283
FXUS63 KDMX 031940
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
140 PM CST Tue Nov 3 2026

.KEY MESSAGES...

- There is a Marginal Risk (Level 1 of 5) for severe weather
  today. A tornado or two is the primary threat through this
  afternoon.

- Showers are expected to continue through Thursday, lasting
  the longest across northern Iowa.

- Cooler, more seasonal temperatures will set in later this
  week.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 100 PM CST Tue Nov 3 2026

Showers are ongoing across the state. There is some clearing noted
on satellite as more showers and thunderstorms move into Iowa from
Missouri. Much like yesterday, there is a conditional risk for a
tornado or two with some of the stronger storms. 0-3km CAPE is
around 250 J/kg with SBCAPE values from 500 to 750 J/kg. This is
much higher compared to yesterday where overall SBCAPE was <500
J/kg. As a result, some of the ongoing showers are looking much more
robust in terms of their structure. Low-level lapse rates are
sitting around 6.5-7.0 degC/km per CAM guidance, however, SPC
mesoanalysis indicates that lapse rates won`t exceed 6.0 degC/km,
which would explain why some of the ongoing showers have struggled.

Over the next several hours, there remains a low potential for a
tornado or two, however, this is dependent on better CAPE reaching
into the area as we continue to see clearing across southern Iowa.
Wind profiles show plenty of spin in the low-levels, with
mesoanalysis indicating 0-500m Storm Relative Helicity (SRH) values
of 100-200 m^2/s^2 in southern to southeastern Iowa. With storm
bases effectively on the ground, updrafts will be able to take
advantage of much of this helicity. Not to beat the dead horse that
is yesterday`s environment, but there is a bit less curvature to the
hodographs modeled today compared to last night. From about 850mb
and up, shear is nearly uniform in its direction. All of this is to
say that while the environment is better in some aspects compared to
yesterday`s already marginal environment, enough factors are there
to mitigate the tornado risk from being anything more than
conditional.

The window for severe weather will end around or just after 6pm
tonight with the loss of instability, however, rain showers are
expected to continue central and northern Iowa through much of the
night along the deformation zone behind the low. The low that is
driving this activity will continue to lift north/northeast into
Minnesota and Wisconsin, a process which will last through much of
tomorrow and into tomorrow night. In addition to the continued rain,
this will usher in much cooler temperatures, particularly in the
north.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 100 PM CST Tue Nov 3 2026

A few showers may linger in the north as lingering moisture feeds
into the area. Once the low clears Iowa, flow aloft will begin to
come from the north and west. The abundant moisture transport into
the area that has helped drive the showers will be choked off, and
cooler, drier air will set in. The Extreme Forecast Index (EFI),
which has been consistently highlighting the area as having above
normal highs and lows is starting to back off on this signal. By the
weekend, overnight lows look to dip into the 30s with the potential
for northern Iowa to see lows in the upper 20s.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1126 AM CST Tue Nov 3 2026

IFR to MVFR conditions are expected through this TAF period. Showers
are ongoing across much of the state and are expected to impact all
TAF sites through the period, PROB30 mentions were introduced to
capture visibility reductions with the heaviest of the showers. At
KOTM, PROB30 mentions of thunder were introduced due to the
potential for thunderstorms to move into southern Iowa. A cold front
will move through the state throughout this TAF period which will
help clear out the shower activity, although ceilings are still
expected to remain low across most TAF sites this issuance.

&&

.HYDROLOGY...
Issued at 136 PM CST Tue Nov 3 2026

The stacked upper level system continues to produce rain today
after giving a round of efficient rain in southern Iowa last
night. MRMS reanalysis shows a region of 2-3 inches from Mount
Ayr to Toledo. Much of the eastern half of the area received
over an inch of rain in the past 24 hours, which will push
several rivers into action stage over the next couple of days.
Runoff is exacerbated by the saturated soil moisture values in
the 90% range as well as the historically high streamflow levels
for November. Thunderstorms will continue to be possible this
afternoon in southeast and eastern Iowa. Flow is nearly parallel
to the front, so storms will train along and produce a thin
region of rainfall exceeding 1". Paired with some of the morning
showers in the warm sector, rainfall amounts could locally
exceed 2". This outcome is most likely in the lower reaches of
the Des Moines River Basin near sites like Ottumwa.

For flash flood potential, 3 hour FFG is slightly more sensitive
than reality. Flash flooding will be most likely where rainfall
amounts exceed 2", especially if it is over an urban area. For river
flooding, HEFS QPF spreads tend to be higher than reality. This is
because of the inherent bias correction to its rainfall totals which
improves skill in warm season convective regimes but hurts it in
cool season synoptic systems where GEFS performs well. This means
that the 50th percentile trace in HEFS is using QPF close to
the worse case scenario in the official forecast. Rises to
action stage are likely, with a few sites nearing Minor Flood
Stage.

Rainfall doesn`t leave the picture Wednesday and Thursday. The vort
max, the culprit for showers and storms in southwest Iowa, will
continue to produce rain in western and later in northern Iowa. It
will traverse over the Raccoon basin tonight and drop rainfall
amounts between 1 and 2". It will drop another 0.5" to 1" in
northern Iowa. The Cedar Basin will see prolonged rises into the end
of the week due to the higher rainfall amounts forecasted in
southern Minnesota. This is because of the def zone/TROWAL. The
Raccoon Basin will see rises tonight and forecast points may reach
minor flooding due to the vort max crossing nearby tonight.

&&

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

&&

$$

SHORT TERM...67
LONG TERM...67
AVIATION...67
HYDROLOGY...Jimenez