING
ABOUT A RETURN TO SEASONABLE CONDITIONS FOR THE WEEKEND. ANOTHER
COLD FRONT...PUSHED BY A STRONG MID LEVEL TROUGH...WILL MOVE ACROSS
THE AREA ON MON. FROPA TIMING STILL SOMEWHAT UNCERTAIN AS IT COULD
BE ANYWHERE FROM MON MORNING TO MON EVENING. LIFT ALONG THE FRONT
AND NARROW BAND OF MOISTURE SHOULD KICK OFF SOME SHOWERS REGARDLESS
OF TIMING. IF THE FRONT ARRIVES LATER AND DIURNAL INSTABILITY IS
ABLE TO DEVELOP COVERAGE WOULD BE INCREASED...AS WOULD THE POTENTIAL
FOR THUNDER. FOR NOW FAVOR THE SLOWER SOLUTION GIVEN THE TENDENCY
FOR MID LEVEL RIDGING TO HOLD ON LONGER THAN EXPECTED.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AS OF 00Z...SATELLITE IMAGERY SHOWS A FEW MORE BREAKS IN THE LOW
CLOUDS AS COMPARED TO YESTERDAY...AND CONDITIONS COULD BRIEFLY
IMPROVE TO VFR THIS EVENING. BUT CIGS ARE EXPECTED TO FILL BACK IN
AND LOWER TO MVFR/IFR OVERNIGHT AS COOL MOIST AIR LINGERS OVER OUR
AREA. THE HRRR...SREF PROBS AND MODEL SOUNDINGS AGREE THAT CIGS AT
KFLO/KLBT WILL DROP TO IFR/LIFR LEVELS AFTER 08Z AND PERSIST THRU
DAYBREAK. COULD ALSO SEE REDUCED VSBYS OVERNIGHT AS WINDS GO CALM.
MVFR CIGS WILL LIKELY PREVAIL AT THE COASTAL TERMINALS EARLY TUE...
AS ANY IFR THAT DEVELOPS ALONG THE COAST WOULD BE BRIEF AND MORE
TEMPO IN NATURE. HAVE ALSO INCLUDED VCSH FOR KILM/KCRE/KMYR EARLY
TUE AS DEEP MOISTURE RETURNS WITH A REMNANT FRONT LIFTING NORTHWARD
AS WELL AS A WEAK UPPER DISTURBANCE. ANY SHOWERS THAT DEVELOP COULD
PRODUCE BRIEF/LOCALIZED PERIODS OF IFR OVER A COASTAL TAF SITE. MVFR
CIGS MAY LINGER THROUGH THE MORNING...BUT EXPECT VFR DURING THE AFTN
HOURS AS LIGHT N-NW WINDS BECOME SOUTHEAST AOB 10 KT AHEAD OF AN
APPROACHING COLD FRONT.

EXTENDED OUTLOOK...POST-FRONTAL MVFR CIGS MAY DEVELOP WED AS COOLER
AIR WEDGES INTO THE REGION. EARLY MORNING MVFR/IFR CIGS POSSIBLE ON
THU. GUSTY NORTHEAST WINDS EXPECTED FRI/SAT AS THE COOL AIR WEDGE
STRENGTHENS OVER THE CAROLINAS.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 PM MONDAY...A LANDBREEZE HAS DEVELOPED OVER THE PAST FEW
HOURS AS INLAND AIR TEMPERATURES HAVE FALLEN INTO THE LOWER 70S BUT
OFFSHORE AIR TEMPERATURES REMAIN IN THE UPPER 70S. THE LIGHT
EASTERLY SYNOPTIC WINDS WERE NOT ENOUGH TO KEEP THIS LANDBREEZE
PINNED TO THE BEACHES AND EVEN RADAR SEES THE LEADING EDGE OF THIS
COOLER AIR 10 MILES OFF THE COAST AND SPREADING SOUTHWARD. THIS
MESOSCALE WIND CIRCULATION IS GOING TO OVERWHELM THE SYNOPTIC WIND
FOR AT LEAST THE NEXT SEVERAL HOURS UNTIL THE COLD FRONT APPROACHES
LATE TONIGHT. THE 23Z NCEP PARALLEL VERSION OF THE HRRR CAPTURED
THIS EFFECT QUITE WELL...AND WAS USED AS THE BASIS FOR THE FORECAST
UPDATE THIS EVENING. PREVIOUS DISCUSSION FROM 730 PM FOLLOWS...

