Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
448 am EST Friday Feb 12 2016
low pressure will move northeast of the region today while a
stalled front lingers to the north of the Savannah River. A cold
front will move offshore early this evening...before a secondary
Arctic cold front pushes through early Saturday. High pressure
will then remain in control early next week before a low pressure
system impacts the region late Monday into Tuesday. Dry high
pressure will then return and persist middle to late week.
Near term /through tonight/...
pre-dawn...overnight clouds have been extremely variable and
transient providing fluctuating surface temperatures across the forecast
area. In northern zones...temperatures that fell to the middle and upper
30s last evening have warmed under cloudiness to the middle 40s but
may fall back a bit by daybreak as clouds are in and out. Dry
weather on tap through 6 am as moisture and isentropic ascent
not enough to produce measurable precipitation.
A consolidating wave of low pressure along a stationary front aligned
just north of the Savannah River this morning will slowly deepen
offshore today moving well off the North Carolina coast later
today. The bulk of the deeper moisture will reside to the north of
the forecast area today as a ribbon of channeled vorticity zips
over north Georgia and South Carolina. There will be a fair
amount of upper difluence and 850 mb to 500 Omega across the area
but today continues to look like a candidate for just slight
chance probability of precipitation across the board. We did extend some lower probability of precipitation
across most of southeast Georgia this afternoon to account for lower
level convergence along the trailing front while high resolution
models suggest there will may a narrow band of light showers
developing through the forecast area but coverage should be
Temperatures will be a challenge today as there is potential for readings
going warmer once again in Georgia and coastal South Carolina and we
have bumped highs into the upper 60s to near 70 south of I-16. We
also trended a bit higher at Charleston but it should remain
cooler up around the Santee Cooper lakes where the pattern stays
more wedged. Models indicate clearing should be after sunset many
areas along and east of I-95...perhaps late afternoon over inland
The cold front will drop south of the area Friday evening with
high pressure building in and cold northwest flow developing. Lows
will dip into the middle 30s inland to lower 40s south tonight after
Short term /Saturday through Monday/...
Saturday...conditions will be dry while an Arctic cold front pushes
through the region early...reinforcing a cold air mass already in
place over the southeastern United States. Temperatures will struggle to
reach the upper 40s to lower 50s early...then begin a cooling trend
during the afternoon as cold air advection dominates any downsloping
wind component aloft. Temperatures will be quite chilly Saturday night as
colder air continues to drop south into the area with little to no
cloud cover aloft. Temperatures in the low/middle 20s in combination with 5-10
miles per hour winds will support wind chill values near 15 degrees over much
of southeast South Carolina. A Wind Chill Advisory could be needed
late Saturday night into Sunday morning.
Sunday...another dry cold day is expected as prevailing northeast
winds occur along high pressure that is anchored over the Middle
Atlantic States. High temperatures should only peak around 40 degrees in
northern areas...and middle 40s in southeast Georgia. A transition in
the pattern should then begin Sunday night as high pressure begins
to slide offshore to our north. Temperatures will likely be warmer than the
previous night as a more onshore wind develops along the southeast
coast. In general...low temperatures should range in the low to middle
Monday...the day will start off chilly and there is a some concern
of frozen precipitation before daybreak should drizzle develop in response
to isentropic ascent. However...latest guidance does not depict
precipitation accumulation over the area and temperatures are expected to warm
quickly as a southerly flow strengthens well ahead of low pressure
tracking over the Mississippi River valley. Chances of precipitation
increase in the afternoon...mainly associated with a coastal trough
that skirts the coast. Afternoon highs should approach the middle/upper
50s over most areas. A few areas could see temperatures in the lower 60s in
Lake winds...another round of strong winds will be possible over
Lake Moultrie late Saturday into Sunday. A lake Wind Advisory could
Long term /Monday night through Thursday/...
a strengthening low pressure will track over the deep south and then
southeast states Monday night into Tuesday...leading to rain/showers
over much of the area. Instability will remain low during this
period...thus thunder remains out of the forecast. However...a 50 to
60 knots low level jet will accompany the system...likely leading to
gusty wind conditions Monday night and Tuesday. Rain/showers are
expected to quickly shift offshore by Tuesday afternoon as dry high
pressure builds over the region behind the departing low. High
pressure is then expected to persist through much of the week.
Overall high temperatures should range in the upper 50s to around 60 on
Tuesday...then gradually warm into the low/middle 60s by the weekend.
Overnight lows will be noticeably warmer than previous days...in the
Aviation /09z Friday through Tuesday/...
VFR will prevail at kchs for several more hours. Current data
support ceilings dropping to MVFR thresholds after sunrise at kchs
while at ksav...MVFR ceilings look to settle in by 10z. The best
chances for IFR ceilings still look to occur at ksav this morning...but
probabilities remain too low to justify an inclusion. Patches of
light rain will likely develop near kchs late tonight...but no
meaningful visibility reductions are expected given the dry sub-cloud
layer. VFR will return to both terminals by late afternoon as low
pressure moves away from the area.
Extended aviation outlook...flight restrictions are likely Monday
night into Tuesday within rain/showers that occur with a passing low
pressure system. Gusty winds are also expected Tuesday.
low pressure will develop off the South Carolina coast this morning
and move well to the NE today while a trailing stationary front
lingers through the northern waters. A cold front will push through
the waters this evening followed by high pressure building in tonight.
Winds will vary from light onshore off Charleston County this
morning to variable off the far southern South Carolina coast
to SW over Georgia waters. We maintained a marginal Small Craft
Advisory for waters 40-60 nm offshore of Georgia today but expect
lighter winds over the chilly shelf waters.
Offshore winds will begin to surge in the wake of cold front
early this evening and then strengthen to advisory levels again
beyond 20 nm overnight. Tonight strong cold air advection and
strong pressure rises could incite advisory conditions for parts of
the near waters...especially in favored jetting areas such as
Grays Reef and seaward from Tybee Island. Seas will build late
tonight to 4-6 feet offshore with a choppy 2-3 feet along the land/sea
interface. Expect additional small craft advisories to be issued
Saturday through Tuesday...an Arctic cold front will shift offshore
early Saturday with strong cold air advection over coastal waters.
Winds will turn to the north and then northeast behind a secondary
surge Saturday night...likely producing solid Small Craft Advisory
level conditions over all waters through Sunday morning. Conditions
should briefly improve Monday as a coastal trough develops off the
southeast coast...but will quickly deteriorate late Monday night
into Tuesday as a strengthening low pressure system tracks over the
deep south and then off the middle Atlantic and southeast coast. Strong
low level winds associated with the system will likely result in small
craft advisories for all waters and potentially gale conditions over
warmer waters offshore.
Marine...Small Craft Advisory until 6 PM EST this evening for amz374.