Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 211338

Area Forecast Discussion
National Weather Service Wilmington NC
938 AM EDT Fri Jul 21 2017

Hot and humid conditions will prevail today through the weekend
with only isolated rain chances. Storms will increase next week
as a series of weak fronts approach the coast, with near normal
temperatures for late July.


As of 935 AM Friday...Analyses of morning sounding data and
latest high-res guidance confirms earlier prognosis of a hot and
dry day. Very dry air above 850 mb will preclude significant
convection today. No changes made to the forecast with the
latest update. Previous discussion from early this morning

Hot and dry day on tap for the region as mid- level ridge
expands atop filling low dropping to the south.

Upper low spinning near N FL will drift SW today as high
pressure  expands both from the west and east across the
Carolinas. As this occurs the Bermuda type ridge will expand at
the surface back into the Southeast, producing increasing warmth
along with continued high RH. 850mb temps are forecast to climb
towards 20C today, as a finger of the strong thermal ridge
across the Great Plains advects eastward around the periphery of
the mid-level ridge. GOES-16 low-level WV imagery shows
exceedingly dry air locally, and forecast profiles suggest very
little in the way of column saturation through the near term.
This suggests that despite heat and humidity driving MLCape over
2000 J/kg, tstms are unlikely today as the dry air and warm
500mb temps of -3 to -4C provide the convective lid. The big
story today is then heat index values approaching advisory
criteria across most of the area. Expect at least some dry air
entrainment and mixing during peak heating, so dewpoints in the
70-73 range this aftn will combine with highs rising well into
the 90s away from the beaches, to produce heat index values of
101-104 degrees. A few locations may touch 105, but these are
not expected to meet the spatial or temporal extent needed for a
heat advisory.

Increasing SW flow tonight as the Bermuda Ridge continues to
back to  the west will create a very warm night as well, with
mins struggling to drop below 75, and may remain near 80 at the
immediate coast.


As of 324 AM Friday...Maximum temperatures will run 3-6 degrees
above normal over the weekend making for hot conditions. The
apparent temperatures during the afternoon hours will generally
range from 98 near the coast to 104 well inland. It is not out
of the question that a Heat Advisory may be needed for portions
of the area with only a slight increase in air temperature or
dewpoint. The heat will drive a vigorous afternoon sea breeze,
prompting gusts of 20-25 mph along the coast and the coastal
interior over the weekend. Frisky nocturnal SW boundary layer
winds will keep minimum temps elevated and above normal, with a
range from the upper 70s to near 80 at the coast to 75-78 over
the interior of NE SC and SE NC. A little bit of mid-level
moisture increase on Sunday brings mentionable POP values into
the isolated range Sunday afternoon.


As of 3 PM Thursday...Long term will be marked by gradually
decreasing temperatures and increasing chances for precipitation
as ridging at the surface and aloft breaks down and a cold front
approaches and then moves across the eastern Carolinas. A
consensus of guidance has the front stalling in our vicinity by
late Tuesday or Wednesday, where it will linger into Thursday.
Above normal temperatures Sunday and Monday will drop back down
to or below climo for the remainder of the long term. Tuesday
looks to be the best day for convection, with deep moisture in
place in advance of the impending front.


As of 10Z...High confidence in VFR through the valid period as
stacked ridge of high pressure dominates the synoptic regime. A
weak piedmont trough and 20 kts of wind at 2kft on VWP early
this morning is preventing winds from going calm in many places
close to the coast. This combined with very warm mins will
prevent any fog this morning. A dry day is expected Friday as
very dry air aloft precludes convection. SCT to at times BKN VFR
CU is likely, but will not create any restrictions. The biggest
impact may be slightly higher winds within the sea breeze at
CRE/MYR this aftn, increasing from the S/SW at 10-15 kts, while
remaining 10 kts or less at the other terminals. Most CU will
erode after dark leaving clear sky conditions and lighter winds,
still from the SW. A nocturnal increase in wind overnight will
likely prevent fog overnight.

Extended Outlook...VFR through Sunday. Brief MVFR/IFR possible
in scattered showers and tstorms Mon and Tue due to a slowly
approaching cold front from the NW.


As of 935 AM Friday...Latest obs show a light WSW flow with seas
of 2 to 3 ft. Forecast good to go with no changes needed.
Previous discussion from early this morning follows:

Bermuda high pressure slowly expanding from the west will
persist SW winds across the waters this period. The gradient
will be slightly pinched compared to the past few days, so
widespread 10-15 kt SW winds are forecast, especially this
evening and tonight. Very hot temperatures inland will produce a
strong sea breeze, so wind gusts up to 20 kts are likely near-
shore as well. A 2ft/10sec SE swell will develop this aftn but
will become increasingly masked by an amplifying 4 sec wind
wave, and seas will grow from around 2 ft this morning, to 2-4
ft late.

As of 324 AM Friday...Conditions will approach `Exercise
Caution` due to 15-20 KT winds and seas around 4 feet offshore.
The afternoon sea breeze circulation will keep winds gusty and
seas choppy near shore each afternoon to early evening. The good
news is that very little TSTM activity is expected over the
weekend although early and late Sunday may see a few showers
offshore. Seas of 3-4 feet will be dominated by S-SW wind-seas
running in 3-4 second intervals mixed with a weakening SE swell
every 9 seconds.

As of 3 PM Thursday...Circulation around high pressure over the
western Atlantic will keep winds from the SW through the
period. An approaching cold front may briefly tighten the
gradient enough to warrant Exercise Caution headlines or a Small
Craft Advisory late on Monday, but confidence on this is low at
this time.





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