Thor, IA Weather

: Updated for the 18z Aviation Discussion:

Key messages

- Scattered showers and thunderstorms will gradually spread northward across Iowa today and tonight, then become more isolated Saturday and Saturday night.

- After a break Sunday, rain and storms will return Sunday night or Monday and last through at least midweek.

Short term

Issued at 121 AM CDT Fri Oct 30 2026

A broad 500 MB trough is moving slowly over the southern/southwestern CONUS early this morning, roughly from around the Texas coast up to near the Four Corners region. This trough will drift steadily northeastward today and tonight and reach Iowa and surrounding states by Saturday night. At the surface, a high pressure ridge currently lies along the far northern U.S. and southern Canada, stretching across North Dakota, Minnesota, and Wisconsin. Its influence reaches into our area in the form of light east northeasterly breezes and low dewpoints in the upper 30s to lower 40s. In our northeastern counties where skies are clear at this hour, temperatures have fallen into the upper 30s. Meanwhile, a nocturnal low-level jet has developed across northern Kansas and MIssouri overnight and will push into Iowa this morning, preceded by a pronounced swath of warm air/theta-e advection aloft. This is producing an area of scattered showers and thunderstorms currently located across far southern Iowa and northern Missouri that will gradually expand into central Iowa later this morning. It will be difficult for convection to spread too far north however, due to dry air entrainment from the aforementioned surface high.

As the LLJ fades out today coverage and intensity of showers/storms should gradually diminish during the afternoon, however, the warm air/moisture advection will continue to bleed northward and there will likely be lingering light showers in the afternoon to evening, with widespread 30-50% POPs carried during that time but little QPF. Tonight into Saturday morning the nocturnal LLJ will be weaker and theta-e advection more nebulous, however, the approach of the 500 MB trough will bring more widespread, though still modest, forcing for ascent that should bring increased coverage of light rain overnight, once again fading and become more isolated during the day on Saturday. POPs remain trended in that direction. Aside from rain chances, temperatures will remain cool today as the surface ridge slides by to our northeast and most of the area remains cloudy. On Saturday winds will come around closer to south and surface warm air advection will bring higher temperatures to our forecast area, though still moderated by persistent cloud cover with highs in the low to mid-60s across much of Iowa.

Long term

Issued at 115 PM CDT Thu Oct 29 2026

Height rises will reside over Iowa on Sunday, and the advection wing will have lifted into Minnesota. This will keep Sunday cloudy and cooler, but dry. The complex synoptic trough will increase southwest flow Sunday night with rain beginning to arrive. Its influence will keep precipitation chances going all the way through at least Wednesday. The highest chance for thunderstorms looks to be Monday afternoon and evening. This is when the lower and upper level jet align parallel to the cold front and the instability axis makes a run north. Severe weather is questionable at this range given the overnight and morning storms; cloud cover from these will make surface destabilization challenging. Beyond Monday, a northern stream wave will usher in another cold front from the northwest, reinforcing the wrap around precip from the first system. Widespread moderate rain is possible from the cumulative rounds of rain. Most of the state could see a total between 1 to 2 inches, but the rainfall will be spread in a large enough time span that hydrology impacts will be minimal. A cooldown follows the complex of waves with high temperatures returning to the 50s by next weekend.

Aviation

Issued at 1245 PM CDT Fri Oct 30 2026

Stratus is breaking apart in parts of southern Iowa which could offer a period of VFr in the short term for DSM and OTM, mainly. Showers have stayed further south than previously anticipated, so the arrival time has been delayed for most sites and rain remains in the short term for KOTM. Lower cigs will gradually focus into northern Iowa overnight. Can't rule out residual sprinkles as cigs lift late in the period, but confidence is low in vsby impacts.

Watches, warnings and advisories

None.