619
FXUS63 KDMX 032047
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
247 PM CST Wed Dec 3 2025

.KEY MESSAGES...

- Record low temperatures tonight (90-100% confidence) with lows
  in the negative single digits to teens. See climate section below for record temperature values.

- Temperatures warm back to 30 degrees Friday. Chance of light
  accumulating snow north.

- Next best chance of accumulating snowfall on Saturday and
  Saturday night (40% chance)

&&

.DISCUSSION...
Issued at 238 PM CST Wed Dec 3 2025

Temperatures continued to slide this afternoon and will continue to
do so as winds ease this evening. Lows tonight will bottom out into
the negative teens for much of the area. The light winds keep wind
chill values largely out of the picture, but there will be a window
of wind chills below -20 in northern Iowa right at sunrise. A Cold
Weather Advisory was not issued due to the short nature (1-2 hours)
of threshold values. Nonetheless, it will be bitter cold Thursday
morning. Dress in warm layers if you`re outside tonight or Thursday
morning. The surface ridge will pivot out of the state through the
morning and increase the influence of southwest flow through the day
and night. Temperatures will actually keep warming through Thursday
night and they`ll get back up to 30 degrees by Friday. At this
point, the northwest flow in the upper air pattern reasserts itself
as a segment of the Hudson Bay low takes a swing at Lake Superior. A
segment of shortwave energy ejects into the Upper Midwest and offers
a small amount (<1") of snow accumulations for northern Iowa on
Friday.

Deterministic solutions deviate on Saturday as they differ in
handling another shortwave sinking into the Rockies. The ECMWF is
hot-handed with QPF (and consequently snow) late Saturday. Most all
its ensemble cousins also support having measurable snowfall, so
does the Canadian ensemble and the AI models. Highest confidence
right now is over northern Iowa. What makes the GEFS and NAM
different right now? They focus on southern stream cyclogenesis
due to the invasion of an arctic high. The ECMWF is slower to
bring in this cold airmass, allowing for a lee cyclone to
intensify in the Central Plains, Iowa receiving the isentropic
aftermath. Saturday into Saturday night will be the portion of
the forecast worth watching.

The arctic high has been a consistent feature in ensembles the past
two days and it will give us another shot at subzero lows sometime
early next week. Northwest flow is here to stay for much of next
week, so the opportunity for more clipper systems remains. What will
also stay is a sub-average temperature regime. There`s enough
consensus in impacts to Iowa that 20-30% chances of precipitation
exist towards the end of the forecast period.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1139 AM CST Wed Dec 3 2025

BLSN causing MVFR vsbys in northern sites. Removed restrictions
from KDSM due to obs showing consistent VFR vsbys. MVFR/IFR
cigs continue to push south and east this afternoon as gusty
northwest winds usher in very cold temperatures tonight. Winds
will become variable after sunset with mostly clear skies after
04z.

&&

.CLIMATE...
Issued at 244 PM CST Wed Dec 3 2025

...Forecast and Record Low Temperatures for Select Central Iowa Cities...

===============================================
            |      Wednesday       |  Period  |
            |  Forecast   Record/  |    of    |
City        |    Low       Year    |  Record  |
===============================================
Des Moines       -11      -6/1886      1878-
Lamoni            -6       2/1991*     1897-
Mason City       -14      -9/1991      1903-
Ottumwa           -9       1/2005*     1923-
Waterloo         -12      -7/1991      1895-
===============================================

*Record occurred in multiple years

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Jimenez
AVIATION...Jimenez
CLIMATE...Dodson