Scientific Forecaster Discussion
fxus63 kfsd 100448
Area forecast discussion
National Weather Service Sioux Falls South Dakota
1048 PM CST Mon Dec 9 2019
Short term...(this evening through tuesday)
issued at 300 PM CST Mon Dec 9 2019
Cold and dry air has spread across the area today, taking the snow
chances to the east. This leaves cold conditions as the main
upcoming weather concerns with a couple of shots for flurries and
A 130 to 140 knots upper level jet will dive south into the western
High Plains tonight, which will bring some warm air advection this
evening into the early overnight, followed by another strong push of
cold air. The weak thermal ridging with this warm push may bring
some patchy light snow and flurries to the area with a bit better
chance in central South Dakota towards northeast NE. Accumulations should be
two tenths of an inch or less, with most locations just seeing a few
As this warm advection shifts southeast and is replaced by fairly
strong cold air advection, a period of 2 or 3 hours overnight into
very early Tuesday morning could see some wind gusts around 30 to 35
mph. Not expecting this to cause any further problems with reduced
visibility but will need to be watched in case the snow on the
ground does loosen and blow around a bit. By early Tuesday morning
temperatures will fall to 5 below to 5 above in most locations but
just a touch warmer near the Missouri River.
Tuesday will prove to be cold, but with much less wind than today as
a weak ridge of high pressure moves through. High temperatures again
in the single digits and teens.
Long term...(tuesday night through monday)
issued at 300 PM CST Mon Dec 9 2019
Clouds will increase on Tuesday night ahead of the next shot of
low to mid level warm advection. This shot appears to be most
focused around 850 mb to 800 mb. Theta-E advection is pretty
strong and frontal forcing in this layer shows some weak
instability above the boundary. The chance for snow will be a
quick shot, likely no more than 2 to 3 hours at any given
location. The better chances appear to be along and south of
Interstate 90. Overall this looks like a better chance for
measurable snow and will have a half an inch to an inch of snow.
As this wave passes it will reinforce the cold air on Wednesday so
highs generally in the teens, but winds will be light as high
pressure builds south.
Once again a wave will pass on Wednesday night and bring a chance
for some light snow. The better chances will be across southwest Minnesota
as this wave is a little stronger and brings a little more warm air
into the area, which shifts the dendritic layer higher into the
atmosphere and saturation at that level more likely north and east
of the area.
As this wave passes it will usher in some less cold air for Thursday
The busy weather pattern continues into the weekend and early next
week. No major system but a continuation of weak, fast moving waves.
So 5 to 7 days out timing of any of these waves difficult so will
have only low chances for now. Temperatures will be a bit below
normal with highs generally in the 20s.
Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1042 PM CST Mon Dec 9 2019
VFR conditions should prevail, but visibility may be reduced at
times in flurries and blowing snow Tuesday morning as gusty
northwest winds develop. Ceilings may also fall into the MVFR
range, but should be temporary. Cloud ceilings are expected to
improve 10-14z Tuesday morning, but gusty winds will remain
throughout the day.
Band of snow is expected to work through the area Tuesday evening.
Have prob 30 group for potential snow at kfsd and ksux tafs for