Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
811 PM EDT Sat Apr 25 2015
a warm front across the region will be the focus for showers and
some thunderstorms tonight. Drier weather returns for Sunday as a
cold front moves across the region. The next chance for
significant rain moves in for the middle of next week as moisture
increases ahead of a low pressure system coming out of the Gulf of
Near term /until 6 am Sunday morning/...
a warm front will continue to slowly lift northward across the
forecast area this evening. Regional radar loop as of 00z shows
showers and isolated storms entering the southern part of the County Warning Area
although a majority of the activity remains south of the forecast area.
Cannot rule out seeing some of this activity across the central
midlands as the evening progresses but with lack of daytime
heating...expect severe threat to remain low in the central
midlands. Shear values remain high through the evening...which
would help support rotating storms if any can push into the area.
The main threat appears to be damaging wind and hail which has
been reported with some of the storms in central Georgia. Storm Prediction Center has
trimmed back the slight risk to cover only our southern and
eastern counties with a marginal risk further north and west. A
Severe Thunderstorm Watch remains in effect through midnight for
Burke...Barnwell...Bamberg and Orangeburg counties.
May still see isolated to scattered showers as the Gulf system
moves south of the area tonight. Behind the Gulf system...a warm
front will continue to push northward through the area. The area
should see some isentropic lift north of the front...which would
bring some showers across northern counties...with much less
activity central and south. Overnight lows remain mild...only
falling into the lower to middle 60s.
Short term /6 am Sunday morning through Sunday night/...
some lingering showers/storms possible into Sunday with the northern
midlands likely to be more favored Sunday as the surface low
sinks southeastward across Virginia/NC and offshore by Sunday evening.
Moderate to strong instability and cold 500 mb temperatures noted on
Sunday but moisture may be lacking to support much convection so
will continue with low chance probability of precipitation across the northern midlands.
Sunday looks to be a warm day with some sunshine and downsloping
northwesterly flow with highs back into the 80s. The exception
will be the extreme northern midlands where cooler behind the area
of low pressure should hold temperatures in the 70s.
Long term /Monday through Saturday/...
medium-range models in fairly good agreement with the overall
pattern next week. On Monday/Tuesday the forecast area will be between
the departing system off the East Coast and yet another slow
moving closed upper low ejecting eastward out of the southwestern
states. Expect dry weather and below normal temperatures with a
persistent northerly flow and surface high pressure ridging into
the area from the north. The southern stream closed low will begin
to open and drift eastward eventually phasing with northern stream
energy bringing unsettled weather to our area Tuesday into
Thursday. However...there are some differences between the latest
GFS run and the previous European model (ecmwf) for the latter part of the period.
The previous European model (ecmwf) shows some lingering precipitation over the
area Friday with high pressure over the area Saturday. The latest
GFS shows dry high pressure building in from the west Friday into
Saturday...but also shows another cut-off upper low forming over
the eastern Gulf Coast. This feature could spread precipitation
back into SC by late Saturday. Due to uncertainty...will keep
Friday and Saturday dry at this time. Temperatures generally at or
just below normal through the extended period.
Aviation /00z Sunday through Thursday/...
regional radar loop as of 00z bringing showers and storms into the
southern part of the forecast area. Cannot rule out storms
reaching the ags/dnl/ogb terminals between 01z and 03z so have
added a tempo group with associated restrictions. Ceilings have
returned to VFR at all of the terminals for now. Models indicate potential
for restrictions returning after 06z. Have added MVFR restrictions
at ags/dnl/ogb toward daybreak although confidence is low at this
time. The low-level jet supports keeping low level wind shear in the terminal
forecasts tonight. Used the NAM for the magnitude of the shear.
The models show the boundary sinking southward Sunday but with
shallow moisture. The thunderstorm chance still appeared too low
to include in the terminal forecast. Based on the GFS lamp and the
NAM BUFKIT momentum Transfer tool we included wind gusts near 24
Extended aviation outlook...no significant impacts expected Monday
and Tuesday. An approaching warm front may result in widespread