


Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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364 FXUS63 KDMX 292343 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 643 PM CDT Sun Jun 29 2025 ...Updated for the 00z Aviation Discussion... .KEY MESSAGES... - Thunderstorm chances (20-50%) remain yet this afternoon/evening, but coverage and magnitude has decreased - Isolated storm chances (20%) have been added to the region Monday, but coverage won`t be all that great - Cooler air mass for Monday & Tuesday, followed by warmer conditions and storm chances returning as early as Wednesday and perhaps into next weekend. && .DISCUSSION... Issued at 240 PM CDT Sun Jun 29 2025 Morning Mesoscale Convective System (MCS) and residual blow-off clouds has put quite the damper on temperatures today - about 5 degrees cooler than was expected at this time yesterday. Lack of insolation and resultant cooler temperatures has significantly reduced storm prospects and severe potential across the CWA this afternoon/evening; a trend that was captured well in 1630z SWODY1 Slight-Marginal shift. All of the 12z CAMs captured this well, with only the 12z HRRR and FV3 convecting along a relatively diffuse "cold" frontal which is progd to be located roughly from Waterloo to Lamoni by mid- later afternoon. If storms are able to materialize along this boundary, northeast portions of the CWA would be best positioned for best thunderstorm organization given proximity to the mid-level shortwave trough. The best updrafts of which would be capable of producing primarily damaging wind (DCAPEs of 1000 j/kg) and brief heavy rain. So - have made wholesale forecast changes to reduce rainfall chances across the board for this afternoon and evening - generally into the 20-50% range. Of course, this will mitigate flooding threat as well, so no longer anticipate a widespread flooding concern. Storms will depart quickly this evening, giving way to drying thru much of the overnight. MCS Fest is set to continue once again later tonight as the next one moves out of Nebraska and into the Midwest. 12z output has a bit more consensus compared to last night`s tracking it mainly into SW Iowa and MO. It doesn`t look to get into the region until sunrise Monday; and have adjusted precipitation chances accordingly. As for Monday, did maintain low storm chances as the mid-level thermal trough moves overhead, steepening mid- level lapse rates, and likely allowing for at least isolated convection. Although expect most areas will stay dry for Monday. A drier air mass works in for Tuesday. Medium range guidance differ on timing and magnitude of thunderstorm chances into the holiday weekend, so confidence decreases after Wednesday. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 634 PM CDT Sun Jun 29 2025 VFR conditions ongoing across much of the area with sporadic, mainly scattered, MVFR CIGs at times. Bulk of storm chances/prob 30 groups pulled for this afternoon into evening with continuing lower storm chances across all sites except KALO. Will need to continue to evaluate shower/storm chances for Monday and generally kept with mentions previously included but did not add any additional at this time with lower confidence in timing/placement of shower/storm activity. Will continue to evaluate trends and add mentions as needed/confidence increases. Otherwise, VFR conditions largely expected to prevail with light and variable winds through the overnight before winds settle out of the northwest and increase during the daytime Monday to around 10-15 knots, with a few higher gusts. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hahn AVIATION...05