textproduct: Des Moines

KEY MESSAGES

- There is a Marginal Risk (Level 1 of 5) for severe weather this evening and overnight, and again tomorrow. Heavy rain and a tornado or two are the primary threats.

- There is a Slight Risk (Level 2 of 4) for excessive rainfall across southern Iowa.

- Rain chances continue overnight tonight, through tomorrow and again Wednesday.

- Drier conditions and more seasonal temperatures, but still slightly above normal, temperatures return late this week.

SHORT TERM /THROUGH TONIGHT/

Issued at 241 PM CST Mon Nov 2 2026

Showers are ongoing across much of the state and cloud cover is currently blanketing the region. SREF hints at a potential for some clearing this afternoon and evening in southeastern Iowa, although with this occurring after today's 5:08pm sunset, any clearing that occurs will do little to impact the looming severe weather threat. Additionally, breezy conditions are ongoing with stronger winds at 925mb being mixed down to the surface leading to gusts as high as 35kts, especially in northern Iowa.

Through the morning, a low has moved from central Kansas into east- central South Dakota judging by surface observations. This places much of central Iowa in the warm sector for today. Strong low-level southerly flow means low-level moisture has no problem making its way into Iowa, and enhanced westerly flow higher up is leading to a push of Pacific moisture into the region. Of note, PWAT values are in the 1.5" to 1.75" range from this push of moisture, which is anomalously high for this time of year. Using Omaha, NE as a proxy for upper-air analysis, the daily max PWAT for this time of year range sit around 1.25" with a 90th percentile number around 0.89". Going further with this, today's 12z sounding shows a PWAT of 1.72" from OAX. While this would normally signal a heavy rain threat, storms should be fast-moving enough to mitigate impacts from heavy rain.

Addressing the elephant that is the aforementioned severe risk, a first glance looks underwhelming at best. A closer look, however, suggests a low potential for a tornado or two after sunset. That said, it isn't a very clear-cut forecast. Traditional CAPE values are generally under 500J/kg and lapse rates in the low-levels are 5.5-6.0degC/km, which normally isn't considered stellar for a severe environment. The more impressive parameters are 0-1km Storm Relative Helicity (SRH) which is approaching 300m^2/s^2 and the large, looping hodographs due to enhanced low-level shear. Another thing that makes this forecast so sensitive is that the modeled sounding profiles show very narrow, skinny CAPE which would mean fairly shallow updrafts. The shallow updrafts combined with directional shear only in the lowest levels means that for any storm to have a tornado threat, it needs to be rooted to the surface with extremely low LCLs for storms to tap into the low-level spin. Notably, Entrainment CAPE (E-CAPE) values are higher than traditional CAPE values, in some areas upwards of 50J/kg more, which would hint at more robust convection. As for timing, the severe weather threat looks to be mainly from 6PM to midnight, as that window looks to be when the most CAPE is present over our area.

In short, enough parameters are in place that the tornado threat should be treated with respect, but there are enough mitigating factors that lead to the risk being very conditional.

Expectations are that showers will continue through much of the night and part of tomorrow as the low sits on top of Iowa. More showers and thunderstorms will lift into southern Iowa as well, leading to a similar, conditional tornado threat. The window for tomorrow looks to be in the early afternoon as opposed to overnight, with CAPE values sitting higher (~1000J/kg) in another highly sheared environment. The enhanced stretching potential for tomorrow is a little bit higher, as are low-level lapse rates which are closer to 7.0degC/km. Pockets of SRH closer to 300m^s/s^2 are also being modeled for the threat tomorrow.

LONG TERM /TUESDAY THROUGH MONDAY/

Issued at 241 PM CST Mon Nov 2 2026

After the low moves out of our area tomorrow evening, showers and storms will begin to wane as dry air moves into the area. Temperatures will begin to get much closer to their seasonal values each day in the extended term. The next system looks to move into the area this weekend, bringing the potential for more precip.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1133 PM CST Mon Nov 2 2026

Mix of VFR to IFR conditions ongoing to start the TAF period with showers and a few storms lifting northward into the area as well. The most likely period for thunderstorms is in the next several hours and over southern into portions of central Iowa. Ceilings in the northeast stay around IFR with ceilings other places mainly MVFR though bouncing into VFR or down to IFR at times. Visibility reductions are also expected at times as coverage and intensity of storms increases before waning again through Tuesday morning. There is then another period of showers and storms Tuesday afternoon with highest chances for storms near KOTM but chances for showers exist for most sites at times, though timing and impacts will likely need adjustment. Winds out of the south overnight gradually shift to out of the north to northwest through the day Tuesday west to east with breezy winds at times gusting to around 10-25 knots.

DMX WATCHES/WARNINGS/ADVISORIES

None.