FXUS63 KDMX 150815 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 315 AM CDT Wed Apr 15 2026 .KEY MESSAGES... - Slight Risk for severe storms expended more to the west today. All modes of severe weather possible, with a locally higher tornado threat along the I-80 corridor. - Enhanced Risk expanded for Friday, covering much of the eastern half of the state. - Much cooler over the weekend with a hard freeze likely in northern Iowa Saturday night. && .SHORT TERM /THROUGH THURSDAY/... Issued at 312 AM CDT Wed Apr 15 2026 Showers and storms continued overnight, with the surface warm front appearing to remain stalled diagonally across the center of the CWA, seen best by the Td discontinuity between sites such as KDSM and KBNW. Water vapor imagery showed the main circulation for today traversing off the Rockies and into the High Plains. A dry slot could be seen intruding into southeastern Nebraska, with the surface dry line residing in Kansas. Showers and isolated storms will continue to fester in the warm sector through at least the early morning hours, fueled in part by the interacting upper-level jet maxes. The southern jet max will round into the warm sector later this morning, the wind field below unidirectional and similarly enhanced. The dry slot will move into Iowa ahead of the cold front this morning, increasing capping and mid-level lapse rates. Trends have favored a lull in precipitation around midday, opening the opportunity for potential clearing ahead of the main severe window in the afternoon. MLCAPE values will approach 1500 J/kg. Deep-layer shear over 50kts will provide good ventilation for storms and favor supercells, but low-level shear lacks today, reducing SRH available for tornadoes. The exception will be near the triple point as localized backing of surface winds will elongate hodographs. 00z CAMs had consensus of a longer-lived UH streak following the path of the triple point, with neighboring super cells taking advantage of the NSE on the warm front. This will be the region where the threat for tornadoes is the highest, and have collaborated with SPC to add in a 5% tornado risk area, focused along and near the I-80 corridor. A line of storms will form along the cold front in southern Iowa and pose a wind threat, although capping will allow for discreet modes to start, adding in large hail and isolated tornadoes to the mix. Cold front initiation will begin near the I-35 corridor. Thunderstorms will follow the departure of the surface low and be fueled mainly by the upper-level trough. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Issued at 1239 PM CDT Tue Apr 14 2026 On Thursday a weak ridge will move through Iowa, providing a most welcome respite in the form of a dry, mostly sunny, and mild day with highs roughly in the 75-80 degree range and modest breezes. By Thursday night however, an even deeper longitudinal 500 MB trough will be moving into the Rockies, heralding more active weather to end the week. A surface cyclone will develop in the Southern High Plains with a long inverted trough and sharp baroclinic zone extending northeastward across the Midwest. By Friday morning this front will span from central Kansas, across northwestern Iowa, and into western Wisconsin. Destabilization will occur ahead of the front during the day Friday, and by the afternoon CAPE of 1500-2500 J/KG is likely in at least parts of our area, mainly the southern half. Deep-layer shear will be fairly modest and mostly in the form of speed shear, however the strong dynamic forcing ahead of the approaching trough, convergence along the front, and increasing instability will combine with this shear to be more than sufficient to support severe weather potential Friday afternoon and evening, as outlined by SPC outlooks. The storm system will push quickly through Friday night and clear us out, though there may be some light wraparound precipitation in our northern counties lingering into Saturday as the final lobe of the 500 MB trough moves by. With much colder air surging in behind the late Friday front and temperatures expected to fall into the 30s across much of our area by early Saturday, a few flakes of snow cannot be ruled out in northern Iowa but no real accumulation or impact would be expected. Highs on Saturday will be nearly 30 degrees cooler than on Friday, ranging in the mid-40s to mid-50s, then falling even further Saturday night into Sunday morning with lows in the upper 20s to mid-30s across Iowa resulting in a frost/freeze in many areas. The good news is this cooler weather will be short- lived, as a ridging pattern sets up in the first half of next week supporting a gradual warming trend. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1242 AM CDT Wed Apr 15 2026 Storms have focused more to the south, affecting KDSM the most in the next 6 hours. Monitoring damaging wind potential upstream as CSQ gusted over 50kts. In other storms, heavy rain and hail up to 1" diameter possible. Severe weather chances decrease after 08z, but MVFR cigs will increase in coverage, lifting into northern Iowa with showers towards the morning. Prob30 groups remain through the morning as showers and storms will be common in the central and east. Midday hours around 18z have begun to trend dry before severe storms return 20z to 00z. Enough confidence in storm timing to put in a prevailing group of TSRA in some sites. All modes of severe weather will be possible in that time frame, along with MVFR cigs and potentially IFR vsbys from rainfall. && .HYDROLOGY... Issued at 119 PM CDT Tue Apr 14 2026 Multiple rounds of seasonally moderate to heavy rain this week will lead to renewed flooding concerns. Concerns will include possible renewed or additional river flooding as well as flash flooding. Output from the GFS- and NBM-forced medium-range National Water Model (NWM) and the Hydrologic Ensemble Forecast System (HEFS) suggest the most likely scenario will be moderate to significant within-bank rises on many rivers and streams across the CWA over the next week, especially across the southeast half. Some locations may see minor river flooding as well. These rises will be due to the additive effect of multiple rounds of rainfall. If rainfall is higher than presently forecast then the risk of several locations seeing minor flooding and a few locations seeing moderate flooding will increase. Flash flooding is less of a concern than river flooding, however the risk is nonzero. The additive effect of rain events will result in a slightly higher risk of flash flooding from Friday into Saturday. The most likely scenario through the end of this week will be ponding of water or low-end flash flooding especially in urban areas or areas that receive repeated heavy rainfall over a relatively short time period. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Jimenez LONG TERM...Lee AVIATION...Jimenez HYDROLOGY...Zogg