Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 040514

Area Forecast Discussion
National Weather Service Sioux Falls SD
1114 PM CST Sun Dec 3 2017

.SHORT TERM...(This evening through Monday)
Issued at 257 PM CST Sun Dec 3 2017

Overall, the synoptic scale still appears similar with strong cold
front associated upper trough over the intermountain west shifting
east into the plains.  Ahead of the front, southerly flow is
expected to prevail with a fairly thick vail of mid and high clouds
across the area.  This should keep temperatures quite mild through
the overnight.

Cold front is expected to work through the area in the morning hours
with temperatures falling behind the front. Northwest winds will
increase behind the front, and look stronger than what were
suggested in the previous model solutions. Have raised winds
tomorrow 3-7 kts across the area putting everyone easily into
advisory level winds. 700 mb frontogenesis is much more fragmented
and unfocused on the latest 12z model runs.  This uncertainty also
translates into forecast soundings, which initially indicate there
could be trouble saturating in the ice production layer. Could be
precip type challenges (rain transitioning to snow) immediately
behind the front for an hour or so, if the atmosphere can re main
saturated.  Appears as deeper saturation develops throughout the day
as fragments of frontogenesis work through, leading to periods of
snow for Eastern South Dakota. Models still continue to hint at weak
instability/neural stability immediately above the frontogenetic
forcing, possibly suggesting enhancements in the bands that develop.
Also get added lift from the left exit region of 150 knot jet streak
across the central plains.

The snow combined with the winds gusting to near 50 mph will lead to
difficult travel conditions when it is falling. Expect visibility to
be poor, with areas of blowing snow in areas where snow accumulates.
 Have opted to go with a winter weather advisory where periods of
snow will combined with the wind to make difficult travel
conditions.  Further to the south and east, there could be a brief
period where snow will make conditions difficult, but it should be
relatively brief. Have outlined the area from Yankton to Slayton MN
and south with wind advisory lingering into Monday night for the
strong winds.

The strong winds usher much colder air into the region with 925 hpa
temps falling 15-20 degrees C.  Have lows Monday night in the teens-
but with the breezy northwest winds continuing wind chills will be
in the single digits above and below zero.

.LONG TERM...(Monday night through Sunday)
Issued at 257 PM CST Sun Dec 3 2017

Cold and more cold, along with a bit of snow, is how we`ll
characterize the medium and extended forecast. As long wave
troughing becomes established over the eastern half of the CONUS,
cold air will have settled into much of the Northern US by Tuesday.
The day itself will be quiet, with a breezy northwest wind

Some concerns for Tuesday evening into Wednesday as a stronger
shortwave pivots southeastward out of Alberta. Favorable jet
dynamics and focused synoptic lift should be capable of producing a
NW to SE oriented light snow band in the evening and overnight. Have
bumped up PoPs slightly (perhaps not high enough) and increased QPF
(not present in blended solutions) to at least mention the potential
for very light snow accumulations. The Tri-State area should remains
in a favorable area for light snow potential into and through
Wednesday. Again, not high amounts, but certainly could be

The pattern really won`t shift much into the weekend, keeping
temperatures below normal and again producing that near daily risk
for light snow. Model guidance is a bit split for a warmup next
weekend. Nearly 6-7 SD differences within ensemble members. Favor
cooler solutions and have lowered temperatures slightly for Friday,
Saturday, and Sunday.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1112 PM CST Sun Dec 3 2017

IFR and MVFR ceilings are still expected to develop late tonight
and continue into tomrrow. The better chances wil be at KHON and
KFSD. Rain and snow will develop tomorrow morning in central SD
and spread east through the afternoon. Along with the developing
snow will be a very strong northwest wind, with gusts likely
around 50 mph. The strong winds and snow will continue into the


SD...Winter Weather Advisory from noon to 8 PM CST Monday for SDZ040-

     Wind Advisory from noon Monday to midnight CST Monday night for

     Winter Weather Advisory from 9 AM to 8 PM CST Monday for SDZ038-

MN...Winter Weather Advisory from noon to 8 PM CST Monday for MNZ071-

     Wind Advisory from noon Monday to midnight CST Monday night for

IA...Wind Advisory from noon Monday to midnight CST Monday night for

NE...Wind Advisory from noon Monday to midnight CST Monday night for



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