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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 250556
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
156 AM EDT Mon May 25 2020

.SYNOPSIS...
A weak cold front will push into the area later tonight and
Monday, and high pressure will build over the region from the
north. A coastal trough should develop around mid week, and low
pressure could track over or near the Southeast coast mid to
late week. A cold front could approach the region next weekend.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
As of 150 AM: A backdoor cold front was pushing across the
Santee River basin. Surface based observations along and north
of the front were observing low ceilings with light fog. Based
on the latest run of the HRRR, it appears that a period
of fog will slide across the SC Lowcountry between 07-11Z and
SE GA between 10-13Z.

Previous Discussion:
One last convective cluster will work west across northern
Jenkins County over the next hours, then dry weather will
prevail. Adjusted pops based on short term radar trends.

Expect low stratus and possible some fog to fill in along/ahead
of the backdoor front early Monday. The fog is not expected to
have much impact, but some areas of reduced visibilities could
occur. Dense fog is not expected at this time.

Warm and humid conditions will persist with lows ranging from
the upper 60s/near 70 inland, lower 70s at the coast, with mid
70s at the beaches and Downtown Charleston.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY/...
Monday: High pressure will build into the region from the north and
will push a weakening cold front toward the south. At least
scattered showers and thunderstorms could develop near this
boundary, with higher PoPs across northern counties during the
morning followed by high PoPs shifting into southern/western
sections during the afternoon. Forecast instability suggests only a
low chance for a brief/isolated pulse severe thunderstorm or two.

Monday night: Due to diurnal stabilization, isolated/scattered
showers and perhaps isolated thunderstorms near the stalling cold
front across southern/western counties should diminish in coverage
through at least the first half of the night. Then, guidance depicts
a band of deeper moisture to spreading from the south in at least
southern counties later on.

Tuesday and Wednesday: Guidance indicates a wet period as a pool of
PWAT values around 2 inches settles over the region. However,
timing/coverage of showers/thunderstorms will be linked with
strength of the surface high N/NE of the region and to the uncertain
evolution of a surface trough/surface low S/SE of the area. The
latest forecast ramps PoPs up to likely all but far northern/inland
counties Tuesday. Then, PoPs vary from likely along the SC coast to
chance elsewhere Tuesday night. Wednesday, PoPs range from likely
north to chance south. However, forecast confidence decreases
Tuesday night and remains rather low through Wednesday.

The potential for locally heavy rain will increase Tuesday through
Wednesday, especially near the coast where tides will be elevated
due to persistent E/NE flow. If stronger low pressure tracks over or
inland from the coast Tuesday night through Wednesday, the potential
for severe weather could increase.

Also of note, greater than expected coverage/persistence of
clouds/precipitation could translate to cooler daytime temperatures
than indicated within the latest forecasts.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
The start of this period remains uncertain and will depend on
whether surface low pressure remains in the vicinity into Thursday.
Otherwise, on the western periphery of Atlantic surface high
pressure/beneath a weak ridge of high pressure aloft, a surface
trough should linger over the region with above normal precipitation
and temps into this weekend. A cold front could approach or move
into the area by late next weekend.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Prior to the 6Z TAFs, a backdoor cold front was pushing across
the Santee River basin. Surface based observations along and
north of the front were observing LIFR to IFR ceilings with MVFR
visibilities. Based on the latest run of the HRRR, it appears
that a period restrictive ceilings will pass over KCHS between
07-11Z and KSAV between 10-13Z, highlighted with TEMPO groups.
The pressure gradient between a developing tropical wave over FL
and high pressure across the Mid-Atlantic states will increase
this afternoon. Gusty SE winds should develop by mid-day and
remain until around sunset. Conditions tonight should feature
steady east winds with VFR ceilings.

Extended Aviation Outlook: Periods of flight restrictions, especially
related to showers/thunderstorms in the area, should persist into
late week.

&&

.MARINE...
Tonight: South to southeast winds will gradually back as a weak
cold front approaches. Speeds will remain <10kt with seas 1-2 ft
nearshore waters and 2-3 ft offshore waters.

Monday through Friday: On Monday, as a high pressure system builds
over the area throughout the day, winds will increase as the
pressure gradient tightens. Then, as a low pressure system lingers
off the east coast of Florida, the pressure gradient will tighten
more, causing winds and seas to gradually increase. Small Craft
Advisories will likely be needed starting Tuesday afternoon into at
least Wednesday morning. While there is still some uncertainty about
the track of the low over or close to the Southeast coast mid to
late week. Some guidance suggests that the pressure gradient starts
to relax mid to late week, but the low pressure could maintain
elevated winds and seas through Friday.

&&

.TIDES/COASTAL FLOODING...
Persistent E/NE flow will support elevated tides this week. Mid to
late week, there exists a low probability for minor salt water
flooding around the times of the overnight high tides. Also, we`ll
continue to assess the potential for heavy rainfall to coincide with
high tides at the coast, especially during the Tuesday-Thursday
period.

&&

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

&&

$$
NEAR TERM...NED
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...
TIDES/COASTAL FLOODING...