Area Forecast Discussion
Issued by NWS Wilmington, NC-- Remove Highlighting --
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FXUS62 KILM 231747
Area Forecast Discussion
National Weather Service Wilmington NC
147 PM EDT SAT JUL 23 2016
A ridge of high pressure will expand across the Carolinas bringing
increasingly hot and humid conditions through the weekend and
much of next week. Isolated showers and thunderstorms are possible
each afternoon, and heat advisories will likely be needed each day
.NEAR TERM /THROUGH TONIGHT/...
As of 1000 AM Saturday...Admittedly surprised at the amount of
convection this morning along the immediate eastern coast of the ILM
CWA. Convection remains in a slowly weakening state, but several
SMW`s and even some FLS`s have been issued due to strong storms
drifting southward. WV imagery does not show any strong impulses,
but there is a 50-60 kt upper jet off the coast into which the RRQ
is above the local area. This increased diffluence is likely
creating enough lift on residual outflow boundaries from last night
to spawn and enhance the tstms across the coast and coastal waters.
Fortunately, this jet will push south late this morning and upper
diffluence will wane, bringing an end to this round of storms.
However, these storms and their associated clouds will create a
complex forecast this morning as they leave residual outflows and
differential heating boundaries - both of which will likely serve as
focus for tstms again this aftn during peak heating. However, clouds
may linger long enough along the coast to affect the temperatures,
and have dropped highs along the immediate coast back into the upper
80s, while maintaining low 90s inland. Humidity will be on the rise
today, but enough dry mixing aloft will allow dewpoints to fall into
the low 70s, which will keep heat indices just below the 105
threshold today, more in the 100-103 range. This will still serve as
fuel for scattered aftn convection, and with PWATS about 0.25 inches
higher on the morning soundings than yesterday, feel the HRRR/NSSL
WRF depiction of more widespread sea breeze and piedmont trough will
be correct and have schc/low chc pop this aftn/eve.
Convection is forecast to wane once again diurnally, and do not see
any forcing to drive tstms nocturnally, so have walked pop back to
silent by midnight. Another warm night is forecast as Bermuda
ridging and SW flow persists. Expect mins falling to a degree or two
either side of 75.
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 400 AM SATURDAY...A HOT AND HUMID AIRMASS WILL CONTINUE TO
DOMINATE THE EASTERN CAROLINAS AS BROAD RIDGING PREVAILS ALOFT AND
THE BERMUDA HIGH PERSISTS AT THE SURFACE. BOTH DAYS WILL FEATURE
AFTERNOON HEAT INDEX VALUES EXCEEDING 100F, WITH A HEAT ADVISORY
QUITE POSSIBLE FOR SUNDAY. MUCH LIKE ON SATURDAY, VERY DRY AIR ALOFT
AND LACK OF STRONG FORCING WILL LIMIT CONVECTIVE COVERAGE TO
ISOLATED STORMS EACH DAY, PRIMARILY ALONG THE SEA BREEZE FRONT AND
ANY OTHER BOUNDRIES THAT HAPPEN BY.
.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 330 AM SATURDAY...OVERALL, BERMUDA HIGH AND PIEDMONT
TROUGH WILL BE THE MAIN PLAYERS IN FORECAST MUCH OF THE WEEK.
THEREFORE PERSISTENT S-SW WINDS WILL CONTINUE TO FEED WARM AND
MOIST AIR INTO THE AREA WITH POTENTIAL FOR LOCALIZED SHWRS/TSTMS
EACH DAY. THE UPPER RIDGE HELPING TO KEEP CONVECTION MORE LIMITED
WILL BREAK DOWN A BIT INTO MID WEEK AS A NORTHERN STREAM TROUGH
DIGS DOWN AS IT PUSHES A COLD FRONT SOUTH AND EAST. ALTHOUGH THE
FRONT DOES NOT LOOK LIKE IT WILL MAKE IT, IT WILL DROP SOUTH INTO
NORTH CAROLINA WHICH IN TURN MAY HELP TO INCREASE THE GRADIENT
FLOW AND LOCALIZED CONVERGENCE AROUND THE BERMUDA HIGH AND
PIEDMONT TROUGH INLAND. IT WILL ALSO TURN THE N-NE UPPER LEVEL
FLOW AROUND THE EAST SIDE OF RIDGE EXTENDING INTO THE CAROLINAS
FROM THE MIDWEST TO A MORE W-NW FLOW ALOFT, AROUND BASE OF
STRETCHED OUT UPPER TROUGH EXTENDING DOWN FROM THE NORTH. SHOULD
ALSO SEE A BIT MORE IN THE WAY OF CLOUDS AND CONVECTION REACHING
INTO AREA FROM UPSTREAM. DO NOT EXPECT MUCH IN THE WAY OF UPPER
LEVEL SUPPORT AS ATLANTIC RIDGE BUILDS QUICKLY BACK IN FROM THE
EAST BY THURS/FRI.
