004 FXUS63 KDMX 171729 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1229 PM CDT Wed Jun 17 2026 ...Updated for the 18z Aviation Discussion... .KEY MESSAGES... - Severe storms to move across the state in the coming hours. Large hail and damaging winds are the primary threats. Wind- driven hail a concern with these. Timing will be sunrise and through rush hour. - Additional severe storms expected beginning around midday in southeast Iowa. All hazards possible with storms, those of which will have fast storm motions over 50mph. - Wind gusts over 45 mph common today, beginning in southern Iowa shortly after sunrise, then in the afternoon in northern IA. - Showers and storms, though more sparse, are possible in northern Iowa this afternoon and evening, locally exacerbating wind gusts. Severe winds (>58 mph) possible with these. && .SHORT TERM /THROUGH THURSDAY/... Issued at 126 AM CDT Wed Jun 17 2026 Seasonably (very) strong kinematics are setting up tonight. The nocturnal LLJ is rapidly advecting 60 dew points into Nebraska. Elevated reflections of the moisture advection have led to convective initiation over South Dakota. More storms have begun to fire on the segment of the warm front in northern Nebraska, which supports the southern trend in convective coverage in the coming hours. The surface cyclone responsible for Wednesdays severe weather is just behind that complex and will rapidly deepen across Iowa. The LLJ will intensify and veer into Iowa, exceeding 60kts, creating large cyclonic hodographs for the morning thunderstorm complex to utilize. This means that despite being elevated in nature, the effective SRH will still be high, perhaps even over 300 m2/sec2. Effective shear from the west at 70kts add support to an eventual MCC with embedded mesocyclones as the complex utilizes 1500 J/kg+ of MUCAPE in the warm sector. The embedded rotating updrafts will lead to hail growth, and the lagging moisture in the PBL will lend to evaporative cooling processes as hydrometeors fall, keeping a damaging wind potential in play despite not being surface-based. The concern in exacerbated given that the wind field, even a few thousand feet above the surface, is over 50kts. Downbursts from storms have the potential to bring more significant winds (70mph+) and the falling hail will become wind-driven at that point. Timing for this setup puts storms along the I-35 corridor by 6am with a southern expansion in convective coverage being the trend this evening. Storms could reach as far south as Highway 34. The synoptic winds themselves add to the wind impacts in two places today for the CWA: southern Iowa this morning and northern Iowa this afternoon. For this morning: right as the mixed layer begins to establish itself near sunrise, the LLJ will still be around 50kts and will be tapped into the top of the mixed layer. While the environment will still favor WAA, convection and the frontal circulation itself will assist in momentum transfer to the surface. Have issued a Wind Advisory to cover this potential. For the afternoon: a PV anomaly will sink into northern Iowa, with the 1.5 PVU surface sinking as low as 500mb triggering enhanced height rises collocated with increasing CAA. The CAA is associated with the main shortwave on the leading edge of the upper jet, which will maintain another extension of a surface cyclone in Minnesota. With that passing cold front, its CAA will extend deep into the atmosphere. This will steepen lapse rates and potentially encourage mixing up to 600 mb in northern IA, re-establishing CAPE values in northern IA up to 1000 J/kg. There will be less moisture to work with and an inverted-V profile forms. Still, showers and storms will form along and behind the passing front, driven first by the frontal circulation and convective processes behind. Coverage and intensity will pale in comparison to the warm sector in eastern Iowa, but will realize the strong wind field, aided by the synoptic wind setup mentioned in the previous paragraph. Wind gusts over 50 mph -- even severe winds over 58 mph -- will be possible with even showers. Confidence in severe winds is highest where the CAA is strongest, mainly north of Highway 30. LCLs lower as the sun sets, but northern Iowa remains mixed. With ambient vorticity present from the surface low just to the north, will need to monitor for landspout potential late in the day. Trends will be monitored. Finally, the warm sector. With a more southern expansion of the MCC, the instability axis will maximize beginning in southeast Iowa and into central Illinois, but will recover north thanks to the sustained LLJ in the day. The warm front will sink southeast just behind the morning convection, igniting as early as far west as the far east DMX CWA. The upper jet will begin to enter the warm sector by midday, creating a midlevel jet max in response on the east side of the trough. All hazards will be possible with these initial updrafts, and storms will be moving very fast -- over 50 mph, per the Bunkers Right Mover Motion in soundings. Hodographs remain very impressive, the looping low-levels look like something normally seen in a Dixie Alley outbreak. Cities including Ottumwa, Bloomfield and Oskaloosa will need to be weather aware around the midday hours, as the main severe weather event of the day will get its start in this area. This is reflective by the Enhanced Risk expansion into the area. The peak severe weather window is east of our CWA, as thermodynamics and kinematics maximize over Illinois and Indiana. See AFDs from WFOs east of here for more information. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Issued at 241 PM CDT Tue Jun 16 2026 Thursday and Friday will be mild and quiet with highs in the upper 70s to low 80s. A quick moving, weak embedded shortwave may move across the area on Thursday and bring a quick shot for precipitation, otherwise conditions will remain dry. Attention will then turn to the deepening low pressure that will move into the area late Saturday into Sunday. This is expected to bring another round of storms, some severe, to Iowa. Details on this system will be better determined in the days ahead. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1229 PM CDT Wed Jun 17 2026 Low IFR ceilings will linger at ALO/MCW for about another hour before pushing out this afternoon; otherwise, prevailing VFR conditions are forecast through this evening. A few showers or thunderstorms will be possible at MCW/ALO between about 20Z and 23Z and have included PROB30 groups at those terminals accordingly. Low clouds are also expected to redevelop in northeastern Iowa overnight into early Thursday, with at least intermittent MVFR ceilings possible at MCW/ALO once again. Meanwhile, winds will shift through southwest to west northwest early this afternoon and increase significantly, with 20+ KT crosswinds possible on some runways until winds gradually subside after sunset. && .DMX WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 9 PM CDT this evening for IAZ004-015-023- 033-034-044. && $$ SHORT TERM...Jimenez LONG TERM...Hagenhoff AVIATION...Lee
