Area Forecast Discussion
Issued by NWS Charleston, SC
FXUS62 KCHS 291443
Area Forecast Discussion
National Weather Service Charleston SC
1043 AM EDT FRI JUL 29 2016
Atlantic high pressure along with an inland trough will prevail into
early next week. High pressure will then become suppressed further
to the south which could allow a weak cold front to approach from
the north by the middle part of next week.
.NEAR TERM /THROUGH TONIGHT/...
Today: 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
within a west/southwest flow. However, we can not rule out a few
isolated showers and/or thunderstorms well inland late afternoon
into early evening given a significant amount of sfc heating under
mostly sunny skies.
Temps will be considerably warm and above normal this afternoon given
a west-southwest flow under a ridge of high pressure and full
sun. In general, a somewhat pinned seabreeze will allow temps to
peak in the upper 90s for most areas away from the immediate
coast. A few locations could hit the 100 degree mark. These temps
in combination with dewpt temps in the upper 60s to lower 70s will
likely produce heat index values between 104-108 this afternoon
and evening, but there could be a small window of time where heat
index values approach 110 degrees where moisture pools near the
seabreeze in Charleston County. At this time, mixing out of low-
lvl moisture should result in conditions remaining below Heat
Tonight: There are hints that isolated storms could sneak in from
the W-NW in the evening in proximity to the Piedmont trough and a
weak short wave, but probabilities are not high enough to generate
any mentionable PoP in the forecast. Overnight there could be a
little activity forming out near the western wall of the Gulf
Stream, but the trajectory forecast would keep anything that forms
offshore. Otherwise it`ll be another very warm and sticky night with
mins to struggle to drop to 75-80F inland and not even any lower
than the lower 80s in downtown Charleston and along many coastal
sites. Record high minimums certainly could be challenged at the 3
official climate sites (See CLIMATE section below).
.SHORT TERM /SATURDAY THROUGH MONDAY/...
Saturday and Saturday night: Aloft, the pattern will continue to
display very slight and gradual weakening of the strong and
persistent ridge aloft. The main ridge axis will become increasingly
narrow and will setup to become more focused across south Georgia
and the Florida peninsula. This will result in a bit of a return in
the inland lee trough as the subtropical surface high is also
further south. Such subtle changes will bring about modestly better
chances for convection and a slightly less hostile environment for
thunderstorm development. Profiles are still quite unimpressive but
should at least allow for isolated thunderstorms. There could be
slightly better coverage further north and away from the ridge axis,
but only enough to carry a 30 PoP for the tri-county. Another very
warm day with highs in the upper 90s, combined with lows in the
upper 70s will further contribute to potentially record breaking
temperatures for the month of July (see Climate section for details).
The overnight is expected to be dry.
Sunday through Monday: Aloft, the forecast area will be solidly
sandwiched between broad troughing to the north and the upper ridge
to the south. Through early next week, the inland lee trough looks
to be increasingly active and with modestly better sounding profiles
across the forecast area, this should result in a much more typical
coverage pattern for thunderstorms. PoP`s are generally in the 30-50
percent change range. The overall severe threat doesn`t look
particularly high. Temperatures may come down a few degrees into the
mid 90s, but with dew points still in the low to mid 70s heat index
values will still be in the 100-105 degree range.
.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
In the long term period through Thursday, the relatively broad
trough will finally break down much of the upper ridge with it
splitting into one part over the south-central CONUS and the other
over the Atlantic. Towards the end of the period the orientation of
the ridge to the west will help turn the large scale flow more
northwesterly across the area which may allow for more embedded
shortwave energy to approach the area. As such, we may need to keep
more of an eye on upstream convection and how it evolves and
potentially heads into the region. Overall convection changes are
higher through this period, thanks in part to the presence of a weak
front situated to the north and the slightly cyclonic flow aloft.
Also of note, temperatures should exhibit a slight cooling trend
with primarily low 90s by Thursday.
.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
VFR. KCHS will be gusty at times during the late morning into the
afternoon with deep mixing profiles, a little less so at KSAV.
Extended Aviation Outlook: Mainly VFR. Brief restrictions will be
possible with afternoon and evening showers/thunderstorms into
early next week.
Today: Atlantic high pressure will dominate the coastal waters while
a sfc trough persists inland. The setup will support a west wind
through late morning before winds begin to back to the southwest and
south near a developing seabreeze this afternoon. In general, wind
speeds will remain around 15 kt, but could gust up to around 20 kt
along coastal locations and in the CHS harbor near the vicinity
of the seabreeze circulation. Seas will range between 2-4 ft,
highest in offshore Georgia waters early.
Tonight: The low level jet will again impact the maritime community,
although geostrophic winds are a bit lower than they were last
night, so we`ll probably not require any SCA headlines. However,
winds and seas will be elevated for the end of July with enough
pinching between the inland trough the sub-tropical ridging to the
south. Expect SW winds of 15 or 20 kt, even some higher gusts at
times, with seas of 3 or 4 ft. Maybe a few showers/T-storms out
near the Gulf Stream after midnight.
Saturday through Wednesday: The overall pattern will generally
remain unchanged into early next week and will feature a trough of
low pressure inland and high pressure over the Atlantic. This will
drive a persistent southwest flow across the local waters, which
will top out in the 15-20 knot range each afternoon/evening. Seas
will be in the 1-3 ft range for the most part, with some 4 ft seas
possible around 20 nm and beyond during the times of strongest
Record high minimums for 29 July...
KCHS: 80 set in 1999.
KCXM: 85 set in 1999.
KSAV: 82 set in 1878.
Record high maximums for 29 July...
KCHS: 100 set in 1993.
KCXM: 99 set in 1999.
KSAV: 103 set in 1993.
Record high minimums for 30 July...
KCHS: 80 set in 2011.
KCXM: 82 set in 1999 and previous.
KSAV: 81 set in 1878.
***Top 5 Warmest Months on Record by Average Temperature***
Charleston International Airport - KCHS (Records Back to 1938)
1. 86.1 - July 1986
2. 85.9 - July 2016 (3 days left)
3. 85.5 - July 1993
4. 83.9 - July 1992
5. 83.8 - July 1998
Savannah International Airport - KSAV (Records Back to 1874)
1. 86.7 - July 1993
2. 85.9 - July 2016 (3 days left)
3. 85.7 - July 1986
4. 85.7 - July 1875
5. 84.8 - August 2011
***Top 5 Driest Months on Record for July***
Savannah International Airport - KSAV (Records back to 1871)
1. 0.82 - 1888
2. 1.21 - 2016 (3 days left)
3. 1.25 - 1881
4. 1.33 - 1949
5. 1.35 - 1972