237
FXUS63 KDMX 101730
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1230 PM CDT Thu Sep 10 2026

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- Mild conditions today and Friday with temps in the upper 70s
  and lower 80s.

- Thunderstorm chances (30-40%) Friday night into early Saturday
  morning.

- Additional thunderstorm chances Saturday into Sunday, with
  more widespread chances Sunday into Monday.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 226 AM CDT Thu Sep 10 2026

Tuesday`s cold front has stalled to our south this morning and
thunderstorms are ongoing from Ohio to Colorado. High level cirrus
from storm outflow is traversing southern parts of the state, but
most locations have clear skies this morning. The calm winds and
clear skies have allowed for another morning of radiation fog
conditions. Visibility reductions have been occurring in southern
Iowa, where humidity is higher, but a low level cloud deck has held
off fog in some spots temporarily at the time of writing. Patchy fog
may form further north as well near sunrise given prolonged clearing.

High pressure dominates today and conditions will be quite mild
today and tomorrow. Highs are expected to reach the upper 70s or
lower 80s this afternoon and Friday afternoon. Worth noting that NBM
highs both today and tomorrow are near the 25th percentile of
guidance, with bias corrected models several degrees higher than
NBM, so perhaps highs in the low 80s will be more widespread than
output by the NBM. Precip chances will remain low today through the
day Friday as profiles will be quite dry.

By Friday evening, the pattern begins to shift again. A shortwave
crosses the Dakotas, associated with a surface low centered over
western Minnesota by evening. Low level winds across the state shift
to southerly, advecting higher theta-e back in, particularly in a
narrow zone just ahead of the cold front. The front does not arrive
into Iowa until 6-12z, so any precip chances likely hold off until
the late evening or overnight. There is decent confidence across
global ensembles in some elevated convection developing along the
front overnight, and this is likely the reasoning for inclusion of
northwest Iowa in the marginal/slight convective risk per SPC
and is the justification for maintaining 30-40% PoPs overnight
across a large part of the state. However, worth noting that the
few CAMs that run out to that hour by this point (RRFS/FV3)
have very little if any robust convection occurring across the
northwest portions of the state overnight which would fit the
conceptual model of being in the jet streak right exit region
and in the divergent entrance region of the LLJ (like what is
being forecast). RAP/NAM suggest the thermodynamic environment
will be decent, with 7-8 C/km mid-level lapse rates and
1000-2000 J/kg MUCAPE. Shear is unlikely to be very strong above
the LLJ. So, the environment is supportive of cells with hail
and strong wind.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Issued at 226 AM CDT Thu Sep 10 2026

The weekend then looks to remain active with several additional
chances for showers and storms from later Saturday into Sunday, and
then again with more widespread chances Sunday through Monday.
Although temperatures remain in the 70s to 80s through the weekend
(though with the higher dew points), we`ll get one more bigger push
of heat into Monday before cooling back into the 70s early next week
behind another cold front. Will continue to evaluate the potential
for severe storms and heavy rain with these subsequent rounds over
the coming days but conditions at first glance to remain more
favorable for heavy rain with pwats over 1.5" through much of the
weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1220 PM CDT Thu Sep 10 2026

VFR conditions are expected the remainder of today, with only
high level clouds, or few diurnal cumulus present. Winds will
remain generally light and variable, but will gradually shift
out of the southeast this evening. Tonight, expecting patchy
fog to develop in southeast Iowa, only impacting KOTM where the
winds will be lightest. At the remaining terminals, winds
should increase enough to preclude any fog development. Breezy
south winds will develop towards the end of the period Friday,
mainly at northern terminals.

&&

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

&&

$$

SHORT TERM...Fowle
LONG TERM...05
AVIATION...De Bruin