Scientific Forecaster Discussion
fxus62 kchs 231519
Area forecast discussion
National Weather Service Charleston SC
1119 am EDT Thu Mar 23 2017
high pressure will build in from the north through tonight before
shifting over the Atlantic through the weekend. A cold front is
expected to affect the area early next week.
Near term /through tonight/...
today: a wedge of high pressure will persist along the eastern
Seaboard, resulting in dry conditions over the southeastern United
States. Expect the sfc wedge to dominate the pattern with a cooler
northeast wind despite mostly sunny skies and an expanding mid/upper
lvl ridge of high from the southwest. In general, high temps will
range in the low to mid 60s, warmest over southeast Georgia.
Tonight: the surface high starts to shift east, allowing a stronger
onshore flow to develop and increase low-level moisture. Some
maritime stratus may move into coastal areas late tonight though
most areas will see no greater than partly cloudy skies.
Short term /Friday through Sunday/...
Friday, the center of sfc high pressure is forecast to shift over
the western Atlantic as low pressure deepens over the southern Great
Plains. This pattern will support steady southeast winds across the
forecast area. Given partly sunny conditions and the passage of the
500 mb ridge axis overhead, conditions should warm considerably from
Thursday. Using a blend of guidance, high temperatures are forecast
to range in the low to mid 70s.
Saturday, a low pressure system is expected to track from the
southern Great Plains to the mid west as high pressure remains over
the Atlantic. Onshore winds from the southeast through continue through the
period. High temperatures may warm two to four degrees warmer than
values reached on Friday.
Sunday, the base of a 500 mb trough is expected to rotate on the southeast side
of a closed low centered over the mid west. The occluded sfc low
will slowly move north toward Lake Michigan through the day. The
region will remain within the warm sector, highs reaching into the
upper 70s to the low 80s with dewpoints in the upper 50s. GFS
indicates that afternoon values of sbcapes are forecast to range
from 500 j/kg near the coast to over 1000 j/kg inland. I will
increase afternoon and evening pops to chc inland to schc over the
marine zones, mentioning both showers and thunderstorms.
Long term /Sunday night through Wednesday/...
conditions appear unsettled across the County Warning Area Sunday night through late
Tuesday. Medium range guidance indicates that a axis of a longwave
trough will ripple across the southeast Continental U.S. Early next week. The
forecast area will remain within the warm sector, with weak to
moderate instability developing each afternoon and evening. The
environment appears the most supportive for deep convection late
Tuesday with the passage of the mid level trough and sfc boundary.
Temperatures early next week should start the day around 60 degrees
and peak around 80 by mid afternoon. Thursday and Friday, the
leading edge of a Canadian air mass is expected to spread across the
County Warning Area. Conditions should feature dry wx with slightly above normal
Aviation /15z Thursday through Monday/...
VFR conditions are expected at both chs and sav terminals through
tonight. Gusty winds today.
Extended aviation outlook: showers and thunderstorms could develop
each afternoon and evening Sunday through Tuesday. Patchy early
morning fog is possible over wet soil.
today and tonight: a strong northeast gradient will persist through
early afternoon with a wedge of high pressure building south over
the coastal waters. Conditions continue to support small craft
advisories for all waters with northeast winds peaking around
25-30 kt and seas as high as 5-7 ft in nearshore waters and 7-9 ft
in offshore Georgia waters. Winds will slowly decrease this
afternoon through tonight though seas will be slower to subside.
The trend suggests conditions will fall below Small Craft
Advisory levels in nearshore waters by midnight while higher
winds/seas remain for a Small Craft Advisory in offshore Georgia
Friday through tuesday: the center of high pressure will
gradually shift over the western Atlantic Friday and Friday
night, allowing seas to decrease to around 5 feet for most areas
by sunset Friday. Scas are scheduled to expire Thursday night,
expect amz374 remaining through most of Friday. Steady south to
southwest winds are forecast to remain over the zones through
the weekend into early next week. Seas could increase to six
feet across eastern amz374 during the weekend. Scattered showers
and thunderstorms are forecast to develop Sunday through
Tuesday, especially during the daylight hours.
Rip currents: a strong northeast wind and a 7-8 second northeast
swell today will produce a moderate risk for rip currents along
Marine...Small Craft Advisory until 4 PM EDT this afternoon for amz330.
Small Craft Advisory until midnight EDT tonight for amz350-352-
Small Craft Advisory until 6 PM EDT Friday for amz374.