Area forecast discussion
National Weather Service Charleston SC
204 PM EDT Sat may 25 2013
Synopsis...
high pressure will build into the region this weekend from the
north and then shift offshore early next week. Unsettled weather
is possible by the end of next week as low pressure moves toward
the area from the south.
&&
Near term /until 6 PM this evening/...
early this afternoon...no changes were needed with this update.
Previous discussion follows below.
Late this morning...a very quiet day is on tap as the closed upper
low pulls away to the northeast and heights begin to rise. The
surface high will extend into the region from the north with a
local center of the high setting up nearly right on top of the
County Warning Area. The 12z chs radiosonde observation had a precipitable water of 0.33 inches which is a paltry
27 percent of normal and very close to climatological minimum for
late may. Needless to say...it will be a dry day. A few thin
cirrus will continue to spill in from the northwest but will have
no affect on the forecast. With the rising heights and the full
affect of a late may sun...temperatures will outperform the cool late may
thickness values. Upper 70s to 80 can be expected for southeast
SC...and low 80s for southeast Georgia.
&&
Short term /6 PM this evening through Tuesday/...
tonight...surface high pressure will shift south and east of the
region...as a weak baroclinic zone develops north of the area.
Overall...dry conditions will prevail...although there will be an
increase in high level clouds from the north in association with
the developing baroclinic zone. Despite the increase in high
clouds...calm winds will allow radiational cooling to take place
with lows around 50 or in the lower 50s away from the immediate
coast.
Sunday through Tuesday...medium range guidance is in pretty good
agreement this period showing the upper trough shifting offshore
Sunday and surface high pressure shifting into the Atlantic.
Meanwhile...upper high pressure will build across the southeast
states Tuesday ahead of a strengthening upper trough across the
western states. With deep moisture and forcing for ascent lacking
there does not appear to be significant rain chances through the
period. The best chance of rain should come Monday
afternoon...mainly north and west of Charleston...as some deeper
moisture moves toward the area in association with an upper
shortwave on the backside of the departing trough. Isolated
showers and storms could pop along the sea breeze again Tuesday
afternoon...mainly across interior southeast South Carolina.
Temperatures will begin the period well below normal Sunday morning
before getting back to normal Tuesday.
&&
Long term /Tuesday night through Saturday/...
decent model agreement this period with above average forecast
confidence. Upper high pressure should build across the region
toward the middle of next week leading to warming temperatures and
slowly increasing low-level moisture. Rain chances will remain low
given the lack of deep moisture and forcing...mainly confined to
inland areas during afternoon peak heating as the sea breeze pushes
inland. However...deeper moisture will be on the increase toward the
end of the week as low pressure lifts northward out of the
Caribbean.
&&
Aviation /18z Saturday through Thursday/...
VFR conditions will prevail through 18z Sunday.
Extended aviation...VFR.
&&
Marine...
today and tonight...conditions will improve considerably late
this morning and especially this afternoon as high pressure
settles over the region from the north and prevails through
tonight.
Sunday through Thursday...high pressure will move offshore early
next week and persist through middle week. A more typical late
springtime pattern will dominate thereafter with some wind
enhancement during the day near the coast as the sea breeze develops
and then offshore overnight with nocturnal surging. However...winds
are expected to remain below advisory levels through the period. As
for seas...they will be building on the persistent east/NE fetch on the
southern edge of the Atlantic high...possibly reaching advisory
levels /6 feet/ beyond 20 nm Thursday.
Rip currents...a moderate risk for rip currents is forecast again
today due in large part to the full moon at perigee and a 2 foot 8-9
second swell.
&&
Tides/coastal flooding...
high astronomical tides due to the full moon could lead to minor
saltwater inundation near the coast during the evening high tide
cycle through Monday...especially across south coastal South
Carolina.
&&
Climate...
record low temperatures for may 26th /sun/...
Charleston International Airport /kchs/.....50 set in 1979
downtown Charleston /kchl/..................50 set in 1979
Savannah/hhi international Airport /ksav/...49 set in 1979
&&
Chs watches/warnings/advisories...
Georgia...none.
SC...none.
Marine...none.
&&
$$
Synopsis...
near term...bsh
short term...jaq/rjb
long term...rjb
aviation...bsh
marine...jaq/rjb
tides/coastal flooding...
climate...
