Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 152138 CCA
AFDILM

AREA FORECAST DISCUSSION...COR
NATIONAL WEATHER SERVICE WILMINGTON NC
331 PM EDT WED APR 15 2015

.SYNOPSIS...
HIGH PRESSURE WEDGING DOWN ACROSS THE CAROLINAS THROUGH TONIGHT
WILL KEEP CLOUDY COOL AND DAMP WEATHER OVERNIGHT. A WAVE OF LOW
PRESSURE WILL DEVELOP ALONG THE FRONT TO THE SOUTH TONIGHT AND
WILL TRACK NORTH JUST OFF THE CAROLINA COAST THROUGH FRIDAY. THE
LOW WILL THEN MOVE OFF TO THE EAST...LEAVING HIGH PRESSURE OVER THE
CAROLINAS BY THE WEEKEND. A WARM FRONT WILL MOVE NORTH THROUGH THE
CAROLINAS ON SUNDAY WITH A COLD FRONT TO FOLLOW MONDAY NIGHT INTO
TUESDAY.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
AS OF 300 PM WEDNESDAY...HIGH PRESSURE WEDGING IN ACROSS THE
CAROLINAS THROUGH TONIGHT WILL KEEP CLOUDY COOL AND DAMP WEATHER
OVERNIGHT. THE COOLER AIR BEHIND FRONT IS BEING OVERRUN BY WARMER
MOISTER AIR ALOFT LEAVING A STRATUS DECK AND LIGHT INTERMITTENT
DRIZZLE OR LIGHT PATCHY RAIN OVER MOST OF FORECAST AREA THIS
AFTERNOON. SOME DRYING NEAR THE SURFACE HAS LIFTED THE STRATUS
DECK IN SPOTS BUT SOUNDINGS AND MOISTURE PROFILES SHOW COLUMN
BECOMING SATURATED THIS EVENING. HRRR SHOWS LARGE AREA OF PCP TO
THE WEST ENTERING OUR WESTERN CWA BY 21Z OR 5PM BUT IT DIMINISHES
IN COVERAGE AS IT MOVES EAST TOWARD THE COAST. FOR NOW WILL
CONTINUE WITH FORECAST AS IS...LEAVING HIGHER POPS BUT LOW END
QPF.

ANY CONVECTION ALONG FRONT DRAPED FROM SOUTH CAROLINA...JUST SW
OF AREA TO THE NE INTO THE COASTAL WATERS WILL MOVE RAPIDLY OFF
TO THE NORTHEAST AS WINDS ALOFT REMAIN OUT OF THE SW ON THE BACK
SIDE OF RIDGE. THEREFORE COULD SEE AN ISOLATED THUNDERSTORM MAKE
IT NEAR OR INTO SOUTHERN PORTION OF CWA...MAINLY WILLIAMSBURG
COUNTY BUT AS FRONT MOVES SLOWLY SOUTH THROUGH THIS EVE EXPECT
CONVECTION TO SHIFT SOUTH AND DIE DOWN AS HEATING OF THE DAY CUTS
OFF.

THIS HIGH PRESSURE WILL BUILD AND WEDGE DOWN THROUGH THE CAROLINAS
THROUGH TONIGHT AS WAVE OF LOW PRESSURE DEVELOPS ALONG LINGERING
FRONT TO THE SOUTHEAST IN THE COASTAL WATERS OFF THE GA/SC COAST.
A TROUGH WILL EXTEND UP FROM THIS LOW PRESSURE TIGHTENING THE
GRADIENT FLOW OUT OF THE NORTHEAST THROUGH TONIGHT ENHANCING THE
SHALLOW COOL NE WINDS. EXPECT INCREASING ISENTROPIC LIFT TO
PRODUCE BETTER CHC OF RAIN BY THIS EVENING INTO TONIGHT WITH
COLUMN BEING SATURATED UP THROUGH H50. OVERALL EXPECT CLOUDY SKIES
AND PERIODS OF RAIN THROUGH AT LEAST THIS EVE BUT NOT CONFIDENT
AS TO THE INTENSITY. MODELS SHOW PERTURBATION IN THE MID TO UPPER
LEVEL FLOW MOVING THROUGH THIS EVENING AND THIS MAY ACT TO ENHANCE
LIFT AND PRODUCE SOME PERIODS OF MORE MODERATE RAIN.

