Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 300233
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1032 PM EDT SAT AUG 29 2015

.SYNOPSIS...
MOISTURE FROM THE GULF OF MEXICO WILL BRING INCREASING
COVERAGE OF SHOWERS AND ISOLATED THUNDERSTORMS FOR THE UPCOMING
WEEK. THE REMNANTS OF ERIKA WILL MOVE INTO SOUTH FLORIDA SUNDAY AND
INTO THE EASTERN GULF OF MEXICO EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 PM SATURDAY...INFRARED SATELLITE IMAGERY SHOWS THE HIGH
LEVEL STREAM OF MOISTURE CONTINUES FROM THE SOUTH...WHILE AIRPORT
ASOS/AWOS OBS SHOW THE 3000-FOOT CLOUD DECK CONTINUES ALONG THE
GRAND STRAND AND AS FAR NORTH AS SOUTHPORT. TEMPERATURES ARE FALLING
INLINE WITH THE UPDATE EARLIER THIS EVENING AND ONLY A FEW TWEAKS
ARE NEEDED TO THE FORECAST. DISCUSSION FROM 730 PM FOLLOWS...

MULTILAYERED CLOUDS ACROSS THE AREA ARE IN AT LEAST THREE DISTINCT
GROUPS: SCATTERED 3000 FOOT CLOUDS WHERE MARINE MOISTURE
EXISTS...SCATTERED 6000 FOOT CLOUDS AT THE TOP OF THE DEEPER MIXED
LAYER...AND BROKEN 18000-30000 FOOT CLOUDS IN A VERY MOIST SOUTH-
SOUTHWEST FLOW ALOFT. THIS MOIST FLOW ALOFT IS KEY TO OUR FORECAST
OVER THE NEXT 12 HOURS AS IT WILL DEEPEN AND EVENTUALLY LEAD TO
SHOWERS CROSSING THE SANTEE RIVER INTO NORTHEASTERN SOUTH CAROLINA.
UNTIL THEN...PARTLY CLOUDY SKIES SHOULD TURN MOSTLY CLOUDY LATE.
VERY FEW CHANGES WERE NEEDED TO THE FORECAST WITH THIS EARLY-EVENING
UPDATE. DISCUSSION FROM 330 PM FOLLOWS...

UNUSUALLY STRONG UPPER LOW OVER THE NE/NORTH-CENTRAL GOMEX TO WEAKEN
AND START MOVING ASHORE IN FL PANHANDLE THROUGH THE PERIOD. MOISTURE
WILL THUS OVERSPREAD THE AREA FROM SW TO NE AND BE MOST PRONOUNCED
AT THE MID LEVELS. LOW LEVEL WILL LAG BEHIND BUT SHOULD STILL KICK
IN OVER SOUTHERN ZONES. SOME RAIN CHANCES WILL THUS RAMP UP LATE
TONIGHT OVER FAR SOUTHERN COUNTIES. IN THE VERY NEAR TERM SOME
MOISTURE MOVING OUT OF CHS CWA APPEARS TO BE DISSIPATING BEFORE
REACHING THE GROUND DUE TO LIGHT FORCING AND LARGE DEWPOINT
DEPRESSIONS. AS THE NIGHT WEARS ON A STRENGTHENING OF THE LIFT AND
LESSENING OF THE DEWPOINT WILL FAVOR SOME LIGHT RAIN BY THE END OF
THE PERIOD OVER ROUGHLY THE SOUTHERN HALF OF THE CWA.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 326 PM SATURDAY...KEY WEATHER CAPTION FOR SUNDAY AND MONDAY
REMAINS EARLY SUNDAY ARRIVAL...FOLLOWED BY PERSISTENCE...OF DEEP
COLUMN MOISTURE. WATER VAPOR PRESENTATIONS SHOW WELL THE UPPER
LOW PRESENTLY OVER THE NORTHERN GULF PUMPING VAPOR RICH AIR INTO
THE SE STATES. THIS GENERAL PATTERN WILL HOLD BOTH DAYS ALLOWING
THE ATMOSPHERE TO BECOME INCREASINGLY SWAMPY...WHILE OPENING A
WINDOW OF MIGRATION OF MESO-SCALE CONVECTIVE VORTICES NNE INTO
THE AREA. DIURNAL WARMING AND DIFFERENTIAL HEATING FROM AFTERNOON
CLOUD BREAKS SHOULD HELP SPUR RAIN SHOWERS AND A FEW STORMS BOTH
DAYS. DUE TO THE ELEVATED MOISTURE CONTENT AND CLOUDS...MAXIMUMS
WILL RUN NEAR TO JUST BELOW AVERAGE...WHILE MINIMUMS DROP NEAR TO
SLIGHTLY ABOVE NORMAL SINCE NOCTURNAL RADIATIONAL COOLING WILL BE
WEAKENED.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 326 PM SATURDAY...UNSETTLED WEATHER THROUGH MUCH OF THE
EXTENDED STILL LOOKS LIKELY AS TROPICAL MOISTURE STREAMS INTO
THE AREA.

