Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 152321

Area Forecast Discussion
National Weather Service Sioux Falls SD
521 PM CST Mon Jan 15 2018

.SHORT TERM...(This evening through Tuesday)
Issued at 321 PM CST Mon Jan 15 2018

The main forecast concern is hazardous cold associated with the
arctic air mass tonight and Tuesday morning.

A combination of ice crystals and blowing snow are resulting in
some reduced visibilities especially in southwestern Minnesota
where sustained winds are approaching 30 mph. Expect flurries/ice
crystals to remain into the evening as an upper level wave rotates
around the upper low over the Great Lakes. Any flurries should
end by dawn. On the other hand, winds will only slowly diminish
after sunset as very cold air aloft and a strong pressure gradient
maintain a mixed boundary layer. As a results winds in
southwestern Minnesota and the Iowa Great Lakes will be 20 to 30
mph through at least midnight only slowly decreasing as a
combination of subsidence and warm air advection aloft limit
mixing of stronger winds to the surface. Farther west, skies will
be clear to partly cloudy and winds will be 10 to 20 mph. With
more clouds and stronger winds, lows will be around -10 in
southwestern Minnesota and northwestern Iowa and around -15 west
of the James River in Huron and Chamberlain. The combination of
cold and wind will produce wind chills from -25 to -40 with the
coldest readings along Highway 14 in SD and across much of
southwestern Minnesota down to Spirit Lake and Spencer in
northwestern Iowa. The small piece of good news that due to the
increased winds and more clouds, temperatures will not be quite as
cold as expected and that means that the area of -35 wind chills
does not extend as far south and west as the previous forecast nor
does it persist for as long with all areas having wind chills
above -35 by 6 AM Tuesday. For this reason, have removed Sioux
Falls, Madison, Luverne, Rock Rapids and Sibley from the wind
chill warning. For the remaining areas have the wind chill warning
expiring at 6 AM with a wind chill advisory until noon. We feel
by reducing the area and time it is better encapsulating the
threat for those who are making decisions based upon the hazardous

Outside the cold, Tuesday will be a sunny day with decreasing winds
as the pressure gradient decreases. Highs will be in the single
digits above zero.

.LONG TERM...(Tuesday night through Monday)
Issued at 321 PM CST Mon Jan 15 2018

The main forecast feature in the long term is the fairly
significant warming trend that begins Tuesday night and continues
through the end of the week.

The surface ridge slowly slides south of the region on Tuesday
night. Strong southwesterly flow aloft will set up from south
central SD into southwestern Minnesota. This favors the
development of downslope winds later in the night east of the
Buffalo Ridge after midnight with gusts over 20 mph. There is the
potential for even stronger winds depending on the strength of
the LLJ. The increasing winds also mean early evening lows for
most areas in southeast SD and southwest MN as warmer moves in.
These areas will see lows from 0 to 5 below before rising above
zero after midnight. Across much of northwestern Iowa and far
northeastern NE, winds will remain light for longer into the
night. Expecting this to allow temperatures to radiate closer to
10 below before becoming steady or slowly rising prior to dawn.

Wednesday and Thursday will see temperatures warm markedly as 850
and 925 mb temperature rise above freezing. On Wednesday, only
the cold start and snow cover will keep temperatures in the upper
20s to mid 30s. With lows only in the teens and even warmer air
moving in, highs on Thursday are expected to rise above freezing
with 40s in the Missouri Valley and mid to upper 30s elsewhere.
Friday looks to be even warmer. Currently have highs in the 40s
but if snow cover is mostly gone it is very possible that the
Missouri Valley could warm into the 50s. But the low sun angle
makes it uncertain how fast the snow will melt.

Heading into the weekend, models are showing a stronger upper
level wave moving into the central US and then toward the Great
Lakes. There remains a lot of uncertainty with this system with a
few ensemble members showing a weak system that produces no
precipitation for the area and a couple have a strong storm for
the central Plains. The best chance for any snow at this point
appears to be in northwestern Iowa but it will be at least a
couple of days before anything more certain can be stated about
this system. Regardless, cooler temperatures appear more likely
for the weekend.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 511 PM CST Mon Jan 15 2018

MVFR ceilings will improve through the evening, with winds slowly
decreasing through the night. As winds taper down, patchy blowing
snow will also diminish, though could still see a few flurries,
mainly east of I-29, through 06Z. By early Tuesday morning
conditions will be VFR across the entire area with light winds
through the day.


SD...Wind Chill Advisory until noon CST Tuesday for SDZ038-050-

     Wind Chill Warning until 6 AM CST Tuesday for SDZ039-040-056.

     Wind Chill Advisory from 6 AM to noon CST Tuesday for SDZ039-040-

MN...Wind Chill Advisory until noon CST Tuesday for MNZ098.

     Wind Chill Warning until 6 AM CST Tuesday for MNZ071-072-080-081-

     Wind Chill Advisory from 6 AM to noon CST Tuesday for MNZ071-072-

IA...Wind Chill Advisory until noon CST Tuesday for IAZ001-002-012-

     Wind Chill Warning until 6 AM CST Tuesday for IAZ003-014-022.

     Wind Chill Advisory from 6 AM to noon CST Tuesday for IAZ003-014-

NE...Wind Chill Advisory until noon CST Tuesday for NEZ013-014.



SHORT TERM...Schumacher
LONG TERM...Schumacher
AVIATION...JM is the U.S. government's official web portal to all federal, state and local government web resources and services.