textproduct: Des Moines

KEY MESSAGES

- Frost Advisory this morning and Thursday morning for lows in the low to mid 30s across the area.

- Rain chances south on Friday into Friday night.

UPDATE

Issued at 226 AM CDT Wed Oct 22 2025

By 2 am stratus has pushed east, leaving clear skies across the area. Behind the departing low, winds have diminished, though a few gusts of 20+ mph remain, mainly east. Temperatures have dropped off under clear skies, reaching the low to mid 30s already west of I-35. Temperatures will drop a few more degrees through the morning with coldest temperatures central and west where a frost advisory is in effect this morning. Winds will increase after sunrise, though nothing like the gusts seen yesterday. Today gusts of 20-25 mph out of the northwest are forecast, mainly east of I-35 nearer the departing low. As high pressure shifts across the area skies will remain clear through the day, and overnight into Thursday. This will allow temperatures to drop off again with low to mid 30s areawide. A frost advisory is in effect for Thursday morning. After a couple days of cold temperatures this will likely be the end of such products for the season.

DISCUSSION

Issued at 237 PM CDT Tue Oct 21 2025

A strengthening area of surface low pressure has moved slightly east/northeast today, centered over the northern Great Lakes as of this afternoon. With the front yesterday now east of Iowa, and the very strong pressure gradient covering the entire state, strong northwesterly flow has increased winds significantly, with very gusty conditions where values of 35-40 mph have been reported through the day so far, especially north and east where gusts up to 45-50 mph have been reported at times. These higher gusts are likely due to better mixing occurring in spots where breaks in the cloud cover have been happening, generally into northern and eastern Iowa. The expectation is that these winds will likely remain with gusts up to 35-45 mph, highest north and east through the rest of the afternoon to early evening, before diminishing across western Iowa and gradually eastward into Wednesday. The Wind Advisory therefore remains in effect over northern to portions of north-central Iowa until the early evening. Outside of winds, clouds cover much of Iowa outside of the far southwest portion this afternoon, with the thickest clouds over northern Iowa in relation to the circulating low pressure in the region. While dry air remains over the majority of the state, at least some moisture from this system in northern to north-central Iowa has allowed for light but isolated returns of radar in these areas occasionally so far, with a few reports of light rain reaching the ground at Mason City this morning, with occasional sprinkles otherwise. Any rain chances should largely remain north/northeast this afternoon before drying into the evening. Clouds decreasing tonight into Wednesday will lead to efficient radiational cooling, with temperatures expected to drop into the 30s across Iowa, coldest west and north. Winds gradually lightening overnight into Wednesday morning as well with the clear skies may also lead to some potential for isolated frost as well, mainly over west/northwest Iowa where winds would be lightest. Therefore, a Frost Advisory has been issued for parts of west- central to north-central Iowa Wednesday morning. Any sensitive plants should be covered or brought indoors as needed.

While the low pressure slowly departs eastward Wednesday, the larger trough becomes quite enlarged, remaining over the Upper Midwest into the eastern CONUS into the late work week. Further west, a mid-level ridge develops into the northwest CONUS and tracks eastward into the region, with surface high pressure extending into the Central Plains thorugh Thursday. Northwest flow and associated cold air advection will remain overhead through the next few days as a result, keeping cooler but more seasonal temperatures overhead as highs in the 50s to low 60s are expected. Chilly overnight temperatures are expected to remain as well, though more widespread into Thursday morning with values in the low to mid 30s across Iowa, while shifting more north and east into Friday morning with values in the northeast half in the low to mid 30s and across southwest Iowa in the upper 30s to low 40s. Certainly more widespread frost potential into Thursday with clear skies and light winds expected, though more isolated into Friday northeast where these conditions are expected to develop again.

The aforementioned mid-level ridge remains into the Northern Plains Friday, with high pressure dropping into the Ohio Valley, while a shortwave trough and developing low moves out of the Southwest CONUS and tracks eastward into the Southern Plains. Models continue to indicate that any rain development with this southern system would largely remain south out of Iowa, as the NAM/GFS/Euro indicate as high pressure wins out, but could reach just north of the MO/IA border Friday. Otherwise, low-level winds turn southerly which will bring slightly warmer air into the state, with highs Friday in the low to mid 60s. The influence of this southern system looks to move very slowly eastward through the region, with gulf moisture reaching into at least southern/eastern Iowa keeping low chances of rain over these areas through the weekend. A weaker shortwave is also signaled per guidance to briefly drop across Minnesota/Wisconsin Saturday into early Sunday that may bring a brief shot of rain into eastern Iowa as well, though chances for this are also low at this time. Low- level southerly flow remains through the weekend, which will keep temperatures more mild in the upper 50s to mid 60s. On and off chances for showers look to become more scattered to widespread into Iowa by early next week with a larger trough out west moving into the Central Plains per model guidance, though further details become more blurry considering the timing ahead of this, so will keep on eye on this time frame over the next several days.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1231 PM CDT Wed Oct 22 2025

Breezy to gusty northwest wind will diminish overnight and may become light and variable at times as high pressure settles over Iowa. VFR conditions are expected through the period with a MVFR stratus later currently over far northeast Iowa and moving east. Some mid-level cloudiness is upstream over the eastern Dakotas and western Minnesota that should gradually erode but may still pass across parts of Iowa at 8-12 kft.

DMX WATCHES/WARNINGS/ADVISORIES

Frost Advisory from 2 AM to 9 AM CDT Thursday for IAZ023>028- 033>039-044>050-057>062-070>075-081>086-092>097.