Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
1249 PM EST Thursday Nov 27 2014
a dry cold front will move offshore this morning. High pressure
will then build into the southeast United States and 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 tonight/...
the reinforcing cold front is pulling further offshore...allowing
for a consolidating region of cool Continental high pressure
building from the west and northwest.
Satellite imagery showing few-scattered cumulus humilis clouds
will continue to develop around the base of the subsidence
inversion around 5000 feet...in response to a strong short wave
passing through the axis of the middle and upper trough. Even
so...mostly sunny or sunny skies will prevail.
Cool advection on west and northwest winds of 15-25 miles per hour with gusts of 30
miles per hour or higher will negate some of the downslope and full
insolating effects. On average upper 50s is about all we/ll
muster...with a few spots near the Altamaha river to hit 60 or 61.
Also due to the gusty winds there is a Special Weather Statement
in effect to remind those traveling to be cautious on bridges and
overpasses. Recent reports from the top of the Don Holt bridge in
Charleston were showing 30-35 miles per hour wind gusts...and this will
continue through the afternoon.
Lake winds...little change in winds across Lake Moultrie through
middle to late afternoon...as ample mixing of much of 30-35 knots within
the boundary layer will make it down to the waters surface.
Boaters can expect west and northwest winds of 20-25 knots and gusty...with
1-2 feet waves. The lake Wind Advisory remains active through 5 PM.
Overnight lows will range between the low/middle 30s away from the
coast...with freezing temperatures inland. There could be some local
upper 20s in sheltered locations bordering the csra and midlands.
Short term /Friday through Sunday/...
Friday through Sunday...surface high pressure will stall along the
East Coast Friday and Saturday...before settling over the nearby
Atlantic waters by Sunday. In the upper levels...a weak shortwave
will pass off the coastline Friday...followed by a building ridge
from the Bahamas through Sunday. Model forecast soundings
indicate a very dry air mass remaining in place...with
precipitable water values held around half an inch or less though
the period. Will thus continue to advertise dry conditions and rain
chances at zero through the weekend. Diminishing cold advection on
the back side of the weak shortwave...increasing southerly
flow...and the building upper ridge...will support a gradual warming
trend late week into the weekend. Temperatures will be suppressed
far below seasonal normals for one more day on Friday. Expect
temperatures to only reach the low to middle 50s during the
afternoon...and then fall below freezing away from the coast
within ideal radiational cooling Friday night. High and low
temperatures will then rebound nearly 10 degrees on
Saturday...peaking in the low to middle 60s for highs and upper 30s
to low 40s for nighttime lows. Temperatures on Sunday could
rebound and rise a degree or two warmer than normal...reaching
the upper 60s to around 70 degrees under continued mostly sunny
Long term /Sunday night through Wednesday/...
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 /18z Thursday through Tuesday/...
VFR conditions will prevail through 18z Friday at kchs and ksav.
Deep mixing will support west/northwest winds 15-20 knots with gusts of
25-30 knots until late afternoon...before winds subside considerably
by sunset through middle morning Friday. Winds will briefly become a
little gusty again late in the valid taf cycle.
Extended aviation outlook...VFR conditions will prevail.
today...the Arctic cold front has cleared the local waters and
has lost most of its characteristics as it becomes absorbed by
Continental high pressure that builds from the west and northwest. A
tight gradient and sufficient mixing within a cool advection
regime will support solid small craft advisories across the board.
West and northwest winds will be 20-25 knots sustained...with frequent
higher gusts. Seas will be restricted some by the offshore
fetch...ranging from 2-4 feet near the coast to 3-6 feet further
out...with peak heights on the outer Georgia waters of 6-8 feet.
Tonight...the best pressure gradient shifts offshore but better
nocturnal mixing profiles will exist and we maintained 15 to 20 knots
outside the land/sea interface with conditions likely remaining in
advisory criteria beyond 20 nm off the Georgia coast through
Friday through Monday...the remaining Small Craft Advisory will
likely end early Friday morning across the outer Georgia waters.
Marine conditions will then continue to improve Friday afternoon
and remain rather benign into Monday...as surface high pressure
becomes centered over the waters and allows the pressure gradient
SC...lake Wind Advisory until 5 PM EST this afternoon for scz045.
Marine...Small Craft Advisory until 10 PM EST this evening for amz350-
Small Craft Advisory until 7 am EST Friday for amz374.
Small Craft Advisory until 5 PM EST this afternoon for amz330.