840 FXUS63 KDMX 211748 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1248 PM CDT Mon Sep 21 2026 ...Updated for the 18z Aviation Discussion... .KEY MESSAGES... - Light drizzle and showers are possible through late Monday night. A rumble or two of thunder is possible with stronger showers. Heavy rain concerns are minimal. - Patchy fog is possible in spots through sunrise. - Cool, dry weather expected for the midweek. Next chances of rain creep into the west late in the period. && .SHORT TERM /THROUGH TUESDAY/... Issued at 204 AM CDT Mon Sep 21 2026 Light showers are ongoing across northern and northwestern Iowa and an increase in coverage is expected over the next several hours. A closed low at 500mb is making its way east across the region and these showers are being kicked off in an area of weak theta-e advection. While some areas may see several showers through the afternoon and evening hours, rain amounts are generally expected to be light due to weak moisture transport. High pressure over Ontario is influencing the flow at 850mb, leading to an unusual easterly flow with just enough moisture transport to keep the low levels saturated. Moisture transport in the mid-level is much weaker due to the track of the low at 500mb, and with low PWAT values (especially compared to last week's heavy rain setups) lead to fairly low heavy rain concerns. This is aided by the scattered nature of showers and the 'slow burn' of this activity before the 500mb low departs. By 12z/7am Tuesday, isolated spots could see a total of nearly 1 inch of new rainfall before we finally dry out. In general, however, rain totals should be much lower (~0.5 inches). Apart from rain chances, with a moist airmass sitting over the state drizzle is possible through the day in spots and a thick stratus layer is expected once again. The stratus deck will help keep temperatures cooler, with northern portions of the state struggling to get out of the 50s. Across southern Iowa, temperatures in the low 60s are expected. The continued cloud cover has led to an increase in overnight lows Monday night into Tuesday, though the potential to dip into the 40s across northern Iowa is still there. We finally begin to dry out as the high in Ontario translates south over the Great Lakes and begins to have more of an influence over the region Tuesday. As the high situates itself, we begin to dry out in the low- levels, though some lingering cloud cover is still expected with decent saturation through much of the day Tuesday. Otherwise, a dry forecast is in store for Tuesday with highs hovering right around the 60 degree mark. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Issued at 145 PM CDT Sun Sep 20 2026 High pressure will skirt along the US-Canada border and east of the Great Lakes with time. As a result, Iowa will keep an easterly fetch. Upper-level ridging will keep us dry until it's broken down at the end of the week. Until we get there, the main theme this week will be partly cloudy skies and highs in the 60s, a timely pattern change for the autumnal equinox. A couple of disturbances will move onshore and set up an active weather pattern for next weekend with rain chances inching their way into western Iowa. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1249 PM CDT Mon Sep 21 2026 Low ceilings, drizzle and showers, and fog are all challenges through the period leading to overall lower than normal confidence forecast. Confidence is highest in MVFR or IFR ceilings prevailing much of the period at all terminals. Low level moisture is resulting in periods of drizzle and/or fog with intermittent showers also possible. Have opted to limit PROB30 groups for shower impacts, though do show for ALO and DSM as they will be near an area of showers forecast to develop to their west and north, respectively. Otherwise, have focused SHRA mentions around most likely period with AMDs to correct course as needed. Fog is expected to remain IFR or higher, though timing and location of impacts is more uncertain. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...67 LONG TERM...Jimenez AVIATION...Ansorge
