textproduct: Des Moines

KEY MESSAGES

- Patchy fog northeast early this morning.

- Hot and humid today. Heat Advisory in effect for much of the southwest half of the state. Heat indicies of 100-105 expected.

- Several rounds of storms are forecast from late tonight through Thursday night. Severe storms are possible, with the strongest storms expected on Wednesday. Large hail, damaging wind gusts, and tornadoes are all possible on Wednesday.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 326 AM CDT Tue Jun 9 2026

All is quiet over Iowa early this morning with the main storm show moving out of Kansas and into Missouri. Although there are storms over western Nebraska early this morning as well, these are expected to dissipate as they cross Nebraska so the forecast remains dry through much of the daytime today. High clouds associated with the activity to the south have moved into the southwest half or so of the state with clearer skies to the north and east. With light winds ongoing, patchy fog has been able to develop in portions of our far north/northeast. Although visibilities in these areas may drop near to below 1/2 mile at times, not expecting widespread sub 1/2 mile fog precluding the need for any fog headlines this morning. This cloud cover moves off to the east by about mid morning with clearing expected behind. South to southwest flow ramps up into this afternoon ushering in ample moisture advection as well as hotter temperatures. Forecast highs are in the 90s for much of the area, with the coolest temperatures in the northeast where cloud cover may hold on longest and hottest in the west where the most clearing is expected as well as the proximity to the thermal ridge. With the high dew points in the 60s to 70s, heat indicies climb to the 100- 105F degree range in much of the southwest half of the state where a Heat Advisory is in place today from midday to mid evening.

Any cloud cover that develops or moves in could potentially spoil the extent of the heat but largely expecting the daytime to be dry with storm development largely inhibited due to a mid-level warm layer. Some CAMs do try to kick off a few storms this afternoon to early evening in our deeply unstable environment characterized by 2000-4000 J/kg of MLCAPE but through the afternoon the better shear is offset from the higher instability and as just noted, forecast soundings suggest a cap to be in place. What seems most likely is storms develop over the Dakotas ahead of the approaching upper level trough this afternoon with upscale growth into a MCS expected to occur into the evening and move eastward with time late evening into the early overnight hours. What remains unclear is if this MCS will impact Iowa or not. Many CAMs keep it mostly north of the IA/MN border but certainly can't rule out this MCS bringing thunderstorms with gusty winds to at least portions of the area late tonight into the early overnight with a 40-60 knot LLJ pointed to our west through eastern NE so should storms make it into NE from the line in the Dakotas, this could certainly help sustain them. As noted in the SPC Day 1, the MCS is generally expected to weaken with eastern extent but certainly this will be something we're watching closely into Wednesday morning.

Then attention turns to Wednesday. Some early day showers or storms are certainly possible in the warm air advection wing. A low over SD early moves north through the day but brings a cold front with it that will start to cross the area on Wednesday afternoon before stalling out on Thursday. This is in tandem with the approaching upper level support which finally crosses through the area on Thursday. Gradient winds become gusty on Wednesday with the warm sector pointed right through the area, an open Gulf, and shear finally catching up to the ballooning instability with MLCAPEs again by afternoon around 2000-4000 J/kg and bulk shear of anywhere from 30-45 knots by afternoon and even greater by evening as the jet kicks in. This environment will support all modes of severe weather from large hail, damaging wind gusts and tornadoes. The strongest tornado and largest hail potential rides with any storms that form earlier in the event and can become sustained supercells which at this point is northeast into east central Iowa (for locations in Iowa). With the aforementioned increasing jet, we may be looking at multiple rounds of storms with some in the afternoon and evening, and then another round developing late. Will also need to watch for another developing MCS to the west which could bring even more storms into early Thursday morning. Locations of any early day outflow boundaries or other mesoscale details could certainly alter locations of features developing. This is similarly true on Thursday as what occurs Wednesday night may affect the location of the stalled out boundary and any lingering outflows though we are certainly looking at another day of storm development in the warm sector which at this point remains over at least the southeast half of the state.

We will also need to continue to monitor the hydro threat in especially southern Iowa where soil moisture remains higher and heavy rain occurred in the last week. Pwats remain near to over 1.5- 2" through this week.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 259 PM CDT Mon Jun 8 2026

The pattern remains on the active side Thursday, with lingering showers and storms mainly over southern and eastern Iowa as the frontal boundary gradually departs the state. A brief reprieve is indicated later in the morning, then another surface low over Southern Plains within the larger western CONUS trough moves into the region. Latest model guidance such as the NAM shows that this system tracking directly over Iowa Thursday afternoon through the evening, with warm frontal showers and storms indicated during the morning followed by additional activity later in the afternoon into the evening. Severe weather looks possible with this activity as well.

Following the frontal passage, dry conditions look to return for some time. The upper level low pressure is signaled to deepen further as it circulates over the Upper Midwest into Canada. This flow pattern overhead will lead to slightly cooler and less humid conditions, with highs in the low to mid 80s and dewpoints in the 50s. Long range members begin to diverge more by the weekend, as the GFS keeps conditions on the dry side before the next system arrives later Sunday, while the Euro passes a few subtle waves across Iowa that keep at least low chances for showers/storms at times. While variations like these are normal this far out, details should become more clear in the coming days, so stay tuned for that.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 634 AM CDT Tue Jun 9 2026

Patchy fog early this morning in the northeast affecting KMCW and KALO is expected to dissipate shortly after sunrise. VFR conditions are largely expected to follow today with high clouds gradually clearing this morning before more clouds move in tonight, though at this point VFR conditions still prevail. Confidence in storm development today is very low through much of the evening with the highest chances (though still less than 40%) late tonight into the overnight hours and in northwest/northern Iowa. However, timing and impacts of storms at any terminals remains quite uncertain given the uncertainty in storm development. Thus, took out/kept out any precipitation mentions with confidence in all cases less than 30%. Light and variable winds this morning will settle out of the south and increase into tonight sustained around 10-20 knots and gusts to around 20-25 knots.

DMX WATCHES/WARNINGS/ADVISORIES

Heat Advisory from 1 PM this afternoon to 9 PM CDT this evening for IAZ015-023-033>035-044>048-057>062-070>075-081>086- 092>097.