Area Forecast Discussion
Issued by NWS Charleston, SC

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461
FXUS62 KCHS 190016
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
716 PM EST Wed Jan 18 2017

.SYNOPSIS...
A weak front will stall across the area through Friday before
lifting north. A series of upper level disturbances will affect
the area Saturday and Saturday night, then a strong low pressure
system and cold front will move through Sunday into Monday.
Drier high pressure will then return into the middle of next
week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Tonight: A h5 shortwave will continue to shift off the Mid-Atlantic
coast, helping push a sfc cold front southward to the region early
tonight and allowing weak high pressure to spill into northern
areas. The front is then expected to stall near the South
Carolina and Georgia state line around midnight as a mid-lvl
ridge of high pressure expands to the northeast from the Gulf of
Mexico and Florida well ahead of a low pressure system developing
over the Mississippi River Valley. The stalling front is expected
to be dry, but we could see a few clouds. Winds should also
become light and variable over most areas, although we could see
light winds gradually veer from west to north/northeast overnight
in South Carolina. There is some hint at the potential for some
patchy fog over southern zones in Southeast Georgia late, where
moisture remains south of the stalled boundary. However, dense
fog is not anticipated at this time. In general, overnight lows
should range in the upper 40s north to low/mid 50s south of the
Tri-County area.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
Weak high pressure to the north of the area Thursday morning
will shift east into the western Atlantic by Thursday night.
Meanwhile a potent upper low shifting into the central United
States will result in diffluence and increasing sky cover during
the day. Slightly cooler air will reside over northern areas,
which along with the increasing clouds will keep highs in the
mid to upper 60s. Elsewhere we should see temps rise into the
low to mid 70s south of the stalled boundary.

Thursday night a series of shortwaves will lift northeast
through the area, strengthening low-level southwest flow and
increasing PWs to around 1.3". We expect scattered showers to
overspread at least inland areas late Thursday night into Friday
morning.

A stronger upper trough will take shape across the central US
Friday afternoon, resulting in broad, strong SW flow into the
southeast states through Saturday. A surface wave will develop
and lift north on Saturday accompanied by extensive upper jet
divergence and PW values approaching the 99th percentile for
late January. Negative Lifted Indices and marginal low-level
CAPE could support scattered thunderstorms mainly Saturday.
Either way we expect moderate to occasionally heavy rainfall on
Saturday.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Unsettled weather expected into Monday as a deeper upper closed low
near Texarkana shifts east through the Deep South. Very unseasonable
amounts of deep moisture will likely advect into the region from the
south and with strong synoptic forcing occurring we think conditions
will be favorable for high rain chances and some heavy rainfall with
several inches possible through early Monday. There is also a slight
chance of strong to possibly severe storms later Sunday as a warm
front shifts northward across the area.  Shear/helicity look
favorable but as usual the amount of instability doesn`t look as
favorable. Conditions should improve Monday night and especially by
Tuesday as the upper low lifts north and high pressure builds into
the region and then continues into Wednesday with dry weather.
Although cooler conditions are expected starting Monday,
temperatures will likely remain above normal.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VFR conditions are expected at both CHS and SAV terminals through
00Z Friday. However, there is a low risk of flight restrictions at
the SAV late tonight due to fog south of a cold front that stalls
near the area. Otherwise, expect a gradual wind shift overnight
from west to northeast, then northeast to southeast Thursday
morning/afternoon with winds below 10 kt.

Extended Aviation Outlook: Brief flight restrictions possible
Friday due to scattered showers. Occasional flight restrictions
expected Friday night through Monday as a series of disturbances
moves through. Thunderstorms possible Saturday and Sunday. Gusty
winds expected Sunday through Tuesday.

&&

.MARINE...
Tonight: A slightly enhanced pressure gradient remains over the
coastal waters early tonight with the most notable wind gusts
seen across northern South Carolina and offshore Georgia waters.
In general, winds could gust around 20 kt for the next couple
hours beyond 15 nm from the coast. Conditions should gradually
improve later tonight as stronger low-lvl winds slide east of
the coastal waters and a cold front approaches from the north
and stalls over the area. In general, winds will become northeast
behind the front as high pressure spills over South Carolina
waters, but cold air advection is weak so no significant surge
is anticipated. Further south, winds could take a bit longer to
ease, but should gradually transition to north after midnight.
Seas will range between 2-3 ft early tonight, then slowly subside
to 1-2 ft after midnight.

Relatively weak flow expected Thursday through Saturday, then
increasing southerly flow ahead of a strong low pressure system
and cold front. Small Craft Advisories increasingly likely
starting Sunday and persisting through early to mid next week.

Sea fog may redevelop over the nearshore waters at some point
Friday into Saturday as higher dewpoint air spreads over the
cool shelf waters.

&&

.CLIMATE...
Record highs for Wednesday, 18 January:
KCHS: 77/1952.
KCXM: 79/1928.
KSAV: 81/1937.

&&

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

&&

$$
NEAR TERM...DPB
SHORT TERM...JRL
LONG TERM...RJB
AVIATION...DPB/JRL
MARINE...DPB/JRL
CLIMATE...



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