Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 141724

Area Forecast Discussion
National Weather Service Sioux Falls SD
1124 AM CST Sat Jan 14 2017

.SHORT TERM...(Today and Tonight)
Issued at 410 AM CST Sat Jan 14 2017

Very few, if any, concerns in the short term portions of the
forecast.  High pressure drifts across the region today, providing
very light winds. With nearly zonal flow aloft, will have a steady
dose of mid and upper lvl clouds today. Temperatures in the middle
to upper 20s will feel quite pleasant today.

High pressure moves eastward and moisture return begins as winds
turn to the south. Overnight lows with the increase in southerly
flow after midnight and cloud cover may warmer. Will need to watch
for the potential of patchy fog over areas east of I-29 tonight with
light winds.

.LONG TERM...(Sunday through Friday)
Issued at 410 AM CST Sat Jan 14 2017

Still looking at a significant storm affecting the area for the
beginning of the week. Models have slowed the onset of precipitation
on Sunday afternoon, so expecting the majority of the day to be dry.
It will be warmer in an increasing southerly low level flow as
surface ridging moves eastward. Highs will upper 20s to mid 30s.

On Sunday night the well advertised Southern stream system over the
Four Corners region lifts northeastward with increasing midlevel
warm air advection/isentropic lift over our area out ahead of the
system. With that will see increasing precipitation chances from
south to north during the night. Still seeing model differences with
regard to thermal profiles aloft, with the ECMWF still trending
warmer than other models. The GFS continues to be much cooler with a
stronger influence from Northern Stream energy diving into the
Northern Plains. Discounting the cooler GFS, at this point it
appears that most precipitation on Sunday night would be in the form
of freezing rain with a possible brief period of sleet. On Monday
the Southern stream upper level low slides just to our east, with
freezing rain transitioning to sleet and snow from northwest to
southeast through the day as colder air filters in on the backside
of the system. Superblend QPF amounts on Monday afternoon came in
much lower than WPC values, so after coordination with surrounding
offices, blended amounts closer to WPC. By Monday evening the entire
area should have changed over to snow, then tapering off from west
to east through the late evening. There are still uncertainties on
exact precipitation types with this system dependent on how quickly
the colder air filters into the region, but confidence is pretty
high that there will be significant ice accumulation over
northwestern IA, far southeastern SD into portions of southwestern
MN through the event. Ice totals over that area could range from a
tenth to a quarter of an inch, or possibly more, by early Monday
evening. Back to the north and west of this area, roughly from
Yankton to Sioux Falls to Marshall, confidence is lower on
precipitation type as this area will be in more of a transition
zone. Dependent on how thermal profiles turn out, this area could
get more ice accumulation than forecasted, with resultant lesser
snow amounts. Based on the current forecast, snowfall amounts will
range from 3 to 4 inches through the Yankton/Sioux
Falls/southwestern MN corridor, with lesser amounts back into the
upper James River Valley and far south central SD. Based on
currently forecasted ice amounts, again expanded the Winter Storm
Watch just a bit, including a couple southwestern MN counties and
another southeastern SD county.

With the departure of this system, will have warming for the middle
and end of next week, with the degree of warming initially dependent
on how much snow occurs with the upcoming system. Based on current
guidance highs could be in the 40s by next weekend.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1123 AM CST Sat Jan 14 2017

VFR conditions are expected through the TAF period.


SD...Winter Storm Watch from Sunday evening through Monday evening
     for SDZ062-066>071.

MN...Winter Storm Watch from Sunday evening through Monday evening
     for MNZ080-081-089-090-098.

IA...Winter Storm Watch from Sunday evening through Monday evening
     for IAZ001>003-012>014-020>022-031-032.

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



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