textproduct: Des Moines

KEY MESSAGES

- Light rain/sprinkles near the Iowa/Missouri border possible tonight.

- Low temperatures approach the mid 30s tonight and low 30s tomorrow night. Frost development and/or temperatures near freezing could damage sensitive plants.

- Warmer temperatures return to start the week. Shower and thunderstorm chances (35 to 45%) late Monday night into Tuesday, mainly over northeast Iowa. A few stronger storms could develop, but severe weather potential is low and conditional at this time.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 252 PM CDT Sat May 9 2026

The surface boundary that passed through the area this morning has started to usher in a cooler air mass over Iowa today, most noticeably across northern Iowa where temperatures are only in the low 60s. Farther into central and southern Iowa, temperatures have reached the mid 70s, but likely won't warm much more as typical diurnal processes wrestle with the cold air advection (CAA) regime. Another byproduct of the CAA are the breezy north northwesterly winds ongoing over much of Iowa today, with sustained winds around 15 to 20 mph and gusts of 25 to 35 mph. Light showers trailed the surface boundary through the morning, roughly co-located with the 850 mb boundary aloft, resulting in some sprinkles/light rain through northern and north central Iowa. However, these have since dissipated as they've encountered the drier air mass farther south. Re-development was expected along this boundary later today and into tonight as a weak lobe of energy tracked eastward out of Nebraska into southern Iowa, but recent trends imply this will now stay south of the state. Weak scattered showers can be seen upstream on MRMS output, but these are on trajectory to stay just south of Iowa. Likewise, the weak swath of instability that was scraping the Iowa/Missouri border yesterday is now well south into north central Missouri in today's guidance. Therefore, signs are pointing towards a dry forecast in Iowa tonight, although have maintained the sprinkle mention along the southern border should the elevated boundary find enough moisture to squeeze out a hydrometeor or two.

The cooler air mass and surface high pressure filling in today will bring diminishing winds and clearer skies overnight tonight. Temperatures are forecast to fall into the mid 30s across the north to mid 40s across the south, although radiational cooling early Sunday morning may cause these to fall even further in areas where skies clear. This introduces some concern for temperatures approaching the low 30s, but have held off on frost headlines given the upper 20 dewpoints and potential for upper level clouds/cirrus to move through.

This air mass and high pressure sticks around through the day on Sunday, keeping temperatures mild in the 60s to near 70 with lighter winds than today, albeit still breezy in northern Iowa. This should make for a pleasant day to celebrate all the great mothers out there. Winds then go light again Sunday night into Monday morning, bringing yet another cool May night in Iowa. Mid-level clouds in place over central and southern Iowa will prevent the floor falling out from under temperatures Monday morning, but northern Iowa may not be so lucky as skies clear out overnight. Temperatures will likely dip into the low 30s, approaching or falling below freezing in far northern Iowa. Dewpoints will be in the mid to upper 20s, suggesting cool, elevated surfaces and/or vegetation could see some light frost development. With temperatures nearing freezing, frost or freeze headlines may be needed tomorrow night.

The upper level pattern transitions a bit to begin the work week, as the 500 mb low over the Hudson Bay begins to break up and ridging builds eastward. This will allow warmer temperatures to the west to build back into Iowa, boosting highs back into the 70s and then 80s on Monday and Tuesday. Before the upper ridging can fully build in, a more prominent shortwave wave will dive southward into North Dakota and Minnesota from Monday night into Tuesday, just to the north of Iowa. Forcing coincident with this wave is expect to bring shower and thunderstorm chances back to the upper midwest through this period, although our forecast are remains partially displaced to the southwest of much of this activity according to deterministic guidance. This puts the greatest precipitation potential over northeastern Iowa, only just scraping our northeastern forecast area. That said, the wave will drag a boundary southwest to northeast oriented boundary behind it, affecting all of our forecast area. Guidance does try to kick off light QPF along this boundary through the morning and into mid-day Tuesday, before departing the area Tuesday evening, but the signal is far from robust. Timing of the wave will be important to watch, as a slower progression would allow for more warming out ahead of the front, resulting in more instability. This scenario was being alluded to in yesterday's guidance, although it has sped up slightly again in today's cadre of models. Even in the slower, more unstable solutions (ie the GFS) parcels are still combating a mid-level warm nose/capping. Shower and thunderstorm chances remain in the forecast for this period, but generally favor areas in northeastern Iowa given the weak signal for activity farther south and east in the more capped environment. At this point, the severe weather threat looks low, but conditional on a more unstable and less capped environment preceding the frontal passage. The more widely experienced feature on Tuesday will be windy conditions occurring along and behind the front, with the strongest winds being over northern Iowa Tuesday afternoon where gusts up to 45 mph are forecast.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1220 PM CDT Sat May 9 2026

VFR conditions prevail through the period. Light showers/sprinkles are passing through the area today, but should produce minimal impacts. Northwest to northerly winds continue this afternoon, sustained around 15 kts with gusts over 25 kts possible at times. Winds will become light and somewhat variable tonight, although the prevailing direction will be out of the north.

DMX WATCHES/WARNINGS/ADVISORIES

None.