Area Forecast Discussion
Issued by NWS Charleston, SC
FXUS62 KCHS 290214
Area Forecast Discussion
National Weather Service Charleston SC
1014 PM EDT THU JUL 28 2016
Atlantic high pressure along with an inland trough will prevail into
early next week. High pressure will then migrate offshore which
could allow a cold front to approach from the north by the middle
part of next week.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
29/02z temperatures were running very near readings from 24 hours
It will be another warm and humid night for the region as
expansive high pressure holds firm. Modest low-level jetting
will prevent a full decoupling of the boundary layer, especially
at the coast, which will help keep temperatures up. Expect lows
from the mid-upper 70s inland with lower 80s at the coast. Similar
to last night, some beach locations will not drop much below 83-84
degrees with heat indices holding over 90 degrees through sunrise.
Clear skies will prevail although some debris cloudiness from
earlier convection along the Northeast Florida coast will impact
the Georgia coastal zones for the next few hours.
The record high minimum (July 29th) of 80 degrees set in 1999
could be challenged at the Charleston Airport Friday morning.
Other than making minor adjustments to sky cover and dewpoints,
the rest of the forecast is on track.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
The pattern will feature a large mid/upper lvl ridge of high
pressure over the southeastern United States while a broad trough of
low pressure persists over the Midwest and Northeast. At the sfc,
the area will remain situated between the western edge of Atlantic
high pressure and the eastern edge of a low pressure trough extended
over the Midlands. The pattern will result in mainly dry conditions
on Friday when the mid/upper lvl ridge is strongest, but should
favor increasing chances of showers and thunderstorms as the ridge
becomes more elongated across the region with weak h5 shortwave
activity passing just to our north on Saturday. By Sunday, a more
direct onshore wind component combined with a gradual eastward shift
of the inland sfc trough could support even higher chances of
showers and/or thunderstorms, particularly within the Tri-County
area where an inland moving seabreeze interacts with the sfc trough
during peak heating. At this time, the threat of strong or severe
thunderstorms remains low given a lack of shear, but an isolated
occurrence cannot be ruled out, especially on Sunday.
Temps will remain above normal through the period given a west-
southwest flow aloft. However, showers and thunderstorms could limit
overall high temps a few degrees on Saturday and Sunday. In general,
highs will range in the mid to upper 90s each day outside convective
activity. These temps in combination with dewpt temps in the upper
60s to lower 70s will likely produce heat index values between 105-
109 each afternoon, but some mixing out of low-lvl moisture should
result in conditions remaining just below Heat Advisory levels.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The upper level ridge will gradually slide off the coast early next
week as the base of a broad upper level trough dips closer to our
area, resulting in a more unsettled period. At the surface: Atlantic
high pressure slides further out to sea, allowing troughing that has
been confined well inland over the past week to gradually spread
toward the coast. A weak cold front may approach, and possibly fully
cross, the area Tuesday, providing at least a temporary break from
the above normal temps for the middle portion of next week.
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Extended Aviation Outlook: Brief flight restrictions are possible
with afternoon showers/thunderstorms Saturday into early next
Tonight: Typical deep summer low-level jetting will keep breezy
conditions in place across the coastal waters tonight. Models have
been similar in showing a corridor of 25-30 kt 1000 hPa winds
developing along the middle and upper South Carolina coast after
midnight. This should translate to several hours of frequent gusts
to 25 kt for the Charleston County waters overnight. A Small Craft
Advisory will be issued to reflect this. Elsewhere, winds will
hold steady 15-20 kt. Seas will average 2-4 ft.
Friday through Tuesday: Atlantic high pressure will
dominate the waters this weekend into early next week while a sfc
trough prevails inland. The pattern will favor a southerly wind
between 10-15 kt over most waters, but occasional surges around 20
kt could occur along the coast each afternoon with a sea breeze
circulation and at night due to nocturnal jetting. Seas will range
between 2-4 ft.
The low temperature so far at KCHS has been 80 deg. If current
trends persist, the record high minimum for the date will be
tied. (80 set in 2014).
Record high minimums for 29 July...
KCHS: 80 set in 1999...
KCXM: 85 set in 1999...
KSAV: 82 set IN 1878...
MARINE...Small Craft Advisory until 8 AM EDT Friday for AMZ350.