Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
416 am EDT Tuesday Jul 7 2015
Atlantic high pressure and an inland trough of low pressure will
prevail into early next week.
Near term /through tonight/...
today...upper ridging looks to build in from the east although some
low-level troughing...the sea breeze and lingering deep moisture
should lead to isolated showers and thunderstorms...mainly late this
morning...likely becoming scattered in coverage this afternoon. Due
to weak shear and moderate instability the convection should be
pulse-like in nature. Thus...expect a low severe risk...mainly a
result of mesoscale boundary collisions...with damaging winds the
biggest hazard. Highs should be near normal in the lower 90s away
from the locally cooler coastal areas...with a few middle 90s possible
over far interior southeast Georgia.
Tonight...lingering convection inland early will weaken/dissipate
and eventually shift over the Atlantic where the best convergence
and instability will be. Low temperatures will be in the lower to
middle 70s...with middle to upper 70s along the coast.
Short term /Wednesday through Friday/...
upper level ridging will expand westward over the region on
Wednesday...build overhead on Thursday...then become centered just
west of the region on Friday. Meanwhile at the surface...high
pressure over the Atlantic will slowly retrograde toward the coast
with its axis eventually extending south of the area toward the end
of the week as a Piedmont trough nears from the northwest.
Strengthening subsidence/mid-level capping will generally act to
suppress convection...but considerable surface-based instability and
enough moisture advection will allow for isolated to maybe scattered
showers and thunderstorms...mainly each afternoon and early
evening...along and ahead of the sea breeze. However...it is very
possible for no convection at all by Friday. As heights aloft
rise...so will temperatures across the area. Highs will generally be
in the middle to upper 90s each afternoon inland from the immediate
coast...with heat index values rising upwards of 105-107 in some
spots. Lows in the lower to middle 70s appear reasonable.
Long term /Friday night through Monday/...
medium range guidance is generally in good agreement through the
long term period. Strong upper level ridging will remain centered
just west of the region on Saturday. The ridge will then shift
westward across the Southern Plains through early next week and
allow a long wave trough to eventually become established over the
eastern United States. At the surface...a west-east orientated ridge
axis will remain south of the area into the weekend...before
Atlantic high pressure centered well offshore becomes reestablished
early next week. Meanwhile...a trough axis will linger near or even
over the area late in the weekend into early next week.
As for expected conditions...it is very possible for rain-free
conditions to be in place over the weekend...although the forecast
does indicate isolated showers/thunderstorms in some areas as is
always possible this time with the sea breeze. Isolated to maybe
even scattered showers and thunderstorms could be more of a factor
early next week as the upper trough deepens over the region. Expect
continued warming into Saturday...which could be one of the hottest
days of the period...before slightly decreasing temperatures into
next week as heights lower aloft. Overall...temperatures will
certainly remain above normal and the heat index could be
problematic with indices just over 105 possible into the weekend.
Aviation /08z Tuesday through Saturday/...
mainly VFR. Can/T rule out some fog toward daybreak as high
clouds thin...mainly at ksav. Expect some showers and thunderstorms to
develop this afternoon along the sea breeze but chances are too
low to mention at this time.
Extended aviation outlook...brief flight restrictions are possible
in mainly isolated afternoon/early evening showers and
today and tonight...Atlantic high pressure to prevail with mainly south
to southwest winds 10-15 knots and seas 2-3 feet.
Wednesday through Sunday...south to southwest winds will prevail
through the period as the region remains along the western periphery
of Atlantic high pressure. Winds will generally average 10-15
knots...possibly a bit higher at night with weak nocturnal surging and
along the land/sea interface with the afternoon sea breeze. Seas
will average 2-4 feet. Both winds and seas look to remain below Small
Craft Advisory thresholds.