Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
1027 am EST Sat Feb 6 2016
low pressure will develop off the southeast coast tonight as an
upper trough moves over the region...then lift away from the
region Sunday. Much colder weather is expected next week as an
upper trough becomes established along the eastern part of the
Near term /until 6 PM this evening/...
surface high pressure will remain entrenched over the forecast
area today with an increase in generally high clouds as an upper
trough approaches from the west. Maximum temperatures today will be
in the lower 50s.
Short term /6 PM this evening through Monday night/...
interesting scenario shaping up tonight into Sunday as upper
trough to the west will become a closed low over the southeastern
states and result in the development of coastal low which will
deepen rapidly through the predawn hours Sunday and through the
day as it then lifts northeastward away from the region. Models
have trended a bit further west compared to last night regarding
the extent of measurable rainfall so have made some pop
adjustments to account for this with chance probability of precipitation into the central
midlands/csra and keeping likely probability of precipitation across the eastern midlands.
There is the potential for some ptype issues as the upper low
moves overhead bringing strong dynamics to the region while the
lower levels cool due to cold advection as the coastal low deepens
and the pressure gradient increases. Most of the model guidance
keeps the significant quantitative precipitation forecast to the east of the forecast area with
the eastern midlands being most affected. The increased pressure
gradient will result in breezy conditions and a lake Wind Advisory
will be posted for Lake Marion...allowing later shifts to expand
if necessary to other lakes.
Examination of the thermal profiles through model soundings and
time heights reveal the potential for a brief period of snow
mixing with rain or even turning to all snow if precipitation is
heavy enough accounting for diabatic cooling effects. The most
likely time frame for this to occur looks to be around 09z-15z.
There is sufficient moisture in the snow growth area to support
winter precipitation and the NAM is by far the most aggressive with cold
air and bringing much more moisture and quantitative precipitation forecast over the region
compared to the rest of the operational model guidance and was
considered the outlier...though if that solution verifies we could
see a winter event. However...looking at ensemble data and analog
guidance there is low confidence at this time in a winter event
with impacts occurring. Wpc also not carrying accumulating snow
over our area with this event. Will carry a period of rain/snow
across the eastern midlands but not anticipating much accumulation
as surface temperatures remain just above freezing and soil/Road temperatures
will be quite warm as well minimizing impacts...unless
precipitation is falling at a very high rate. So overall...low
confidence in the eventual precipitation type late tonight into Sunday as
it will likely be highly dependent on where the surface low ends
up tracking but for now will continue with a conservative low
impact forecast. Temperatures will warm through the day Sunday but
remain below normal...especially in the eastern midlands where
precipitation will occur.
A brief dry period is expected late Sunday into Monday morning but
a deep and expansive closed upper low will descend upon the Great
Lakes and Ohio Valley region on Monday. Strong height falls and
increased lapse rates will support scattered showers during the
afternoon and will continue low chance probability of precipitation.
Long term /Tuesday through Friday/...
the extended forecast period will be characterized by below normal
temperatures and generally dry weather. Upper low over the Ohio
Valley will lift northeastward into southeast Canada by Wednesday
morning as dry northwesterly flow continues across the forecast
area. Much cooler air will settle over the region through middle week
with highs nearly 15-20 degrees below normal in the 40s and
overnight lows in the 20s. Upper flow becomes a bit more zonal by
the end of the week allowing for a slight warming trend to near
Aviation /16z Saturday through Wednesday/...
VFR conditions expected through this afternoon.
Surface high pressure currently over the region...with dry low
level air in place. Satellite indicating some thin high level
cloudiness streaming across. Strong upper trough currently over
the central Continental U.S. Will dive into the southeast Continental U.S. Tonight. Strong
upper lift and divergence over top of low level baroclinic zones
associated with old frontal boundary and the Gulf Stream allows a
low pressure area to begin developing offshore late today and this
evening which is expected to intensify and shift NE. General model
consensus has moisture shifting north into mainly the southern and
eastern portions of our forecast area this evening and tonight.
This will favor better precipitation chances and associated
restrictions at ogb and points to the south and east of there.
There is a chance for a rain/snow mix...mainly at ogb. Current
indications are that surface temperatures will be warm enough that if
snow fell it would melt without significant accumulation.
Extended aviation outlook...restrictions may linger Sunday...mainly
at ogb. A cold front will move through late Monday with a slight
chance of showers and possible restrictions. Breezy conditions
possible at times Monday through Wednesday.
minor flooding continues on the Congaree River at Carolina
Eastman and for the North Fork of the edisto river at Orangeburg.
SC...lake Wind Advisory from 4 am to 6 PM EST Sunday for scz031-