Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Charleston SC
1002 am EDT Wednesday Apr 23 2014
a cold front will cross the area later this morning. High
pressure will build into the region on Wednesday and then prevail
through the end of the week. A weak cold front could drift in from
the north late this weekend before high pressure returns over the
area ahead of a stronger cold front passing over the region
Tuesday or Wednesday next week.
Near term /until 6 PM this evening/...
late this morning...clear skies prevail across the forecast area
except for a small patch of stratus stretching across portions of
southeast Georgia. Aloft...a high amplitude ridge currently across
the central Continental U.S. Will translate eastward and begin to build into
the eastern Continental U.S.. at the surface...high pressure over the Great
Lakes region will extend southward into the forecast area through
the day. Current observations show that considerable low level
moisture remains with drier air noted to the north near the NC/SC
state line. Temperatures have a warm start this morning with many
areas already in the low 70s. With very warm low level thickness
values from the 12z sounding and model data...I have warmed highs
a degree or two. Otherwise...a very quiet day is on tap with no
real forecast concerns.
Short term /6 PM this evening through Saturday/...
tonight...high pressure will finally bridge the central
Appalachians tonight as the remnants of the cold front sink across
northern Florida. Models show the gradient tightening between
these two synoptic features after midnight...which will likely
prevent full decoupling of the boundary layer...especially from
late evening on. Lows will range from the lower 50s inland to the
upper 50s/lower 60s at the coast with a few middle 60s along the
Georgia barrier islands where onshore winds will have more
Thursday...quiet/dry weather conditions will persist as high
pressure gradually slides off the southeast coast...causing
northerly flow to become southerly by the afternoon. The pattern
will result in warming temperatures throughout the course of the day while
a downsloping wind component occurs aloft. Latest 1000-850 mb
thickness values along with the downsloping wind support overall
high temperatures in the upper 70s to lower 80s...warmest away from the
coast in southeast Georgia. Overnight lows will be more mild than
the previous night...in the upper 50s to lower 60s.
Friday...we should see a fair amount of clouds to start off the day
as modest isentropic ascent occurs ahead of a weakening cold front
that shifts over the southeast Friday evening. A few showers will
be possible as a 500 mb shortwave passes over the area ahead of the
front early Friday. Thunderstorms will then be possible Friday
afternoon as instability increases during peak heating with sbcapes
approaching 500-1000 j/kg. Thunderstorms chances appear highest over
inland areas in southeast South Carolina where forcing from the
front will be greatest. Activity will likely diminish with frontal passage
and diurnal heat loss early Friday night. 1000-850 mb thickness
values along with a persistent downslope flow should support overall
high temperatures in the lower 80s away from the coast. We could see a few
middle 80s as well over southeast Georgia. Overnight lows will range in
low to middle 60s behind the front.
Saturday...high pressure will hold over the area under a zonal flow
aloft. A downsloping wind component will likely support another day
of warmer temperatures with 1000-850 mb thicknesses favoring afternoon high
temperatures in the middle 80s over most locations away from the immediate
coast. A weak and dry cold front could approach from the north late
before stalling or dissipating near or over the area. Regardless of
position...the weak front will only have a marginal influence to
temperatures as a light northerly wind develops behind it.
Long term /Saturday night through Tuesday/...
conditions look fairly dry to start off the week as high pressure
lingers over the area well ahead of a low pressure system tracking
east over the central United States. Light southerly flow along
with middle level ridging over the southeast will likely result in a
warming trend into early next week ahead of the approaching
system. In general...high temperatures will be in the low/middle 80s Sunday
and possibly Monday before cooling a few degrees for afternoon
highs on Tuesday and Wednesday as the low pressure system shifts
over the eastern Continental U.S.. a slight chance of showers and
thunderstorms will remain in the forecast on Monday with southerly
flow in place...before precipitation chances increase Tuesday ahead of a
cold front associated with the low pressure system. Greatest
chances of precipitation should occur as a cold front pushes over the
region late Tuesday into Wednesday.
Aviation /14z Wednesday through Sunday/...
ksav...IFR ceilings will likely hang on through 15z and then
quickly scatter out. VFR otherwise. VFR at kchs through the
Extended aviation outlook...VFR conditions are expected to
today...west winds will become north and weaken during the morning
in the wake of a backdoor cold front. The wind field will become
light and muddled this afternoon as the synoptic flow becomes
intertwined with the formation of a weak sea breeze circulation.
Seas will range 1-2 feet nearshore...2-3 feet offshore.
Tonight...a more solid east to northeast flow will become
established overnight as high pressure bridges the Appalachians
and builds south. Winds will generally remain 10 knots or less with
seas building 2-3 feet all legs.
Thursday through Monday...high pressure will slide offshore Thursday
into early Friday...veering northerly winds to southerly by early
weekend. A weak cold front will then quickly advance over the waters
Friday night with more high pressure to follow into early next week.
Winds/seas are expected to remain well below Small Craft Advisory
levels into early next week with south/southwest winds at or below
15 kts and seas building no higher than 3-5 feet...highest in outer
Georgia waters on Monday.