


Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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324 FXUS63 KDMX 070401 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1101 PM CDT Sun Jul 6 2025 ...Updated for the 06z Aviation Discussion... .KEY MESSAGES... - Thunderstorms reach western Iowa on Monday morning with more widespread thunderstorms in the evening and into Tuesday. A few stronger storms are possible, however the overall severe threat is low. - Additional chances for thunderstorms by Thursday and through the end of the week into next weekend. && .DISCUSSION... Issued at 224 PM CDT Sun Jul 6 2025 Lingering fog this morning diminished quickly with sunrise but moisture has lingered over the area. This afternoon dewpoints have been in the upper 60s to mid 70s across the area, something pretty evident if you step outside today. With plenty of moisture around, low cumulus has bloomed across the area. Conditions are pretty unstable out there with only a weak boundary out across far eastern Iowa. CAMs have picked up on this and most develop spotty convection late this afternoon and evening for our neighbors over in the Quad Cities CWA. Closer to home there is little forcing of note, but with so much instability to work with, subtle small scale features could result in a very isolated shower or t-storm popping in southern Iowa today. An overnight MCS across Nebraska is then expected to reach far western Iowa Monday morning, moving across central Iowa into the afternoon. As instability increases into the afternoon with 1500+ J/KG of available MLCAPE, expect some restrengthening of the storms with this wave, even though shear remains quite low. Later convection across South Dakota is expected to have grown upscale into an MCS, approaching northwest Iowa by evening. Again, 0-6 km shear remains low, under 20 kts in most cases, so storms will struggle to organize, but the MCS is expected to ride the instability gradient into Iowa through the overnight. The question is where this gradient and any remnant outflows from earlier convection set up. There is also indication that afternoon convection in Nebraska will grow upscale and into Iowa in the evening, but CAMs continue to struggle with little flow available. Some, like the NAM nest and ARW , attempt to combine the SD and NE convection into a larger line across the area late Monday night and thorugh Tuesday while the HRRR favors keeping the activity separate. Others like the RAP and Fv3 favor a scenario where earlier convection delays and weakens the overnight convection. While the evolution is uncertain, the lack of shear available to help organize storms should mitigate most of the severe risk. A few stronger storms are possible, along with pockets of heavier rain with PWATs over 2" and deep warm cloud depths for efficient rain production. High pressure provide a reprieve mid week, but by Thursday and into the weekend an approaching more robust shortwave passes across the area. The better forcing, for now, appears to be concentrated north of the area. We`ll have to watch how this evolves later this week as available AI and ML data indicates some severe potential into the area. As continues to be the case, efficient rain production looks likely regardless of severe potential with PWATs exceeding 2 inches. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1057 PM CDT Sun Jul 6 2025 Although VFR conditions ongoing and largely expected to continue during much of the TAF period, watching the potential for developing fog again overnight, especially near eastern sites KMCW, KALO, and KOTM. Confidence in extent of impacts remains lower as typical with patchy fog development, but started with some fog mentions into MVFR or even IFR visibilities though adjustments are likely as fog begins to develop. Additionally, showers/storms are forecast at times on Monday, especially later in the day into the evening, but confidence in timing or location has not increased enough with this package to include any precipitation mentions at this time and will be addressed in future issuances. Winds remain light and variable overnight and through much of Monday. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hagenhoff AVIATION...05