Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
1027 PM EDT Sat may 23 2015
high pressure ridging into the forecast area from the Delaware-Maryland-Virginia
region will slowly shift farther offshore through Wednesday.
An onshore flow into the forecast area associated with the ridge
will result in higher humidity beginning Sunday. A small increase
in the thunderstorm chance will begin Monday afternoon.
Near term /until 8 am Sunday morning/...
surface high pressure along the middle-Atlantic coast will continue
ridging into the region overnight. The air mass will remain dry
with precipitable water 0.75 inches or less. The models indicate a building middle
and upper level ridge across the southeastern states. Should see
an increase in shallow low-level moisture toward morning given
onshore low level flow. Used the guidance consensus for the
temperature forecast with lows in the middle and upper 50s.
Short term /8 am Sunday morning through Monday night/...
middle and upper level ridge expected to hold across the southeastern
states through Monday night. At the surface...high pressure will
be slowly shifting farther off the middle-Atlantic coast with an
onshore flow circulating into the forecast area Sunday through
Monday. Moisture should remain shallow because of upper-level
ridging. There may be enough of a moisture increase combined with
strong daytime heating to help support a few widely scattered
thunderstorms Monday afternoon/evening. However...the chance
should remain low because of upper ridging. The NAM and GFS MOS
probability of precipitation that were higher with prior run have lowered slightly and
mainly in the 10 to 30 percent range. Have continued to lean
toward the lower values of 10 to 20 percent because of expected
dominate upper ridging. The temperature guidance was close. With
ridging in place...expect a gradual increase in temperatures
through the period.
Long term /Tuesday through Saturday/...
the strong middle/upper level ridging across the southeast will begin
to move offshore by midweek. From late week/weekend both GFS/European model (ecmwf)
show the ridging breaking down with a better chance for diurnal
showers/thunderstorms. The GFS and European model (ecmwf) display the ridge
circulating an onshore flow into the forecast area during much of
the medium-range period. The GFS...ECMWF...and ekd MOS have probability of precipitation
of 20 to 50 percent. Have continued with a blend of probability of precipitation for the
period...leaning toward the lower side. The MOS has temperatures
slightly above normal through the period.
Aviation /03z Sunday through Thursday/...
VFR conditions expected throughout the period.
Models indicate a low level jet setting up over the area
tonight...suggesting easterly surface winds will stay up
overnight. Low level moisture will increase overnight...especially
along the Savannah River including the ags vicinity. Patchy fog may
develop over bodies of water however the airmass remains
relatively dry and winds overnight will help mix out the moisture.
On Sunday...surface winds will again be out of the east/southeast with
gusts up to 15 kts. Increased moisture may allow for scattered
clouds to develop in the afternoon.
Extended aviation outlook...return flow will allow some low-level
moisture to spread over the area Monday into middle-week which may lead
to some MVFR restrictions especially during the early morning