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446 
FXUS63 KDMX 211134
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
534 AM CST Fri Jan 21 2022

...Updated for the 12z Aviation Discussion...

.DISCUSSION.../Today through Thursday/
Issued at 253 AM CST Fri Jan 21 2022

Key Messages:

- Bitter cold this morning, then less cold through the weekend.
- Light snow chances tonight, Saturday night, Sunday night into
  Monday morning, all mainly northeast half of Iowa.
- More bitter cold around Monday night to Wednesday next week.

The high pressure center primarily responsible for our bitter cold
weather the last couple days is currently parked over eastern
Iowa. Temperatures have plummeted in many areas tonight given the
light/calm winds and clear skies, with a few stations reaching -20
or colder. In spite of the light winds, this is resulting in
widespread wind chills of -20 or colder across the northern half
or so of Iowa, and the ongoing Wind Chill Advisory is solid in
conveying the threat. Conditions will improve steadily after
sunrise as temperatures rise, though highs will only be in the
teens to lower 20s west this afternoon.

A low pressure trough will approach from the northwest today,
moving across our service area tonight and bringing thick cloud
cover and a brief shot of light snow overnight, mainly to 
northern and eastern areas. While POPs are very high in those
areas, QPF and associated snow amounts are very light, less than
an inch, and coming in the middle of the night with relatively
light winds any impact should be minimal. A second trough will
traverse Iowa on Saturday night into Sunday morning, providing a
second opportunity for light snowfall, again, mainly across the
northeast half or so. The mid-level shortwave and associated
surface low are stronger with this second system, and it appears
there will be a zone of good frontogenetical forcing along the
northeastern quadrant of the surface cyclone, somewhere around
southern Minnesota/northeastern Iowa, resulting in a band of more
moderate snowfall accumulation somewhere in that area. Previously
it appeared this would fall northeast of our CWA, but things have
trended slightly southward and we are now forecasting potentially
2-3 inches of snow around or just north of Mason City/Waterloo
early Saturday night. This could lead to a period of travel 
impacts due to snow covered roads, and we will be closely 
monitoring forecast trends during this time. The third and final 
system in this rapid succession will cross the region from Sunday 
night into Monday morning, and once again carries stronger forcing
and a wider swath of moderately accumulating snowfall. However, 
with the third event the parent system will pass by further north,
and the bulk of the snow will fall from Minnesota into Wisconsin,
at least in current projections. Again, we will be keeping an eye
on this in case of any southward shift into Iowa.

The third system will push through another fairly strong cold
front around Monday morning, sweeping out any lingering snow but
also ushering in another cold snap in the first half of next week,
which appears generally similar to the cold snap we are just
concluding this morning. Once again a large Arctic high pressure
area will build down from the northwest, with initially brisk and
gusty winds on Monday diminishing by Monday night, but very cold
air again spilling into the region and the high pressure center
building around eastern Iowa by Tuesday night/Wednesday morning.
This scenario will result in more bitter cold temperatures/wind
chills from around Monday night into Wednesday, and additional
wind chill headlines are likely during this time. As the surface
high moves off to the east on Wednesday we should see a gradual
moderation of temperatures, though another low pressure trough
appears poised to move through around Thursday or Thursday night,
right at the end of the forecast period, dampening any hope of a
warming trend at least temporarily.

&&

.AVIATION.../For the 12Z TAFS through 12Z Saturday morning/
Issued at 534 AM CST Fri Jan 21 2022

VFR conditions are forecast through the day with nearly clear
skies and gradually strengthening southerly breezes. Tonight lower
clouds and light snow will move into the area, along with periods
of LLWS between 30 and 40 KT. Reduced visibility and MVFR ceilings
are most likely at MCW after 03Z, with lower probability heading
southward. Expect these details to be better delineated in
subsequent TAF issuances today and tonight.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory until noon CST today for IAZ004>007-015>017-
023>028-033>039-044>050-057>062-070>075.

&&

$$

DISCUSSION...Lee
AVIATION...Lee