Scientific Forecaster Discussion
fxus63 kfsd 102350
Area forecast discussion
National Weather Service Sioux Falls South Dakota
550 PM CST Tue Dec 10 2019
Short term...(this evening through wednesday)
issued at 306 PM CST Tue Dec 10 2019
A band of light snowfall still looks likely tonight. Luckily right
now this looks like a fast moving system without a whole lot of wind
and most of the snow will end a couple of hours before the morning
rush, so there should not be any big impacts to morning travel.
Maybe a little slower where the snow falls, but luckily it should
not be falling between 6 am and 8 am. The challenge with this band
of snow is placement since the band will likely only be 20-30 miles
wide, and snowfall rates. Overall the models look pretty similar to
yesterday which places the better chances through The Heart of the
County Warning Area, which means that the lower chances will be near
Highway 14 as well as through most of the Missouri River corridor.
The latest guidance brings about 2-3 hours of potential snow to most
locations within this band but there could be a few spots where the
snow lingers for 3 to 5 hours. This could lead towards amounts
approaching 2 inches but will keep forecast amounts to an inch or
less for now. This snowfall is in response to frontal forcing in
roughly the 800 mb to 850 mb layer. Still hints of some weak
instability above the front.
As this system slides southeast late tonight clearing will settle in
from the north and with lighter winds temperatures will likely drop
quite a bit north of Interstate 90. Will aim for 5 below to 10 below
over most of southwest Minnesota and near 10 above through the Missouri
River where clouds should linger longest.
This reinforcing shot of cold air will keep highs on the cold side
again Wednesday as east winds gradually develop. Highs will be
mostly in the teens.
Long term...(wednesday night through tuesday)
issued at 306 PM CST Tue Dec 10 2019
East winds turn a bot more southeast on Wednesday night as the
next wave passes by. Most of the effects of this system will be to
the north and east of the area, but will see a quick potential
for light snow Wednesday night into Thursday morning with the
better chances in southwest Minnesota. Temperatures should be non diurnal
in most locations as the winds slowly bring in milder air. This
will lead to a less cold day Thursday as winds become light and
variable and most locations climb into the 20s to lower 30s.
Thursday night into Friday will see a continuation of the warming
pattern with lows in the teens and 20s and highs in the 30s, even a
few lower 40s near the Missouri River. With broad warm advection
ahead of the next wave some mixed precipitation will become
possible, with the better chances in the afternoon or early evening.
For now amounts look to remain light so hopefully no travel
Cold air slams back into the area on Friday night, bringing with it
cold conditions and some patchy light snow. Wind chill values late
Friday night into Saturday morning will likely be about 10 below to
20 below zero. Snow amounts should be on the light side.
The busy roller coaster of temperatures and light precipitation
chances continues into early next week. Temperatures look to remain
below normal Saturday through Tuesday.
Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 533 PM CST Tue Dec 10 2019
Predominantly VFR conditions through the taf period. However,
snow moving across the area during the late evening and overnight,
periods of MVFR conditions are likely within the band of snow.
Brief IFR conditions may occur within the heaviest portion of the
band, along a Wessington Springs - Sioux Falls - Storm Lake line.
With lower confidence of snow at ksux, omitted from taf at this
point. Winds remain light and predominantly variable, with changes
in direction as system moves through. Low level wind shear is possible for a few
hours around midnight at ksux.