Area Forecast Discussion
Issued by NWS Wilmington, NC-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS62 KILM 261132
Area Forecast Discussion
National Weather Service Wilmington NC
732 AM EDT TUE JUL 26 2016
High pressure will expand across the Carolinas, maintaining
uncomfortable levels of heat and humidity this week. Isolated to
scattered showers and thunderstorms are possible each afternoon
and evening. The chances increase heading into early next week.
.NEAR TERM /THROUGH TONIGHT/...
As of 645 AM Tuesday...Ridging surface and aloft will be the main
players across the ILM CWA this period. Expect the diurnally
driven sea breeze to develop by noon, and progress inland this
afternoon and early evening. The low and mid levels of the
atmosphere remain quite warm, ie. 500 mb progged temps will be -3
to -4 degrees Celsius. This will create a convective lid across
the area basically preventing any thunderstorm development. Even
the forcing along the sea breeze will have trouble breaking
through this lid. As a result, have kept pops below the isolated
threshold of 15 percent. Even if an isolated storm develops, it
will not last long in this environment. The low level nocturnal
jet will develop this evening and peak during the pre-dawn Wed
hours. The mixing in the low levels should prevent fog development
Used a consensus of the GFS and NAM mos guidance since both are at
the top of the max/min temp verification here at ILM. Heat
advisory criteria will be met for the majority of the ILM CWA
today. In addition, the forecast worked out to where heat indices
will begin exceeding thresholds a bit earlier. As a result, will
change the start time of the advisory from 2 pm to noon.
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 400 AM Tuesday...Ridging aloft and at the sfc will dominate
the weather across the ILM CWA this period. The upper ridging and
warm temps aloft will limit lapse rates and maintain the
convective lid across the fa this period. Some weakness in this
lid could occur especially on Thu, in which the sea breeze could
end up with a few or more than a few isolated storms along it.
The sfc ridge axis from the high`s center well offshore, will
shunt slightly southward this period. This will result in sw-wsw
winds on Wed and mainly wsw-w winds on Thu. This westerly
direction may also result in isolated storm(s) drifting into the
ILM CWA from CAE or RAH CWAs. The sfc pg will remain semi-
tightened this period, resulting with active overnight winds
around 5 mph, and 5 to 15 mph, during the midday thru early
evening hrs. The winds associated with the inland progressing sea
breeze will keep speeds in the higher end of this range. Wind
gusts of 20+ mph will occur along the immediate coast at the
height of the sea breeze and could approach these gusts again at
the coast during the overnight period due to the mixing of the
nocturnal low level jet to the sfc. Basically, sfc mixing will
keep fog formation to a minimum at best. Used a consensus of the
GFS and NAM mos guidance for daily max/min temps due to their
better performance verification-wise as of late. With mid to upper
90s for highs and sfc dewpoints slightly increasing to the 75 to
80 degree range, the late morning thru early evening heat indices
should easily surpass heat advisory thresholds and is currently
advertised in the Hazardous Weather Outlook.
.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 330 AM Tuesday...Atlantic ridge of high pressure will slip
farther to the south and east and weaken into early next week as
trough moves east from the mississippi valley. This will allow h5
heights to slip and temps to lower slightly, as well as, reduce
the subsidence and dry air aloft giving way to increased chance of
shwrs/tstms heading into the latter half of the weekend and early
Initially expect only isolated convection along sea breeze front
with main convective development farther west along piedmont
trough and farther north along lingering frontal boundary on Fri.
The persistent moist SW flow around atlantic high will bring pcp
water values up above 2 inches over the weekend into early next
week. This will combine with enhanced lift as mid to upper trough
moves east into the Carolinas to produce stronger and more
widespread shwr/tstm activity...especially Sun/Mon. By Late Mon,
it looks like front/trough will move east into local forecast
Temperatures in the mid 90s on Fri into Sat will drop down
slowly, aided by lowering h5 heights and increasing clouds and
convection into early next week. Heat indices will remain high,
remaining between 100 and 105 most days.
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --As of 12Z...Except for low confidence brief MVFR cigs at the coastal
terminals early this morning as the sea breeze boundary develops,
VFR expected through this 24 hour TAF valid period. Light SW-WSW
winds will back to the S-SW as the morning progresses, highest
speeds around 15 KT in the afternoon at the coastal terminals. A
subsidence inversion will keep any convection isolated at best.
Even if development occurs activity will not last long. Winds
will slowly veer TO SW-WSW and decrease this evening.
EXTENDED OUTLOOK...Isolated to scattered afternoon convection
through Saturday may create periods of MVFR/IFR. Otherwise expect
-- End Changed Discussion --
NEAR TERM /THROUGH TONIGHT/...
As of 645 AM Tuesday...High pressure will ridge across the area
waters from the high`s center well offshore from the Southeast
U.S. States. The Carolinas trof...aka Piedmont...will orient
itself across the western Carolinas. Enough of a sfc pg will
result across the ILM waters, producing SW 10 to 15 kt winds.
Nearshore this afternoon and evening, winds will become
temporarily SSW at 10 to 20 kt due to the inland progressing sea
breeze. Significant seas will range between 2 and 3 ft today, and
up to 4 ft for the ILM NC Waters late tonight. This due to SW
winds around 15 kt with gusts 20+ kt across all waters due to the
mixing of the low level SW jet to the ocean sfc.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 330 AM Tuesday...The ridging from the sfc high will be
suppressed slightly to the south of its current location this
period. This will increase the westerly component in the wind
directions during this period. The sfc pg will also tighten
slightly as a result of the ridge axis oriented further south.
The daily inland progression of the sea breeze may be limited due
to the increase in the westerly component of the winds...and
speeds. A daily nocturnal low level jet will develop each evening
and peak during the pre-dawn hrs. Overall, looking at sw-wsw winds
at 10 to 15 kt except up to 20 kt during the overnight
periods...and...nearshore during the peak of the sea breeze
cycle, from the late afternoon thru mid evening hrs. Significant
seas will run 2 to 4 ft with the 4 footers primarily occurring
during the overnight periods and possibly nearshore in the
aftn/mid evening. Convection, if any, will mainly be isolated.
LONG TERM /FRIDAY THROUGH SATURDAY/...
As of 330 AM Tuesday...South to SW flow will continue between
Bermuda High pressure and Piedmont trough inland. Winds will
basically remain between 10 and 15 kts, but should become gusty
each aftn due to sea breeze and may increase again overnight in
nocturnal jet. This will produce a spike in seas late aftn into
the evening with overall seas remaining in the 2 to 4 ft range.
SC...Heat Advisory from noon today to 7 PM EDT this evening for
NC...Heat Advisory from noon today to 7 PM EDT this evening for