National Weather Service Raw Text Product

912 
FXUS63 KDMX 161948
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
248 PM CDT Mon Jun 16 2025

.KEY MESSAGES...

- Periods with thunderstorms, some strong will continue into
  Tuesday night and early Wednesday. 

- Areas with heavy rainfall also likely through Wednesday with
  the focus shifting south into central and southern Iowa.

- Turning hot and humid late week and into the weekend.

&&

.UPDATE...
Issued at 255 AM CDT Mon Jun 16 2025

The most immediate hazard this morning is the potential for patchy 
fog development across the area with an environment with plenty of 
available moisture and very little wind. Patchy valley fog has 
already been reported overnight and expect that this will continue, 
with perhaps some expansion, through sunrise. 

Our attention remains focused on severe and hydro hazards, 
primarily today and Tuesday. Early this morning convection 
continues to bubble along the stationary boundary that is still 
draped across northern Iowa. As has been the case the past 
several nights now, shear is very weak and the severe potential
remains low with any of the overnight activity. While a lull is
likely into the morning hours, an isolated thunderstorm at any 
time through today cannot be ruled out. CAMs struggle, as they 
have all weekend, in handling convection in this environment 
with plenty of instability and very little organizing shear. The
main window for convection with come later today when a 
shortwave drops out of South Dakota and across northern into 
central Iowa. This should provide a little better focus for 
convective development compared to the last several days, and 
shear is incrementally better as well. With 0-6 km shear 
approaching 30-35 kts and MLCAPE 2500-3500+ J/kg across northern
Iowa strong to severe storms are anticipated. Wind and hail are
the primary concerns, given steep lapse rates over 7 C/km and 
DCAPE nearing 1000 J/kg. There is also a low end tornado threat 
in northwest Iowa with shear sufficient for sustaining rotating 
updrafts and 0-3 CAPE around 100- 150 J/kg. At the same time, 
expect continued efficient rain producers with 1-2" of QPF 
across mainly northern Iowa today. This falls across areas that 
received 1-3" of rain late last week, increasing the chance for 
ponding of water, river rises, and isolated chances for flash 
flooding in urban areas. 

Remnants of a decaying central plains MCW are expected to move into 
Iowa overnight into the early Tuesday morning hours. This may impact 
convection later in the day as a more robust (the most robust 
in this series) is set to move across the area on Tuesday. The 
instability gradient continues to bisect the state on Tuesday 
and expect that convection will ride along that gradient. Shear 
is also a bit better but could be a little displaced from the 
better instability. An important component on Tuesday is that in
addition to the best shear in this series, the directional shear
component will increase potential for sustained rotating 
updrafts to produce hail and a tornado threat. Of course the 
details of Monday's convection and the remnant MCS across the 
area on Tuesday morning will influence how these details come 
together. And in addition to the severe potential, another 
widespread 2" of rain is anticipated across central Iowa with 
pockets of 3+" likely. With the repeated days of heavy rain the 
hydro concerns increase, particularly in areas that may receive 
back to back hits. We'll be keeping a careful eye on these areas
towards Tuesday and into Wednesday as cumulative effects are 
finally realized. With convection continue overnight and into 
Wednesday as the system finally pushes off to the east, 
lingering hydro concerns are expected as water filters into 
river basins.

&&

.DISCUSSION...
Issued at 243 PM CDT Mon Jun 16 2025

Storms are still ongoing over parts of the northeast county warning 
area including near Waterloo. This convection has been moving slowly 
east/southeast since earlier this morning as it fired along an 
outflow boundary from overnight storms. A few of the storms have 
been strong and near severe and they are beginning to have stronger 
cold pools associated with them, as indicated by the the 20+ degree 
drop in temperatures. Wind gusts have responded as well with a few 
gusts of 40 to 55 mph now being recorded. These storms have also 
produced rainfall amounts of 1-2 inches. A pseudo boundary has setup 
also as a result of the storms with south/southwest wind and 
temperatures in the mid 80s mainly south of Highway 20 to near 
Waterloo to Fort Dodge then arcing northwest into Minnesota. 

The convective allowing models (CAMs) have not performed well today 
and outside the HiRes ARW, the remainder of the CAMs have combined 
for a near zero batting average on this mornings convection and the 
new convection firing over southeast South Dakota along the primary 
cold front. The lack of consistency with the CAMs and the turned 
over air north and the pseudo boundary a bit south, the confidence 
on the evolution of storms going into this evening is lower than 
normal. Once potential outcome is the storms over southeast South 
Dakota become rooted and then travel southeast along the pseudo 
boundary where and instability axis is situated and eventually move 
into central Iowa this evening. Otherwise, it could be a waiting 
game for the development of an MCS over Nebraska mid to late 
evening, though that system should turn southeast. The main cold 
front will move into Iowa tonight and stall somewhere over central 
Iowa. That will eventually become the focus for storm development 
overnight or through the day Tuesday. The triple point will move 
into should move into south central Iowa late Tuesday into Tuesday 
night which may bring the tornado threat into the state. 

Heavy rain potential will remain through Wednesday. The strongest 
moisture advection will remain just south of Iowa but PWATs in 
excess of 2" will be over Iowa at times from late Tuesday into early 
Wednesday. Warm cloud depths by Tuesday night will be approaching 13 
kft so efficient warm rain processes and slow storm motions will 
lead to areas with heavy rainfall. At this point, much of the heavy 
rain has been over northern Iowa. That focus should shift south into 
central and southern Iowa. Will continue to monitor the situation as 
several streams are running above normal.

After the short wave passage on Wednesday, 500 mb heights will be on 
the increase and a transition to a very warm and humid pattern will 
occur. High temperatures in the 90s with dew points in the 70s at 
times will be the warmest weather so far this year. Eventually the 
upper flow will undergo another transition late weekend into early 
next week with a large upper high developing to the east and and 
upper low to the west and southwest upper flow into Iowa. One period 
to watch is Thursday night as this transition occurs as an MCS could 
develop over Minnesota and drop southeast into Iowa. Otherwise, the 
next convective chances, barring the presence of a stout enhanced 
mixed layer (EML), will be next week, which may be stormy at times 
after a lull late week and into the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1240 PM CDT Mon Jun 16 2025

Storms over northern Iowa continue and will impact KALO early in
the period. Gusty winds are also possible with these storms.
Less certainty in storm timing and potential and any given site
so limited the storm mention in this forecast. Wind will be
erratic over northern Iowa also early this afternoon before
re-establishing from the south. A cold will enter central Iowa
overnight and stall on Tuesday. This boundary will likely become
the focus for renewed convection.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Donavon
AVIATION...Donavon