Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
1239 PM EST Sat Dec 7 2013
a cold front will move south through the area this afternoon and
evening. The front will stall south of the area Saturday afternoon
through Sunday...then lift back north as a warm front Sunday
night. A cold front will move through Tuesday followed by high
pressure for middle to late next week.
Near term /until 6 PM this evening/...
radar shows a few more showers over inland areas than earlier this
morning but still rather isolated. The cold front is moving
fairly quickly toward the Santee river so areas of northern
Berkeley and Charleston County should see quite a change over the
next few hours as the front pushes through. Still indicate
scattered showers in the forecast for most areas by late
afternoon as the front moves into a slightly unstable environment...although
rain amounts will be rather light through this
afternoon...generally less than 0.15 inch. Temperatures have
likely already peaked in the middle/upper 70s most areas...especially
north and west...and will begin to level off and/or fall the
remainder of the day due to increasing cloud cover and the frontal
Short term /6 PM this evening through Tuesday/...
tonight...The Wedge front will move rapidly south this evening...
clearing the Altamaha river by midnight. Rain chances will peak
this evening...then gradually wane after midnight as the strongest
isentropic lift shifts inland. Will continue to advertise the
highest probability of precipitation--up to 60 percent--from Jenkins northeast to inland
Berkeley with probability of precipitation layered to 30 percent along the Georgia coast.
Quantitative precipitation forecast will once again be very light...averaging 0.01-0.05 inch. In
fact...the rain may actually transition to drizzle versus steadier
stratiform rains after midnight. Lows will range from the middle 40s
north to around 60 south.
Sunday...the stalled front south of the area will form the
periphery of a strong yet transient high pressure wedge
developing during the daytime hours. Isentropic ascent within The
Wedge will be greatest across the inland areas...and have
indicated rain chances ranging from near 50 percent for the far
northwest zones down to 20 percent in the far southeast corner of
the forecast area for the first half of the day. High temperatures
will be significantly cooler than the previous day...with a
notable north to south gradient as is typical in a wedge scenario.
Expect temperatures to be suppressed in the low/middle 50s inland
tier zones within thick sky cover and cool northerly winds...while
warming into the upper 60s to near 70 degrees farther south toward
the Altamaha river where the boundary lingers.
Sunday night...the center of the parent high pressure system will
steadily pull farther north into the New England states during the
evening hours...allowing the lingering boundary to lift back as
a warm front through the diminishing inland wedge. Best isentropic
ascent will shift north as a result...and expect rain chances to
decrease from south to north overnight accordingly. A decent
temperature gradient will remain...with lows falling into the
upper 40s north to upper 50s/near 60 south.
Monday...the upper level pattern will be relatively
unchanged...with the southeast states located between strong upper
ridging over the Bahamas and broad troughing across the western
two thirds of the United States. A cold front will be taking shape
in the far eastern Tennessee Valley and western Carolinas late in
the day...while the forecast area falls within solid southerly
flow and warm advection. Thus expect a rapid warming trend...as
high temperatures surge back into the middle to upper 70s Monday
afternoon and low temperatures only fall into the upper 50s/lower
60s. Moisture convergence associated with the developing cold
front and an associated wave of low pressure will support 20 to 30
percent rain chances through the day...highest inland and northern
zones closest to the upstream features.
Tuesday...the cold front will make slow progress into the
forecast area by late day...as elongated shortwave energy moving
through the Ohio/Tennessee valleys flattens the upper ridging over
the Bahamas. Best rain potential of the period will be Tuesday
afternoon with the frontal zone and associated convergence
directly over the region. Due to the slow passage of the
front...temperatures will still be able to rise well above
seasonal normals...peaking in the upper 60s inland to the low 70s
Long term /Tuesday night through Friday/...
lacking stronger shortwave energy or a more amplified upper
trough following frontal passage...high pressure will struggle to
solidly build over the area until late week. The front will settle
across the western Atlantic waters...while waves of low pressure
track along the feature. As a result...have continued to include
lingering 20 to 30 percent rain chances across at least the
coastal counties and marine zones through much of the period. High
pressure will finally shift over the Middle Atlantic States by Friday
in the wake of a stronger shortwave...yet a rapidly developing
coastal trough could still support isolated shower activity for
portions of the forecast area into the weekend. Temperatures will
generally run a few degrees cooler than climatology through the
extended period...as north/northeast flow prevails until the
Aviation /18z Saturday through Wednesday/...
visible satellite and surface observation show MVFR ceilings nearing both
kchs and ksav. Despite some lingering breaks in the clouds...have
initiated both terminals with MVFR conditions...which will mainly
prevail through the afternoon. A cold front will progress
southward through the evening...veering westerly winds to the north
and eventually to the northeast. In the wake of the front...ceilings
will steadily lower...increasing probabilities of IFR or lower
ceilings overnight. Guidance and model soundings suggest winds will
diminish somewhat Sunday morning...potentially allowing fog to
develop in conjunction with low stratus. As deep moisture remains
wedged across the area...little to no improvement is expected after
sunrise at kchs and ksav. Patchy showers could impact the terminals
this afternoon and overnight...but due to expected limited coverage
and timing inconsistencies within the models...will exclude mention
in the tafs for now.
Extended aviation outlook...MVFR/IFR ceilings...as well as MVFR
or lower visibility in fog...are possible Sunday night. Ceiling/visibility
restrictions again possible Monday night into Tuesday with a slow-
moving cold front.
today...web cams/satellite indicate dense sea fog still off the
Georgia/lower SC coast and with similar conditions expected to
persist into this afternoon we have extended the dense fog
advisory until 4 PM for the nearshore waters S of Edisto Beach.
Patchy dense fog is possible however over the Charleston County
nearshore waters...mainly S of Charleston.
Southerly wind regime will hold for much of the day before The
Wedge front pushes south through the local marine area. Winds look
to turn northeast abruptly in the wake of the front...which should
reach the Savannah River by sunset. Winds will increase to 15-20
knots as the front passes south and seas will begin to build. Still
could see some patchy sea fog over the waters ahead of the front
with conditions still favoring sea fog formation.
Tonight...winds will turn northeast across all waters this evening
as The Wedge front drop south. Winds look to increase to 20-25 knots
over the South Carolina waters with 15-20 knots elsewhere. Seas will
correspondingly increase...peaking 4-6 feet South Carolina waters and
2-4 feet Georgia waters. Will hoist a Small Craft Advisory for both
South Carolina nearshore zones from late this afternoon/early
evening through Sunday morning. Conditions in the Charleston
Harbor and the Georgia waters look to remain below Small Craft
Sunday through Wednesday...moderate northeast flow will steadily
veer to the south by Sunday night as a warm front lifts through
the region. A cold front will shift through the waters by Tuesday
night...allowing flow once again become northerly in its wake. An
enhanced gradient following frontal passage could support Small
Craft Advisory winds and seas Tuesday night into Wednesday over
portions of the waters.
Marine...dense fog advisory until 4 PM EST this afternoon for amz352-
Small Craft Advisory from 10 PM this evening to 8 am EST
Sunday for amz352.
Small Craft Advisory from 6 PM this evening to 11 am EST
Sunday for amz350.