Area Forecast Discussion
Issued by NWS Wilmington, NC-- Remove Highlighting --
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FXUS62 KILM 271136
Area Forecast Discussion
National Weather Service Wilmington NC
736 AM EDT WED JUL 27 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 635 AM Wednesday...Will go with a persistence type
forecast, using yesterday as the model day to work off of. Near
term models such as the Hi-Res WRF, the HRRR, and the RAP all
indicate a repeat of yesterday with only isolated convection
possible along the sea breeze...and just north of the ILM CWA
running from RAH to MHX CWAs. The outlier of those 3 models is the
hi-res WRF where it paints a possible cluster of storms along the
ILM to FAY line. At this point it seems too far south given the
strength of the upper ridge and the strength of the convective lid
and continued warm temps in the low and mid levels. Of note for
the ILM NC CWA, various model sounding data indicate 500 mb temps
slightly decrease to between -3 to -4.5 degrees C this aftn and
evening...and the subsidence inversion is not as strong or
prevalent. Again, this is mainly for the ILM NC portions. As
mentioned b4, will continue with persistence from yesterday and
not jump on the WRF bandwagon to increase POPs as of yet.
For max temps, stayed closer to the GFS Mos guidance and for
lows, stayed closer to the NAM Mos guidance. This based on the
latest verification for the ILM CWA. The mid and upper 90s for
Highs combined with low to mid 70s dewpoints yield heat indices in
the 105 to 109 degree range. Even after the sea breeze pushes
thru, temps may drop to around 90 but dewpoints will increase to
the upper 70s. This will not improve the Heat indices, in fact, it
may actually make them worse. The Heat Advisory will run from 11
AM to 7 PM today.
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 415 AM Wednesday...Ridging aloft and at the sfc will
dominate once again the ILM CWA this period with the beginnings of
this ridge breaking down late Friday. The upper ridging and warm
temps aloft will again limit lapse rates and maintain a convective
lid across the fa this period, with weaknesses in this lid
occurring by fri. Models indicate some decrease in progged 500mb
temps to -5 degrees C or a degree lower by late Fri. However, the
GFS still indicates some remaining decent subsidence aloft and
associated inversion during Fri. Overall, will highlight a low
chance POP across the entire ILM CWA on Fri, not just along and
ahead of the sea breeze which is highlighted on Thursday.
Heat advisories will be needed for both Thu and Fri. There is a
remote possibility that Heat Indices could breach Excessive Heat
Warning criteria, which are Heat indices 110 degrees or higher.
For daily max temps, stayed closer to the GFS Mos guidance. And
for daily Min temps, stayed closer to the NAM Mos guidance. This
is a carry over from the Near term forecast with the reasoning
remaining the same.
Each day during the late evening thru pre-dawn hours, a low level
SW to WSW 20 to 30 kt jet will occur. This will keep a well mixed
sfc layer, in turn keeping fog development to a minimum, if any.
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 415 AM Wednesday...Mid level heights will fall very slowly
through the period allowing and along with an increase in PWs,
chance of convection will increase. Profiles for Saturday are
still somewhat unfavorable although there is plenty of moisture.
Mid level cooling along with similar moisture profiles increases
chances Sunday through Tuesday. We go from slight chance to just
under likely by Monday which continues through Tuesday. Regarding
temperatures, I really don`t see much in the way of cold air
advection in the lower levels but more convection should shave a
couple degrees off the middle and upper 90s we are seeing now.
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --As of 12Z...VFR this TAF valid period. SW-WSW winds will back to the
S-SW by afternoon, earlier at the coastal terminals. Highest speeds
of 15-20 KT during the afternoon at the coastal terminals. Isolated
aftn/evng convection is possible mainly north of the terminals
along an old outflow boundary, and near KLBT along the NC portion
of the Piedmont trough. Any activity that is able to develop will
move east in the mid-level flow and stay N of the terminals, but
will monitor in case activity develops further S. Chances are low
attm that any of this activity will affect KILM/KLBT, but have
added VCSH to the KILM terminal 17-19Z associated with the sea
breeze. Winds will slowly veer TO SW-WSW and decrease later in the
EXTENDED OUTLOOK...Isolated to scattered afternoon convection
through Sunday may create brief periods of MVFR/IFR. Otherwise
-- End Changed Discussion --
NEAR TERM /THROUGH TONIGHT/...
As of 635 AM Wednesday...Early this morning, the low level SW jet
will keep the SW winds busy across the ILM local waters. By
daylight mid-morning, these winds will slightly diminish to 10 to
15 kt. This afternoon thru mid-evening...the sea breeze will
provide an increase in winds near shore, with SSW at 15 kt with
gusts to 20 kt. The winds late this evening and overnight will
transition away from the sea breeze...to another low level jet
episode with sw winds mixing down to the ocean sfc. Significant
seas will basically run in the 2 to 4 foot range with locally
produced wind driven waves at 3 to 6 second periods dominating the
overall seas. Convection coverage, if any, will be isolated at
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 415 AM Wednesday...The ridging from the sfc high will be
suppressed southward. 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. in addition, the Carolinas sfc trof, aka the Piedmont trof,
will orient itself across the Central and western portions of the
Carolinas this period. This will produce some tightening of the
sfc pg across the area waters this period. The daily inland
progression of the sea breeze may be limited due to the increase
in the westerly component of the winds...and their speeds during
this period. A daily nocturnal low level jet will again occur
during the late Thu evening through the pre-dawn hrs of Friday.
However, models indicate this will not be the case Friday night
and early Saturday.
Overall wind speeds will run in the 10 to 20 kt range with the 20 kt
mainly in the form of gusts. Significant seas will run 2 to 4 ft and
possibly 3 to 5 ft late Thursday Night thru early Friday.
If the latter occurs, then a SCEC may be needed. Convection will
again be limited, with the best possibility occurring late Friday.
LONG TERM /SATURDAY THROUGH SUNDAY/...
As of 415 AM Wednesday...Bermuda high pressure along with the
inland Piedmont trough will be the main drivers of winds and seas
for the coastal waters. A south to southwest flow of 10-15 knots
will prevail with significant seas of 1-3 feet.
SC...Heat Advisory from 11 AM this morning to 7 PM EDT this evening
NC...Heat Advisory from 11 AM this morning to 7 PM EDT this evening