422
FXUS63 KDMX 151214
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
714 AM CDT Sun Jun 15 2025

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- Isolated thunderstorms this morning will become more
  widespread by this afternoon and evening. A few strong to
  severe storms are possible with gusty winds and small hail the
  primary threats.


- High confidence in stormy pattern through next week. While
  lacking specifics such as timing, location, and hazards, one
  and likely more than one round of strong to severe storms will
  be possible over the state in this period.

- Increasing confidence in heavy rainfall next week that could
  lead to flash flooding and/or river flooding later in the
  week. Similar to above, the location is not clear, but chances
  will increase if rain can repeat over the same basins and as
  time goes on in the week.

- Staying warm and humid most days through late next week.

&&

.UPDATE...
Issued at 320 AM CDT Sun Jun 15 2025

Convection has pushed across central into eastern Iowa through the
overnight hours, riding along the instability gradient that is
draped across the state. Despite ample instability to work with last
evening and overnight, shear remains lacking and has prevented
any more robust development. This convection is expected to
continue to percolate through the early morning hours, very
slowly moving to the east. Convection has been quite efficient
at producing rain thanks to deep warm cloud layers in place.
That, combined with slow storm motions, has resulted in 1-2" in
areas that received rain. New convection has developed in far
northwestern Iowa very early this morning on the nose of a weak
low level jet. This is along the warm front that has been
across northern Iowa for the past several days and has been the
daily impetus for convective development. Convection is
anticipated to bubble along this boundary overnight, likely
diminishing towards sunrise as the LLJ diminishes.

By this afternoon a shortwave will move into the area, bringing the
next wave of convection across the area. CAMs vary widely in how to
handle this, likely due to very little flow aloft to steer storms
and weak shear available to organize storms. Deep layer shear across
the area quiet weak, only approaching 30+ kts across parts of
western Iowa. The instability axis is further into Iowa with 1000-
1500 J/kg of available MLCAPE. As with today, convection is expected
to ride along the instability gradient from northwest into central
Iowa through the evening and overnight. Severe potential remains
low, though a few stronger storms may produce gusty winds or hail.
This is most likely in western Iowa near the better shear.

A more robust shortwave will move across the area on Monday, though
the best forcing at this time looks to remain north of the area. The
axis of 2000-3000+ MLCAPE cuts across far northwest Iowa and into
South Dakota and Minnesota with better shear north of the area. With
better shear in place north and a more organized shortwave,
expect associated convection to also be more organized than has
occurred through the weekend. In addition to the severe threat
for hail and wind which is primarily over northern Iowa, this is
also expected to be another efficient rain producer with
pockets of 1-2" expected. This will set the stage as we move
into Tuesday when the most robust wave is set to move across the
area. The instability gradient has shifted south towards
central compared to previous runs and deep layer shear has
increased to 40-50+kts across the area. With this set up Tuesday
will be the biggest window for severe storms across the largest
portion of the area. Additionally, yet another day of efficient
rain across the area will increase the cumulative impacts of
repeated heavy rain, increasing chances for flash flood and
river flood potential. Cumulative QPF through the end of the
upcoming week is a widespread 3-5" across much of the area with
pockets of heavier totals likely.

Importantly, with multiple rounds of storms over the next several
days, each day will be impacted by the convection from the day
before. This is especially true when it comes to placement of
convection. Be prepared for adjustments to this in the coming days,
and additional detail as more data is available.

