Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
1206 am EST Friday Dec 26 2014
high pressure will persist overnight through Friday before
shifting off the coast Saturday. A weak frontal system will lift
north Saturday night and Sunday...then a cold front will move
through the area Tuesday and Tuesday night. Another storm system
could threaten the area beginning on Thursday.
Near term /until 6 am Friday morning/...
surface high pressure will extend across the region tonight as
upper level ridging builds aloft. Clear skies and calm winds are
promoting solid radiational conditions...although some thin high
clouds along the Georgia coast are disrupting that processes just
a bit. Generally expect clear skies to dominate for the rest of
the night with only occasional passing of very thin cirrus patches
late. Lows will range from the lower 30s inland to the upper
30s/lower 40s along the immediate coast.
Wet grounds and small dewpoint depressions will support patchy fog
overnight. The fog should remain patchy and fairly shallow...but
could become dense at times...especially in and near low lying
areas such as swamps...rivers...marshes and ditches. With
temperatures expected to drop to near freezing inland...this opens
the possibility that a little freezing fog could form. While this
is not expected to be significant...a few slick spots could form...
especially on small bridges. Will monitor trends carefully in case
a freezing fog advisory is needed.
Change summary for the midnight update...
* added patchy freezing fog inland where hourly temperatures are
expected to drop to or just below freezing.
* Nudged lows down several degrees along the Georgia coast where
26/05z temperatures were already below forecast minimums.
Short term /6 am Friday morning through Sunday/...
a broad 500 mb ridge centered over northern Cuba will maintain a
warm and deep southwesterly flow across the southeast United States.
With the exception of some jet-induced cirrus...Friday will be sunny
with thicknesses supporting middle-60s high temperatures.
On Saturday the low-level ridge will shift slightly east with
increasing southerly flow. This will yield moisture advection and
increasing cloud cover. Some shortwave energy will ripple through
central SC Saturday afternoon through Sunday...producing scattered
showers across the area...especially inland areas. We show 20-30
probability of precipitation during this period. Despite the overcast skies...low-level warm
advection will allow high temperatures to reach the upper 60s Saturday and
lower 70s Sunday.
Long term /Sunday night through Thursday/...
models are in unusually good agreement during the long term period
this forecast cycle. The long term will start out quite warm with
lows Sunday night not too far from 60...which is near the normal
high temperatures during this time of the year. Highs on Monday
expected to be in the 70s. A gradual cool down will begin on Tuesday
as cold front moves through. There will be a threat for showers
Sunday night through Tuesday night. It currently appears that
Wednesday and Wednesday night will be dry before the next storm
systems brings a threat for showers again on Thursday.
Aviation /06z Friday through Tuesday/...
ground fog could occasionally/briefly reduce visibility at kchs
and ksav overnight/early Friday. 06z tafs limit the mention to a
couple of hours of MVFR visibility in bcfg around daybreak. VFR
conditions will otherwise prevail through Friday.
Extended aviation outlook...low chances of MVFR ceilings/visibilities Saturday
into Tuesday as moisture increases over the area.
overnight...high pressure will and marine layer mixing will
support winds 10 knots or less...veering from northwest to north/NE overnight.
Seas will range from 1-2 feet within nearshore waters to 2-3 feet
beyond 20 nm.
Friday through Tuesday...high pressure will be in control into
early next week with fairly weak winds and seas mainly at or below
3 feet. Increasing moisture with dewpoints at or above 60 could
result in sea fog starting as early as Saturday night. The threat
for sea fog could continue until a cold front moves through on
Tuesday or Tuesday night.