


Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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642 FXUS63 KDMX 161109 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 609 AM CDT Thu Oct 16 2025 ...Updated for the 12z Aviation Discussion... .KEY MESSAGES... - Low chances (20-40%) of intermittent showers and thunderstorms early today, tapering off toward the northeast and ending by this afternoon. - Warm and breezy to end the week, with highs today and Friday in the mid-70s to lower 80s. - An approaching cool front will bring more showers and thunderstorms at times from Friday through Saturday. The overall severe weather threat is low, but a few storms could be strong mainly across the southeastern half of Iowa late Friday. - Dry and breezy conditions on Sunday may promote elevated fire weather concerns. && .UPDATE... Issued at 203 AM CDT Thu Oct 16 2025 Ripples of forcing moving through a relatively saturated column continue to produce additional rounds of isolated to scattered showers and thunderstorms overnight. This will continue through the morning but then the rain will finally depart to our northeast during the afternoon as deep-layer ridging builds in overhead. Have thus expanded POPs initially this morning but maintained a decreasing trend exiting our northeastern counties around mid-afternoon. Thereafter, dry conditions will set in through tonight. Also, forecast soundings indicate that as we dry out somewhat in the afternoon, particularly in our southern and western counties where clouds will clear earlier, mixing depths should increase and winds will become gusty. Have maintained a wind speed/gust forecast above median guidance but this will still be below hazardous levels. && .DISCUSSION... Issued at 236 PM CDT Wed Oct 15 2025 Broad mid-level ridging continues to track slowly eastward across the central CONUS today, with a large area of surface high pressure centered over far northern Wisconsin, covering the Upper Midwest into the Ohio Valley. Further analysis of surface observations shows the very slow moving frontal boundary overhead, draped just north of I-80. Plenty of moisture remaining overhead with weak forcing allowed for isolated to scattered shower activity this morning, which has largely faded this afternoon with the main shower activity in southern to eastern Iowa. On and off showers are expected to continue at times for the remainder of the day and into Thursday, with the highest chances (25-35%) over northern Iowa where the higher moisture content remains. Little instability overhead will keep storm chances low into Thursday, though a few lightning strikes here and there may occur with a stronger shower. A look at temperatures across the state shows a large difference of values from north to south, with much cooler conditions over northern Iowa in the 50s to low 60s where thicker clouds are located, while south of the boundary, values are in the upper 60s through the 70s where some patchy clear skies are noted per satellite imagery. With little change anticipated in the overall setup, have lowered the previously anticipated high temperatures today mainly across the north as thicker cloud cover will limit the extent of warming for the rest of the day, though the initial push of warm air advection ongoing should allow for values to increase a bit more this afternoon to reach the 60s in northern Iowa, while the southern half reaches the mid to upper 70s. Further west of the aforementioned ridge, a defined mid- level low pressure area within the large trough over California today is expected to eject east/northeast into the Northern Plains by Thursday, which will gradually push the current boundary and ridge out of the area later in the day. Lingering rain showers are expected to remain at least through the morning over northern Iowa, before drying occurs across the state through the rest of the day. The thermal ridge will continue to build into Thursday, with low level southwesterly flow increasing across the state, with increased warm air advection overhead. Temperatures therefore will increase with highs expected in the 70s to low 80s across Iowa. With the increased southwesterly flow, breezy winds are expected with gusts up to 25-30 mph, isolated to 35 mph in northern Iowa. By Friday, the surface low is expected to track further northeastward into the Dakotas, with Iowa remaining in the warm sector as the warm front remains well north of the state, keeping the area dry at least into the morning. However, just west into Nebraska, a cold front moving eastward is expected to arrive into Iowa as moisture returns into the state, which will bring the next notable chance for showers and thunderstorms. Initial development looks to occur Friday morning into western Iowa, tracking slowly eastward across the state into the afternoon. By the evening, better forcing for lift and an increase in theta-e advection sets up into central to eastern Iowa, with more scattered to widespread development of showers and storms. Models indicate instability values generally less than 500J/kg though better shear around 30 knots or so over east/southeast Iowa Friday evening, leading to at least low chances of pulse storms, though not expecting severe weather at this time. Lingering showers and storms look to continue through Saturday morning mainly over eastern Iowa, while at least much of western Iowa dries out. Later in the day, a shortwave trough over the Southern Plains looks to lift northeast and become ingested by the larger trough circulation over southern Canada, which looks to bring an enhancement to the larger system. Coming from this looks to be the potential for yet another though stronger surge of forcing and moisture into east/southeast Iowa Saturday afternoon to evening as the front still looks to remain over that area, developing a heavier band of rain showers over the Ohio Valley and extending into eastern Iowa, and lingering into Sunday. In terms of storm potential, higher shear values increase a bit to 30-35 knots, along with slightly higher instability, so this could hold the highest potential for some stronger storms. There still however remains some slight differences between long-range guidance on the overall timing, placement and intensity of the previously mentioned features, so there will likely be changes over the next few days as additional model members capture these time periods and more details are better known. Northwesterly flow takes over with much drier air overtaking the region later Sunday into early next week. Ridging develops into the Central Plains into early next week before models diverge on solutions beyond this, where the GFS keeps the region dry until Tuesday when the next trough arrives in the central CONUS, whereas the Euro has an earlier arrival by Monday. Therefore, not much to really be specific on at this time and will be monitored over the coming days. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 609 AM CDT Thu Oct 16 2025 IFR/LIFR ceilings will affect MCW early this morning, and FOD/ALo at times, before gradually rising and moving away to the north. VFR conditions will prevail by 18Z, except perhaps at MCW where MVFR ceilings may linger into the afternoon before improving. Widely scattered SHRA/TSRA are also ongoing early today and will slowly diminish by the afternoon, but even this morning any impacts will be infrequent and brief and thus are not included in the 12Z TAFs except for a couple of TEMPOs. Overnight tonight, toward the end of the TAF period, VFR conditions are forecast but LLWS of 30-40 KT is anticipated as winds increase just above the surface. && .DMX WATCHES/WARNINGS/ADVISORIES...None. && $$ UPDATE...Lee DISCUSSION...Bury AVIATION...Lee