Dense fog settles in again tonight, upcoming shift in pattern

Today, widespread stratus clouds and fog have dominated much of Iowa, with some improvements seen in west-central and southwest regions. Partial clearing in those areas has allowed temperatures to climb into the 40s, while the rest of the state remains under a blanket of clouds, holding temperatures in the mid-30s. The main challenge tonight will be the redevelopment of dense fog, especially in eastern Iowa.

Dense Fog Advisory Issued

A Dense Fog Advisory has been issued for areas east of Interstate 35, extending southeast toward Oskaloosa. In some locations, visibility has already dropped to half a mile or less, and this fog is expected to expand further north and northwest tonight under south/southeast winds.

While the advisory is set to expire at 9:00 AM tomorrow, improving conditions could lead to an early cancellation. A boundary moving through overnight into Monday morning will bring drier air and increasing westerly winds, which will help dissipate the fog.

Light Drizzle Possible in Northern Iowa

Northern Iowa could see light drizzle tonight due to a deepening layer of saturation (reaching up to 3,000–4,000 feet). Although temperatures in that area are expected to stay above freezing, this is something to monitor for any localized impacts.

Rising Temperatures Overnight in Southeast Iowa

A surge of moisture from Kansas and Missouri is lifting into southeast Iowa this evening, bringing dew points in the upper 30s and 40s. This will lead to a brief period of rising temperatures before the moisture moves eastward.

Monday: Breezy with Temperature Swings

On Monday, a boundary will continue moving through the state, initially bringing a warming effect due to downslope winds. This will push daytime highs into the 30s and 40s. However, colder air aloft will follow, mixing down to the surface and increasing wind gusts.

Far northern Iowa may experience gusts near 40 mph, especially during the afternoon. Expect a mix of warming early in the day, followed by a cooler and breezy afternoon.

Looking Ahead: Light Snow and Temperature Roller Coaster

By late Tuesday into Tuesday night, another weather system will approach northern Iowa, bringing the potential for light snow. The primary snowfall axis is expected to remain north of the area, but some northern counties may see minor accumulations.

Beyond Tuesday, the active weather pattern will continue with a new system passing through the region every 36–48 hours. This will bring fluctuating temperatures and alternating periods of warm and cold air.

• Friday and Saturday: Below-normal temperatures are expected.

• Sunday: There’s potential for a warm-up as an upper ridge approaches, though confidence in the forecast remains low.

Aviation Impacts

Pilots should be aware of dense fog tonight, particularly in eastern Iowa, where visibility could drop as low as 1/4 mile. While visibility may improve earlier in some areas like Des Moines (KDSM), low stratus clouds are likely to persist through Monday morning.