textproduct: Des Moines

KEY MESSAGES

- Quiet weather through the day Thursday, then a chance of showers and thunderstorms overnight Thursday night into Friday morning. No strong storms or heavy rain anticipated.

- Warmer Friday and Saturday. Breezy and dry on Saturday, with elevated fire weather concerns.

- Rain chances return to northern Iowa around Monday, then perhaps more widespread toward the middle of next week but details remain unclear at that range.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 1253 PM CDT Wed Oct 7 2026

It is another sunny and glorious autumn day across Iowa. Skies are nearly clear with just a few shreds of cirrus clouds overhead, and winds are light from the northwest to north following a weak surface trough that moved through last night. The resplendent sunshine is allowing temperatures to rise steadily toward highs in the upper 70s to lower 80s later this afternoon. A surface high pressure area currently over the Dakotas will spill southeastward into Iowa tonight and slide by on Thursday, allowing winds to go light to calm overnight and then eventually come around to east southeast by late Thursday. This should make for favorable radiational cooling conditions early Thursday morning, and have maintained lows in the upper 40s to lower 50s, close to expected dewpoints. The fly in the ointment there is that model guidance almost unanimously brings high cirrus clouds in by around sunrise Thursday, especially in our northern counties. However, good cooling will likely occur before those clouds spread in, and even once they do forecast soundings indicate they may be quite thin, thus the lack of change in overnight lows from the previous forecast. There is also some possibility of patchy fog again overnight given the expected radiational cooling, however, coverage was extremely limited this morning and may be so again Thursday morning especially if the cirrus is thick enough by sunrise to mitigate fog development. High temperatures Thursday afternoon will also be a bit lower than recent days with the high sliding by, however, this effect will be mitigated by continuing sunshine and light winds and have bumped up temperatures just a bit above guidance accordingly.

On Thursday night, the 500 MB flow overhead will turn from west northwesterly toward a more zonal pattern and also slacken, signaling a pattern change coming for the end of the week. As the aforementioned surface high moves off to our east Thursday night, a broad surface low pressure trough will develop along the High Plains. A developing nocturnal low-level jet over eastern Nebraska will pivot into Iowa overnight, helping to sharpen a wind shift/effective surface warm front across our area that will move northeastward into Friday morning. There is good model consensus for a swath of theta-e advection along this boundary, enhanced by the LLJ, and resulting in MUCAPEs of 500-1000 J/KG especially in our western, central and southern counties late Thursday night. Global models unanimously spit out light QPF within this swath as it migrates through the area, however, forecast soundings indicate the saturated layer will be quite shallow for much of the night with a near-surface dry layer undercutting it, and surprisingly some of the high-res/CAM solutions (particularly the SPC-WRF and HRRR) are nearly completely dry during this time. Still, the mesoscale set-up favors scattered showers and thunderstorms, and have maintained chance (30-50%) POPs accordingly. In any event, no significant impacts are anticipated from this convection in terms of any strong storms or substantive rainfall amounts before it departs later Friday morning.

By around midday Friday any lingering showers will move east/northeast of our area, and behind the effective warm front surface winds will turn from southeast to south southwest and increase on Friday afternoon, especially across about the western half of our area. Forecast soundings show good low-level mixing and dry air in the column, along with sunny skies and warm air advection supporting a notably warmer day across much of the area.

LONG TERM /SATURDAY THROUGH TUESDAY/

Issued at 1253 PM CDT Wed Oct 7 2026

The remnants of tropical cyclone Isaias, which is predicted to make landfall along the central Gulf coast sometime around Friday night, will drift northward up the Mississippi River valley on Saturday and Saturday night, before shunting off to the east on Sunday. As it approaches the midwest, its primary effects including clouds and rain will remain southeast of our area, but it will pinch off the weak 500 MB ridging in place prior to its passage, resulting in lighter mid-level flow over Iowa. It may also cause a slackening of the low-level pressure gradient and winds in our southeastern counties on Saturday. Our northwestern counties, however, will reside closer to the broad surface low pressure trough slowly approaching from the High Plains, and within a tighter pressure gradient resulting in stronger winds in those areas. This will be enhanced by deeper surface-layer mixing evidenced by forecast soundings, which support peak gusts in the 35-40 KT range around Estherville and farther north and west. Have maintained a forecast in that range, and also trended dewpoints downward by several degrees given the efficient mixing anticipated as well as recent model tendencies for overforecasting daytime moisture. The combination of gusty winds and relatively low RH may support some elevated fire weather concerns Saturday in areas with cured fuels, namely most croplands. This concern will be monitored over the next few days.

As the remnants of Isaias move eastward away from Iowa on Sunday, the surface trough will continue to slowly approach and the pressure gradient and mixing depth will decrease, leading to more modest south southwest breezes and slightly less warm temperatures Sunday afternoon, but still peaking in the upper 70s. By Monday morning, another pattern change will be underway as a 500 MB low develops near the Pacific coast of southern California, while a northern stream 500 MB trough moves quickly near the central U.S./Canada border. As the latter feature scoots by to our north it will spread clouds and rain across the Dakotas, Minnesota, and Wisconsin that may just scrape northern Iowa where low (20-30%) POPs are maintained. Of possibly greater sensible weather impact is that the passage of this mid-level trough will also cause the surface trough, which had been creeping over the High Plains for several preceding days, to surge quickly southeastward through Iowa during the day and into Monday evening. This will bring brisk northerly breezes Monday night followed by a quick passage of surface high pressure on Tuesday. A somewhat more active weather pattern is expected thereafter as the southwestern U.S. 500 MB low evolves, however, model depictions of this evolution and particularly the degree of phasing between that system and the northern stream is quite erratic at this range, and will leave resolution of any details for the coming days.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1218 PM CDT Wed Oct 7 2026

VFR conditions will prevail through the TAF period. Clear to mostly clear skies cover the region this afternoon, with winds light from the NNW at 5-10kts. This evening, winds will turn light and variable. A low probability of patchy/shallow fog exists tonight; however, the chances of it affecting any terminal remains very low so have left out of the TAFs. Upper level cloud cover looks to increase early Thursday morning and stick around through the end of the TAF period.

DMX WATCHES/WARNINGS/ADVISORIES

None.