Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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798
FXUS63 KFSD 170451
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1051 PM CST Fri Feb 16 2018

.UPDATE...
Issued at 856 PM CST Fri Feb 16 2018

Updated some of the zones for late tonight and early Saturday.
Strong warm air advection tonight will usher in some low level
moisture with a broad area of ascent enhanced by a subtle short
wave. Many of the cams are painting enough moisture to produce a
dusting to close to a half inch of snow between midnight tonight
and 9 am Saturday, especially in extreme northwest Iowa north and
northeast of Sioux City, and along the I 90 corridor in southeast
SD and southwest MN, from near McCook county over to Windom and
Jackson MN.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 345 PM CST Fri Feb 16 2018

After a chilly start today, southwesterly surface winds have brought
warmer air into the region. Nevertheless, temperatures will stay
below seasonal averages for the day. The light south winds are being
forced by the exiting surface high pressure and an approaching upper-
level shortwave trough.

Overnight into Saturday morning, this trough will cause enough lift
to produce some light snow showers over northwest Iowa.
Accumulations look minimal, with a dusting for most, but a few areas
could see up to half an inch of new snow. During the daylight hours,
a subtle secondary trough could bring another dusting to the tri-
state area, but again, this looks to be of minimum impact. Daytime
temperatures will likely reach into the upper 20s north of I-90, and
low 30s south of the interstate. Any light snow showers look to end
during the evening hours.

.LONG TERM...(Saturday night through Friday)
Issued at 345 PM CST Fri Feb 16 2018

Sunday will bring a return of breezy southerly winds, as a surface
low pressure slides eastward across South Dakota. Gusts into the 30
mph range look likely, with temperatures 5 to 10 degrees above
normal. Given the current track, snow chances look to stay north of
our area, sticking to the northern third of South Dakota into
central Minnesota, although flurries north of Hwy 14 are not out of
the question.

A more impactful period of winter weather looks to begin Sunday
night through Tuesday morning. Given the event is still 3 days out,
many details are still being worked out by models; however, the
overall picture looks to be the following: A longwave trough will
move over the western U.S. An embedded shortwave will move east onto
the Plains during Sunday evening into Monday morning. Light snow
from this system could start as early as midnight for locations in
south central South Dakota through Chamberlain and Huron. Meanwhile,
a surface low pressure developing on the Kansas-Nebraska border will
slide east early Monday morning. A warm-frontal band of
precipitation looks to set-up to the northeast of this surface
cyclone center, bringing mixed wintry precipitation to parts of Iowa
and southwest Minnesota. Freezing drizzle and freezing rain is
possible in these types of situations, but there is still a lot of
uncertainty where freezing precipitation could develop. Worth
keeping on eye on for anyone traveling Monday. By Monday evening,
colder air moves into the area as snow spreads south and east,
giving better chances for accumulating snow to the entire area by
Tuesday morning. Snow looks to end during the day Tuesday. Again,
it`s too early to focus on exact amounts, but expect winter travel
conditions to start Sunday night and last into Tuesday.

The rest of next week currently looks less active, with a cold
Canadian air mass keeping high temperatures well below normal for
Tuesday and Wednesday, with slight moderation to near seasonal
values by the later part of next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1047 PM CST Fri Feb 16 2018

VFR is expected through the 06Z TAF period except for one
exception in the near term. An upper air disturbance coupled with
warm air advection aloft and a strong low level jet, will likely
bring areas of light snow in the 08Z to 10Z time frame for the
KFSD TAF site. The snowfall could lower the visibilities down into
the MVFR range, and possibly brief periods of IFR before moving
off to the east between 10Z and 12Z. At this time, it is expected
that KSUX will only receive flurries starting around 09Z but with
little in the way of visibility reduction. In addition Saturday
morning between 12Z and 18Z, areas of snow may set up toward
central South Dakota, but south of the KHON TAF location.
Otherwise, non convective low level wind shear will be prevalent
at KSUX through 09Z Saturday.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

UPDATE...MJ
SHORT TERM...VandenBoogart
LONG TERM...VandenBoogart
AVIATION...MJ



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