Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
645 am EST Sat Mar 8 2014
high pressure will build from the west today...and will generally
prevail into early next week with a warming trend. A cold front
will move through the area during the middle of next week...before
high pressure returns late next week.
Near term /through tonight/...
today...we finally get a reprieve from the recent spell of cold
and wet weather with the return of considerably warmer conditions
and abundant sunshine...with only a few thin jet stream cirrus.
Yesterdays coastal low is far to the NE and pulling even further
away...allowing for a 1021 mb high centered over the Florida
Panhandle to nose in. Meanwhile...aloft we/ll find short wave
ridging arriving from the west. With plentiful insolation...an
increasing March sun angle...a low level thickness expansion of
around 40 meters from yesterday and some downslope of the
Appalachians we/re looking at temperatures actually very close to
seasonal norms. In fact we/ll be as much as 20 degrees warmer than
we were on Friday...with a huge 30-35 degree swing from this
mornings lows to the afternoon highs. Keep in mind that if you
venture to the beaches...given the chilly ocean waters and a
developing sea breeze that it will be some 5-10 degrees cooler
Tonight...under the influence of flat ridging upstairs with the
surface and low level ridge to our south...a quiet and warmer night
is in store. A weak cold front will be heading toward the
southeast...crossing the central and southern appalachian chain overnight.
This allows our synoptic flow to veer from south/SW in the evening
around to the west late. This in turn limits minimum temperatures to mainly
the middle 40s inland and upper 40s to near 50 on the barrier islands.
We/ll come close to our cross-over temperatures in some locales very late
at night. But given a drier ground...geostrophic winds no lower than
10 knots and condensation pressure deficits not as favorable as this
morning...the fog potential is low.
Short term /Sunday through Tuesday/...
Sunday and Sunday night...nearly zonal flow aloft will continue
through Sunday night across the southeast downstream of a trough to
the west and associated upper low. An embedded channeled vorticity maximum
will push through late Sunday...with a quick shot of increased
low/middle level moisture. At the surface...high pressure will remain
the primary feature...positioned to the south of the forecast area.
In general skies will be made up of passing high clouds associated
with a 120+ knots 300 mb jet...as well as some low/middle level clouds
associated with the passing wave. The forecast remains dry...and the
main question is how warm will we get in the afternoon. I have
maintained low 70s...though there is some potential for middle 70s in
Monday through Tuesday...the zonal flow aloft will begin to amplify
as shortwave riding moves eastward in advance of the deepening
southern stream trough. Weak high pressure and dry conditions will
prevail through much of the period until an organizing system
associated with the southern stream trough approaches from the west
on Tuesday. So far it appears that best moisture and lift will
remain just to our west through the day on Tuesday...so I have
trimmed probability of precipitation back to feature a dry forecast through Tuesday. Clouds
will be on the increase...but we should still see yet another well
above normal period for temperatures with highs still in the low/middle
Long term /Tuesday night through Friday/...
the models continue to differ significantly regarding the middle week
system...especially given the complexity of the middle/upper trough
interaction and phasing. The GFS is considerably weaker with the
developing surface low that crosses the southern Appalachians...and
is much drier compared to the European model (ecmwf). The overall timing is not
significantly different...but the sensible weather is. I have leaned
more towards the European model (ecmwf) which results in a wetter forecast for
Wednesday as the cold front pushes through. High pressure builds in
thereafter for the late week time period. Temperatures look to cool
off significantly behind the front...especially on Thursday...and
then moderate back to near normal for the start of the weekend.
Aviation /12z Saturday through Wednesday/...
other than a little ground fog through middle morning...VFR
conditions will prevail at both kchs and ksav through 12z Sunday.
Extended aviation outlook...VFR conditions are expected through
early next week. Possible flight restrictions with a cold front
today...the low pressure system that was off our SC coast this time
yesterday is continuing to Blossom and is located not far from
Bermuda this morning. There is an extensive cyclonic circulation
around this impressive feature...and the last portions of it have
only recently pulled outside our coastal waters. Continental high
over the southeast will continue to build from the west and improving
conditions will settle in. Winds and seas will peak early this
morning then steadily fall thereafter...and with a light pressure
pattern developing we/ll actually experience a resultant sea
breeze this afternoon. We still have one last Small Craft Advisory
across our outer Georgia waters...where seas will still be as high as 6
feet through midday before dropping to 5 feet or less this afternoon.
Tonight...an east-West Ridge of high pressure will be located
just south of the waters from the parent high over the Florida
Panhandle. Further upstream we/ll find a weak cold front that will
drop southeast into the Carolinas and northern Georgia late. The synoptic flow
will start the night from the south and SW...then veers around to
more westerly late. While there is a subtle rise in wind
speeds...nothing more than 10-15 knots. Seas will be restricted to
2-4ft and highest across amz374.
Sunday through Wednesday...conditions across the local waters appear
to be quiet for much of the upcoming period. Weak high pressure to
the south and southwest of the waters will drive westerly flow less
than 15 knots in to early next week. Winds will then turn more
southwesterly and begin to increase late Tuesday night into
Wednesday ahead of the approaching cold front. Seas will be up to 3
feet at times for the nearshore waters...and will range 2-3 feet for the
outer Georgia waters. Overall...conditions will remain below Small
Craft Advisory thresholds through the middle week time period.
Marine...Small Craft Advisory until noon EST today for amz374.