RECENTLY DEGENERATED TROPICAL DEPRESSION ERIKA WILL MEANDER
INTO THE GULF OF MEXICO AND THEN SIT AND SPIN ACROSS THE GULF COAST
THROUGH MUCH OF NEXT WEEK. WHILE DIRECT IMPACTS WILL BE MINIMAL...A
DEEP MOISTURE FEED FROM THE CARIBBEAN WILL STREAM UP INTO THE
CAROLINAS BEGINNING LATE TUESDAY AND PERSISTING INTO FRIDAY. OBVIOUS
PWAT PLUME WILL ADVECT INTO THE CAROLINAS AND THEN MAINTAIN OR
REASSERT ITSELF THROUGH THE WEEK. AT THE SAME TIME...WEAK MID-LEVEL
IMPULSES SPUN OFF FROM THE RESIDUAL VORTICITY OF ERIKA WILL MOVE
OVERHEAD...AIDING LIFT EVEN THOUGH JET LEVEL SUPPORT IS MINIMAL.
HARD TO FIND ANY SPECIFIC SURFACE FORCING MECHANISMS...ALTHOUGH A
RESULTANT AND PIEDMONT TROUGH WILL LIKELY DEVELOP EACH AFTN...AND
EXPECT SCATTERED SHOWERS AND THUNDERSTORMS WITH PERIODS OF HEAVY
RAIN EACH DAY TUE...WED...THU...AND FRI...ALTHOUGH TUESDAY MAY BE
THE LEAST ACTIVE OF THE STRETCH. WPC HAS 1-3 INCHES OF QPF DURING
THIS TIME...BUT ISOLATED HIGHER TOTALS ARE POSSIBLE...FOCUSED MOSTLY
ACROSS SC WHICH MAY GET INTO THE HIGHEST PWAT AIR. BY SATURDAY A
SURGE OF DRIER AIR WILL PUSH INTO THE AREA BRINGING A REPRIEVE TO
THE ACTIVE WEATHER.

TEMPS TUESDAY WILL FEATURE SEASONABLE TO SLIGHTLY ABOVE
TEMPERATURES...BUT THE WED-FRI TIMEFRAME IS EXPECTED TO HAVE BELOW
NORMAL HIGHS WITH ABOVE NORMAL LOWS THANKS TO WIDESPREAD CLOUDS AND
RAIN. A RETURN TO SEASONABLE TEMPERATURES ARE ANTICIPATED BY
SATURDAY.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/... AS OF 00Z...EXPECT VFR
THROUGH THE VALID PERIOD WITH INCREASING CLOUD COVER OVERNIGHT AND
ISOLATED SHRA ON SUNDAY.

