388
FXUS63 KDMX 030546
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1146 PM CST Mon Nov 2 2026

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- There is a Marginal Risk (Level 1 of 5) for severe weather
  this evening and overnight, and again tomorrow. Heavy rain
  and a tornado or two are the primary threats.

- There is a Slight Risk (Level 2 of 4) for excessive rainfall
  across southern Iowa.

- Rain chances continue overnight tonight, through tomorrow and
  again Wednesday.

- Drier conditions and more seasonal temperatures, but still
  slightly above normal, temperatures return late this week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 241 PM CST Mon Nov 2 2026

Showers are ongoing across much of the state and cloud cover is
currently blanketing the region. SREF hints at a potential for some
clearing this afternoon and evening in southeastern Iowa, although
with this occurring after today`s 5:08pm sunset, any clearing that
occurs will do little to impact the looming severe weather threat.
Additionally, breezy conditions are ongoing with stronger winds at
925mb being mixed down to the surface leading to gusts as high as
35kts, especially in northern Iowa.

Through the morning, a low has moved from central Kansas into east-
central South Dakota judging by surface observations. This places
much of central Iowa in the warm sector for today. Strong low-level
southerly flow means low-level moisture has no problem making its
way into Iowa, and enhanced westerly flow higher up is leading to a
push of Pacific moisture into the region. Of note, PWAT values are
in the 1.5" to 1.75" range from this push of moisture, which is
anomalously high for this time of year. Using Omaha, NE as a proxy
for upper-air analysis, the daily max PWAT for this time of year
range sit around 1.25" with a 90th percentile number around 0.89".
Going further with this, today`s 12z sounding shows a PWAT of 1.72"
from OAX. While this would normally signal a heavy rain threat,
storms should be fast-moving enough to mitigate impacts from heavy
rain.

Addressing the elephant that is the aforementioned severe risk, a
first glance looks underwhelming at best. A closer look, however,
suggests a low potential for a tornado or two after sunset. That
said, it isn`t a very clear-cut forecast. Traditional CAPE values
are generally under 500J/kg and lapse rates in the low-levels are
5.5-6.0degC/km, which normally isn`t considered stellar for a severe
environment. The more impressive parameters are 0-1km Storm Relative
Helicity (SRH) which is approaching 300m^2/s^2 and the large,
looping hodographs due to enhanced low-level shear. Another thing
that makes this forecast so sensitive is that the modeled sounding
profiles show very narrow, skinny CAPE which would mean fairly
shallow updrafts. The shallow updrafts combined with directional
shear only in the lowest levels means that for any storm to have a
tornado threat, it needs to be rooted to the surface with extremely
low LCLs for storms to tap into the low-level spin. Notably,
Entrainment CAPE (E-CAPE) values are higher than traditional CAPE
values, in some areas upwards of 50J/kg more, which would hint at
more robust convection. As for timing, the severe weather threat
looks to be mainly from 6PM to midnight, as that window looks to be
when the most CAPE is present over our area.

In short, enough parameters are in place that the tornado threat
should be treated with respect, but there are enough mitigating
factors that lead to the risk being very conditional.

Expectations are that showers will continue through much of the
night and part of tomorrow as the low sits on top of Iowa. More
showers and thunderstorms will lift into southern Iowa as well,
leading to a similar, conditional tornado threat. The window for
tomorrow looks to be in the early afternoon as opposed to overnight,
with CAPE values sitting higher (~1000J/kg) in another highly
sheared environment. The enhanced stretching potential for tomorrow
is a little bit higher, as are low-level lapse rates which are
closer to 7.0degC/km. Pockets of SRH closer to 300m^s/s^2 are also
being modeled for the threat tomorrow.

&&

.LONG TERM /TUESDAY THROUGH MONDAY/...
Issued at 241 PM CST Mon Nov 2 2026

After the low moves out of our area tomorrow evening, showers and
storms will begin to wane as dry air moves into the area.
Temperatures will begin to get much closer to their seasonal values
each day in the extended term. The next system looks to move into
the area this weekend, bringing the potential for more precip.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1133 PM CST Mon Nov 2 2026

Mix of VFR to IFR conditions ongoing to start the TAF period
with showers and a few storms lifting northward into the area as
well. The most likely period for thunderstorms is in the next
several hours and over southern into portions of central Iowa.
Ceilings in the northeast stay around IFR with ceilings other
places mainly MVFR though bouncing into VFR or down to IFR at
times. Visibility reductions are also expected at times as
coverage and intensity of storms increases before waning again
through Tuesday morning. There is then another period of showers
and storms Tuesday afternoon with highest chances for storms
near KOTM but chances for showers exist for most sites at times,
though timing and impacts will likely need adjustment. Winds out
of the south overnight gradually shift to out of the north to
northwest through the day Tuesday west to east with breezy winds
at times gusting to around 10-25 knots.

&&

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

&&

$$

SHORT TERM...67
LONG TERM...67
AVIATION...05/De Bruin