Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
710 am EDT Wednesday Aug 5 2015
an inland trough will develop today and persist into Friday. A cold
front will drop through the area on Saturday...then another front
may move in from the northwest during the early to middle part of
Near term /through tonight/...
the Piedmont surface trough across the inland Carolinas will
setup today while Bermuda high pressure extends across the SW Atlantic
into Florida. Temperatures are expected to rapidly warm into the lower
90s many areas around noon with readings on their way to the upper
90s across our northwest tier of zones bordering the csra and southeast midlands
to the solid middle 90s along the U.S. 17 corridor. Surface dew
points well inland to the north of I-16 are expected to mix out
enough to maintain heat indices closer to 105 degrees this
afternoon. Even closer to the coast...soundings indicate that
subtle mixing trends will occur and we are still not expecting
excessive heat index values of 110 degrees today.
Drier air aloft that invaded much of Georgia and South Carolina on
Tuesday is forecast to slowly give way to increasing deeper
layered moisture from the Gulf of Mexico later today. Mainly
isolated convection is expected this afternoon with the exception
of slight better late afternoon shower and thunderstorm chances across southeast
Georgia...especially along and south of I-16 where some 2 inch
precipitable waters return. Cannot totally rule out a few strong pulse thunderstorms in
this region but overall there still seems to be a lingering
subsidence inversion between 12 kft and 15 kft which will temper
updraft strength potential.
Isolated convection could linger into the evening hours and trended
dry overnight despite some elevated instability lingering after
midnight. Skies should be partly cloudy with low temperatures typical for
the season...middle 70s to near 80 beaches and barrier islands.
Short term /Thursday through Saturday/...
Thursday into Friday look fairly active due to a series of strong
shortwaves dropping into the area beginning late Thursday.
Increasing southwest flow in the lower levels will advect 2"+
precipitable water values into the region. On Thursday the initial
convection is likely to be triggered by both the sea breeze and
convergence along the inland trough. Thursday night there is fairly
strong model consensus that scattered showers and thunderstorms will move
through the area in association with the upper vorticity energy.
Friday...the brunt of the shortwave energy will push off the coast
but several models show a continued stream of vorticity energy dropping
southeast. A cold front is prognosticated to drop into the area Friday
evening. Precipitable waters will remain above 2" for most areas during the day.
The best convective coverage is expected across southeast Georgia and
coastal sections of SC where the deepest moisture resides.
Slightly drier air will filter in from the north on Saturday...
reducing rain chances over northern areas though deeper moisture
across southeast Georgia may allow for slightly better afternoon shower
and thunderstorm coverage.
Long term /Saturday night through Tuesday/...
drier high pressure will prevail Saturday night through Sunday
before Atlantic high pressure rebuilds and increases moisture across
the southeast states. Isolated mainly afternoon and evening showers
and thunderstorms expected Sunday into Monday. A cold front approaches from
the northwest Tuesday with increasing rain chances Tuesday into Wednesday.
Aviation /12z Wednesday through Sunday/...
VFR conditions will prevail at both kchs and ksav through 12z
Thursday. Isolated convection is possible along the coastal
corridor this afternoon...potential much too low for any taf
Extended aviation outlook...main concerns are occasional
reductions in visibility and/or ceiling due to showers and thunderstorms
Thursday through Monday...especially in the afternoon and evening.
southwest synoptic flow will prevail across the local marine
waters through tonight. Typical warm-season surges are expected
with winds increasing to 15g20kt middle to late afternoon along the
Charleston County coast while the near shore waters down to gray
reef nms see a similar surge initiate late in the day and
continuing into the overnight before ebbing late. Seas in the 2-3
feet range today will build to 2-4 feet tonight...highest beyond 20
A persistent SW flow continues Thursday through Friday night until a
cold front stalls over or just south of the waters. Fairly weak wind
flow expected over the weekend into early next week due to a weak
Rip currents...we maintained a moderate risk along Charleston
County beaches today.