VFR WILL PREVAIL THROUGH OVERNIGHT WITH LIGHT WINDS. LATEST RADAR
REMAINS QUIET ACROSS LAND...WITH SATELLITE IMAGERY DEPICTING A
GRADUAL INCREASING TREND OF MAINLY HIGH CLOUDS ACROSS THE AREA.
EXPECT THIS TREND TO CONTINUE WELL OVERNIGHT AS FCST SOUNDINGS
SUPPORT INCREASING MOISTURE INTO THE AREA...GIVING WAY TO BKN/OVC
SKIES INTO THE EARLY MORNING HOURS. SOME GUIDANCE DOES SUGGESTS
POSSIBLE LOW CIGS WHICH COULD CREATE MVFR TOWARDS MORNING...BUT
CONFIDENCE IS LOW...THUS HAVE NOT INTRODUCED IN GOING FCST. ON
SUNDAY...ANTICIPATE ISOLATED SHOWERS THROUGHOUT THE DAY WITH LIGHT
NORTHEAST WINDS BECOMING EAST-SOUTHEAST AOB 10 KTS IN THE EARLY
AFTERNOON HOURS.

EXTENDED OUTLOOK...PREDOMINATELY VFR WITH ISOLATED TO SCATTERED
SHOWERS AND THUNDERSTORMS THROUGH THE EXTENDED. BRIEF MORNING
FOG/STRATUS IS ALSO EXPECTED EACH DAY.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...AS OF 1030 PM SATURDAY...WIND
DIRECTIONS ARE FROM THE NE OFFSHORE BUT VEER MORE EASTERLY AT THE
BEACHES. WITH THE EXCEPTION OF THE 18Z NAM ALL MODELS SHOW WINDS
BACKING TO THE NE EVEN ALONG THE COAST OVERNIGHT. VERY FEW CHANGES
WERE NEEDED TO THE FORECAST WITH THIS EARLY-EVENING UPDATE.
DISCUSSION FROM 330 PM FOLLOWS...

DROPPED THE SCEC A BIT EARLY AS SEAS HAVE DECREASED TO 3 FT AT NEAR
SHORE BUOY 41110 AND 4.5 FT ALL THE WAY OUT AT FRYING PAN SHOALS
BUOY 41035. CONDITIONS ARE STILL QUITE CHOPPY WITH EVEN THE LATTER
BUOY SHOWING A WAVE POWER PEAK AT JUST 5 SECONDS. THE HIGH TO OUR
NORTH IS FORECAST TO WEAKEN THIS EVENING AND THE LOCAL GRADIENT AND
RESULTING WINDS WILL DO THE SAME.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 326 PM SATURDAY...A VEERING WIND DIRECTION PROFILE EXPECTED
SUNDAY AND MONDAY AS HIGH PRESSURE MIGRATES OFFSHORE AND ALLOWS
A RETURN FLOW. THE FETCH LENGTH OF WINDS ONSHORE IS A LONG AND
SEAS WILL REMAIN ELEVATED RELATIVE TO THE LOCAL WIND SPEEDS.
SEAS EAST 3-4 FEET RUNNING EVERY 9-10 SECONDS ACCOMPANIED LIGHT
TO MODERATE CHOP. SHOWERS AND TSTMS WILL DOT THE 0-20NM MARINE
WATERS BOTH DAYS AND MARINERS SHOULD MAINTAIN RADAR UPDATES.

LONG TERM /TUESDAY THROUGH THURSDAY/...
AS OF 326 PM SATURDAY...HIGH PRESSURE OFFSHORE AND THE REMNANTS
OF ERIKA SOUTH OF FLORIDA WILL DRIVE AN EXTENDED PERIOD OF
EASTERLY WINDS ACROSS THE WATERS...WITH FLUCTUATIONS TO NE AND SE
POSSIBLE AS WELL. THE OVERALL GRADIENT WILL REMAIN WEAK
THOUGH...SO WIND SPEEDS ARE EXPECTED TO TOP OUT AROUND 10
KTS...BUT WILL BE BELOW THIS THRESHOLDS MOST OF THE PERIOD. THE
LONG PERIOD SWELL WILL ACTUALLY DECREASE THROUGH THIS PERIOD...NO
SWELL FROM ERIKA WILL ADVECT LOCALLY...SO THE WEAKENING SWELL
COMBINED WITH LIGHT WINDS WILL KEEP SEAS AT 1-3 FT THROUGH THE
PERIOD.

&&

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

&&

$$

NEAR TERM...MBB/TRA
SHORT TERM...MJC
LONG TERM...JDW
AVIATION...SGL


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