Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 300227
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1027 PM EDT TUE JUL 29 2014

.SYNOPSIS...
DRIER AND COOLER AIR WILL SETTLE INTO THE REGION AS CANADIAN HIGH
PRESSURE MIGRATES INTO THE AREA THIS WEEK. A COASTAL FRONT WILL
LIFT BACK NORTHWARD ACROSS OUR AREA THIS WEEKEND...BRINGING
INCREASED RAIN CHANCES FRIDAY THROUGH MONDAY.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AS OF 1030 PM TUESDAY...ACROSS EASTERN PENDER AND NEW HANOVER
COUNTIES THIS WAS THE LITTLE AIRMASS THAT COULD!  DESPITE SHALLOW
INSTABILITY ONLY AMOUNTING TO 1000 J/KG...SHOWERS OVER THE PAST
THREE HOURS DROPPED 0.59 INCHES AT THE ILM AIRPORT...0.27 INCHES IN
THE KINGS GRANT NEIGHBORHOOD A FEW MILES TO THE EAST...0.25 INCHES
IN SURF CITY...AND 0.17 INCHES IN WRIGHTSVILLE BEACH. WET GROUND HAS
PRIMED THIS AREA FOR SOME PATCHY FOG OVERNIGHT AS WINDS BECOME CALM.
OTHERWISE NO SIGNIFICANT CHANGES ARE NEEDED TO THE FORECAST.
PREVIOUS DISCUSSION FROM 730 PM FOLLOWS...

AN ANOMALOUSLY DEEP UPPER TROUGH COVERS THE EASTERN THIRD OF NORTH
AMERICA. 500 MB HEIGHTS ARE THREE STANDARD DEVIATIONS BELOW THE
SEASONAL MEAN WITH 850 MB TEMPS AT -2 STANDARD DEVIATIONS.

STEEP LAPSE RATES FROM THE SURFACE UP THROUGH 800 MB PRODUCED A
MODERATE CUMULUS FIELD ACROSS THE CAROLINAS THIS AFTERNOON. A
SUBSIDENCE INVERSION AROUND 700 EFFECTIVELY CAPPED OFF THESE CUMULUS
CLOUDS...AT LEAST UP UNTIL A COUPLE HOURS AGO. WHERE BOUNDARY LAYER
MOISTURE HAS BEEN ENHANCED BY SEABREEZE WINDS BLOWING ONSHORE
ISOLATED SHOWERS HAVE DEVELOPED ACROSS COASTAL PORTIONS OF SOUTHEAST
NC FROM CAPE FEAR NORTHWARD. THE 21Z RUC SHOWS UNCAPPED INSTABILITY
ON THE ORDER OF 500-1000 J/KG ALONG AND EAST OF THE SEABREEZE
BOUNDARY. THIS CONVECTIVE ACTIVITY SHOULD SETTLE DOWN IN THE NEXT
COUPLE OF HOURS AS THE BOUNDARY LAYER COOLS AND INSTABILITY
SUBSIDES...HOWEVER WITH STEEP LAPSE RATES REMAINING UNDER THE
SUBSIDENCE INVERSION WE WILL PROBABLY KEEP AT LEAST SCATTERED
CUMULUS OR LOW ALTOCUMULUS THROUGH THE NIGHT.

WEAK LOW PRESSURE HAS DEVELOPED ALONG LAST NIGHT`S COLD FRONT...NOW
LOCATED 150 MILES OFFSHORE. HIGH PRESSURE CENTERED OVER THE CENTRAL
PLAINS STATES WILL BUILD EASTWARD...WITH LIGHT NORTH WINDS BETWEEN
THESE TWO SYSTEMS DRAINING UNSEASONABLY COOL DRY AIR SOUTHWARD INTO
THE CAROLINAS. LOWS SHOULD REACH THE MID TO UPPER 60S AWAY FROM THE
BEACHES TONIGHT. THIS IS STILL SEVERAL DEGREES ABOVE RECORD LOWS FOR
WEDNESDAY MORNING WHICH INCLUDE:

 61 IN WILMINGTON...1914
 63 IN FLORENCE...1997
 62 AT NORTH MYRTLE BEACH...1954.

(NOTE: THESE RECORDS ARE CORRECTED FROM THE 300 PM DISCUSSION)

