textproduct: Des Moines

KEY MESSAGES

- Mild temperatures and melting snow expected to continue for the rest of the afternoon to evening. Increasing winds this afternoon and evening. - Precipitation chances return along a cold front late tonight into Thursday morning, falling as rain.

- Windy conditions, scattered snow showers, and falling temperatures then arrive mid-day Thursday behind a secondary cold front. Sudden travel impacts may develop under snow showers.

DISCUSSION

Issued at 249 PM CST Wed Dec 17 2025

Quiet conditions remain over Iowa today as the region sits between two systems: the first being an area of high pressure covering much of the east/southeastern CONUS, and the second over the northwest part of the country where surface low pressure is deepening. Low level flow out of the southwest has led to another day of mild temperatures with values currently in the upper 30s to low 40s where the snowpack yet remains, and in the upper 40s to low 50s in the southwest where bare ground is located. These temperatures will allows for more snow melting to occur, likely continuing into the evening with temperatures remaining above freezing. As the low level southwest flow continues to increase through the rest of the day, southerly winds will turn breezy into the evening and overnight, with gusts up to 20 to 25 mph which is what will be keeping these temperatures more mild. This will occur along with a gradual increase in cloud cover ahead of precipitation chances returning through this evening.

A dynamic system (the aforementioned low pressure currently over the Pacific Northwest into Southern Canada) is still on track to gradually track eastward into the Dakotas and through the Upper Midwest tonight into Thursday, with a cold front extending in Iowa this evening that will come with light rain showers tracking eastward across the state. Guidance generally has the rain entering western Iowa just before midnight, though very light activity just ahead of the main wave may struggle to reach the ground with the initial dry air. The overall forcing for lift will be maximized after midnight until around sunrise where the highest chances for rain will move across central Iowa, before exiting eastward by mid- morning. Following a dry slot filling into Iowa mid to late morning for a short period, a secondary frontal passage from northwest to southeast is expected, along with a more defined sharp decrease in , passing through by late morning through the afternoon. Winds are going to become very gusty during this time following right behind the departing secondary front. Low level winds, particularly at 850mb, depict values around 45-50 knots arriving into Iowa shortly after sunrise through the afternoon, which given the cold air advection with this and sinking air should be easier to see these gusts mix down to the surface at times. The expectation overall remains for surface winds to increase with sustained values around 25-30+ mph and gusts up to 40-45+ mph, especially across northwest Iowa by mid-morning through the early evening. With increased confidence on this winds covering much of central Iowa, have expanded the coverage of the Wind Advisory further east in collaboration with neighboring offices to include much of the eastern part of the CWA given trends in latest guidance. These winds will slowly decrease into Thursday evening and especially by Friday. Given the previously discussed concern about flash freeze given the morning rain followed by cold temperatures moving in, the window for drying to occur, which will likely be enhanced by the windy conditions, should dry many surfaces that should limit flash freeze potential, though isolated areas such as those in shade may be more at risk. Will continue to monitor this potential closely. Additionally, in regards to the secondary frontal passage late Thursday morning to afternoon, notable frontogenesis occurring and forcing for lift moving northwest to southeast, along with indicated CAPE values in around 40-60 J/kg suggests that the potential for snow bursts or even a few snow squalls remains possible. However there still remains uncertainty in the extent of available moisture, as soundings indicate relatively dry low levels, especially further south across Iowa. The better potential does appear to be in northern Iowa where the moisture availability is higher, but still will be battling some low level dry air. Will have to continue monitoring the latest guidance and conditions over the next several hours. In summary, after the rain moves through tomorrow morning, snow showers with some squall potential remains, with the higher potential north, while advisory level winds are increasing in likelihood over much of central Iowa. Impacts from the gusty winds alone, along with the added potential for any light snowfall will lead at least some travel impacts. Please stay tuned for additional updates. As dry conditions return into Thursday evening, temperatures will be quite chilly into early Friday with the cold air overhead, with overnight lows expected in the single digits to the north and in the teens to the south. Surface high pressure quickly passes through Friday, with low level flow switching back southwesterly that will bring some ''warmer'' air back into the region, with highs expected in the upper 20s to the northeast and in the upper 30s to the southwest.

The weekend looks mainly dry, though a system scraping the Canadian/US border looks to bring a sagging frontal boundary into Iowa, though the dry air overhead looks to keep any precipitation chances quite minimal. Surface weak high pressure will move in late Saturday to Sunday, followed by another large area of high pressure passing southeast across the eastern portion of the Upper Midwest into the eastern CONUS into next week. This will lead to dry and generally quiet weather through Tuesday/Wednesday before the next precipitation chance is suggested later Wednesday. Generally mild temperatures are expected to continue this weekend into next week with highs in the 30s to 40s and lows in the teens to 20s.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 534 PM CST Wed Dec 17 2025

Stratus lifting north from Kansas and Missouri will arrive overnight and will bring MVFR to local IFR cigs. A period of rain is expected at all sites overnight as well. A brief break with a return to VFR is possible, mainly in the morning. A cold front will move across Iowa late morning and into the afternoon. Strong west to northwest winds will arrive with the boundary passage along with more MVFR stratus. A few periods of snow may occur, mainly over northern Iowa including KMCW.

DMX WATCHES/WARNINGS/ADVISORIES

Wind Advisory from 9 AM to 6 PM CST Thursday for IAZ004>006- 015-016-023>025-033>036-044>048-057>060-070>073-081>083- 092>094. Wind Advisory from noon to 6 PM CST Thursday for IAZ007-017- 026>028-037>039-049-050-061-062-074-075-084-085-095-096.