Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 211414
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1014 AM EDT Fri Jul 21 2017

.SYNOPSIS...
Atlantic high pressure will extend west into the southeast
coast through this weekend as a surface trough remains inland.
A cold front will approach the area during the middle of next
week. Low pressure should then linger into late week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Previous forecast package remains on track and only minor
adjustments were needed to account for observed trends.
A weak mid level low pressure area will continue to slowly
retrograde across the Florida panhandle while a 700 MB shear
axis extends northeast off our coastal zones. Decreased diurnal
convection is expected today thanks to warming mid levels and
subsidence aloft expanding into the Carolinas from the Bermuda
High. Only slight chance pops, mainly this afternoon, are
warranted. Best potential for isolated mid/late afternoon
convection will be along the seabreeze and west of I-95,
somewhat closer to the mid level low over north Florida. Weak
low and mid-level lapse rates and low shear indicate pulse-type
storms with weaker updraft potential, resulting in primarily
sub-severe showers and thunderstorms, though an isolated strong
to severe thunderstorm cannot be entirely ruled out. It will be
warm with high temps in the mid 90s and some heat indices
peaking around 105 in the warmest spots.

Tonight: Tranquil weather conditions are expected with skies
mostly clear with lows in the mid 70s most areas once again,
warmer on the beaches and barrier islands where some southerly
nocturnal breezes linger.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
Saturday: Atlantic high pressure will nudge west over the Southeast
United States while a mid-lvl low gradually weakens over Georgia and
Florida. Although a light westerly flow could limit overall
convection, sufficient heating and moisture should trigger a few
afternoon showers and thunderstorms inland near the vicinity of a
lee trough developing over the Midlands, along an afternoon
seabreeze and over parts of Southeast Georgia where mid-lvl energy
meanders near the weakening mid-lvl low. Any convection that
develops during the day will likely weaken and or dissipate within a
few hours of sunset. Temps will be fairly warm during the day,
peaking in the mid 90s away from the coast. Overnight lows will
range in the mid 70s away from the immediate coast.

Sunday and Monday: Showers and thunderstorms are forecast over the
area early next week as high pressure gradually retreats over the
Western Atlantic and a mid-lvl shortwave shifts north along the
Southeast coast. Precip coverage should be greatest on Monday as an
inland sfc trough strengthens, instability increases and PWATs
approach 2.25 inches. In general, afternoon highs will peak in the
lower 90s both days. Overnight lows will range in the mid 70s away
from the immediate coast.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
A more active/unsettled weather pattern is expected next week as a
southwest sfc flow advects deep moisture to the region ahead of a
cold front that approaches from the north/northwest. The cold front
should struggle to push south of the region, likely stalling over or
near the area as its parent mid/upper lvl trough of low pressure
shifts off the Northeast coast. The setup will favor at least
chances of showers and thunderstorms each day with greatest coverage
expected over the area on Wednesday near the stalling front. Weak
low pressure should then persist along the stalled front into late
week, supporting afternoon showers and thunderstorms into next
weekend. High temps will generally be near normal during the week,
peaking near 90 degrees away from the coast. Overnight lows will
remain mild under extensive cloud cover, ranging in the low to mid
70s.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
VFR at KCHS/KSAV through 12Z Saturday. Isolated convection
possible along the sea breeze corridor but the chances will be
lower today and thus no mentions in the TAFs.

Extended Aviation Outlook: Afternoon showers/thunderstorms could
provide brief flight restrictions next week. Greatest chances should
occur on Wednesday as a cold front approaches the area. Otherwise,
VFR conditions will prevail.

&&

.MARINE...
The marine area will remain on the western periphery of the Atlantic
high, winds mainly south to southwest with speeds less than 15 KT
through tonight and seas 2 to 3 ft.

Saturday through Wednesday: High pressure will prevail over the
waters this weekend and early next week while a trough of low
pressure develops inland. A cold front will then approach the area
during the middle of next week. In general, winds/seas are expected
to remain below Small Craft Advisory levels through the period.
However, we could see southwest winds gusting as high as 20 kts
Sunday and Monday while the pressure gradient is somewhat enhanced
over coastal waters. Seas will range between 2-4 ft.

&&

.TIDES/COASTAL FLOODING...
Elevated tide levels due to the lunar perigee and new moon will
result in the possibility for minor coastal flooding during the
evening high tides this weekend into early next week, especially
along the SC coast. A coastal flood advisory may be required
for this evening`s tide later today.

&&

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

&&

$$
NEAR TERM...
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...
MARINE...DPB
TIDES/COASTAL FLOODING...



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