Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 240432
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1032 PM CST Thu Feb 23 2017

.SHORT TERM...(This evening through Friday)
Issued at 237 PM CST Thu Feb 23 2017

A very complex system taking shape this afternoon and these
complexities will continue into the evening. A northern mid level
band has allowed snow to develop through the day, but as of 20z
accumulations were mainly limited to areas along and west of the
James River and along and south of I-90. Expect this to change as
this mid level band will continue to gradually grow to the
northeast into the early evening and bring snow to those areas.

After this, everything changes and confidence begins to dip. The
main culprit to decreased confidence is a mid level convective
threat across parts of central and eastern Nebraska. The past few
runs have been fairly confident with capping in the 925mb to 850mb
layer which is where some of the better instability is expected to
reside. However there are more indications with the latest runs that
there may be just enough instability to allow an area of
thunderstorms to develop eastern Nebraska. What this convection has
the potential to do is divert mid level flow to the east a bit more,
which in turn decreases moisture convergence on the expected mid
level band over southeast SD, northwest IA and southwest MN, which
then lowers precipitation amounts. Not completely buying into this
threat, but it will be one that needs to be watched through this
evening.

Earlier today decreased snowfall amounts along highway 14 and also a
bit along and north of Interstate 90. This was in response to the
dry slot and mid level boundary being a bit farther south and also
because the drier air to the north allowed for a sharper cut off on
the northern edge.

So, the biggest challenge for tonight into Friday are with some
decreased snow amounts along and north of Interstate 90 and even
just a touch south will 4 to 6 inches of snow with 30 to 40 mph wind
gusts be enough to produce blizzard conditions. For now not really
going to change the blizzard warning but if the convection does get
going we will probably need some bigger changes. What this means is
if you have any decisions to make for Friday it might help waiting
until 9pm to 10 pm to make them.

.LONG TERM...(Friday night through Thursday)
Issued at 237 PM CST Thu Feb 23 2017

With attention on the significant snow event, have made few changes
in the forecast for the weekend and into next week. On Friday
evening, light snow may linger in northwestern Iowa during the
early evening however, any accumulation will be less than a half
inch. Winds will remain gusty up to 35 mph and with 6 to 12 inches
of snow expected, there will likely be blowing snow in open areas
into the evening. As the winds decrease and snowfall ends, the
blowing snow should also end by midnight. Lows overnight will be
in the teens.

For the weekend, the main changes involved lowering temperatures in
parts of northwestern Iowa as the deep snowcover will limit warning
during the day due to the increased albedo.  This will mean highs in
the mid 20s around SPW and SLB on Saturday and upper 20s to around
30 on Sunday.  There is the potential that if HON and BKX get little
snowfall today and tonight that temperatures will be 3 to 5 degrees
on Sunday but will wait to see snowfall evolves in the next 24 h
before adjusting temperatures.

For next week, there will be a series of weak waves that could bring
light rain or snow but no significant storm is expected. Due to the
potential snow over the next 24 h, did not make changes to the
forecast at this time.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1028 PM CST Thu Feb 23 2017

IFR ceilings at KHON through 09Z, then improving through the
remainder of the night. Otherwise, snow will continue to the south
and east, with widespread MVFR/IFR ceilings and visibilities into
Friday morning at KFSD, and into the afternoon at KSUX. Northerly
winds will continue be strong through Friday, gusting at 30 to 35
kts at times.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Winter Storm Warning until noon CST Friday for SDZ060-061-065-
     066-068-069.

     Blizzard Warning until noon CST Friday for SDZ062-067-070-071.

     Winter Storm Warning until 9 AM CST Friday for SDZ050-063-064.

     Winter Weather Advisory until 9 AM CST Friday for SDZ054>059.

MN...Blizzard Warning until noon CST Friday for MNZ080-097-098.

     Blizzard Warning until midnight CST Friday night for MNZ081-089-
     090.

IA...Blizzard Warning until noon CST Friday for IAZ001-012-020-031.

     Blizzard Warning until midnight CST Friday night for IAZ002-003-
     013-014-021-022-032.

NE...Blizzard Warning until noon CST Friday for NEZ013-014.

&&

$$

SHORT TERM...08
LONG TERM...Schumacher
AVIATION...JM



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