Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
945 PM EST Thursday Dec 25 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/...
high pressure will continue to build from the west
overnight...supporting excellent radiational cooling conditions.
By daybreak...temperatures away from the coast will fall into the
lower to middle 30s at many locations. Along the immediate
coast...variable/offshore winds this evening will give way to north/NE
winds overnight. Thus...temperatures overnight could level off or even
rise on the beaches/Sea Islands.
Given the wet ground due to recent heavy rain and efficient
radiational cooling conditions featuring light low-level winds and
very dry air above the boundary layer...parameters appear
sufficiently favorable for radiation fog to justify a mention
within public forecasts away from the beaches/Sea Islands
overnight into early Friday.
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 /03z Friday through Tuesday/...
ground fog could occasionally/briefly reduce visibility at kchs
and ksav overnight/early Friday. 00z tafs limit the mention to a
couple of hours of MVFR visibility and 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.
high pressure will and marine layer mixing will support winds
15 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
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.