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389
FXUS62 KCHS 251050
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
650 AM EDT Tue Jun 25 2024

.SYNOPSIS...
High pressure will remain over the western Atlantic while a
weak cold front approaches our area. This front will likely
linger near our area through mid-week, followed by another
front towards the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
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Early morning update: No significant changes made to the going
forecast.

Overnight composite analysis reveals broad upper level ridging
across much of the western and central U.S. feeding into an
upper level trough pushing off the Atlantic Coast. Stalled
surface boundary arcs from the off the Mid Atlantic Coast and
down through southeast South Carolina into central Georgia with
some hint of a closed weak surface low sitting across the
forecast area. Some ongoing convection is occurring along the
boundary in the Atlantic. Earlier convection across our region
has dwindled although there is one recent lone small shower
along the Tattnall/Evans county border. Otherwise...quiet and
mild conditions are the rule.

Today: Boundary is expected to remain more or less stalled
across the region while the weak surface low drifts into
southern Georgia. With no discernible thermal profile change,
another very warm and humid day is on tap with temperatures
quickly warming through the 80s this morning and into the 90s by
noon...with highs once again reaching the middle to upper 90s
away from the coast. Similar to the last few days, surface
dewpoints well inland (west of the I-95 corridor) will tend to
mix/lower this afternoon, keeping heat index readings in check.
But east of the I-95 corridor and especially along the coast,
middle 70s to near 80 dewpoints will lead to heat index values
at or above 108F for a period of time this afternoon. A Heat
Advisory has been issued accordingly.

Precip-wise...not much in the way of larger scale forcing
mechanisms to work with. But with 1500-2500 J/Kg (or better)
MLCAPE to work with, particularly within the pooled moisture
along the coast and modest convergence with the weak boundary
and/or marine layer, some showers/thunderstorms are a
possibility. Forecast will continue to advertise isolated to
scattered pops during the afternoon.

Tonight: Any convection will diminish through the early to mid
evening timeframe with quiet/mild conditions thereafter. Lows
dip into the middle to upper 70s overnight...warmer along the
coast.
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&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
Wednesday: The mid-levels will consist of troughing gradually
developing over the East Coast. At the surface, a weak stationary
front should be located to our west and north at daybreak. It`s
forecasted to dissipate into the afternoon. Though, surface
troughing should remain in place across our region. A cold front
should approach from the northwest overnight. Though, it`s not
expected to reach our area during that time frame. Higher PWATs
should gradually creep into our area as time progresses. It`s
possible they could exceed 2" closer to the coast, which is above
normal for this time of year. The heat will be the main concern due
to 850 mb temperatures, low-level thickness values, and compression
near the front. Highs are expected to reach the mid to upper 90s
across most of our area, except cooler at the beaches. Dew points
well into the 70s near the coast will cause heat indices to rise to
~108 degrees, which is borderline Heat Advisory criteria. Though,
any could be brief due to afternoon convection lowering the
temperatures. Both the synoptic models and the long-range CAMs have
afternoon convection developing along the inland moving sea breeze.
Scattered coverage seems reasonable, especially further south.
MLCAPEs should approach 1,500-2,000 J/kg across portions of our area
with some shear. With DCAPEs exceeding 1,000 J/kg, a few marginally
severe storms with damaging winds are possible just about anywhere.
Additionally, there will be the potential for locally heavy rainfall
underneath the thunderstorms due to fairly weak steering flow and
the potential for training. Convection should quickly decrease
during the evening, with the overnight being mainly dry. Lows will
be in the 70s.

