Scientific Forecaster Discussion
fxus62 kchs 220128
Area forecast discussion
National Weather Service Charleston SC
928 PM EDT Fri Jul 21 2017
Atlantic high pressure will extend west into the southeast
coast through this weekend as broad low pressure remains
inland. A weak cold front will approach the area during the
middle of next week. A low pressure system may develop over the
Carolinas during the late work week.
Near term /until 6 am Saturday morning/...
dry and mostly clear conditions will prevail overnight. Lows
will range from the mid 70s inland to around 80 at the beaches.
For the late evening update, mentionable pops were removed
across far interior areas. The rest of the forecast is on
Short term /6 am Saturday morning through Monday/...
saturday: the mid level pattern over the region will feature a
broad weakness, with a large ridge centered over the Atlantic
and another ridge centered over the mid Mississippi River
valley. At the sfc, a trough should develop by Saturday
afternoon across Piedmont of the Carolinas. Sfc winds across the
region are forecast to range from SW inland to from the south
near the coast. High temperatures are forecast to range in the
mid 90s inland to near 90 over the beaches. Given the
temperature and wind forecast, a sea breeze should develop
during the mid to late afternoon, but should slowly move inland.
The sea breeze should support a line of cu and isolated deep
convection. Forecast soundings indicate that the level of free convection may range
between 4.5-5 kft. I will keep the pops schc and will delay
mentionable values until 20z.
Sunday: the pattern will generally remain the same from
Saturday. However, low pressure is expected to develop across
the mid Atlantic states, with the trough remaining across the
Piedmont. The pressure gradient across the forecast area will
slowly steepen through the day, with gusts expected across the
marine zones and near the coast. A slight increase in llvl
moisture convergence should support scattered thunderstorms
inland, with slight chcs generally east of I- 95.
Monday: using a blend of temperature guidance, high temperatures
are forecast to range a degree or two below values reached Sat
and sun. Dewpoints are expected to remain in the low to mid 70s
as the region remains on the east side of the sfc trough. Given
the temps and dewpoints, any cin should erode during the late
afternoon hours. Short range guidance indicates that a weak
short wave is expected to ripple across the forecast area during
the late afternoon. Pops should range from 40 percent over Georgia
and around 30 near the coast and coastal waters.
Long term /Monday night through Friday/...
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
Aviation /02z Saturday through Wednesday/...
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.
tonight: marine zones will remain on the western periphery of
the Bermuda high, resulting in mainly S to SW winds with speeds
less than 15 knots through tonight and seas 2 to 3 ft.
Saturday through wednesday: broad high pressure will remain across
the marine zones through the period. Low pressure is expected to
develop across the mid Atlantic states Sunday into Monday. South-southwest winds
are forecast to become gusty across the marine zones on Sunday and
Monday, with gusts below 25 kts. Otherwise, winds should remain
generally from the south. Wave heights are forecast to range between
2 to 4 feet.
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.