Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 041515
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1015 AM EST Thu Mar 4 2021

.SYNOPSIS...
High pressure will generally prevail into next week, aside from
a low pressure system to the south brushing the area late this
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, the area will be placed within a northwest flow as a
large trough persists across the Northeast and a cutoff low shifts
into the Central Plains. At the sfc, broad high pressure will remain
centered near the southern Mississippi River Valley, resulting in a
light west-northwest wind across the Southeast United States.
Given these features, conditions will be dry and notably warmer
than the previous day due to a northwest downsloping wind
component, strong sfc heating under a full day of sun, and mid-
lvl ridging nudging into the area from the west late in the day.
Latest 1000-850 mb thickness levels suggest and mos guidance
suggest temps peaking in the lower 70s across much of the area
while locations along the immediate coast peak in the mid 60s.

Tonight: A backdoor cold front will drop south into our South
Carolina counties prior to midnight, then into the Georgia zones
overnight. The front comes through dry, even void of any clouds,
and arrives as high pressure builds across the western Great
Lakes. Temperatures will drop quickly this evening with a dry
atmosphere and winds decoupling. the boundary layer becomes
more mixed during the late evening and after midnight as cold
advection develops behind the front. Temperatures at 850 mb will
drop to 3 to 5C, north to south by 12Z, as the 0C isotherm at
850 makes it to near the North Carolina/South Carolina border.
The end result is for minimum temperatures in our area to range
from the upper 30s in Berkeley and northern Dorchester County,
to the mid and upper 40s near and over the barrier islands and
in downtown Charleston and Savannah.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Moderate confidence through Saturday, then moderate to high
confidence Saturday night and Sunday. High pressure is expected to
generally prevail but an upper disturbance will be moving through
Friday night through Saturday night which could bring a few showers,
especially near the GA coast. Either way it doesn`t look like a big
rain-maker due to limited moisture/forcing. Temperatures will be
below normal, mainly in the 50s/60s for highs and 30s/40s for lows.
Will have to watch temperatures closely Saturday night for the
possibility of a freeze well inland in areas closer to the Pee
Dee/Midlands/CSRA, or at least some frost, although there may be too
little humidity and/or too much wind for significant frost
development. Note that now that we`re back into the growing season
we will be issuing Frost Advisories and Freeze Watches/Warnings as
needed.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
High confidence this period as models are in decent agreement
keeping high pressure in control with mainly dry weather, although
there is a small chance for a few showers mid week as a coastal
trough develops. The main forecast challenge will revolve around
temperatures, which should stay below normal until possibly getting
back near normal Tuesday. Still possible to see some frost and/or
freezing temperatures inland each morning through Tuesday, with the
best chance of a freeze Sunday night. Note that now that we`re back
into the growing season we will be issuing Frost Advisories and
Freeze Watches/Warnings as needed.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
VFR at both KCHS and KSAV through 12Z Friday. A backdoor cold
front will push through the terminals late tonight, with nothing
more noticeable than a wind shift to the N around 5-10 kt.

Extended Aviation Outlook: High confidence in VFR through Friday
night and again starting Sunday. However, there is a low risk of
flight restrictions Saturday into early Saturday night, especially
at KSAV, as an upper disturbance moves through the area.

&&

.MARINE...
Today: The local waters will be situated along the eastern side of
expansive high pressure from central Canada to the Gulf of Mexico.
The pattern suggest a fairly relaxed pressure gradient across the
area with northwest-west winds no more than 10 kt throughout the
day. Seas will be no higher than 2-4 ft across nearshore waters and
4-5 ft across offshore Georgia waters (largest late morning into
early afternoon).

Tonight: A backdoor cold front will move into the South Carolina
waters from the north prior to midnight, then into the Georgia
waters thereafter. Cold advection, a tightening gradient and
steady pressure rises behind the front will produce a decent N
to NE surge as high pressure builds out of the western Great
Lakes. Wind gusts will be close to 25 kt by daybreak Friday, but
limited enough in time and space to not require a Small Craft
Advisory.

Friday through Tuesday: Moderate to high confidence this period.
Conditions are expected to mostly remain below Small Craft Advisory
levels due to high pressure prevailing, although can`t rule out
mainly marginal SCA conditions pretty much anytime through Sunday,
especially in the offshore GA waters.

&&

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

&&

$$

NEAR TERM...DPB
SHORT TERM...RJB
LONG TERM...RJB
AVIATION...DPB
MARINE...DPB



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