Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
118 am EST Friday Nov 28 2014
Arctic high pressure will build from the west and northwest tonight.
High pressure will then prevail through early next week. A cold
front will approach from the north Tuesday...with an inland wedge
of high pressure building in its wake for the middle of next week.
Near term /through today/...
overnight...the axis of a broad upper level trough will continue to
shift well east of the area...with subsidence in its wake.
Meanwhile at the surface...a large area of high pressure will
build into the region from the Mississippi Valley.
Advection of cold and dry air will occur...resulting in a cold
night. Clear skies will prevail...with a coupled northwest to
north flow allowing temperatures to fall below freezing all the
way to the US-17 corridor by morning. Upper 20s to near 30 will be
common across most inland areas...with with 33-37 on and near the
Short term /tonight through Monday/...
Friday...a quiet/dry pattern will remain in place this weekend as
high pressure dominates the southeastern United States. Temperatures will
be coldest on Friday as surface high pressure becomes centered over the
southeast along the back edge of a weak 500 mb shortwave shifting off
the southeast coast. Overall high temperatures should range in the low 50s
over northern areas to middle 50s in southeast Georgia. Strong
radiational cooling under clear skies at night will likely result in
Friday night low temperatures between the low
to middle 30s...with freezing temperatures inland.
Saturday and Sunday...deep layered dry air will maintain a rain-free
forecast Saturday through Sunday...but temperatures will warm as middle/upper
level ridging occurs over the area while a light southerly surface flow
returns along the western edge of surface high pressure shifting
offshore. Latest 1000-850 mb thickness values support overall high
temperatures in the low/middle 60s on Saturday...then upper 60s to around 70
on Sunday...warmest in southeast Georgia. Saturday night lows will
also be warmer than previous nights...in the upper 30s inland to
low/middle 40s closer to the coast.
Long term /Monday night through Thursday/...
the unseasonably warm conditions will continue through
Monday...with high temperatures rising into the low 70s away from
the coast during the afternoon. Atlantic high pressure at the
surface and aloft will steadily shift east/southeast through
Monday...as a cold front approaches the appalachian region late
Monday into early Tuesday. Latest numerical model solutions
suggest the weakening front could transition into the leading edge
of high pressure building an inland wedge from the Middle Atlantic
States through northern Georgia. Northeast flow within the
developing inland wedge/coastal trough pattern will contribute to
a cooling trend...with high temperatures ranging from the middle to
upper 60s each afternoon Tuesday through Thursday. Slight rain
chances could also return early to middle week...depending on the
progression of the front. Highest confidence is in isolated rain
over the marine zones and perhaps the immediate coastline
associated with the coastal trough on the periphery of the inland
Aviation /06z Friday through Tuesday/...
VFR conditions will prevail at kchs and ksav through 06z Saturday.
Extended aviation outlook...VFR conditions will prevail.
tonight...ongoing small craft advisories will continue overnight
for the Atlantic coastal waters. Continued cold advection...a
tight gradient on the eastern flank of Continental high pressure
and steady isallobaric pressure rises will promote mostly northwest and
north winds of 15-25 knots with occasional higher gusts. It/S
possible that winds in Charleston Harbor could remain close to
advisory levels through the night...especially overnight when the
best cold advection occurs in sync with the strongest geostrophic
Friday through Tuesday...elevated winds/seas will likely persist
into early Friday while colder air advects over the waters and an
enhanced pressure gradient remains along the southeast coast. As a
result...small craft advisories will likely continue into early
Friday until high pressure becomes more centered along the southeast
coast by Friday afternoon. Expect winds/seas to drop below Small
Craft Advisory levels by middle morning Friday...with outer Georgia
waters holding onto elevated conditions the longest. Marine
conditions will then continue to improve Friday afternoon and remain
rather benign into Monday as the pressure gradient relaxes in
response to high pressure settling over the waters. Winds/seas
should increase/build starting on Tuesday and could approach Small
Craft Advisory levels by the afternoon as a cold front approaches
from the west.
Tides...moderate to strong offshore flow will continue to drive
tides down below predicted levels tonight. Although not blow out
tides per southeast...departures will still be as much as 1/2 to 3/4 feet
MLLW below forecast levels. Navigate with care due to the lower
than typical tide heights.
Marine...Small Craft Advisory until 6 am EST early this morning for
Small Craft Advisory until 11 am EST this morning for amz374.