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000
FXUS62 KCHS 240836
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
436 AM EDT Sat Aug 24 2019

.SYNOPSIS...
A cold front will cross through the region today and tonight,
then stall near the coast on Sunday. Low pressure is expected
to pass well offshore early next week, before another cold
front impacts the area later in the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Pre-dawn: A cold front was moving south across the Carolinas,
still north of our region early this morning. Dry weather has
prevailed overnight to this point as convection associated with
a fairly well-defined MCV dissipated earlier. Weak low level
moisture and speed convergence along coastal zones may result in
a few showers/tstms around daybreak but the majority of the
area should remain dry.

Today: The pattern will favor unsettled weather conditions as
a cold front drops south into the area while deep moisture
builds, leading to increasing clouds and expanding diurnal
convective rains. The greater potential for showers and a
few tstms during the mid/late morning hours should be across
our northwest tier of zones and perhaps along the Charleston
County coast in the vicinity of a decent stability gradient
and near the tail of the weak remnant MCV drifting toward the
SC Pee Dee region. We will otherwise see surface heating across
the remainder of the region with temps warming toward 90 degrees
after midday in Southeast GA.

This afternoon: A complex mesoscale environment is anticipated
as convection become scattered to locally numerous across the
region, especially along and north of I-16 where deep layered
moisture convergence is progged along the frontal zone. We
maintained categorical POPs along our northwest fringe of zones
from Millen and Sylvania GA, northeast in SC bordering the
Midlands. Likely POPs down to I-16 and then chance POPs into the
zones bordering the Altamaha River. Deep layered instability is
rather unimpressive with warm mid levels and poor lapse rates,
severe weather potential looks low but stronger tstms may be
possible to the west of I-95 where frequent mesoscale boundary
interactions are hinted by various CAMs. A flux of Atlantic
moisture along with elevated PWATs suggest heavy downpours will
accompany tstms and localized ponding water in low lying areas
and on area roadways is possibly with any persistent deep
convection. Tstms along coastal areas near time of mid afternoon
high tides would be an issue but confidence in timing this
occurrence is low at this time.

Tonight: The front will drop south of the area while high
pressure builds south to the lee of the mountains and surface
low pressure shifts east of the Florida coast toward the Gulf
Stream. Scattered rains and a few tstms will continue into the
evening hours across the region with instability on the wane and
coverage likely decreasing inland areas. Shower chances will
linger into the night with light northeast winds and expanding
low clouds after midnight and especially toward Sunday morning.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
At the start of the period, surface high pressure will be building
inland while a cold front stalls offshore and to the south. This
general wedge-like pattern will remain in place through Monday. The
main deviation will be a low that is forecast to develop near the
Florida peninsula, which will then track northeast well off the
Southeast coast. The National Hurricane Center has high
probabilities for tropical development of this low. Some
discrepancies remain in regards to timing and strength of the low,
but consensus has the center staying far east of the area.

The highest rain chances will be focused across southeast Georgia in
proximity to deeper moisture and best forcing both Sunday and
Monday. Areas further north and inland should see less activity,
especially on Monday. Limited instability will keep severe threat
pretty low. Pockets of heavy rainfall will be possible with fairly
weak storm motions and 2+ inch PWats.

Models hint at a weak wave of low pressure shifting across the
region on Tuesday. Shortwave energy and plenty of moisture will
promote another fairly wet day. Current rain chances are in the 40-
60% range, highest across the Georgia zones.

Temperatures throughout the period are expected to be at or below
normal. Highs Sunday and Monday will mainly stay in the mid 80s,
then warm to upper 80s/near 90 on Tuesday. Lows will be in the 70s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
A tropical low off the mid-Atlantic coast Tuesday night will
continue to lift northeast away from the region on Wednesday.
Another cold front is forecast to cross the area later Wednesday or
Thursday. The front will likely stall off the coast through late
week while high pressure builds inland. Given the front lingering in
the vicinity, rain chances will remain in the forecast. Highest PoPs
will be near the coast. Temperatures are expected to be near normal.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
Conditions are expected to be VFR a large portion of the time at
both KCHS and KSAV this morning. However, there are concerns
for possible restrictions at KSAV between about 10Z and 13Z
Saturday due to fog and/or stratus.

There then looks to be scattered to numerous SHRA/TSRA across
the local region this afternoon and evening as a cold front
draws closer from the north. Aided by a low level flow off the
ocean and upper difluence, there is a good chance that at least
occasional flight restrictions (if not more prolonged sub-VFR
weather) will occur. For now we have just VCTS and CB clouds at
both terminals, but adjustments will definitely be required in
later TAF issuances with the potential for some heavy rainfall.

Extended Aviation Outlook: Sub-VFR ceilings possible Sunday into
Monday behind a front stalled offshore. Brief restrictions also
possible with any shower/thunderstorm that impacts the terminals
through mid-week.

&&

.MARINE...
Light and variable winds this morning will tend to become onshore
this afternoon as a cold front moves into the waters. Winds will
increase late tonight as the gradient tightens between high
pressure to the north and low pressure off the Florida coast.
Wind should increase closer to 15 kt late tonight and seas will
build to 2-4 ft.

Waterspouts: Conditions were looking favorable for waterspouts
this morning, we will access the potential for a Marine Weather
Statement after examination of the first visible satellite images.

Sunday through Thursday: Marine conditions will deteriorate Sunday
into Monday as the pressure gradient tightens between high pressure
inland and a tropical low passing well offshore. Small Craft
Advisories could be needed for portions of the waters as northeast
winds increase and seas build. Conditions will improve Tuesday as
the low pulls away from the local area. A cold front will impact the
area later in the week. Additional marine concerns are not expected
at this time.

Rip currents: Increasing east/northeast winds could contribute to an
enhanced risk of rip currents on area beaches late this weekend into
early next week, especially if tropical low pressure intensifies
while tracking well offshore.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will be running close to minor Coastal Flood
Advisory levels next week and onshore winds could lead to even
higher tides, mainly during the evening high tide cycles starting
Monday. In addition, there is the potential for some heavy rain
around the times of high tide which could exacerbate any flooding
issues.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

$$
NEAR TERM...
SHORT TERM...ETM
LONG TERM...ETM
AVIATION...ETM
MARINE...ETM
TIDES/COASTAL FLOODING...