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 300 PM TUESDAY...A FLATTENED 500 MB TROUGH WILL REMAIN PARKED
OVER THE EASTERN U.S. ON WED...WHILE AT THE SURFACE BROAD HIGH
PRESSURE WILL BE POSITIONED TO OUR WEST. FORECAST SOUNDINGS REMAIN
FAIRLY DRY FOR WED...ESPECIALLY ABOVE ABOUT 700 MB. AS THE TROUGH
AXIS RETROGRADES A BIT ON THU...PWATS INCREASE IN THE AFTN HOURS
WITH THE MID LEVEL FLOW BECOMING MORE SOUTHWESTERLY. THE REMNANT
FRONT/SFC TROUGH OFFSHORE MAY ALSO DRIFT BACK TOWARD THE COAST LATE
THU...FURTHER MOISTENING THE COLUMN WITH INCREASING EASTERLY LOW
LEVEL WINDS. A FEW SPRINKLES CANNOT BE RULED OUT DURING THE DAY
WED...BUT WILL MAINTAIN INHERITED DRY FORECAST ATTM GIVEN THE LACK
OF A SEA BREEZE DUE TO WEAK LAND/SEA TEMP CONTRASTS. THU SEEMS LIKE
THE BETTER CANDIDATE FOR ISOLATED SHOWERS/TSTMS...ESPECIALLY LATE IN
THE PERIOD. HAVE SLOWLY RAMPED UP POPS THU AFTN INTO THE OVERNIGHT
HOURS...GENERALLY SLIGHT CHC WITH SOME CHC POPS ALONG THE COAST.

TEMPS WILL REMAIN BELOW NORMAL THANKS TO THE PERSISTENT UPPER TROUGH
AND EASTERLY SFC FLOW. HIGHS WILL BE IN THE MID TO UPPER 80S BOTH
DAYS. WED NIGHT LOWS WILL FALL INTO THE MID 60S INLAND AND UPPER 60S
ALONG THE COAST. INCREASING CLOUDS THU NIGHT WILL KEEP LOWS A FEW
DEGREES WARMER...GENERALLY UPPER 60S TO LOWER 70S.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 3 PM TUESDAY...FRIDAY THROUGH SUNDAY FINALLY SEES THE DEEP
CUTOFF NORTH OF THE GREAT LAKES OPEN UP AND RETREAT. DEEP
TROUGHINESS LINGERS SOUTH OF THIS FEATURE HOWEVER AS THE FLOW SPLITS
WITH SOUTHERN BRANCH TROUGH COVERING MUCH OF THE OHIO AND MID/UPPER
MS VALLEY REGIONS. HERE IN THE CAROLINAS THIS LEADS TO A DEEP
MOISTURE-LADEN SOUTHWESTERLY FLOW THAT SHOULD LEAVE THE AREA PRONE
TO AT LEAST A CLIMATOLOGICAL SCATTERING OF DIURNAL CONVECTION.
DURING THIS SAME TIME FRAME A WARM FRONT WILL SLOWLY RETROGRADE FROM
A NEARLY COASTAL POSITION ON FRIDAY TO WEST OF THE AREA/CENTRAL
CAROLINAS BY SUNDAY. THIS WILL BOLSTER THE LL MOISTURE AND SHOULD
YIELD AND UPTICK IN CONVECTIVE COVERAGE AS THE WEEKEND TRANSPIRES.
THE SURFACE BOUNDARY BECOMES ILL-DEFINED IF NOT WASHED OUT
ALTOGETHER BY MONDAY. THIS COULD LEAD TO A SMALL DOWNWARD TREND IN
RAIN CHANCES...BUT WOULD LIKE TO BE CAUTIOUS WITH OPTIMISM AS THERE
WILL LIKELY BE OUTFLOW AND DIFFERENTIAL HEATING BOUNDARIES TO STILL
SERVE AS CONVECTIVE INITIATION FOCI. THE DEEP LAYER SWRLY FLOW WILL
ALSO BE WEAKENING. THE BETTER BET FOR A SLIGHTLY QUIETER FORECAST
COMES ON TUESDAY WHEN THE MID LEVEL TROUGHINESS NO LONGER HAS ANY
LOCAL EFFECTS AND THE FLOW VEERS TO MORE WESTERLY.

&&

.AVIATION /00Z TUESDAY THROUGH SUNDAY/...
AS OF 00Z...SOME MODERATE CU IS WANING IN THE DYING LIGHT. HIGH
CONFIDENCE FOR VFR CONDITIONS THROUGH THE FORECAST PERIOD. LIGHT
NORTHEAST WINDS TONIGHT AFTER THE SOUTHEAST SEA BREEZE DIES IN AN
HOUR OR SO. SCATTERED SKIES WEDNESDAY WITH CONTINUED NORTHEAST
FLOW...SWITCHING AGAIN TO THE EAST SOUTHEAST WITH THE RESULTANT IN
THE AFTERNOON.

