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000
FXUS62 KCHS 220620
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
220 AM EDT Tue Oct 22 2019

.SYNOPSIS...
A cold front will approach from the west late tonight and move
off the coast late Tuesday. High pressure will rebuild Tuesday
night through Thursday before another storm system potentially
moves in Friday or Saturday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Early this morning: Radar imagery shows that convection is
mostly limited to the adjacent coastal waters. This convection
is being forced ahead of an advancing warm front and on the
leading edge of low level thetaE advection. Instability is
mainly limited to the coastal waters, so it doesn`t appear much
is going to develop over land areas through sunrise. The main
question is what is going to happen to a convective complex
ongoing along the Florida panhandle. The good news is that IR
satellite shows warming cloud tops so it should be on a
weakening trend. The forecast issue is that no model seems to be
initializing this feature very well, so it is difficult to
determine what it will do as it progresses downstream into
southeast Georgia. The forecast tentatively follows the model
consensus which is for minimal rain chances through sunrise.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/...
Tuesday: The base of a deep eastern U.S. upper trough is
forecast to shift through the Tennessee and Ohio Valley regions.
A cold front at the surface is expected to move into our inland
zones to near the I-95 corridor during the early afternoon
hours. The window for potential destabilization ahead of the
front appears to be short and rather limited due to the
progressive nature of the front. Surface dew points are expected
to fall after mid afternoon as the front shifts to the coast.
Prior to fropa, forecast soundings along zones along and east of
I-95 show surface based CAPEs 1000-1500 J/KG along with Pwats
near 2 inches along with bulk shear of 30 kt and rather
unidirectional deep layer flow by early afternoon. There appears
to be a brief potential for isolated strong to severe tstms
just ahead of the cold front over coastal SC, especially along
the Charleston Tri-County in the 17Z-20Z time frame. The overall
risk for severe weather otherwise looks rather low given the
timing of the front into the I-95 corridor by 18Z. We maintained
high chance POPs all areas as convective rains will likely
remained scattered. Temps will be warm in the lower to mid 80s
with frontal compression and periods of insolation.

Wednesday and Thursday: High pressure and dry weather will
return to the region. It will be cooler on Wednesday with highs
in the mid 70s. We also lowered temps Wednesday night as strong
radiational cooling likely to send temps into the mid to upper
40s northwest tier to near 50 at both Charleston and Savannah.
Northeast flow on Thursday should keep afternoon temps in the
mid 70s most areas once again with a few high clouds around and
some increasing coastal stratocumulus south of the Savannah
River.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
An upper level trough will develop to the west late in the
week. A frontal system is expected to impact the area Friday
into Sunday, likely bringing periods of showers though the
heaviest rain may remain just inland.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Challenging forecast ahead at KCHS and KSAV as ceilings impact
both locations through the morning. MVFR ceilings are in place
at both sites, and upstream observations show IFR ceilings
poised to impact KSAV over the next few hours at least on a
TEMPO basis. Thinking is that IFR will eventually reach KCHS
too, and the forecast contains a TEMPO from 08-12z. MVFR
ceilings will remain through the morning until a cold front
clears the area from the west. Overall rain chances aren`t that
high, so we only carry showers in the TAF`s. VFR will return in
the early afternoon at KSAV, and the late afternoon at KCHS.
Some low end wind gusts around 20 knots will be possible in
southwesterly flow.

Extended Aviation Outlook: VFR Tuesday night through Thursday.
Increasing chances for low clouds late Thursday night through
the weekend along with scattered showers.

&&

.MARINE...
Tonight: A warm front will lift north through the waters
overnight, allowing winds to veer from the southeast to the
south. Speeds are expected to remain well below Small Craft
Advisory criteria, topping out in the 10 to 15 kt range. Seas
will average 2-3 ft nearshore and 3-4 ft offshore.

Tuesday through Friday: A cold front will move offshore late
Tuesday with winds veering from southwest to northwest in the
wake of the front. We expect a nice punch of cooler and drier
air over the waters Tuesday night and this will result in
surging and jetting offshore flow. We will likely need a Small
Craft Advisory for GA waters 20-60 NM during this time before
flow begins to subside on Wednesday. The near shore waters will
see decent surging but it appears we may not reach SCA criteria
for a substantial length of time.

The surface high will build north of the waters mid to late
week with moderate onshore flow continuing. Seas may increase to
advisory levels next weekend due to persistent northeast fetch
and an increasing pressure gradient.

&&

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

&&

$$

NEAR TERM...BSH
SHORT TERM...
LONG TERM...JRL
AVIATION...BSH
MARINE...