TEMPS WILL HOLD IN THE MID 60S THROUGH THIS AFTERNOON BEHIND COLD
FRONT WITH EXTENSIVE CLOUD COVER AND CAA AS 850 TEMPS DROP DOWN
FROM 14C THIS MORNING TO 9C BY THURS MORNING. TEMPS WILL DROP INTO
THE UPPER 40S TO MID 50S TONIGHT IN CONTINUED CAA.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
AS OF 300 PM WEDNESDAY...THE FORECAST HAS BECOME NO LESS COMPLICATED
AND IN FACT...IN SOME RESPECTS...MODELS HAVE DIVERGED EVEN FURTHER
IN THE LAST 24 HOURS. THE GFS SOLUTION LOOKS VERY DIFFERENT FROM
PREVIOUS RUNS. THE NAM SOLUTION LOOKS SIMILAR TO PREVIOUS
THINKING...BUT THE PROGRESSION OF OFFSHORE LOW PRESSURE IS SLOWER
AND FURTHER EASTWARD THAN 24 HOURS AGO AND CERTAINLY MUCH STRONGER.
THE CANADIAN IS CONSIDERABLY SLOWER AND WEAKER THAN THE NAM AS IS
THE EUROPEAN...BUT BOTH DO CLOSE OFF LOW PRESSURE ALONG THE COAST OF
SOUTH CAROLINA. SLOWER SEEMS REASONABLE GIVEN THE STRENGTH OF HIGH
PRESSURE TO THE NORTH AND RESULTING WEDGE...THUS THE BEST WE CAN DO
AT THIS POINT IS TO GO ALONG WITH PERSISTENCE...BUT SLOW PROGRESSION.

WILL INCLUDE HIGHEST POPS THU ALONG THE COAST AND UP TO CATEGORICAL
THU MORNING ALONG THE CAPE FEAR COAST DUE TO STRENGTH OF ISENTROPIC
LIFT COUPLED WITH THE LIFT ASSOCIATED WITH LOW PRESSURE/TROUGH. WILL
THEN TREND POPS LOWER THU AFTERNOON AND NIGHT FROM SW TO NE WITH A
LINGERING RISK ALONG THE CAPE FEAR COAST FRI MORNING. GIVEN
PROXIMITY OF COASTAL TROUGH AND ELEVATED INSTABILITY...WILL INCLUDE
MENTION OF THUNDER FOR PORTIONS OF THE FORECAST AREA.

THE MOISTURE PROFILES DRY OUT CONSIDERABLY AS A RIDGE OF HIGH
PRESSURE ALOFT BUILDS TO THE COAST FROM THE WEST TOWARD THE END OF
THE PERIOD. WILL FINALLY DROP POPS BELOW THRESHOLD FRI AFTERNOON AND
NIGHT...EVEN ALONG THE SEABREEZE BOUNDARY.

BELOW NORMAL HIGH TEMPS ARE EXPECTED AGAIN ON THU AS WEDGE KEEPS LOW-
LEVEL MOISTURE TRAPPED BENEATH INVERSION. HIGHS WILL ONLY BE IN THE
LOWER TO MID 60S. DEVELOPING SUNSHINE ON FRI SHOULD ALLOW TEMPS TO
RETURN TO MORE SEASONABLE LEVELS...LOW AND MID 70S. LOWS THIS PERIOD
WILL BE MAINLY IN THE 50S.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 300 PM WEDNESDAY...GUIDANCE HAS SHIFTED PRETTY DRAMATICALLY
FROM JUST YESTERDAY...LEADING TO ENHANCED UNCERTAINTY DURING THE
EXTENDED. LARGE CLOSED LOW ACROSS THE SOUTHWEST WILL ONLY VERY
SLOWLY FILL AND EJECT TO THE NORTHEAST THROUGH THE WEEKEND...PHASING
WITH A DEEPENING NORTHERN STREAM CUTOFF LOW ACROSS THE GREAT LAKES
LATE MONDAY. THIS FEATURE WILL THEN AMPLIFY AND STALL ACROSS THE
GREAT LAKES THROUGH THE MIDDLE OF NEXT WEEK...PRODUCING 500MB
HEIGHTS OF -2 TO -3 SD`S BELOW CLIMO ACROSS THE NORTHEAST AND INTO
THE MID-ATLANTIC.

INITIALLY THE EXTENDED WILL BE WARM AND PLEASANT. SATURDAY IS
SHAPING UP TO BE A GORGEOUS DAY LOCALLY...WITH HIGHS ABOVE CLIMO AND
A LOT OF SUNSHINE. MOISTURE RETURNS SUNDAY IN A PRE-FRONTAL AIR MASS
WHICH WILL CONTINUE INTO MONDAY AHEAD OF A COLD FRONT. SUNDAY AND
MONDAY WILL BOTH FEATURE ABOVE CLIMO TEMPS...BUT WITH INCREASING
RAIN CHANCES AHEAD OF THE COLD FRONT. ATTM THE FRONT DOES NOT LOOK
TO BE STRONGLY FORCED SO WIDESPREAD CONVECTION IS NOT ANTICIPATED
MONDAY EVENING WITH THE FROPA. COOLER HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT FOR TUE/WED OF NEXT WEEK WITH TEMPS RETURNING TO
SEASONABLE LEVELS.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AS OF 18Z...CONVECTION MAKING HEADWAY NORTHWARD AND COULD AFFECT
THE MYRTLES FOR THE NEXT HOUR OR SO WITH LOWER VISIBILITIES IN THE
HEAVIER SHOWERS. WEDGE FIRMLY IN PLACE WITH A STRONG INVERSION
JUST OFF THE DECK. CEILINGS HAVE LIFTED IN PLACES TO MVFR...BUT
EXPECT ALL TERMINALS TO SEE IFR CEILINGS AGAIN THIS EVENING.
OVERNIGHT...NOT MUCH CHANGE HOWEVER THE COASTAL TERMINALS WILL SEE
GUSTY WINDS AS THE GRADIENT TIGHTENS WITH THE CYCLOGENESIS.
THURSDAY...CONTINUED IFR CONDITIONS WITH EAST NORTHEAST WINDS AND
INTERMITTENT LIGHT TO MODERATE RAIN.