&&

.DISCUSSION...
Issued at 342 PM CDT Sat Jun 14 2025

Highly active pattern today through much of next week as has been
discussed in the last several discussions. Lingering warm front that
has been hanging out nearby for many days now is noted over northern
Iowa with clouds bubbling in much of the area south of the boundary
through the daytime today. As of early afternoon, convection has
begun to develop along this front as expected with a warm, moist
airmass to the south as temperatures have warmed well into the 80s,
and even low 90s in some cases, with widespread dew points in the
60s to near 70. Meanwhile, Estherville north of the boundary, is
only in the 70s. Although shear remains quite weak through the
profile, MLCAPEs have reached towards 2000 J/kg per SPC mesoanalysis
which is more than plenty to kick off some storms which have the
potential to become strong to even severe in north central Iowa as
they develop before these storms drift south into portions of
central Iowa into the rest of the evening. With the marginal shear,
storms will struggle to remain organized with gusty winds the
primary threat from a combination of collapsing storms and gusty &
erratic storm outflow, but some small hail is certainly possible in
the better updrafts. Additionally, with the frontal placement and
associated vorticity interacting with the surface-3km CAPE,
conditions are favorable for funnel cloud development this afternoon
into early evening. This is most true in northeast to north central
Iowa per objective analysis but is also where the non-supercell
tornado (NST) parameter is highest per SPC mesoanalysis and RAP
projected NST parameters through the afternoon. Any funnels that do
form are expected to be brief and only drop a few hundred feet with
high enough bases (LCLs largely near to over 1000 m) that a brief
tornado is not expected, but conditions will be monitored
closely.

Although the initial afternoon development will largely diminish by
mid to late evening, additional development is forecasted in
northern Iowa late tonight into portions of the overnight as the
pressure trough slides through largely still along the lingering
boundary. There are varying degrees of how long this activity will
last in CAMs and how robust, but a few hundred J/kg of MUCAPE
may still be present enough for some rumbles of thunder, but not
expected any severe weather overnight with shear still quite
weak and much of the instability used up this afternoon/evening
and no great LLJ placement to help enhance activity further.
However, the boundary doesn`t go much of anywhere Sunday with
additional thunderstorm development expected in northern Iowa by
mid to late morning as instability increases with activity
drifting east and south with time through the afternoon and
evening hours. Although the better parameter space remains to
the west could see some more strong to even marginally severe
storms develop, not too dissimilar from today, with gusty winds
and small hail. This activity largely ends again by mid to late
evening Sunday with a short break per current CAMs though will
need to watch a potential MCS coming out of NE that the global
models in some cases still bring into at least portions of the
area, while the CAMs have it diminish before it gets to the
Missouri River. Will certainly be watching this threat closely.
With expected convection at times, did lower highs slightly
Sunday, though conditions will still be warm and largely in the
80s.

Few updates from the 06.13.25 afternoon discussion with regards to
next week as the upper level pattern continues to remain supportive
for several ridge riding waves bringing several rounds of storms
through the week. Instability and shear both become increasingly
more favorable by Tuesday with pwats 1-2"+ at various times and
locations through much of the week promoting efficient rainfall when
combined with deep, warm cloud depths. Hydro concerns certainly
increase with time after subsequent rounds of rain and storms over
multiple days, with flash flooding concerns heightened over areas
that see repeated storms. In addition, several rounds of storms will
increase rain in the rivers and could lead to at least increased
flows on area rivers if not some possible river flooding by the
end of the week. On the severe side of things, location,
placement, and timing remain a bit more uncertain, but much of
the area is in a SPC Day 3 Level 1 with the far north to
northwest in a level 2 (of 5 in both cases) risk for Monday and
a 15% draped across much of southern Iowa in the SPC Day 4 for
Tuesday with the 15% for Wednesday just off to the east per the
overnight severe weather outlooks. Details will continue to be
fine-tuned but certainly an active period with several rounds of
storms and rain that will need to be watched closely.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 646 AM CDT Sun Jun 15 2025

Scattered showers and thunderstorms are ongoing this morning
over portions of northern into central Iowa with some patchy fog
also occurring in the north. The combination of these things
have dropped visibilities in some cases as low as LIFR with
ceilings varying between VFR and IFR. Although the fog should
improve over the next couple hours, the scattered showers and
thunderstorms will remain at times today into tonight with at
least sporadic MVFR impacts, especially in the north into the
overnight when CIGs look to drop again. Confidence in timing
and impacts of showers/storms, especially this afternoon into
evening, remains low with model guidance not in good agreement
of timing/placement of the next round of storms. Models are also
not handling current activity well further lowering confidence
in future rounds. Adjustments will likely be needed whether in
amendments or future issuances as confidence increases in
shower/storm placement. Winds will be out of the south to
variable at times, especially near the lingering boundary, with
speeds generally remaining light through the period except with
higher gusts at times near storms.

&&

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

&&

$$

UPDATE...Hagenhoff
DISCUSSION...05
AVIATION...05