Area Forecast Discussion
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FXUS62 KILM 220837
Area Forecast Discussion
National Weather Service Wilmington NC
437 AM 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 330 AM Friday...Mid and upper levels illustrate a ridge axis
extending from the amplified South Central U.S. High will lie
across or just north of the ILM CWA this period. Since the ILM CWA
is downstream from this axis, NVA and subsidence aloft will result
in a convective lid across the area. The GFS idea of low instability
looks more realistic when compared to the NAM and thus will adhere
to its fcst. Forcing along the mesoscale diurnally driven sea
breeze may allow a tstorm or 2 to break thru this lid and for that
indicated a 15 to 20 POP along the sea breeze as it progresses
inland. Otherwise, looking at scattered diurnally driven cu
dissipating around sunset. Popcorn type showers or tstorms will
develop offshore after midnight but do not expect them to move
onshore. Stayed closer to the GFS Mos guidance which has been
performing better than the NAM and European Mos respectively as of
.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. With a subsidence inversion
aloft as well as warming temps aloft, ie. models indicate 500MB
temps climb to -4 degrees C, resulting in limited lapse rates
not very conducive for Tstorm activity during this 2 day period.
The central U.S. high de-amplifys 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 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.
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...ie. increasing RH. 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 /08Z FRIDAY THROUGH TUESDAY/...
As of 06Z...Predawn fog will generally be MVFR at worst at
coastal terminals. Inland still not quite clear as to whether IFR
or even LIFR develops. Some guidance hitting FLO with LIFR (though
oddly not LBT). Since FLO has a higher dewpoint depression than
LBT at this time have limited to IFR and relegated to tempo. VFR
for the rest of the forecast for all terminals.
Winds lt and var through the overnight hours. around mid-morning
winds will become southerly 5-10 kts, highest at the coastal
EXTENDED OUTLOOK...Brief periods of MVFR/IFR from isolated
afternoon convection Saturday through Tuesday. Otherwise expect
NEAR TERM /THROUGH TONIGHT/...
As of 330 AM Friday...Weak ridging from the center of high
pressure well offshore from the Southeast States will extend
across the area thruout this period. Looking at a land breeze to
start this morning that will eventually transition to a se to s
direction by midday and persist through tonight. With the sfc pg
rather relaxed, speeds will run 10 kt or less. The exception will
come from a weak sea breeze circulation that will result in wind
speeds at 10 to possibly 15 kt this aftn thru early this evening.
Significant seas will run 2 to 3 ft with the ese 1 to 2 foot
8 to 9 second period ground swell dominating, power-wise, when
looking at the spectral density plots thru tonight. Isolated
popcorn convection just offshore early this morning will fade away
by late morning, then re-occur during the pre-dawn Sat hours.
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 push it westward across the central
and north Florida coasts late Sunday. Some wind speed enhancement
across the local waters may result from this low on Sunday.
Significant seas will run 2 to 4 ft with the 4 footers primarily
off Cape Fear. 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 the ground swell.
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.