EXTENDED OUTLOOK...PREDOMINATELY IFR CONDITIONS ARE EXPECTED INTO
EARLY FRIDAY MORNING WITH THE WEDGE. IMPROVING CONDITIONS DURING THE
DAY FRI. DETERIORATING CONDITIONS AGAIN SATURDAY NIGHT THROUGH
SUNDAY WITH A SLOW MOVING FRONT. SLIGHT CHANCE FOR SHOWERS MONDAY.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 300 PM WEDNESDAY...NE WINDS WILL INCREASE THROUGH THIS
AFTERNOON INTO TONIGHT AS PINCHED GRADIENT DEVELOPS BETWEEN WEDGE
OF HIGH PRESSURE BUILDING DOWN INTO THE CAROLINAS AND TROUGH OF
LOW PRESSURE DEVELOPING OFF THE SOUTHEAST COAST. OVERALL EXPECT
INCREASING WINDS AND SEAS THROUGH THIS EVENING INTO THE OVERNIGHT
HOURS. A SMALL CRAFT ADVISORY IS EFFECT STARTING THIS EVENING IN
AS NE WINDS OF 20 TO 25 KTS AND 4 TO 7 FT SEAS DEVELOP INTO THE
OVERNIGHT HOURS.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 PM WEDNESDAY...ONGOING SMALL CRAFT ADVISORY CONDITIONS ARE
EXPECTED AT THE BEGINNING OF THE PERIOD AS LOW PRESSURE MOVES UP THE
SOUTHEAST COAST. THE PRESSURE GRADIENT BETWEEN DEVELOPING LOW
PRESSURE AND THE STRONG HIGH TO THE NORTH WILL ALLOW A TIGHT
PRESSURE GRADIENT TO PERSIST INTO THU AND THIS IS WHEN WE EXPECT THE
STRONGEST WINDS AND HIGHEST SEAS...UP TO 20 TO 30 KT...HIGHEST
NORTHERN WATERS AND SEAS UP TO 5 TO 8 FT THROUGHOUT. AS THE PRESSURE
GRADIENT SLACKENS AND LOW PRESSURE MOVES TO OUR N...WINDS AND SEAS
WILL SUBSIDE THU NIGHT AND FRI WITH THIS TREND PERSISTING INTO FRI
NIGHT. ENE WINDS THU WILL BACK TO NE THU NIGHT WITH NNE TO NE
WINDS THEN PERSISTING THROUGH THE END OF THE PERIOD.

LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 300 PM WEDNESDAY...HIGH PRESSURE WILL BUILD DOWN THE COAST AND
THEN MOVE OFFSHORE SATURDAY...CREATING A WEAK PRESSURE GRADIENT AND
WINDS SHIFTING FROM NE EARLY...TO E/SE LATE. WINDS SPEEDS THEN
STEADILY INCREASE SUNDAY AS THE GRADIENT STARTS TO PINCH AHEAD OF AN
APPROACHING COLD FRONT...BECOMING S/SW AT AROUND 15 KTS MOST OF
SUNDAY...AND THEN SW AT 15-20 KTS ON MONDAY DIRECTLY AHEAD OF THE
FROPA. COLD FRONT WILL CROSS THE WATERS AT THE VERY END OF THE
PERIOD WITH A WIND SHIFT TO THE NW AT 10-15 KTS. ALTHOUGH A WEAK SE
GROUND SWELL WILL BE PRESENT IN THE SPECTRUM DURING THE
EXTENDED...MUCH OF THE WAVE AMPLITUDE WILL BE FORMED VIA WIND
WAVES...AND SEAS WILL BE 2-3 FT SATURDAY...BUILDING TO 3-5 FT SUNDAY
AND MONDAY AHEAD OF THE COLD FRONT.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 2 AM EDT FRIDAY
     FOR AMZ250-252-254-256.

&&

$$
NEAR TERM...RGZ
SHORT TERM...RJD
LONG TERM...JDW
AVIATION...RGZ/DL



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