textproduct: Des Moines

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.

..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.