Mason City, IA Weather

Key Messages

- Light rain chances (30 to 50%) north and west tonight into Monday. Cloudy and mild central and south.

- Relatively active pattern with multiple rain chances through the week. Widespread rain and thunderstorm chances (40 to 70%) return on Wednesday night into Thursday morning and again Friday through Saturday.

Short Term

Issued at 213 PM CDT Sun Oct 25 2026

All but far northwest Iowa is sitting under sunny skies and dry conditions today. Northwest Iowa has seen slightly cloudier conditions, along with a sprinkle or light shower drifting through this morning. Surface analysis shows a weak quasi-stationary boundary stretched from southwest Iowa up to northeast Iowa, bisecting central Iowa. Along the boundary is an area of relative low pressure and weakening of winds, separating surface high pressure to the northwest and southeast. Areas north and west of the boundary, are characterized by cooler temperatures in the 50s to low 60s and light north northeasterly winds. Areas to the south and east of the boundary are seeing slightly warmer temperatures in the upper 60s to mid 70s and calm winds or weak southerly flow.

Through this evening, the high to the northwest is expected to meander south and eastward, pushing the stationary boundary slightly farther south and eventually flipping flow to more easterly by Monday. At the same time, a 500 mb wave and coincident surface low will be lifting northeastward into the Plains, bringing more rain chances to the region through Monday. Most of this activity will stay to the west of the state tonight, but works it's way into our northwestern CWA on Monday. Some CAM guidance does depict shower activity farther south and east into central Iowa Monday night into Tuesday morning, but dry, easterly surface flow will likely inhibit most of this rain from reaching the ground. Therefore, the forecast remains dry for all but western and northern Iowa through Tuesday morning. Cloud cover will span much of Iowa on Monday morning, but some afternoon clearing in southern Iowa should help boost temperatures into the mid 70s. Temperatures only reach the 50s to low 60s in northern Iowa where cloud cover will be more persistent through the day.

Long Term

Issued at 213 PM CDT Sun Oct 25 2026

A southwest to zonal flow patterns sets up from Tuesday through the remainder of the forecast, with multiple shortwaves passing through at various times in the week. This will keep the forecast semi- active, with at least low chances for rain in Iowa each day Wednesday through Sunday. Wednesday night into early Thursday will be our next chance for widespread rain, primarily overnight. This precipitation may also be accompanied by some marginal instability (~500 to 1000 J/kg of MUCAPE), as well as a healthy 30 to 40 kt low level jet overnight. It's of course far too early to get deep into specifics, but if that scenario plays out, a few stronger storms could be possible in that Wednesday/Thursday timeframe, likely leaning toward elevated, nocturnal storms for our area.

Beyond the mid-week system, there is actually pretty good agreement among deterministic and ensemble guidance for another wave and healthy plume of moisture to lift up into Iowa Friday through Saturday, bringing the potential for more widespread rain and thunderstorms. Both 23.13z NBM probabilities and 23.12z LREF (GEFS, EPS, and GEPS driven) probabilities show a widespread 40 to 50% chance for greater than 0.01" of 6 hr rainfall throughout Friday into Friday evening, increasing to a 50 to 70% probability for the same on Saturday. The LREF cluster analysis is also quite impressive, with 3 of the 4 cluster solutions indicating a 50% or greater chance for rain on Saturday, and the remaining solution depicting stronger ridging and a delayed arrival of the rainfall into Saturday night or Sunday. All this to say, the current guidance is pointing toward a good chance for rain falling over the area next weekend. However, keep in mind that while ensemble models are more dispersive, they do still change as the pattern does. We will have to keep an eye on how things trend in the coming days. Regardless, the current forecast looks relatively active for Iowa through the long term.

Aviation

Issued at 1218 PM CDT Sun Oct 25 2026

VFR conditions prevail through the TAF period. Primary feature is the wind shift currently around KDSM and KALO, which is leading to light and variable winds. This will continue sagging southward today and tonight, eventually flipping flow to more north northeasterly at KDSM, KALO, and KOTM. That said, winds will be light around 10 kts or less through that entire period. Mid- level cloud cover is supposed to increase tonight, with some lower MVFR clouds drifting over northwest Iowa. That said, the low clouds stay away from any TAF sites.