BY MID WEEK, THE INFLUENCE OF THE FRONT TO THE NORTH AND
RETREAT OF RIDGE EXTENDING IN FROM THE MIDWEST SHOULD INCREASE
CHC OF CONVECTION AND CLOUDS ACROSS THE AREA WHICH MAY SHAVE A FEW
DEGREES OFF THE MAX TEMPS. BUT RIDGE BUILDS BACK IN FROM ATLANTIC
AND OVERALL EXPECT VERY WARM TEMPS MOST OF THE WEEK. RIGHT NOW, IT
LOOKS LIKE HEAT ADVISORY CONDITIONS MAY EXIST OVER SEVERAL DAYS
.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --As of 18Z...Potential for MVFR in afternoon thunderstorms at KLBT
and KFLO. Otherwise, expect VFR through the valid TAF period at
all the terminals.
Scattered showers and thunderstorms are expected to develop along
the seabreeze and Piedmont trough as well as along residual
outflow boundaries left over from morning convection. The high
resolution models are showing the convection developing W of the
coastal terminals with only slight movement to the S. Thus, will
only include tempo for MVFR ceilings and visibilities at the
inland terminals 18-21z. Winds may briefly gust to 25 kt or
higher in slow moving thunderstorms, otherwise south winds will be
10 kt or less and up to 11 kt at KMYR and KCRE into early eve.
EXTENDED OUTLOOK...Isolated to scattered afternoon convection
Tuesday through Thursday may create periods of MVFR/IFR.
Otherwise expect VFR.
-- End Changed Discussion --
NEAR TERM /THROUGH TONIGHT/...
As of 1000 AM Saturday...Bermuda high will remain the dominant
feature through tonight as it expands slowly from the Atlantic. The
gradient will remain rather light, so SW winds will be only around
10 kts, rising to 10-15 kts tonight. A SE 9 sec swell will remain in
the spectrum but in a slowly deamplifying manner, as a SW wind wave
develops. Wave heights will remain at 2-3 ft through the near term,
but develop a slightly lower average period tonight.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 400 AM SATURDAY...HIGH PRESSURE OVER THE WESTERN ATLANTIC
WILL CONTINUE TO KEEP WINDS FROM THE SW AT 10 TO 15 KTS THROUGH
MUCH OF THE THE PERIOD, WITH SEAS OF 2 OR 3 FT.
LONG TERM /TUESDAY THROUGH WEDNESDAY/...
AS OF 330 AM SATURDAY...SOUTH TO SOUTHWEST WINDS WILL CONTINUE
AROUND THE BERMUDA HIGH. WINDS WILL GENERALLY STAY IN THE 10 TO
15 KT RANGE WITH A SLIGHT SPIKE IN LATE AFTN INTO EARLY EVE,
ENHANCED BY THE SEA BREEZE AND PIEDMONT TROUGH. BY LATE WED
GRADIENT WILL TIGHTEN AS COLD FRONT DROPS INTO NORTH CAROLINA.
THIS SHOULD INCREASE WINDS AND SEAS WED NIGHT. OVERALL EXPECT SEAS
2 TO 3 FT BUT INCREASING SLIGHTLY THROUGH WED UP TO 3 TO 4 FT AND
MAY SEE A FEW 5 FTERS IN OUTER WATERS IN STIFFER 15 TO 20 KT SW