Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 162337

Area Forecast Discussion
National Weather Service Sioux Falls SD
537 PM CST Sat Dec 16 2017

.SHORT TERM...(This evening through Sunday)
Issued at 216 PM CST Sat Dec 16 2017

The right entrance region of the upper level jet is working
across the area this afternoon and evening. The mid-level thermal
field, especially the dendritic temperatures, are not overly
favorable for precipitation production. Suspect a sprinkle or
flurry will be possible, but no concerns on any banded light
snowfall. However there is plenty of mid and upper level moisture,
so cloud cover should be fairly thick through the night. This
will bring another seasonally mild night with lows in the mid to
upper 20s.

As this right entrance region exits overnight, a cool surface
high pressure will settle in, but without snow cover anywhere to
be found, temperatures will remain above normal, just not as warm
as today. Clouds will gradually thin through the day but the big
benefit of this high pressure will be light winds, so that highs
in the mid 30s to lower 40s will feel fairly comfortable.

.LONG TERM...(Sunday night through Saturday)
Issued at 216 PM CST Sat Dec 16 2017

Sunday night into Monday a jet max will cruise to the north of the
area, which will set up westerly flow in the low levels. This should
allow for some nice warming, albeit a bit breezy. Lows should be in
the 20s with highs 45 to 55.

Monday night into Tuesday the upper level jet will begin to move to
the east of the area, which will allow cooler air to settle in.
This will not have a huge affect on conditions with lows again in
the 20s while lows are tempered back a touch and expected to range
from about 35 to 45.

Wednesday night into Thursday will continues to be the time frame to
watch as the right entrance region of the northern jet enters the
area and low pressure strengthens. Still too far out to really grab
onto any higher potential solutions but initially think that there
could be two bands of snow. The first would develop with the right
entrance region of the jet near the most favorable thermal layer
Wednesday afternoon and night. Right now this chance looks best from
central SD into northeast SD as the effects of the jet drop
southeast. Late Thursday morning into Thursday afternoon the
southern stream jet will eject onto the Plains and will likely allow
for more rapid banded development either south of the area or in the
far southern parts from the Missouri River into northwest IA. Even
some hints of instability above the mid level boundary. But again,
just something to track right now as this is still 5 days out.

With the idea that we will have some snow on the ground, went
below superblend for temperatures on Friday and Saturday. Should
see lows in the single digits and highs in the teens to lower 20s.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 536 PM CST Sat Dec 16 2017

This evening and overnight, light northeast winds will develop as
a weak surface high pressure is positioned over MN and WI. There
is enough moisture in the shallow, near-surface layer for some low
clouds decks and areas of fog, especially along and east of the
Buffalo Ridge in southwest MN. Locations west of the Buffalo
Ridge, such as KFSD and KSUX could see low MVFR or IFR cloud decks
at times during the night, but fog here should be limited in
coverage, given the lack of upslope flow. Sunrise will bring a
weakening pressure gradient, so after 17/1500z, low cloud layers
are forecast to thin. Light winds shift to west and southwesterly
Sunday evening. No precipitation is expected for the area over the
next 24 hours.




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