Area forecast discussion
National Weather Service Charleston SC
420 am 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/...
a deep upper level trough over southern New England and an upper
level ridge over the central U.S. Will prevail today...maintaining
a northwest flow aloft across the region. Meanwhile at the
surface...high pressure building from the Great Lakes region this
morning will shift overhead this afternoon.
A very dry and unseasonably cool airmass will be in place today.
In fact...precipitable water values will be as low as 0.3 to 0.4
inches today...which is greater than 2 Standard deviations below
normal. Afternoon dewpoints should also mix out into the lower to
middle 30s in many areas...impressive for this time of year. Even
with nearly full sunshine...outside of a few wisps of
cirrus...temperatures will struggle to reach highs in the upper
70s to lower 80s today away from the cooler beaches.
&&
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 Friday/...
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 /08z Saturday through Wednesday/...
VFR conditions will prevail through 06z Sunday.
Extended aviation...VFR.
&&
Marine...
today and tonight...a Small Craft Advisory remains in effect for all
waters outside of Charleston Harbor through middle-morning to account
for the ongoing northerly wind surge. Conditions will improve
considerably late this morning and 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 25th /today/...
Charleston International Airport /kchs/.....47 set in 1967
downtown Charleston /kchl/..................54 set in 1979
Savannah/hhi international Airport /ksav/...49 set in 1967
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...Small Craft Advisory until 8 am EDT this morning for amz350-
352-354-374.
&&
$$
Synopsis...
near term...jaq
short term...jaq/rjb
long term...rjb
aviation...jaq/rjb
marine...jaq/rjb
tides/coastal flooding...jaq
climate...
