301
FXUS62 KCHS 211426
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1026 AM EDT Tue May 21 2024

.SYNOPSIS...
High pressure will persist for most of this week. Diurnal
convection is expected during the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Latest KCHS observed sounding (21.12z) revealed a very
dry air mass in place with a PWAT of 0.90" (or near the 25th
percentile according the SPC sounding climatology page). This is
thanks to surface high pressure centered right over the Piedmont
of NC with the ridge axis extending northeast and southwest.
This morning there was a thin stratus deck that built down to
areas of fog. That has since lifted to a strato-cu/ cu deck
with partly to mostly cloudy skies forecast. 850 mb temperatures
have risen to 14 degrees C this morning (compared to 11/ 12
degrees C this time yesterday morning) with 1000/ 850 mb
thicknesses rising to around 1395 m (or around 5 m). High
temperatures will likely be 2 - 4 degrees warmer than yesterday
or around 84/ 85 degrees.

Tonight: Diurnally driven cloud cover fades quickly this evening
leaving mainly clear skies and light winds. Blended guidance fog
probabilities as well as MOS guidance suggest some fog
potential...which has been added to the forecast for the
overnight/early Wednesday morning timeframe.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
Wednesday: The mid-levels will consist of a cut-off Low off the
Southeast coast in the morning. It`ll move further offshore as time
progresses. Meanwhile, a ridge will prevail 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 during the evening and
overnight. Though, it won`t make it near our area as the periphery
of the High remains the dominant synoptic feature. Ongoing low and
mid-level subsidence will bring our area dry conditions with mostly
sunny/clear skies. Expect a sea breeze quickly moving inland during
the afternoon. Low-level thickness values and 850 mb temperatures
support highs in the upper 80s before the passage of the sea breeze,
except cooler at the beaches. Lows should range from the lower 60s
far inland to the lower 70s along the immediate coast.

Thursday: A mid-level ridge over the Southeast U.S. in the morning
will weaken as time progresses, leading to west southwest flow
overhead. Surface High pressure just off the Southeast coast in the
morning will move further offshore as time progresses. Meanwhile, a
front to our north and northwest will continue to approach,
especially overnight. However, it`s not expected to reach our area.
The periphery of the High will bring another day with dry
conditions. Though, subsidence won`t be as strong, so expect more
cumulus clouds in the afternoon along with a strong sea breeze
quickly moving inland. Low-level thickness values and 850 mb
temperatures support highs around 90 degrees before the passage of
the sea breeze, except cooler at the beaches. Lows will be mild, in
the mid 60s far inland to the lower 70s along the immediate coast.

Friday: The mid-levels will consist of west southwest flow overhead.
At the surface, High pressure will be centered in the western
Atlantic, with it`s periphery trying to extend into the Southeast. A
front to our north and northwest during the morning will dissipate
into the afternoon, partly due to the High trying to build back into
our area. Increased moisture ahead of the front and circling around
the High will be in place across our area during the afternoon.
Temperatures peaking in the lower 90s will help to increase
instability. Therefore, a few thunderstorms may form around the
vicinity of the weakening front and along the sea breeze in the
afternoon, especially across our SC counties. But it`s not looking
like a washout at this time. These details will be ironed out with
future forecast updates.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
A weak trough should pass to our north Friday night into early
Saturday, followed by zonal flow over the Southeast through Monday.
Surface High pressure will remain in the western Atlantic while
fronts are forecasted to pass to our north. Expect convection
along/near the sea breeze each afternoon/evening, decreasing during
the overnight hours. Temperatures will remain a few degrees above
normal each day and night.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
KCHS/KJZI/KSAV: Satellite data shows some fog and lower cloud
cover across the region trying to spread down toward the KSAV
terminal. 12Z forecast will have a brief period of sct lower
clouds at KSAV. Otherwise, a SCT Cumulus deck will likely
develop later this morning hours and into the afternoon across
the region. A brief period of BKN cloud cover is possible.

Meanwhile, an uptick in northeasterly winds up to 10 knots will
take place during the morning, veering easterly or southeasterly
through the afternoon. Winds diminish during the evening.

Extended Aviation Outlook: VFR through Friday. Brief flight
restrictions are possible due to showers/thunderstorms later
Saturday.

&&

.MARINE...
Northeasterly winds persist across the coastal waters today with
speeds running 10 to 15 knots and seas 2 to 4 feet in the
nearshore waters, 3 to 5 feet in the outer waters. Winds and
seas diminishing tonight.

Extended Marine: High pressure remains the main synoptic feature
through Thursday. A cold front should approach from the north and
northwest later Friday, but it`s not expected to reach our area.
Otherwise, expect a typical summer wind pattern beginning Thursday.
That`s when each day winds will back and be stronger along the
land/sea interface with the formation of the afternoon breeze. Gusts
could approach 20 kt in the Charleston Harbor with the passage of
the sea breeze. Each night, winds should veer as the low level jet
sets up along the coast. Additionally, convection should return
during the weekend.

Rip Currents: With the approaching Full Moon, it won`t take more
than a small swell to lead to an enhanced risk of rip currents at
the local beaches. Both internal calculations and RCMOS point to a
Low Risk through Wednesday. But if the swell is higher than
anticipated, then the risk will need to be raised.

&&

.TIDES/COASTAL FLOODING...
The combination of rising astronomical tides with the upcoming Full
Moon and onshore winds will cause tides to be elevated through the
middle of this week. Minor flooding is possible with the evening
high tides through Thursday along coastal Charleston and coastal
Colleton Counties. There are no concerns at this time along the
remainder of our coast.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Coastal Flood Advisory from 6 PM to 10 PM EDT this evening for
     SCZ049-050.
MARINE...None.

&&

$$

NEAR TERM...Adam/Haines
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...