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Area forecast discussion 
National Weather Service Charleston SC
420 am EDT Wednesday Jul 27 2016

Synopsis...
Atlantic high pressure will prevail through the weekend while a weak
trough persists inland.

&&

Near term /through tonight/...
pre-dawn: the gradient in the boundary layer is a bit tighter early
this morning and turbulent low level mixing was more evident along
the coast keeping temps in the lower 80s overnight around Charleston
and Beaufort, while Savannah Airport had fallen to 79 degrees at
4 am. We may see a few more inland readings fall to the mid 70s
toward dawn as the surface winds veers a bit more westerly. Mainly
clear skies will continue.

The center of the expansive subtropical ridge will continue to stagnate
right along the southeast U.S. Coast providing a continuation of hot
and humid weather with only spotty diurnal convection expected
once again. Most areas will reach the mid to upper 90s this afternoon
with the sea breeze progression slowed by a 15 kt west wind in the
boundary layer during the morning hours. Forecast proximity soundings
across inland areas indicate that low level dew points should mix
out sufficiently during the afternoon. Peak heat indices along the
near coastal sea breeze corridor may approach advisory criteria
for a brief period during the mid/late afternoon hours. On average
our forecast heat indices came out in the 105 to 109 degree range
in the grids and daily heat safety precautions continue to be advised
as this long duration hot weather pattern drags on.

Convection allowing high resolution models are very scant on
shower/tstm coverage this afternoon as anticipated with the high
pres dome providing subsidence and quite warm temps aloft. We
maintained a slight chance pops for a brief period this afternoon
as soundings do show slightly better moisture profiles today and
reasonable instability along the sea breeze corridor after mid
afternoon. Most locations can expect a rain chance that is below
20 percent for today.

Tranquil weather for tonight with very warm temps once again,
probably similar to this morning. Skies should be mainly clear
overnight after any evening debris clouds dissipate.

&&

Short term /Thursday through Saturday/...
strong ridging overhead and the associated subsidence will keep the
mid and upper levels warm and dry through the end of the workweek.
Only slight chance pops included mainly along the resultant
seabreeze Thursday afternoon, with mainly dry conditions expected
Friday afternoon as the ridge shifts directly overhead, leading to
the least impressive lapse rates and moisture profile of the period.

Moving into Friday night, the ridge will begin to slide off the
coast and the mid-levels will moisten/destabilize. Pops nudge closer
to climo Saturday afternoon, near 30% focused along the sea-breeze
corridor, though modest instability will keep the severe threat low.

No relief from the heat will come this week, as high temps reach
into the upper 90s for most away from the coast each day. With
little to no downsloping component to the wind, triple digit highs
seem unlikely at this point. Deep mixing will lower dew points into
the upper 60s during peak heating daily, resulting in heat indices
in the mid-100s for most. No heat advisories are anticipated at this
time.

&&

Long term /Saturday night through Tuesday/...
west-southwesterly low level flow keeps a warm and humid airmass in
place through the long term period. Increasingly unsettled weather
will ensure as the ridge continues to slide off the southeast coast
and deep-layer moisture increases early next week. Global model
solutions begin to diverge significantly heading into the middle of
next week as a deteriorating cold front may approach the area
Tuesday night into Wednesday. Pops have been increased well into the
chance range, especially north of I-16, to account for this. Temps
will remain at least a few degrees above normal through the
period.

&&

Aviation /08z Wednesday through Sunday/...
VFR with relatively minute chances for vcsh/vcts between 18z and
22z today.

Extended aviation outlook: VFR will prevail at both sites. Brief
flight restrictions possible with isolated afternoon
showers/thunderstorms mainly over the weekend.

&&

Marine...
persistence forecasting continues to drive the coastal waters
forecast under the deep layer ridge and Atlantic surface high
pressure. Winds will continue to peak from late afternoon into
the overnight again today after this morning's surge ebbs by
mid morning. West to southwest flow will back to south to
southwest today then veer slightly again later tonight. Speeds
will average 10 to 15 kt with 15 to 20 kt flow during peak
nocturnal surges. Seas continue to average 2 to 3 ft.

Thursday through monday: Atlantic high pressure will prevail through
the period with south-southwest winds mainly 10 to 15 knots and a 2
to 4 foot wind swell in the water. Isolated to scattered early
morning thunderstorms will be a threat beginning Saturday.

&&

Chs watches/warnings/advisories...
Georgia...none.
SC...none.
Marine...none.

&&

$$
Synopsis...
near term...
short term...ceb
long term...ceb
aviation...ceb
marine...ceb

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