311 FXUS63 KDMX 131137 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 637 AM CDT Tue Oct 13 2026 ...Updated for the 12z Aviation Discussion... .KEY MESSAGES... - Isolated areas of showers and storms remain possible near/south of the I-80 corridor through sunrise. - Shower and storm coverage increases through the afternoon and especially this evening/early Wednesday, with highest chances (70-90%) over southern Iowa. A Marginal (1 out of 5) Risk of severe weather exists tonight/early Wednesday, with hail, gusty winds, and/or pockets of heavy rain possible. - More widespread precipitation expected Wednesday night and Thursday. - Seasonal temperatures through mid week and then turning much cooler to end the week and start next weekend. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 343 AM CDT Tue Oct 13 2026 A look at surface features early this morning shows an area of low pressure centered over Wisconsin, with it's associated surface front across the large majority of central Iowa, outside of the far southeast fringe as of 2am. This is seen really well from a look at temperatures across the forecast area, with values behind the front reading in the mid 50s to low 60s, while ahead of the front (Centerville and Bloomfield area), values are reading in the upper 60s to low 70s. While much of Iowa is dry, latest trends on radar returns are showing a few clusters of shower/storm activity near over southwest Iowa that have been relatively slow in movement to the northeast over the last few hours, but have increased in intensity given the increase in cloud-top cooling and subsequent lightning detections per GOES satellite imagery. These storms are behind the surface front, anchored more so aloft with the 850mb boundary that remains over central Iowa, and are being fueled by the push of moisture within the southwesterly flow aloft, and lift occurring as a low level jet extends across Iowa. With the nose of the jet and much better moisture near the warm frontal region of the surface low over the Great Lakes, concerns for storms to become strong this morning are very low, given limited instability and very weak shear overhead. CAM guidance indicates that this pulsey activity will generally remain near to south of the I-80 corridor over the next several hours as this activity moves east/northeastward, before decreasing in coverage as the jet fades beyond sunrise. The aforementioned surface front will continue moving south/southeast through the morning, exiting Iowa within the next few hours and generally remaining over northern Missouri through the remainder of today. Given the faster movement of the front, as well as a general increase in cloud cover behind the front, high temperatures have been lowered even further, with values expected in the 60s to low 70s through the northern two-thirds of the state and into the mid 70s to low 80s further south were clear skies may remain longer. Further lowering of temperatures may be needed if cloud cover becomes more widespread than anticipated, which is certainly possible given observations further upstream, but will further monitor trends through the day. By this afternoon and especially into the evening, will begin to see chances for showers and thunderstorms increase, as a stronger push of moisture surges into the state and converges with the elevated boundary that will remain overhead. Coverage of this activity is expected to occur over central and especially southern Iowa, where the potential for some strong to severe storms remains. This is supported by forecast soundings showing slightly higher instability values overhead of 1000-1500 J and favorable shear values of 30-40 knots, with higher values further south into northern Missouri in closer proximity to the core of the low level jet and deeper moisture convergence. The primary hazard of concern is potential large hail given the elevated nature of this activity, while heavy rain at times is also possible with any stronger storms and isolated stronger gusts. Rainfall amounts generally around or less than an inch are expected, though isolated areas up to 2 inches cannot be completely ruled out. Timing of this activity in terms of potential severe weather remains roughly in the late evening hours tonight to early morning Wednesday. The environment becomes less favorable through Wednesday morning, with the expectation of a gradual decrease in shower/storm activity as dry air takes over with high pressure to the northwest moving into the region. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Issued at 244 PM CDT Mon Oct 12 2026 A dry period is then expected some of Wednesday daytime as surface high pressure returns to the area briefly. By evening, theta-e advection increases ahead of the approaching upper low off the Rockies and the lee surface low moves through the region on Thursday followed by the upper trough with a strong system also coming out of Canada later Thursday into Friday. This will bring more widespread precipitation chances from Wednesday night through Thursday. Temperatures will be closer to normal and in the 60s to low 70s through midweek. Then, behind the departing system, stronger cold air advection will arrive sending temperatures into the 50s to low 60s for Friday and Saturday and low temperatures in the 30s Friday night/Saturday morning. Will need to watch for frost potential to start the weekend with a surface high swinging through. With this high and an upper ridge, conditions are looking drier Friday through the weekend. Friday does look to be breezy to windy which could make it feel even cooler and will have to monitor for any fire weather conditions should there be enough time for fuels to dry after the rain on Thursday. && .AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 637 AM CDT Tue Oct 13 2026 MVFR conditions are ongoing over all sites but KOTM as stratus sinks southward, and will likely remain at least through the remainder of the morning before some improvement occurs. Otherwise, storms are moving over southeastern Iowa, which may impact KOTM at times over the next few hours before drying into mid-late morning. Chances for showers and storms then increase after 21-00z, especially late evening into the overnight at KALO, KDSM and more likely at KOTM, which may lead to periods of lowered ceilings and vsbys, with MVFR and possible IFR further southeast into Wednesday morning. Winds will generally remain light through the period out of the north/northeast. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Bury LONG TERM...05 AVIATION...Bury
