Area Forecast Discussion
Issued by NWS Wilmington, NC-- Remove Highlighting --
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FXUS62 KILM 221735
Area Forecast Discussion
National Weather Service Wilmington NC
135 PM EDT FRI JUL 22 2016
Seasonable temperatures today will yield to hotter weather over the
weekend. The heat wave will last into the early or middle part of
next week all while rain chances remain minimal.
.NEAR TERM /THROUGH TONIGHT/...
As of 1000 AM Friday...Massive ridge across the middle of the
country responsible for the extreme heat through the Plains will
shift eastward today, with a piece of the ridge extending into the
Carolinas by this evening. As this ridge axis spreads east, a weak
mid-level low off the east coast will get driven SW, allowing for
heights to rise across the area. 850mb temps this morning on the
local U/A soundings were around 16C, and are progged to rise to 18-
19C, as a string of some very hot temperatures develop beginning
tonight. Highs today will rise into the low 90s, but dry air evident
on WV imagery will mix down this aftn/eve, and heat indices will
rise "only" into the upper 90s to around 100. Sea breeze convergence
may be enough to spawn a few isolated showers/tstms today, but very
dry mid-levels and a capping inversion will limit growth, and even
lightning will be difficult to achieve this aftn. The NSSL WRF has a
lot of convection today, but the much less robust NAM and HRRR are
preferred. Any convection will wane after dark, and a warm/humid
night is forecast with mins dropping into the mid 70s.
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 330 AM Friday...Will continue to hold onto the idea of less
than 20 POPS this fcst period, with mainly isolated tstorms along
the sea breeze and possibly tstorms drifting in from the west.
Even with the development and persistent Piedmont trof across the
central Carolinas, convection will be hard pressed to develop and
push through the convective lid. This aided by a subsidence
inversion aloft as well as warming temps aloft, ie. models
indicate 500MB temps only dropping to -4 degrees C, resulting in
limited lapse rates that are not very conducive for Tstorm
activity during this 2 day period. The central U.S. high
de-amplifies some and broadens it`s coverage across the entire
southern U.S. from coast to coast by Sunday. The ILM CWA will
remain under its umbrella.
Will have to watch the mid-level Low that develops offshore from
Florida late Saturday, with models pushing it onshore across the
central and northern Fl peninsula late Sunday. Not much of an
effect this far north illustrated by the models but bears watching
to see if it will increase convection probabilities late this
period as it does south of the ILM CWA.
Once again stayed closer to the GFS Mos guidance which shows
increasing temps, both max and min, during this period. In
addition, it slowly increases the sfc dewpoints to widespread
70s. Heat indices will be just shy of advisory criteria on
Saturday but Sunday should push to and above 105 degrees. Will
convey this within the hazardous weather outlook.
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 3 AM Friday... The long term will be characterized by very hot
and humid and generally rain-free conditions. The main questions
appear to be the degree and length of the heat and when meaningful
rain chances return. Early in the period upper level ridging will be
broad and covering much of the lower CONUS (though there may be a
weak upper low retrograding across FL/NE GOMEX). Locally this ridge
will bring hot conditions and suppress precipiation despite
increasing low level moisture in SW flow around Bermuda high and
east of piedmont troughiness. Heights are not as high nor are BL
temps as the last heat wave earlier this month as the core of the
heat appears to stay relegated out west. Even so we will see mid to
upper 90s and heat indices in the advisory realm through at least
Tuesday. Previously it appeared that this setup would start to break
down on Wednesday but now this may be a bit slower. And indeed some
guidance is showing a slight abating of the heat by then this is
likely due to the MOS increased bias towards climatology further out
in time. Have reduced the amount of "cooling" and increase in POPS
shown in previous forecast. This is especially supported by the 00z
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --As of 18Z...High confidence in VFR through the Valid TAF period.
Bermuda High will bring warm temps aloft and subsidence which
will help to squash any significant cumulus buildups. Thus, have
left any mention of showers and thunderstorms out of the valid TAF
period. Few to sct cumulus will continue into the eve, 3-4 kft
with cirrus above that. Once the heating of the day is through, we
only expect some cirrus late eve and overnight as the cumulus
clouds slowly dissipate. Southerly winds will be 10 kt or less
through the early eve and then less than 5 kt overnight.
EXTENDED OUTLOOK...Brief periods of MVFR/IFR from isolated
afternoon convection Sunday through Wednesday. Otherwise expect
-- End Changed Discussion --
NEAR TERM /THROUGH TONIGHT/...
As of 1000 AM Friday...Weak Bermuda high pressure will expand slowly
this aftn and evening, with winds becoming SE to SW tonight at
around 10 kts after being light and variable through this aftn. A
weak sea breeze will develop as well, but little change in overall
conditions in the near shore waters are expected. These light winds
will ensure the 3ft/9sec SE swell remains the dominant wave group,
producing 2-3 ft seas through tonight.
SHORT TERM /Saturday THROUGH SundAY NIGHT/...
As of 400 AM Friday...Ridging across the area from high pressure
centered well offshore from the SE States will persist thruout
this period. The Piedmont trof across the central Carolinas will
develop on Saturday and persist into early next week. The slightly
tightened sfc pg between the 2 wx features will result in sw
winds at 10 to occasionally 15 kt speeds each day. Models are now
indicating a weak mid-level low that develops offshore from the
Florida coast by Sunday and pushes it westward across the central
and north Florida coasts late Sunday. Some wind speed enhancement
across the local waters may result from this low late Saturday
Significant seas will run 2 to 3 ft with the 4 footers primarily
off Cape Fear Sat into Sun. The 2 foot ese ground swell will
mainly dominate the sig. seas, however, at times the 3 to 5 second
period locally produced wind driven waves may prevail over this
LONG TERM /MONDAY THROUGH TUESDAY/...
As of 3 AM Friday...Seasonable lack of variability in the
forecast for the long term. South to southwesterly flow well
established between the bermuda high and piedmont trough. If
anything changes at all it may be a slight lengthening of the
dominant period as the weak swell energy competes in the frequency
spectrum with the shorter period wind wave. Even so combined seas
leading to a dominant height of 2-3ft.