Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
354 am EDT Sat Jul 23 2016
high pressure will gradually shift offshore and persist through
much of next week.
Near term /through tonight/...
today: high pressure will shift offshore while a trough
strengthens east of the Appalachians. Meanwhile some upper level
shortwave energy will drop south between the ridge to the west and
trough to the east. Some showers/thunderstorms could drop south
toward the central SC coast this morning before diminishing with
attention then turning to convection along the sea breeze this
afternoon. Think rain coverage will be isolated and thus
maintained chances around 20 percent, although could become more
scattered near mesoscale boundary interactions. Model soundings
indicate downdraft cape over 1000 j/kg with cape near 3000 j/kg so
can't rule out a few severe storms with damaging wind gusts
especially. Highs will be above normal with mid to possibly upper
90s inland and closer to 90 near the coast. Heat indices should
top out around 100 most places except closer to 105 south of I-16.
Tonight: generally dry after early evening convection wanes.
Low temperatures will range from the mid 70s inland to closer to
80 at the coast.
Short term /Sunday through Tuesday/...
Sunday through tuesday: relatively stagnant synoptic pattern
expected early next week. The forecast area will remain under the
influence of broad mid/upper level ridging through the period. At
the surface, Atlantic high pressure will prevail while a weak
Piedmont trough sits inland. Convective initiation will largely be
driven by the sea breeze and mesoscale boundaries with no larger
scale forcing mechanisms in play. Coverage should remain fairly
limited given subsidence and dry mid levels, and current forecast
features only slight chance pops in the afternoon and evenings.
Organized severe threat is low, however isolated severe storms are
possible especially where boundary interactions occur.
High temperatures mainly in the mid 90s will combine with dew points
in the low 70s to yield heat indices 103-106 each afternoon. Thus no
heat advisories are expected. Lows in the mid to upper 70s.
Long term /Tuesday night through Friday/...
little change in the weather pattern expected through late week,
with the primary surface features being Atlantic high pressure and a
weak Piedmont trough. Fairly typical summertime pop scheme, with
shower/thunderstorm coverage peaking in the afternoon and evening
when instability is greatest. No more than 20-30% chances warranted
at this time. Temperatures forecast to be above normal through the
Aviation /08z Saturday through Wednesday/...
VFR conditions are expected to prevail at kchs and ksav through
06z Sunday. There could be some patchy fog/stratus this morning,
but chances are too low to mention. Isolated showers and
thunderstorms will be possible this afternoon, mainly 17-21z, as
the sea breeze pushes inland but chances are also too low to
Extended aviation outlook: brief flight restrictions possible with
today and tonight: high pressure will remain in control with winds
mainly 15 kt or less, greatest near the coast this afternoon due
to the sea breeze. Seas will be a mix of around 9 second swells
and shorter period wind waves, with significant wave heights
mainly 3 feet or less, highest near the Gulf Stream. Also,
conditions look pretty favorable for waterspouts again this
morning within the nearshore waters along any cumulus lines
associated with the land breeze. Thus, will likely issue a marine
weather statement to highlight.
Sunday through thursday: rather benign conditions expected over
the waters through mid week. Atlantic high pressure will persist
while a weak trough sits inland. This will maintain a
south/southwest flow over the marine zones. Speeds generally at or
below 15 knots, peaking in the afternoon with the sea breeze
circulation and again overnight due to nocturnal jetting. Seas 2-3
feet on average.