PREVIOUS FORECAST IS IN PRETTY GOOD SHAPE. THE ONLY CHANGES WERE TO
BACK WINDS AROUND MORE EAST TO NORTHEASTERLY EARLY THIS EVENING
BASED ON CURRENT OBSERVATIONS ALONG THE COAST. WIND DIRECTIONS
SHOULD VEER OFFSHORE EARLY TUESDAY MORNING AS PREVIOUSLY EXPECTED.
RADAR SHOWS AN AREA OF RAIN AND EMBEDDED T-STORMS JUST WEST OF
GEORGETOWN WHICH SHOULD AFFECT THE WATERS MAINLY SOUTH OF MYRTLE
BEACH OVER THE NEXT FEW HOURS. PREVIOUS DISCUSSION FROM 300 PM
FOLLOWS...

EASTERLY WINDS THROUGH THIS EVE WILL VEER AS
HIGH PRESSURE REORIENTS AND A TROUGH REACHES THE AREA TUE MORNING.
WINDS SHOULD TURN TO SOUTHERLY LATER THIS EVE AND THEN ALL THE WAY
AROUND TO A WNW DIRECTION BY MORNING. WIND SPEEDS WILL BE 10 KT OR
LESS THROUGH THE NIGHT. SEAS WILL GENERALLY BE 2 FT OR LESS. SEAS
WILL BUILD ON TUE AS SWELL FROM DISTANT HURRICANE EDOUARD BEGIN TO
REACH THE AREA.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 300 PM MONDAY...WINDS WILL BE VARIABLE ON TUES AS A WAVE OF
LOW PRESSURE DEVELOPS ALONG LINGERING FRONT TO THE SOUTH AS IT MAKES
ITS WAY BACK NORTH. AT THE SAME TIME A COLD FRONT WILL MOVE IN
FROM THE NORTHWEST. EVENTUALLY WINDS WILL TAKE ON A MORE
NORTHERLY FLOW. OVERALL WINDS WILL REMAIN LIGHT AND VARIABLE WITH
SEAS HOLDING BELOW 3 FT TUES. AS WINDS SHIFT TO THE E-NE THROUGH
WED EXPECT AN INCREASE UP TO 10 TO 15 KTS. THIS WILL COMBINE WITH
A LONG PERIOD UP TO 16 SEC EASTERLY SWELL TO PUSH SEAS UP TO 2 TO
4 FT WITH SOME 5 FTERS IN OUTER WATERS ON WED. THE LONGER PERIOD
EASTERLY SWELLS FROM EDOUARD WELL OUT IN THE ATLANTIC WATERS WILL
BEGIN TO ENTER THE LOCAL WATERS TUES AFTN PEAKING AROUND 16
SECONDS OVERNIGHT TUES.

LONG TERM /THURSDAY THROUGH SATURDAY/...
AS OF 300 PM MONDAY...A COMBINATION OF SCEC AND SCA HEADLINES WILL
LIKELY BE REQUIRED FOR MUCH IF NOT ALL OF THE PERIOD. HIGH
PRESSURE BUILDING DOWN THE COAST THU AND FRI WILL MAINTAIN PINCHED
GRADIENT WITH SPEEDS APPROACHING 20 KT AT TIMES. GRADIENT STARTS
TO RELAX A LITTLE SAT AS HIGH ELONGATES. HOWEVER...NORTHEAST FLOW
WILL REMAIN A SOLID 15 KT THROUGH THE END OF THE PERIOD. SEAS 3 TO
5 FT AT THE START OF THE PERIOD WILL BUILD TO 4 TO 7 FT THU NIGHT
OR FRI...MAINLY IN WATERS EXPOSED TO PROLONGED NORTHEAST FLOW.
SHELTERED WATERS MAY SEE AS LOW AS 2 FT. SEAS THU WILL BE A
COMBINATION OF THE BUILDING WIND WAVE AND SWELL FROM EDOUARD. SEAS
FRI AND SAT WILL BE WIND WAVE DOMINATED.

&&

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

MARINE...NONE.

&&

$$

NEAR TERM...RJD/TRA
SHORT TERM...RGZ
LONG TERM...III
AVIATION...BJR





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