FXUS63 KDMX 261803

AFDDMX



Area Forecast Discussion

National Weather Service Des Moines IA

103 PM CDT Thu Jun 26 2025



 ...Updated for the 18z Aviation Discussion...



.KEY MESSAGES...



- Showers and thunderstorms persist into the morning hours

  today, mainly over west central into northern Iowa. Heavy

  rainfall and localized ponding/flash flooding remain the main

  threat with this activity.



- Thunderstorms develop over western and northwestern Iowa

  through mid-day, tracking east southeastward through the state

  into the afternoon and evening. Severe weather is possible

  today, with damaging winds and tornadoes being the main

  concern, especially over northern and northeastern Iowa.



- Thunderstorm activity moves out after midnight. Warm

  temperatures build in over the weekend with additional rain

  and thunderstorm chances through the second half of the

  weekend.



&&



.DISCUSSION...

Issued at 337 PM CDT Wed Jun 25 2025



After another active overnight period with heavy rain lingering well 

into this morning, focus becomes on how mesoscale details will 

evolve for the next round this afternoon into evening. Rain showers 

continued well into midday over portions of northern Iowa with cloud 

cover persisting as well, though some clearing has occurred early 

this afternoon. Over central to southern Iowa, clearing occurred 

early this morning with sunshine returning and instability values 

this afternoon rising to 2000-3000+ J/kg of MLCAPE with temperatures 

well into the 80s to low 90s and very humid conditions given dew 

points in the 70s. Although temperatures in the far north are a 

little lower with the cloud cover, the entire area is in the warm, 

moist sector with the surface boundary in southern MN. Of concern is 

our southeast surface flow this afternoon with largely flow out of 

the southwest in the mid to upper levels allowing for the solution 

presented on in the previous update to gradually develop with some 

clockwise-curved hodographs, especially in portions of northeast 

Iowa up towards the surface boundary in MN. The far north to 

northeast is also where SRH values are highest through the afternoon 

to early evening hours, all of this presenting a threat for some 

tornadoes to develop. To the west, wind and heavy rain remain the 

primary concern with the rest of the convection expected to develop 

from Nebraska into portions of western and northern Iowa. More 

organized storms may still be able to develop some small to 

marginally large hail as well though wind shear remains the primary 

limiting factor, as it has the last several days. Storms this 

afternoon and evening are expected to move mainly east-northeast 

with time and be a bit more progressive than previous days but the 

hydro threat remains a concern, see the hydro discussion for further 

details. 



Additional shower/storm development is expected late tonight to the 

west as the LLJ ramps up again. This will once again present a heavy 

rain threat into Thursday morning, but CAMs continue to suggest some 

bowing clusters at times so will continue to watch any additional 

wind threat that develops late tonight into the early overnight. 

This remains a lower probability, though still possible with some 

lingering instability late and the best shear in the north where 

storms are expected to track. 



Pending somewhat how activity plays out tonight into Thursday 

morning will set the stage for our next threat Thursday afternoon 

into evening. A boundary is expected to gradually orient north to 

south allowing storms to develop and move through much of the area 

from west to east. Plenty of instability is expected to redevelop 

into the afternoon, though shear remains more marginal, though 

continually better than previous days. The main threats with these 

developing afternoon storms will once again be wind and heavy rain, 

though storm progression should be faster again than in previous 

days. Storm organization will be a big factor in the extent of the 

severe threat with timing actually moving up faster than in previous 

days and pushing storms through earlier in the day. Will need to 

continue to monitor into the morning to evaluate the mesoscale 

details further but at least one more day of continued active 

weather with both severe and hydro threats. 



Conditions quiet down temporarily Thursday night into Friday before 

additional chances for showers and storms return at times into the 

weekend but more so late weekend into early next week. Additional 

details to be provided in the coming days.



&&



.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...

Issued at 1258 PM CDT Thu Jun 26 2025



Thunderstorms developed over central and western Iowa early 

this afternoon ahead of strengthening low pressure centered over

eastern Nebraska. Expect the individual thunderstorms to move 

generally north-northeastward as the line advances east through 

this evening. Hail and gusty winds are possible at the terminals

as storms pass. Look for IFR ceilings after storms depart 

tonight through late morning Friday.



&&



.HYDROLOGY...

Issued at 337 PM CDT Wed Jun 25 2025



The main takeaways...one final round of heavy rainfall and possible 

flash flooding is expected today before at least a short break in 

precipitation on Friday. However, as water is routed through the 

basins and river systems, river flooding concerns persist well into 

next week.



This morning...showers and storms will impact portions of west-

central and north-central Iowa, mainly driven by moisture 

convergence associated with the nocturnal LLJ.  Rainfall amounts of 

1-3" are possible with this activity, so will keep the Flood Watch 

in place through 18z as scheduled.



After a short lull, a broken line of storms will re-develop along a 

cold front and move from west to east across much of the CWA today. 

As in past days, robust moisture content, high freezing levels, and 

ample instability will again lead to efficient rain rates. However, 

this line of storms should be progressive, moving eastward around 30 

mph. Many of the global models and CAMs are indicating widespread 1-

2" rainfall amounts, but the progressive nature of the storms should 

prevent rainfall amounts from getting out of hand. The 26/00Z HREF 

24hr PMM valid from 12z Thu to 12z Fri shows this nicely, with only 

very sporadic amounts over 3" indicated. However, with the recent 

rainfall and areas of saturated ground, these amounts of precip 

could still cause issues so at least pockets of flash flooding is 

still possible, especially if any training of storms occurs. 



In terms of river flooding, we continue to use 48 hrs of QPF in our 

going river forecasts instead of the normal duration of 24 hrs, 

recognizing the longer term duration of the heavy rainfall. This 

change to QPF duration pertains only to those streams in the 

Mississippi River drainage portion of our CWA, or roughly across the 

northeast 2/3rds of our CWA. The river forecasts, compared to 

yesterday, are higher in some locations, lower in other locations, 

and near the same at some locations. The main reasons for the 

forecast changes are mainly shifting of the QPF location. Most 

changes, however, have remained within the same flood category. It 

should also be noted that for many locations where action stage is 

forecast, those forecast crests are near flood stage.



The larger streams of most concern presently include the Iowa, 

Cedar, Winnebago, Shell Rock and Raccoon Rivers. For some locations, 

the elevated stages and river flooding is expected to continue well 

into next week.



Given the timing in those forecasts (i.e., forecast to reach flood 

stage generally 2, 3 or more days out from the present time), as 

well as lower confidence since it so far out in time, we opted to 

continue mentioning these threats in our Hazardous Weather Outlook 

(HWO) instead of issuing river flood watches or warnings at this 

time. As confidence grows, we expect to begin transitioning to river 

flood watches and warnings perhaps with the river forecasts issued 

later this morning.



&&



.DMX WATCHES/WARNINGS/ADVISORIES...

None.



&&



$$



DISCUSSION...05

AVIATION...WFO Duluth

HYDROLOGY...05/Zogg

