Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
406 PM EST Tuesday Feb 9 2016
..wind chills in the teens tonight...
a series of reinforcing cold fronts will cross the region through
Wednesday. Weak high pressure early Thursday will give way to
another cold front Thursday night. An Arctic cold front will then
move through Friday night or Saturday. A frontal system could
impact the region next Monday or Tuesday.
Near term /until 6 am Wednesday morning/...
broad deep troughing over the region will lose a bit of ground
overnight as it lifts to the northeast and high pressure builds
from the west. Some low-middle level moisture will
linger...especially the first part of the night...and this could
lead to a few light sprinkles...sleet pellets and/or snowflakes.
However...no accumulation or impacts are expected and thus left
any mention of precipitation out of the forecast. Gusty winds
will linger into the evening before diminishing...although will
remain elevated through the night due to a persistent pressure
gradient and low- level jet. Skies will clear out through the
night...becoming mostly clear late. Low-level cold advection will
push temperatures into the upper 20s by daybreak...with a few
places well inland possibly reaching the middle 20s. In addition...the
10-20 miles per hour sustained winds will lead to wind chills in the
middle/upper teens late...just above advisory criteria.
Lake winds...strong west winds will continue to produce 25 knots
gusts across Lake Moultrie through tonight with peak gusts around
30 knots. Thus...a lake Wind Advisory will remain in effect.
Short term /6 am Wednesday morning through Friday/...
a highly amplified upper trough will persist over the eastern
United States Wednesday through Friday. A reinforcing blast of
cold air will drop southeast into the area on Wednesday behind a
dry cold front. 850 mb temperatures of -8 to -10c across southern SC will
yield a cold morning on Wednesday with temperatures only warming into the
lower to middle 40s during the day under sunny skies. Without the
downslope wind component...highs would struggle to climb out of
the 30s. 30-35 knots geostrophic winds with 5-6,000 feet mixing heights
will result in a windy day across the area though the current
forecast keeps conditions below Wind Advisory criteria.
Strong cold advection continues into Wednesday night with mainly
clear skies and lows in the middle 2os. Positive low-level
thickness advection on Thursday with mostly sunny skies will allow
temperatures to jump into the low to middle 50s during peak heating.
An embedded shortwave will drop toward the area late Thursday
night...pushing a mainly dry cold front into the area. Weak low
pressure will develop off our coast along the front. There may be
enough moisture and forcing mainly over our coastal waters to
support light rain Friday morning. Elsewhere there will be
abundant low and middle clouds but little chance for rain. Thursday
night low temperatures are tricky based on the exact location of the low
and timing of the front. We bumped temperatures up a few degrees based on
the expectation of extensive cloud cover and decent low-level
mixing. A relatively zonal flow on Friday will maintain moderate
temperatures though the clouds will somewhat limit surface heating. Highs
will range from lower 50s far north to lower 60s far South.
Lake winds...conditions favor a continuation of the lake Wind
Advisory on Lake Moultrie Wednesday into Wednesday evening.
Long term /Friday night through Tuesday/...
the large scale East Coast trough will persist into early
Sunday...followed by a progressive short wave ridge later Sunday
into early Monday...with again the East Coast trough in place
An Arctic blast is still expected to occur behind an Arctic cold
front that traverses the region Saturday...as a 1048 mb high punches
south/southeast from the northern Great Plains late in the week. The core
of the high reaches the Carolinas on Sunday...then pulls into the
Atlantic on Monday...giving way to another frontal system either
Monday or Tuesday.
Strong cold advection arrives later Saturday and continues into
Sunday...before starting to wane Sunday night. We/re still not
completely certain on the degree of magnitude of the cold air...but
it/ll certainly be cold enough where hard freezes are anticipated
most inland sections both Saturday and Sunday night. Highs on Sunday
will be fortunate to even reach the lower and middle 40s...if that.
Wind chills Saturday night and Sunday could flirt with Wind
Chill Advisory thresholds.
Warm advection in advance of the early next week frontal system will
allow for a little warmer weather...but also the risk for some
Lake winds...another round of strong winds will be possible over
Lake Moultrie this weekend. Another lake Wind Advisory could
eventually be needed.
Aviation /21z Tuesday through Sunday/...
VFR conditions are expected to prevail at kchs and ksav through
18z Wednesday. Winds will gust around 30 knots this afternoon...with
gusts at least 20 knots much of the overnight period...then back to
25-30 knots after about 14z. VFR ceilings expected this afternoon
within an expansive stratocumulus deck...before skies clear out
Extended aviation outlook...generally VFR...although strong and
gusty winds will occur again on Wednesday. A brief period of MVFR
ceilings is possible Friday night as a front moves through.
tonight...very poor conditions expected due to a strong pressure
gradient...low-level jetting and cold advection. Winds will be
westerly gusting up to 30 knots across the nearshore waters and up
to 40 knots beyond 20 nm. Thus...advisories continue for near shore
waters with gale warnings beyond 20 nm. Seas will generally be 4-6
feet within 20 nm and up to 10 feet beyond 40 nm near the Gulf Stream.
Wednesday and Wednesday night...blustery conditions will prevail
across the marine community with a tight pressure gradient between
low pressure off New England and high pressure in the Gulf of
Mexico. A marginal Gale Warning will continue through Wednesday
evening for the offshore Georgia waters...primarily for 34 knots gusts...
while all other waters have a Small Craft Advisory through much of
Thursday through Friday...much better conditions will prevail...as
high pressure moves in on Thursday...then gives way to a cold front
and wave of low pressure by early Friday. For the most part winds
and seas will be below any advisory levels.
Saturday through Sunday...an Arctic cold front will sweep through
Saturday...followed by a powerful 1040-1045 mb or greater high that
builds from the plains Saturday to the eastern states Sunday. We/ll
most likely experience at least Small Craft Advisory conditions yet
breezy to windy conditions are expected again Wednesday with 30 to
35 miles per hour gusts over interior portions and minimum relative humidity
as low as 25-28 percent. Fire weather agencies indicate fuel
moisture is too high to warrant a red flag warning for Wednesday.
However later shifts may consider a Fire Danger Statement if
weather conditions are expected to be close to red flag criteria.
a strong offshore flow will produce blow out tides near and during
each low tide cycle this afternoon through Wednesday night.
SC...lake Wind Advisory until 11 PM EST Wednesday for scz045.
Marine...Small Craft Advisory until 5 am EST Thursday for amz350-352-
Gale Warning until 11 PM EST Wednesday for amz374.
Small Craft Advisory until 11 PM EST Wednesday for amz330.