textproduct: Des Moines

KEY MESSAGES

- Localized river valley fog this morning.

- Dry conditions are expected with a warming trend through the first part of this week.

- Breezy winds over western Iowa today and much of Iowa Tuesday.

- Scattered thunderstorms return and are possible late Thursday into early Friday, especially over western and southern Iowa.

UPDATE

Issued at 402 AM CDT Mon Oct 5 2026

Recent satellite imagery from Nighttime Microphysics RGB imagery is showing a signal for river fog, which is readily apparent over the Des Moines River from Lee County up into Wapello County/Ottumwa to as far north as southern Mahaska County. This is confirmed with several live webcam views from Ottumwa. There may also be a signal for fog in the satellite imagery on the Des Moines River from the northern tip of Saylorville Lake through Boone County to perhaps southeastern Webster County, but this is more faint/less apparent. This same faint signal also be showing up in the satellite imagery in parts of the South Skunk River in Mahaska County and the Iowa River Valley in Tama County. With Ankeny, near Fourmile Creek, and Pella, near Red Rock Reservoir, it is theorized that while area webcam imagery do not show fog, there is localized fog that the AWOS sensor are observing. Thus, have added fog in the Des Moines River from near Fort Dodge through Ottumwa, the South Skunk River from Ames through Oskaloosa, and the Iowa River from Iowa Falls to near Belle Plaine.

SHORT TERM /THROUGH TONIGHT/

Issued at 207 AM CDT Mon Oct 5 2026

It is a clear sky over the state of Iowa early this morning as viewed from GOES-East Nighttime Microphysics RGB imagery. As has been the case in general the last few nights, there have been a surface observation or two that has reported fog. It is a good setup for fog with the clear sky, light winds due to high pressure nosing over the state, and recent wet conditions. The one site that is reporting fog in the state is Lamoni, but viewing Iowa DOT cameras in the area do not reveal any fog present. From personal experience Sunday morning seeing a fog patch in the Beaver Creek valley in Johnston, IA, the fog may be very localized. From a forecast standpoint, the HRRR has been the most consistent model with fog generation and has trended toward less fog and the rest of the models do not develop any fog at all. Forecast soundings point to too much dry air in the low levels with near saturation not achieved, even in the HRRR as well as the NAM, which tends to show more cooling/saturation than reality. All this said, the forecast continues without fog mentions this morning.

As the high pressure region departs to the east today, will see winds become a bit breezier as the pressure gradient tightens, especially over the western half of the state. Increased sustained winds from the initial National Blend of Models (NBM), but gusts from the NBM seemed representative when viewing top of the mixed layer winds in soundings. The same soundings reveal a similar signal for good boundary layer mixing, which will warm and dry the surface temperature and dewpoints. Sunday's forecast highs were adjusted upward toward the 75th percentile of model guidance and this was not enough compared to observed highs. So, will give it another go with a bit more upward adjustment using a blend of NBM 50th and 90th. Comparing this adjustment to MOS guidance has forecast temperatures on par or within a degree of the highest MOS, which is the MAV. On the dewpoint side, lowered dewpoints toward a blend of the NBM and 10th percentile of model guidance. This will push relative humidity values back solidly into the 30 percent range. The HRRR tends to overmix, but even if some part of that verifies this may push dewpoints below 30% in a few places. Tonight will see a continuation of dry conditions under a mainly clear sky. Winds will stay breezy beneath low level warm air advection so lows by daybreak Tuesday will remain in the 50s, which will be about 10 degrees warmer than Monday morning.

LONG TERM /TUESDAY THROUGH SUNDAY/

Issued at 224 PM CDT Sun Oct 4 2026

A slowly building area of large scale ridging will lead to persistent upper-level northwest flow into the Midwest region throughout the remainder of the work week. Dry conditions are expected to keep hold, with warming temperatures Tuesday as increasing 850mb temps move into the state, especially west around 18-20C, and increasing winds from a tightened pressure gradient and efficient daytime mixing, leading to highs in the mid to upper 70s across Central Iowa. An area of Canadian high pressure sinks down into the region once again by midweek, with temperatures a touch cooler in the low to mid 70s forecast as winds shift north/northwesterly. By Thursday into Friday, a weak shortwave descending the eastern fringe of the aforementioned ridge looks to make its way into Iowa, with a return of mid-level moisture and forcing that will introduce the next potential for rain/storm activity. The GFS is showing coverage over the southwest portion of the state Thursday evening into Friday, with dry conditions elsewhere given the lingering area of high pressure centered over the Ohio Valley. The Euro however has a direct west to east passage of this activity across Central Iowa Thursday afternoon to evening. Certainly notable differences between long range models, but consensus on rain and storms returning somewhere nonetheless, so will have to monitor trends over the next several days to better pinpoint coverage and timing details. Late week into the weekend shows a building ridge over the central US, with temperatures warming overhead as highs in the mid to upper 70s are expected, along with a return of dry conditions once again, but also notably breezy.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 614 AM CDT Mon Oct 5 2026

There is some patchy, river valley fog, namely over the Des Moines River near OTM. However, this does not seem to be impacting OTM so have VFR conditions prevailing all sites through the period. A few cumulus clouds may develop later this morning or this afternoon over southern into central Iowa and have FEW050 at DSM for this chance. Otherwise, calm winds at the start of the period will become from the south by afternoon. Winds will be strongest in northwestern Iowa between 8 and 13 knots northwest of a MCW to FOD line.

DMX WATCHES/WARNINGS/ADVISORIES

None.