Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 122125

Area Forecast Discussion
National Weather Service Sioux Falls SD
325 PM CST Thu Jan 12 2017

.SHORT TERM...(This evening through Friday)
Issued at 325 PM CST Thu Jan 12 2017

After the passage of a weak cold front, Arctic high will settle into
the area tonight. Winds will start waning down late in the evening,
but temperatures will continue to fall through around midnight.
Temperatures rise gradually after 06z with the increase of clouds
from the southwest. Wind chills are expected to fall to 20 below to
30 below tonight, with the coldest readings around 06z. Lowest
readings are likely across southwest Minnesota, and areas along and
north of Highway 14. A wind chill advisory will be issued from 00z
tonight to 13z Friday.

Behind this Arctic high, unsettled weather conditions return again
across the area early Friday morning. As the Arctic air moves
northeast, an area of warm and more moist air will be advecting
northward, increasing risk of precipitation, with thermal profiles
suggesting all snow. Given that dry air from the Arctic ridge in the
northeast area will persist, snow will have difficulties to keep
developing across southwest Minnesota. Higher chances will occur in
the morning along and west of the James River. In terms of snow
amounts, less than a half inch is possible in most areas.

.LONG TERM...(Friday night through Thursday)
Issued at 325 PM CST Thu Jan 12 2017

Relatively quiet first half of the weekend with zonal flow resulting
in near seasonal temperatures.

Southerly flow develops on Sunday with saturation deepening
throughout the day. Models are suggesting a cold layer near the
surface with warm layer near 850 mb developing aloft.  12Z suite of
models are starting to align resulting in greater confidence in
track of the system.  With that said, degree of warming aloft is
still inconsistent, with the ECMWF running 2-3 degrees C warmer than
Canadian/GFS.  Have begun to raise wet bulb aloft to increase areal
coverage of icing potential Sunday night into Monday.  Appears the
greatest threat will be ahead of inverted trough type feature that
appears to set up near the James River Valley, and shift east
throughout the day on Monday. Models differing on the amount of
cooling behind the trough, but all suggest a transition to snow on
the backside of this system.  With coordination, have issued a
Winter Storm Watch for the southern most tier of counties across
northeast Nebraska into northwest Iowa.

Chinook pattern develops mid week next week resulting in mild
temperatures expanding east of the Rockies. Still may be a struggle
to warm too much above average across the eastern half of the
forecast area-as mixing will be fairly limited. If we are able to
draw the warm air aloft to the surface, potential exists for warming
well above normal.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1125 AM CST Thu Jan 12 2017

Main concern over next few hours is the wind conditions as a cold
front passes through, mainly across KHON and KFSD locations. Look
for winds becoming NNW 15 to 20 kts, gusting to 25 kts through
23z. VFR conditions will prevail through most of the period.
Periods of MVFR ceilings possible north and east of KFSD at the
end of the TAF period as a shortwave moves through the area.


SD...Wind Chill Advisory until 7 AM CST Friday for SDZ038>040-055-056.

MN...Wind Chill Advisory until 7 AM CST Friday for MNZ071-072-080-081-

IA...Wind Chill Advisory until 7 AM CST Friday for IAZ002-003.

     Winter Storm Watch from Sunday afternoon through Monday evening
     for IAZ031-032.

NE...Winter Storm Watch from Sunday afternoon through Monday evening
     for NEZ013-014.



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