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348
FXUS62 KCHS 070053
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
853 PM EDT Mon May 6 2024

.SYNOPSIS...
Atlantic high pressure will remain across the region through
mid week. A cold front will move through the region late week
bringing cooler conditions heading into the weekend.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
-- Changed Discussion --
The convection has been slowly winding down this evening. The
upper shortwave moving through the area has been the primary
driving factor behind the eastward progression of the activity.
There remains some untapped instability in southeast GA which
explains why the activity remains more discrete and stronger
than what`s in SC. We`re seeing a brief flare-up of stratiform
rain over the Charleston Tri-County Area which should be off the
coast by 10p.

For the rest of the night, another weak shortwave is forecast to
move through, and given marginal instability and high theta-e
air, we can`t rule out isolated convection redeveloping
overnight. A mild night is on tap with lows in the middle 60s
inland to the lower 70s along the coast.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
Tuesday through Wednesday: Mid and upper level ridging will build
across the region on Tuesday and persist into Wednesday. At the
surface, the pattern will look very summer-like with high pressure
over the subtropical Atlantic extending back to the west and into
the region. The main story during this period will be increasing low-
level thickness values and likely the warmest temperatures of the
year so far (see Climate section below). Highs are forecast to reach
the low 90s away from the immediate coast each day, with even some
mid 90s possible for Wednesday. The good news is that dew points
should mix out each afternoon, keeping heat index values only a few
degrees higher than the ambient air temperatures. Thanks to the
ridge and warm profiles, the atmosphere becomes less supportive of
diurnal convection each day. The forecast is dry, other than a small
area of slight chances in place for portions of the Charleston Tri-
County region early on Tuesday.

Thursday: Mostly a continuation of the warm up on Tuesday and
Wednesday, with highs again forecast into the low to mid 90s. The
main change is that the ridge flattens out aloft and a strong cold
front will approach the region from the northwest. While the bulk of
the day appears to be dry, by as early as the late afternoon
upstream thunderstorms could develop and begin to move into the
forecast area. The environment ahead of these storms could be
supportive of a notable severe weather threat with CAPE in excess of
2,000 J/kg and deep layer shear on the order of 30-40 knots. The
timing of the severe potential remains a bit uncertain, but the area
remains within a 15% threat area on SPC`s day 4 severe weather
outlook. The highest rain chances are across the interior, 50-60
percent, ranging to just 20s along portions of the coast.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
The Thursday night and Friday portion of the period remains quite
uncertain and will depend on the progression of the cold front
through the area. Some guidance would suggest that the front does
not clear the forecast area and another round of convection could
pass through while other guidance pushes the front further south and
feature a much drier and quieter solution. Either way, the front
will be offshore by Friday night and a notable airmass change is in
store for the weekend. The forecast is dry and temperatures are
expected to be down to right around normal for mid May, and this
should continue into early next week as well.

&&

.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
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Convection has been impacting the terminals this evening after
inland convection marched back to the coast. The strongest
storms will impact KSAV. Brief vsby and/or ceiling restrictions
possible through late evening, then dry conditions overnight
into Tuesday.

There could be some ground fog at the terminals toward morning,
although fog probabilities are too low to include in the
forecast for now.

Extended Aviation Outlook: Primarily VFR. Chances of showers
and thunderstorms will increase late Thursday through Friday.
-- End Changed Discussion --

&&

.MARINE...
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At the sfc, the pattern will feature high pressure from the western
Atlantic to the northern Gulf of Mexico and a warm front across the
Ohio River Valley. This pattern should yield south-southwest
winds 10-15 kt with seas 2-4 ft through tonight.

Tuesday through Saturday: For the first half of the period, the
pattern will be quite similar to a summertime pattern with the local
waters sitting under the western edge of high pressure over the
Atlantic. The result will be south to southwest flow that surges
closer to the land/sea interface each afternoon and evening. For the
late part of the week, this will change as a cold front approaches
on Thursday and then passes through by Friday. This will support
stronger winds, and possibly necessitate Small Craft Advisories for
portions of the waters. Behind the front Friday night and into the
weekend, winds will be northwesterly though not as strong and any
ongoing advisories should end.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
-- Changed Discussion --
The upcoming New Moon (May 8) and recent Perigee (May 5) will lead
to elevated astronomical tides over the next few days. Minor
coastal flooding is possible along Charleston and coastal
Colleton Counties, including Downtown Charleston, during the
evening high tides Tuesday through Thursday.
-- End Changed Discussion --

&&

.CLIMATE...
May 7:
KCHS: 93/1977
KSAV: 94/1977

May 8:
KCHS: 93/1986
KSAV: 96/1986

May 9:
KCHS: 95/1963
KSAV: 95/1962

&&

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

&&

$$

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