Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
404 PM EST sun Feb 14 2016
a low pressure system will impact the region Monday into Tuesday
morning. High pressure will dominate the weather pattern middle to
Near term /until 6 am Monday morning/...
cold high pressure will remain north of the area tonight while an
approaching upper shortwave enhances a coastal trough off the
SC/Georgia coast. Late tonight a weak coupled jet sets up over southern
SC...strengthening the coastal trough and allowing patchy rain to
develop over SC coastal areas and the adjacent waters.
Although stratocumulus will continue to overspread the area as
warm moist advection strengthens atop the cool boundary layer...
cold advection over far northern areas will drop temperatures into the
low to middle 30s by late this evening. However...the coastal trough
will shift inland late...weakening the cold advection while cloud
cover increases. Temperatures will be nearly steady or slowly
warming late tonight. Any precipitation that develops tonight would be
late and mainly over coastal portions so we do not expect any
issues with freezing rain.
Patchy fog may develop over inland southeast Georgia with a stratus
build-down situation though our ongoing forecast of 4-6 knots of
surface winds should prevent anything especially dense from
Short term /6 am Monday morning through Wednesday/...
Monday...a coastal trough will move northward and begin impacting
the southeast coast. Most areas will start out dry in the morning.
The exception will be the Charleston County coast where some light
showers are possible. South to southeast winds at the surface
combined with southerly flow aloft will advect moisture into the
region. The increasing moisture will coincide with developing
isentropic ascent, which will lead to increasing probability of precipitation and
rain/showers developing across the entire area in the afternoon.
High temperatures will range from the upper 50s across the tri-
County to the middle/upper 60s in southeast Georgia.
Monday night...low pressure over the Tennessee Valley will move
northeastward and a cold front will pass through our area after
midnight. The entire will have rain. Precipitable waters approaching 1.35 inches
could equate to periods of moderate to heavy rain. Additionally, the
combination of the forcing associated with the front, modest middle
level lapse rates, and weak instability could generate isolated
thunderstorms before the front moves through. Shear that is
forecasted to strengthen could support isolated supercells.
Severe winds are the main concern, but an isolated tornado is not
out of the question given the decent hodographs. But we stress the
severe weather potential remains low. As for temperatures, they will
be in lower to middle 50s.
Tuesday...deepening low pressure will move over the northeastern U.S
while high pressure to our west builds towards our area. Rainfall
will quickly end from southwest to northeast in the morning hours,
ending by around noon. Clearing skies within a west flow will
support high temperatures in the middle 60s on Tuesday, which is a few
degrees above normal for this time of year. Lows Tuesday night will
also be above normal, in the middle 40s.
Wednesday...high pressure across the lower Mississippi Valley will
build towards our area. Mostly sunny skies and west winds will
support high temperatures in the middle 60s.
Long term /Wednesday night through Sunday/...
dry high pressure will build over the area...resulting in a light
northerly wind through Thursday. In general...afternoon highs should
peak near 60 degrees on Thursday...then modify into the middle/upper
60s on Friday as an onshore wind develops in response to high
pressure slowly shifting off the eastern Seaboard. Overnight lows
will be in the upper 30s to around 40 Wednesday night...before
returning to the low/middle 40s Thursday night. Dry high pressure will
then become more established over the western Atlantic...setting up
slightly warmer conditions within a light southerly flow. In
general...temperatures will peak near 70 degrees Saturday and Sunday.
Aviation /21z Sunday through Friday/...
MVFR ceilings will persist through much if not all of the 18z taf
period at ksav as the coastal trough strengthens and moisture
streams in from the Atlantic. The stratocumulus deck will expand
north and lower across southern SC this evening. We expect MVFR
ceilings to overtake kchs early to middle evening and continue
through much of Monday. There remains a possibility of IFR
ceilings at either site...especially between 08 and 14z when the
trough is closest to the coast. We hinted at lower ceilings but
held off on introducing IFR conditions at this time given some
uncertainty in the statistical guidance. Could see some light rain
at kchs Monday morning but visibility restrictions would be minimal.
Extended aviation outlook...flight restrictions are expected Monday
night into Tuesday morning as widespread showers and/or isolated
thunderstorms occur with a passing low pressure system. A strong low
level jet will also bring gusty winds on Tuesday.
pinched northeast gradient will persist into the early evening
before the axis of strongest winds shifts toward the coast and
weakens as the coastal trough lifts north. We extended the small
craft advisories for the nearshore waters until 8 PM mainly for
the 25 knots gusts we continue to see at nearshore buoys. The
Charleston Harbor maintains an advisory until 6 PM due to some
gustier winds continuing close to feet Sumter. For the offshore Georgia
waters we expect a brief lull in Small Craft Advisory conditions late this evening
but increasing back above 6 feet over outer portions late tonight.
Thus we extended the advisory for the offshore Georgia waters through
A coastal trough will lift north along the southeast coast early
Monday...followed by deteriorating conditions Monday afternoon and
Monday night as a strengthening low pressure tracks inland and to
the northeast coast. Strong low level winds associated with the
system will result in a period of Small Craft Advisory level
winds/seas for most waters Monday night into early Tuesday.
Widespread showers and a few thunderstorms will also be possible
until a cold front pushes through the waters late Tuesday morning.
Conditions will then improve Tuesday afternoon as high pressure
builds over the coastal waters from the west. West winds at or
below 10 kts will slowly shift to north/northwest on Thursday as
high pressure continues to build along/over the eastern Seaboard.
Marine...Small Craft Advisory until 6 PM EST this evening for amz330.
Small Craft Advisory until 8 PM EST this evening for amz350-
Small Craft Advisory until 5 PM EST Wednesday for amz374.