Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 132135

Area Forecast Discussion
National Weather Service Des Moines IA
335 PM CST Fri Dec 13 2019

.DISCUSSION.../Tonight through Friday/
Issued at 334 PM CST Fri Dec 13 2019

The wintry mix of precipitation from this morning and early
afternoon has moved east of Interstate 35 and is diminishing in
areal coverage. Impacts this afternoon have been limited by rising
road temperatures which have responded to solar radiation that has
penetrated the cloud cover. By mid afternoon, road temperatures have
risen above freezing south of Highway 20 and in the area that was
receiving freezing rain. Farther north the precipitation type has
been mainly light snow.

A cold front over South Dakota will pass through the state this
evening and will have a trailing stronger push of cold advection
that will arrive after midnight. A broad area of stratus will
accompany the colder air overnight. In addition to the stratus,
areas of fog will also be possible. As of now, drizzle does not
appear to be much threat with the saturation layer expected to
remain relatively shallow. Did maintain a freezing drizzle mention
over the far east for a short period overnight where better moisture
depths are achieved.

Saturday will be cold as Canadian High pressure begins to move into
the state. High temperatures Saturday will be in the single digits
north to the 20s south. Saturday night will be quite cold north with
good radiational cooling conditions setting up. Overnight lows of 5
to 10 below are expected north to around 10 above far south.

The next system to impact the region will arrive late Sunday
afternoon and persist into early Monday as low pressure develops
over the Southern Plains with a deformation band of snow developing
in vicinity the stronger theta-e advection north into Missouri and
into far southern Iowa. The x factor with this system will be the
aforementioned Canadian High pressure that will remain situated over
southern Minnesota/northern Iowa during this period and will create
a significant amount of dry air to overcome and will set the
northern edge of the precipitation band. Current probabilities in
the forecast are likely over stretched north of Interstate 80,
mainly accounting for a northern buffer zone, but expect will be
able to contract these pops further south over the next few forecast
for the focus of light snow chances. Some accumulations will be
possible in Iowa but the greater impacts still look to be south from
Kansas, northern Missouri and into Illinois.

Quiet and cooler weather will follow for Monday and Tuesday with
high temperatures remaining in the teens and 20s and overnight lows
in the single digits and teens. Thermal ridging is on track for mid
next week which will bring warmer temperatures mid to late next week.


.AVIATION.../For the 18Z TAFS through 18Z Saturday afternoon/
Issued at 1139 AM CST Fri Dec 13 2019

A wintry mix of precipitation is moving across sites early this
afternoon mainly from 18-21z. IFR to LIFR conditions will occur
vicinity of KALO/KOTM this afternoon as areas of fog and low
stratus impact those areas. A period of VFR is possible at all
areas once the precipitation moves to the east. Another area of
IFR to LIFR stratus over far northwest IA/SD will move into the
northern IA later this afternoon and impact the remainder of the
state overnight.




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