Area Forecast Discussion
Issued by NWS Charleston, SC
FXUS62 KCHS 251947
Area Forecast Discussion
National Weather Service Charleston SC
347 PM EDT Sun Sep 25 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
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Tonight: The center of the upper low will continue to sit over the
Florida panhandle while another upper level disturbance north of the
Bahamas will begin to draw northwestward toward the coast of the
forecast area. This disturbance north of the Bahamas has helped to
generate considerable convection off the east coast of Florida
today. As this feature aloft draws closer to the area overnight, a
coastal trough is expected to sharpen along the coast. Moisture will
begin to increase in depth and virtually all of the models show some
degree of increase in showers over the coastal waters and along the
coast. For land areas, the best rain chances are expected to be for
the southeast South Carolina coast where the better low level
convergence should reside. Still unclear just how far inland showers
will be able to penetrate, so have favored just the coast for now.
Setup and guidance again point to stratus development. Can`t rule
out fog, but if it were to occur it would likely be more from
stratus build down. Lows are expected to fall into the upper 60s
inland and low 70s elsewhere.
.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
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
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
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.
.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
VFR conditions will prevail this afternoon and evening. Overnight,
a coastal trough is expected to sharpen to the east of the
terminals as high pressure becomes more prominent inland.
Probabilities continue to be high for more stratus development
across the region and the airmass is essentially the same as it
was last night. Have introduced MVFR ceilings at both sites in the
09-10z time period. Chances for showers to move onshore and impact
the area will be highest at KCHS so a VCSH has been added there.
MVFR ceilings should linger into mid morning before lifting to
VFR. Could also see some fog, but ceilings are the biggest
concern. Can`t totally rule out ceilings dropping to IFR, but
chances are too low to advertise as of now. Coverage of showers
and isolated thunderstorms will increase late morning and into the
early afternoon on Monday.
Extended Aviation Outlook: Flight restrictions will be possible in
showers and thunderstorms through Wednesday.
Tonight: 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.