Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 110151

Area Forecast Discussion
National Weather Service Sioux Falls SD
751 PM CST Tue Jan 10 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 315 PM CST Tue Jan 10 2017

Messy forecast over the next 24 to 36 hours as multiple weak waves
continue the threat for precipitation. The stronger wave that
brought a more widespread light snow and very strong winds to the
area earlier today is moving out. The next wave is poised to move
into the area later tonight and will allow for a little weak warm
air advection to occur in the mid levels. As this warm advection
lifts north some light snow will become likely from about I-90 north
into southwest Minnesota by late tonight. There will be a small area
from about Yankton towards Sioux Falls, east towards Jackson MN and
Spencer IA where a bit of mixed precipitation will be possible. At
this time the low level air should be too dry to allow this to
happen but if a bit more moisture can work into about the 850mb to
750mb layer some instability could be released and a little sleet or
freezing rain would be possible. Again, confidence too low for this
to occur but that is the area where mixed precipitation would be

Cold air at the surface will drain into the area overnight and keep
on heading south through Wednesday. Another wave to the south will
likely interact with this southward moving boundary and bring
another shot for light snow Wednesday afternoon into south central
and southeast SD. Amounts are not expected to be too much but a half
an inch to an inch and a half will be possible. Temperatures will
slowly get colder overnight and will struggle to recover on
Wednesday. Lowered highs a bit on Wednesday with the focus along and
north of I-90.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 315 PM CST Tue Jan 10 2017

A weak mid-level wave will continue to shift east into the area
Wednesday night into Thursday morning. With the thermal boundary and
the near surface dendritic layer resulting in an efficient
atmosphere, periods of light snow showers will be possible through
Monday morning.

The attention then turns towards very cold temperatures in the
middle of the week. Another Arctic air mass will be moving southward
into the area as a high pressure system settles in on Thursday.
Overnight temperatures will be plunging to the single digits below
zero. Breezy north-westerly winds from 15 to 25 mph will also
prevail on Thursday. Given the much colder air and brisk
northwesterly winds, dangerous wind chills will be expected Thursday
night into Friday morning. Therefore the potential for a wind chill
advisory exists Thursday night into Friday morning...especially
north of I-90.  Winds are not overly strong during that time
frame,but with surface temperatures of -10F to -15F it would not
take much wind to reach advisory level wind chills.

A weak wave will arrive on Friday, along with southerly winds. GFS
and ECMWF are suggesting a saturated atmosphere; but NAM looks drier
for this time frame. With warm air advecting in the afternoon,and
decent 700 mb frontogenesis, decided to go with a slight chance
mainly for portions of northwest Iowa.

The rest of the weekend looks mostly quiet with a warming trend
arriving Saturday into Tuesday. Conditions will change by the
beginning of the work week with the arrival of a low pressure
system. Have slowed the progression of pops on Sunday afternoon into
Sunday night.  Model soundings suggest a warm nose around 850 mb
possibly creating precip type issues, but for now kept precipitation


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 512 PM CST Tue Jan 10 2017

VFR through the evening, then conditions will deteriorate into the
MVFR/IFR range as light snow develops across portions of the
area. Conditions will improve after 15Z on Wednesday.




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