Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
629 am EST sun Jan 25 2015
weak high pressure will be in control today with the next fast
moving low pressure system crossing the region tonight and
Monday with a slight chance showers. Dry high pressure will build
into the area Wednesday. Temperatures expected to be below
normal through mid-week.
Near term /until 6 PM this evening/...
a low pressure clipper type system will move from the Midwest this
morning southeast toward the region later this afternoon and
tonight. Ahead of the system air mass dry with surface ridge in
the Gulf of Mexico extending northeast across Carolinas. South
flow will result in weak warm advection and expect afternoon
temperatures to be slightly warmer than yesterday and skies mostly
sunny with bulk of clouds associated with clipper west of region
through the day.
Short term /6 PM this evening through Tuesday/...
high pressure moving offshore as clipper approaches North
Carolina mountains tonight. Increasing clouds tonight with a
slight chance showers late tonight mainly across the northern
midlands ahead of cold front. The low will swing to coastal North
Carolina Monday afternoon and away from the region Monday night.
The cold front and amplified upper trough/short waves will cross
the region Monday. Steepening low to middle level lapse rates will
result in weak elevated instability. Considerable clouds Monday
with cold advection. Lift appears weak and mainly north
midlands/Pee Dee through afternoon. Kept low chance probability of precipitation for
showers Monday. Expect rainfall amounts to be light. Cut maximum
temperatures Monday slightly from previous forecast given cold
advection/upper trough. Lows Monday night in the lower to middle 30s
with decreasing clouds and diminishing winds. Upper trough along
the East Coast Tuesday. A few clouds associated with short waves
rotating around base of upper trough mainly north midlands/Pee
Dee...but moisture overall appears limited. Temperatures below
normal Tuesday due to cold advection.
Long term /Tuesday night through Saturday/...
models continue in good agreement through Thursday with
increasing differences for Friday. Pattern will remain active
through the long term with low pressure moving away from the
region Tuesday and high pressure along with drier air building in
Tuesday night through Thursday.
Model differences begin Thursday as the GFS tracks low pressure
through the southern Great Lakes and through the Ohio Valley
Thursday night while the European model (ecmwf) keeps the low in the northern Great
Lakes. Both models bring a cold front through the forecast area
Thursday night with the GFS being stronger with the front due to
the low center much further south than the European model (ecmwf). On Friday the
European model (ecmwf) brings moisture northward into the forecast area along the
stalled frontal remains with the GFS pushes the cold front
offshore allowing drier air into the area. With the model
difference for Thursday night Onward confidence remains low.
Models have backed off on precipitation Thursday night so cut probability of precipitation
from previous forecast. GFS ensemble probability of precipitation through period low.
Temperatures near normal end of period as upper flow becomes more
Aviation /11z Sunday through Thursday/...
VFR conditions to dominate the taf period...with lowering
conditions late in the period.
High pressure over the taf sites will move offshore with afternoon
as low pressure moves through the middle MS valley. The low will move
into the Middle Atlantic States tonight spreading middle and upper clouds
across the region this evening with clouds lowering toward
daybreak Monday. Chances of rain will also move into the taf sites
near the end of the period...confidence remains low in regard to
timing and coverage so have included vcsh at all sites and will
adjust as confidence improves. Winds through the period will be
southwesterly at 8 knots or less.
Extended aviation outlook...low confidence in restrictions Monday
as low pressure moves north of the taf sites. Breezy conditions
possible Monday and Tuesday.