Thursday: Mid-level troughing initially over the East Coast will
gradually shift offshore. Additionally, a shortwave is expected to
move over our region during the late afternoon or evening. A cold
front located just to our northwest at daybreak should very slowly
move across our area during the day and into the night. There will
be a plume of deep moisture ahead of the front. PWATs could exceed
2", which is above normal for this time of year. Similar to
Wednesday, high temperatures are expected to reach well into the 90s
for most areas, perhaps reaching 1-2 degrees higher. Dew points well
into the 70s near the coast will cause heat indices to rise to ~110
degrees. So Heat Advisories may be needed for the coastal counties.
Forcing from the front, the afternoon sea breeze, and the shortwave
will generate convection in the afternoon. All of the models point
towards scattered to numerous coverage, which is why we have high
end chance POPs. It`s a bit uncertain how much instability and shear
will be in place. But given the setup a few marginally severe storms
with damaging winds are possible just about anywhere. Additionally,
there will be the potential for locally heavy rainfall underneath
the thunderstorms due to fairly weak steering flow and the potential
for training. Convection should gradually decrease during the
evening. But remnant convection could persist everywhere overnight.
Lows will be in the 70s.

Friday: The mid-levels should consist of zonal flow over our region.
At the surface, a stationary front should be over our area in the
morning. It`s expected to dissipate into the afternoon. Deep
moisture will persist across the region. Forcing from the front and
the afternoon sea breeze are expected to generate convection.
Though, the coverage will depend on how much instability is in place
and the amount of shear. Similar to the previous two days, high
temperatures are expected to reach well into the 90s for most areas.
Dew points well into the 70s near the coast will cause heat indices
to rise as high as 108 degrees along the coast, which could prompt
Heat Advisories.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
Surface troughing or weak fronts will be impacting the Southeast
U.S. while High pressure is near Bermuda. This summertime pattern
will yield diurnal convection. The highest POPs are each afternoon
and evening, then trending lower overnight. High temperatures will
be well into the 90s each day. Additionally, heat indices could
approach 108 degrees along the coast each day.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
KCHS/KJZI: A few clusters of showers and thunderstorms will move
through the terminals through around 06Z or so and heavy rainfall
could drop visibilities into the MVFR range. Thereafter, cannot
rule out a touch of fog develop across the tri-county region
overnight including the terminals. On Tuesday, VFR conditions
prevail through the day into Tuesday night. Hit and miss shower
and thunderstorms are possible during the afternoon hours
although confidence in coverage/timing and duration is too low
to include in the forecasts at this juncture.

KSAV: VFR conditions prevail through the TAF period. Hit and
miss showers and thunderstorms are possible across southeast
Georgia during the afternoon hours. But again, confidence in
coverage/timing and duration is too low to include in the
forecasts at this juncture.

Extended Aviation Outlook: Mostly VFR. However, convection could
bring brief flight restrictions, mainly each afternoon and
evening.

&&

.MARINE...
Southwest gustiness lingers along the South Carolina nearshore
waters currently, but will be diminishing over the next few
hours. Small Craft Advisories have been extended out through 6
am to allow for winds and seas to lower. Winds will continue to
weaken through the morning and for the afternoon while backing
southeasterly in time. Seas running 3 to 5 feet early this
morning will subside to 3 feet or less tonight.

Extended Marine: A typical summertime pattern is expected with High
pressure in the western Atlantic and occasional surface troughing or
fronts over the Southeast. Each day, expect gradually backing winds.
They`ll be strongest along the land/sea interface and the Charleston
Harbor with the formation of the afternoon sea breeze. Each night,
winds will gradually veer, possibly surging closer to the coast.
Seas will be 2-3 ft.

Rip Currents: Wednesday a 1-2 ft SE swell around 8 seconds will be
impacting the beaches. Though, there are hints that an additional SE
swell of 1 ft around 10 seconds could also impact the beaches during
the afternoon. Per internal calculations, this would bump up the rip
current risk to Moderate at all of our beaches. Given the
uncertainty, we opted to maintain a Low risk for now. But this will
need to be reevaluated during the day.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
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GA...Heat Advisory from noon today to 6 PM EDT this evening for
     GAZ117>119-139>141.
SC...Heat Advisory from noon today to 6 PM EDT this evening for
     SCZ047>052.
MARINE...None.
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&&

$$