EXTENDED OUTLOOK...MVFR VSBYS DUE TO MORNING FOG FRIDAY AND
SATURDAY...OTHERWISE VFR. CHANCE MAINLY AFTN/EVNG SHRA/ISOLATED
TSRA THROUGH THE PERIOD.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 PM WEDNESDAY...LAST OF THE SHOWERS NORTH OF CAPE FEAR
HAVE CLEARED THE COAST AND ARE MOVING OFFSHORE. THIS ACTIVITY BECAME
FAIRLY WIDESPREAD AN HOUR AGO BUT TRENDS SUGGEST IT SHOULD DISSIPATE
IN THE NEXT HOUR. NORTHEAST WIND DIRECTIONS ARE ALREADY ESTABLISHED
DOWN TO CAPE FEAR...AND WINDS SHOULD BACK FROM THE SOUTHEAST TO THE
EAST AND NORTHEAST AFTER MIDNIGHT ALONG THE SC COAST. PREVIOUS
DISCUSSION FROM 730 PM FOLLOWS...

WEAK LOW PRESSURE HAS DEVELOPED ABOUT 150 MILES OFFSHORE ALONG THE
COLD FRONT THAT MOVED THROUGH THE AREA LAST NIGHT. THIS LOW IN
COMBINATION WITH HIGH PRESSURE IN THE CENTRAL PLAINS SHOULD GIVE US
A PREVAILING EAST TO NORTHEAST WIND TONIGHT. THIS AFTERNOON`S
SEABREEZE CIRCULATION AND ITS SOUTHEAST WINDS SHOULD DIE AWAY IN THE
NEXT FEW HOURS.

SEAS CONSIST LARGELY OF A 1-2 FOOT 9 SECOND SOUTHEAST SWELL...PLUS
SHORTER PERIOD WIND WAVES PRODUCED BY WINDS CLOSER TO SHORE.
COMBINED SEAS ARE AVERAGING 2-3 FEET...HIGHEST NEAR AND NORTH OF
CAPE FEAR WHERE THE SWELL IS HAVING THE EASIEST TIME MAKING IT INTO
THE NEARSHORE WATERS.

RADAR REVEALS SEVERAL SHOWERS NORTH OF CAPE FEAR DEVELOPING NEAR AND
JUST EAST OF THE SEABREEZE BOUNDARY. ADDITIONAL SLOW-MOVING SHOWERS
MAY DEVELOP THROUGH THE EARLY EVENING HOURS...BUT DRY WEATHER WILL
PREVAIL OVERNIGHT.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 300 PM TUESDAY...NORTHEAST TO EAST WINDS AROUND 10 KTS WILL
PREVAIL THROUGH THE PERIOD AS SFC HIGH PRESSURE TO OUR NORTHWEST
GRADUALLY MOVES OFFSHORE DURING THU. SEAS WILL REMAIN IN THE 2-3 FT
RANGE BOTH DAYS...HIGHEST ACROSS AMZ250 WHERE SEAS WILL BECOME AROUND
3 FT ON THU. AS THE REMNANT FRONT/SFC TROUGH OFFSHORE LIFTS BACK
TOWARD THE COAST...SHOWER/TSTM CHANCES OVER THE WATERS INCREASE
OVERNIGHT THU.

LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 3 PM TUESDAY...WITH A BOUNDARY STALLED VERY CLOSE TO IF NOT
RIGHT OVER THE COAST ON FRIDAY THE WATERS WILL EXPERIENCE A LIGHT
ONSHORE FLOW. ONSHORE WINDS ACT TO LESSEN THE GRADIENT IN WAVE
HEIGHT ACROSS THE 20NM WIDTH OF THE FORECAST ZONES SO A GENERAL 3 FT
SEA STATE EXPECTED...A COMBINATION OF THE WIND WAVE AND A LIGHT
SOUTHEASTERLY SWELL. OVER THE WEEKEND THE BOUNDARY WILL SLOWLY DRAW
INLAND...REACHING THE CENTRAL CAROLINAS BY SUNDAY. THE ONLY REAL
LOCAL EFFECT WILL BE A VEERING TO SE OR EVEN S AT TIMES. LAND/SEA
TEMPERATURE DIFFERENCES WILL BE MINIMAL FOR THE TIME OF YEAR AND NO
APPRECIABLE SEA BREEZE EXPECTED TO PRODUCE THE NORMAL NEARSHORE WIND
INCREASE AND CHOP.

&&

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

&&

$$

NEAR TERM...TRA
SHORT TERM...BJR
LONG TERM...MBB
AVIATION...43





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