ia discuss
Office: DMX
FXUS63 KDMX 062350
AFDDMX
Area Forecast Discussion
National Weather Service Des Moines IA
650 PM CDT Sun Jul 6 2025
...Updated for the 00z Aviation Discussion...
.KEY MESSAGES...
- Thunderstorms reach western Iowa on Monday morning with more
widespread thunderstorms in the evening and into Tuesday. A
few stronger storms are possible, however the overall severe
threat is low.
- Additional chances for thunderstorms by Thursday and through
the end of the week into next weekend.
&&
.DISCUSSION...
Issued at 224 PM CDT Sun Jul 6 2025
Lingering fog this morning diminished quickly with sunrise but
moisture has lingered over the area. This afternoon dewpoints have
been in the upper 60s to mid 70s across the area, something pretty
evident if you step outside today. With plenty of moisture around,
low cumulus has bloomed across the area. Conditions are pretty
unstable out there with only a weak boundary out across far eastern
Iowa. CAMs have picked up on this and most develop spotty convection
late this afternoon and evening for our neighbors over in the Quad
Cities CWA. Closer to home there is little forcing of note, but with
so much instability to work with, subtle small scale features could
result in a very isolated shower or t-storm popping in southern Iowa
today.
An overnight MCS across Nebraska is then expected to reach far
western Iowa Monday morning, moving across central Iowa into the
afternoon. As instability increases into the afternoon with
1500+ J/KG of available MLCAPE, expect some restrengthening of
the storms with this wave, even though shear remains quite low.
Later convection across South Dakota is expected to have grown
upscale into an MCS, approaching northwest Iowa by evening.
Again, 0-6 km shear remains low, under 20 kts in most cases, so
storms will struggle to organize, but the MCS is expected to
ride the instability gradient into Iowa through the overnight.
The question is where this gradient and any remnant outflows
from earlier convection set up. There is also indication that
afternoon convection in Nebraska will grow upscale and into Iowa
in the evening, but CAMs continue to struggle with little flow
available. Some, like the NAM nest and ARW , attempt to combine
the SD and NE convection into a larger line across the area late
Monday night and thorugh Tuesday while the HRRR favors keeping
the activity separate. Others like the RAP and Fv3 favor a
scenario where earlier convection delays and weakens the
overnight convection. While the evolution is uncertain, the lack
of shear available to help organize storms should mitigate most
of the severe risk. A few stronger storms are possible, along
with pockets of heavier rain with PWATs over 2" and deep warm
cloud depths for efficient rain production.
High pressure provide a reprieve mid week, but by Thursday and into
the weekend an approaching more robust shortwave passes across the
area. The better forcing, for now, appears to be concentrated north
of the area. We'll have to watch how this evolves later this week as
available AI and ML data indicates some severe potential into the
area. As continues to be the case, efficient rain production
looks likely regardless of severe potential with PWATs exceeding
2 inches.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 644 PM CDT Sun Jul 6 2025
Scattered diurnal CU will continue to diminish this evening with
VFR conditions otherwise continuing through the TAF period.
Showers/storms are forecast at times on Monday, especially later
in the day into evening, though confidence in timing and
location precludes any precipitation mentions at this time.
Winds become light and variable tonight into much of Monday.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Hagenhoff
AVIATION...05
Office: DVN
FXUS63 KDVN 062321
AFDDVN
Area Forecast Discussion
National Weather Service Quad Cities IA IL
621 PM CDT Sun Jul 6 2025
.KEY MESSAGES...
- Scattered showers and a few embedded thunderstorms (30-60%)
are possible this afternoon into this evening, most likely
for locations along and east of the Mississippi River.
Otherwise, most other locations will remain dry today.
- Periodic chances of showers and storms remain in the picture
Tuesday through Friday, but with plenty of dry periods
interspersed.
&&
.SHORT TERM /THROUGH MONDAY/...
Issued at 202 PM CDT Sun Jul 6 2025
A mid-level trough will continue to hang around our region this
afternoon into the evening hours, which will lead to a period of
scattered showers and a few thunderstorms (30-60%) at times through
this evening, mainly for locations along and east of the Mississippi
River. An associated surface trough axis will be the main forcing
mechanism for this activity, which extends from a surface low over
central lower Michigan. The convective parameter space looks to be
weaker for stronger storms compared to yesterday, with weaker low-
level lapse rates (<7.5 C/km) and PWAT values around 1.7 to 2.0
inches. MLCAPE values remain around 1000-1500 J/kg per the latest
SPC Mesoanalysis/RAP13 output.
Although severe storms are not anticipated today, a few brief funnel
clouds are possible as hi-res models are showing enhanced surface
vorticity along the surface trough, combined with moderate low-level
CAPE (0-3 km 100+ J/kg). Latest RAP NST parameter values are
highlighting the boundary with values of ~1-3.
Monday looks to be seasonably warm and humid, with highs in the 80s
and dewpoints between 65 to 70 degrees. An area of high pressure is
progged to move through the Corn Belt region, so most of the day
should remain dry. However, a few showers or storms can't be ruled
out entirely during the late afternoon hours along a mid-level
shortwave that will approach the area, but the 06.12z HREF ensemble
shows a pretty strong signal for any activity to remain isolated, so
again, most locations will remain dry.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 202 PM CDT Sun Jul 6 2025
A fairly active period is on tap for Tuesday through Friday, with
occasional chances of showers and storms in the forecast. A few mid-
level impulses are progged to sweep through the CWA during this time
frame, particularly on Tuesday and again on Friday. SPC has
introduced a Marginal Risk (level 1 of 5) for our southwestern areas
Tuesday for the threat of a strong to severe storm in the afternoon
and evening hours. Analysis of the convective parameter space shows
a similar environment to the last few severe weather events we've
had, with damaging winds being the primary threat. Steep low-level
lapse rates and PWATs exceeding 2" once again will support the
potential for wet microbursts. Seems like the potential for hail and
tornadoes is very low, given very weak mid-level lapse rates, and a
more uni-directional shear profile to preclude any tornado threat.
Another mid-level trough looks to move through on Friday, with some
signals in the various extended machine learning output for the
potential for isolated strong to severe storms, but with this threat
so far out, confidence remains lower for severe weather potential.
Still, something to be mindful of though as we go through the
week.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 607 PM CDT Sun Jul 6 2025
Isolated showers across portions of eastern Iowa and northwest
Illinois will continue to weaken and dissipate over the next
hour or two. VFR conditions and light northerly winds are
expected by evening. Patchy fog may develop across northeast
Iowa during the morning hours. Currently, highest confidence is
at CID and DBQ during the 09Z and 13Z timeframe. MVFR visibility
is likely in any fog that develops with brief reductions to IFR
possible. Otherwise, mostly clear skies and light and variable
winds are expected across the area into the afternoon on
Monday.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.
&&
$$
SHORT TERM...Schultz
LONG TERM...Schultz
AVIATION...Schultz/NWS
