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Area Forecast Discussion

FXUS62 KCHS 260522

Area Forecast Discussion
National Weather Service Charleston SC
122 AM EDT Mon Sep 26 2016

High pressure will continue to build into the area tonight but
will weaken by late Monday ahead of an approaching cold front. The
front will cross the forecast area and push off the coast by mid
week and high pressure will build into the region by the end of
the week.


Minor tweaks to forecast at the midnight hour. The rest of the
forecast is on track.

A weak vorticity center located well to the north of the Bahamas
will slowly draw closer to the forecast area overnight. The
feature is supporting numerous showers with a few tstms along the
west wall of the Gulf Stream. This activity will gradually expand
closer to the beaches through the night as surface moisture
convergence increases in response to the formation of a weak
coastal trough off along the Georgia coast. An increase in layered
clouds will keep temps warm along coastal areas overnight.


Mid level heights will fall in response to a closed low and potent
shortwave energy digging into the Upper Midwest and Great Lakes. At
the surface, high pressure centered over the northeastern U.S.
early Monday will gradually shift offshore as a cold front
approaches from the west. This will place the forecast area solidly
in the warm sector through much of the period. Elevated moisture and
proximity to a coastal trough will keep precipitation chances in the
forecast each day. Decent instability will support mention of
thunder, however severe threat will remain low.

Temperatures are forecast to be a few degrees above late September
climo, with highs in the mid/upper 80s and lows in the upper 60s/low


The cold front will move through the area Wednesday night, with
global models showing the front over the coastal waters by sunrise
Thursday morning. However, given the uncertainty in terms of the
weakening parent low near the Great Lakes, the front may drag its
feet getting through the area, moving over the waters and stalling
out well to our south and west by midday Thursday. Either way,
strong, dry continental high pressure will fill in behind the front
and quiet weather will ensure for the second half of the week. Temps
will be near to a few degrees below normal through the period.


Mostly VFR but we could still see a period of MVFR cigs at both
terminals prior to sunrise, with KSAV perhaps having a slightly
higher chance between 08Z and 12Z and KCHS toward dawn. Periodic
showers are possible along the South Carolina Coast today as
moisture advects onshore to the the north of a weak low pressure
area trying to pinch off along the Gulf Stream. Any showers at
KSAV will probably be more isolated by late morning and afternoon.

Extended Aviation Outlook: Flight restrictions will be possible in
showers and thunderstorms through Wednesday.


Overnight: High pressure will continue to build inland and as
coastal trough will develop and sharpen through the night. As this
occurs, a tightening northeast gradient will result in
strengthening flow, especially along the South Carolina coast. The
forecast features 15-20 knots for the Charleston County coast with
lesser winds elsewhere. The setup favors another round of showers
and isolated thunderstorms developing tonight, and the highest
rain chances are across the coastal waters. Seas will range 2-4
feet through the night.

Monday through Friday...marine conditions will be fairly quiet
through the work week. A coastal trough will develop Monday and
persist through Tuesday before a cold front approaches from the
west. The front is expected to move offshore mid-week with high
pressure to return late week. Wind speeds on average will be at or
below 15 knots, with seas 2-3 feet.





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