267
FXUS62 KCHS 190836
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
436 AM EDT Sun May 19 2024

.SYNOPSIS...
A cold front will cross through our area later today. High
pressure then prevails for most of this week, followed by
another storm system potentially impacting our area late this
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Smaller scale convectively induced circulation continues to
advance northeastward off the Georgia coast early this morning.
Strong low level jet axis ahead of the wave extends up through
the coastal waters...evidenced by some unexpected gusty winds
from Savannah up through the Charleston coastal waters, while
also driving an axis of showers and thunderstorms across the
coastal waters. Convection will push away from the coast over
the next several hours.

Meanwhile, positive tilt mid level trough axis extends from the
mid Atlantic region down into the central Gulf, and attending
short-wave circulation pressing into northern Georgia. Surface
boundary extends across the far SE sliver of North Carolina and
back into the upstate South Carolina region along with some
convection that is slowly sagging into the central part of the
state.

Short-wave circulation and attending surface boundary will
advance down through the forecast area during the course of the
afternoon and off the coast tonight. Larger scale forcing for
ascent with the wave...in tandem with the boundary, daytime
heating and destabilization (1-2K J/Kg MLCAPE by early afternoon
south of the boundary) will kick off a compact area of showers
and thunderstorms that will track down through the forecast
area during the course of the afternoon. Given the high PWAT
values (1.5-2 inches) south of the boundary, heavy rainfall will
be a possibility and concern.

Biggest issue revolves around where convection develops and
the subsequent main area of impact. Recent CAM guidance
runs/trends press the surface boundary south of the Charleston
tri-county area quickly this morning and fire off convection
largely across the southern half of the forecast area. We have
made some southward adjustments to the highest pops/QPF amounts
with this forecast.

Tonight: Short-wave trough axis will slowly push off the coast
while surface high pressure wedges down from the north.
Convection will run its course this evening with thinning cloud
cover during the overnight hours. Cooler temperatures...dipping
down through the 60s for lows.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
Monday: The mid-levels will consist of a positively tilted trough
just off the Southeast U.S. coast in the morning, and a ridge just
to our west. The ridge will slowly build into our area as time
progresses. At the surface, High pressure centered well to our north
will build down the coast as time progresses, with it`s southern
periphery making its way into our area. The High will bring dry
conditions with skies becoming mostly sunny/clear. Low-level
thickness values support temperatures in the middle 80s. But we went
a little below this due to the northeasterly surface winds and the
expectation that surface evaporation should limit temperatures.
Highs should peak in the lower 80s. Lows should range from the upper
50s far inland to the mid 60s closer to the coast.

Tuesday: A positively tilted mid-level trough will be just off the
Southeast U.S. coast in the morning, transitioning into a cut- off
Low in the evening and overnight. Meanwhile, a ridge will strengthen
over the Southeast U.S. Broad High pressure centered to our north in
the morning will shift off the Mid-Atlantic Coast as the day
progresses. Though, it`s southern periphery will continue to
dominate our weather during the day and into the night. Subsidence
will yield dry conditions with mostly sunny/clear skies. High
temperatures should be in the mid 80s, except cooler at the beaches.
Lows should range from the upper 50s far inland to the mid 60s
closer to the coast.

Wednesday: The mid-levels will consist of a cut-off Low meandering
off the Southeast coast, while a ridge prevails over the Southeast
U.S. At the surface, High pressure along the Southeast coast in the
morning will shift offshore into the afternoon. A front will slowly
approach from the north and northwest. Though, it won`t make it near
our area as the High will remain the dominant synoptic feature. Some
of the models hint at isolated weak showers trying to form along the
inland moving sea breeze late in the afternoon. But it`s still a
little too early to determine if the dry air in place will
completely squash these weak showers. Expect at least partly sunny
skies. Highs will peak in the mid to upper 80s, except cooler at the
beaches.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
Mid-level ridging will be over our region Wednesday night, followed
by west southwest flow on Thursday. A weak trough may pass to our
north Friday night into Saturday. Surface High pressure in the
western Atlantic on Thursday will shift further offshore as time
progresses. A cold front could approach from the north and northwest
later Friday, then lift north on Saturday. Expect mainly dry
conditions Thursday, with increasing diurnal convection Friday and
Saturday. High temperatures will be a few degrees above normal each
day.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
Largely VFR conditions anticipated through the overnight hours
although with an increased risk for MVFR cigs as daybreak
approaches. There could be a little ground fog that develops,
mainly at KSAV and possibly KJZI, but the best fog/stratus
parameters look to remain to the west of all three terminals.

The risk for showers/tstms will increase during the day Sunday
as a cold front moves through. The best focus for showers/tstms
looks to settle just south of KCHS and impacting KJZI and KSAV.
A TEMPO for TSRA was included from 18-21z at KCHS to account for
some coverage/timing uncertainties. Prevailing TSRA was
mentioned for both KJZI (18-21z) and KSAV (20-00z). Conditions
were limited to MVFR for now with both cigs/vsbys holding above
alternate minimums. However, lower conditions may eventually be
needed as confidence in the timing, placement and intensity of
showers/tstms increases.

Extended Aviation Outlook: VFR.

&&

.MARINE...
A brief period of gustier southerly winds will impact the
coastal waters early this morning. Surface boundary will move
down through the region as we go through the day and kick off
another round of showers and thunderstorms during the afternoon.
Winds veer northerly behind the front and will be increasing as
we go through tonight.

Monday: A cold front will be shifting offshore early in the
morning. Meanwhile, High pressure centered well to our north will
build down the coast and into our area as time progresses. The
strongest gradient will occur in the morning, with wind gusts just
short of 25 kt possible across much of the waters, and seas 3-5 ft.
The gradient will gradually weaken into the afternoon and overnight,
with seas gradually subsiding as well.

Tuesday and Beyond: NE winds on Tuesday will shift around to the SE
by later Wednesday as High pressure gradually shifts off our coast.
This will lead to a more typical summer wind pattern on Thursday
with the formation of the afternoon sea breeze.

&&

.TIDES/COASTAL FLOODING...
The combination of rising astronomical tides with the upcoming Full
Moon and moderate NE winds will cause tides to be elevated early
this week. Minor flooding is possible with the evening high tides
Monday and Tuesday, mainly along the South Carolina coast.
&&

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

&&

$$