248
FXUS63 KDMX 110803
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
303 AM CDT Fri Sep 11 2026

.KEY MESSAGES...

-  Patchy fog possible overnight /mainly SE/ otherwise
   seasonally cool.

-  Breezy Friday afternoon, with a chance for showers and
   thunderstorms /20-40%/ returning Friday night.

-  An active weather pattern expected this weekend into the middle
   of next week with periods of thunderstorms, some strong to
   severe, along with the risk of heavy rainfall.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 300 AM CDT Fri Sep 11 2026

The latest surface analysis shows a 1017 mb surface high pressure
center parked over the Great Lakes, with its influence extending
across the region. Clear skies associated with the surface high are
prevalent across the area, allowing temperatures to drop into the
lower 60s, with a few upper 50s reported. To the northwest, a 992 mb
surface low is tracking across central Canada with a trailing cold
front oriented southwestward across Montana and North Dakota.

Today will feature the continued influence of the surface high
pressure system; however, an upper-level trough and associated
surface low will dive southeastward toward the area. Nonetheless,
conditions today will remain dry, with temperatures climbing into
the low to mid-80s by this afternoon. Along with rising
temperatures, increasing southwesterly winds are expected as a LLJ
develops ahead of the cold front advancing into the Northern Plains
and Upper Mississippi Valley. The strongest winds will align with
the LLJ core primarily over South Dakota and Minnesota, but the
northwesternmost locations in the DMX CWA could see gusts up to 30
mph this afternoon. The area will remain dry through much of the day
courtesy of a deep layer of dry air. However, subtle moisture
advection driven by the LLJ will support the potential for elevated
convection later tonight as the front finally moves into the DMX
area. Due to persistent low-level dry air into the overnight hours,
PoPs are capped at 30 percent along the boundary. While the
strongest forcing is forecast over the Dakotas and Minnesota, the
SPC has placed the far northwestern counties in a Day 1 Slight Risk,
with the adjacent tier of counties to the southeast in a Day 1
Marginal Risk for localized severe winds or severe hail.

The front will progress through the region overnight Friday into
Saturday morning, bringing isolated to scattered convective
activity. The boundary is progged to move mostly through the area by
Saturday morning before decelerating significantly. This slow
movement will foster a differential heating boundary where showers
and thunderstorms could redevelop Saturday afternoon. The precise
placement of this differential heating boundary will dictate where
CI occurs Saturday afternoon. Overnight CAM guidance places the
boundary and subsequent CI primarily along and south of the I-80
corridor, rapidly translating southeastward into Missouri.

A dome of high pressure sitting over the Great Lakes is currently
providing clear and mild conditions, but an approaching surface low
and upper trough will push a cold front toward the area. Highs will
reach the 80s today with gusty southwesterly winds ahead of the
front, followed by a slight chance of elevated thunderstorms
overnights. As the front slows on Saturday, daytime differential
heating could initiate scattered severe-capable storms, primarily
along and south of Interstate 80 into Missouri.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 1255 PM CDT Thu Sep 10 2026

The latest guidance continues to suggest quite an active
pattern across much of the Midwest, including Iowa, from this
weekend into the middle of next week. There will be a risk for
strong to severe storms at times along with heavy rainfall.

Periods of showers and thunderstorms are likely on Sunday into
Wednesday as a series of shortwaves move across the area. In
addition, a strong LLJ is expected remain very active during the
period, most notably on Sunday night and Monday and again on
Tuesday night. While mesoscale details are likely play a large
role in the convective evolution each day, the deterministic
models/ensembles along with various NCAR AI guidance and the
ECMWF Extreme Forecast Index remain consistent in showing both
the potential for severe weather /Monday/ and heavy rainfall
from Sunday through Wednesday. Correspondingly, the SPC
currently has a Day 5 Slight Risk for severe storms and the WPC
has noted multiple days of Marginal/Slight via the Excessive
Rainfall Outlooks (EROs). Again, its too early to get into
specific details during this period but 7-day rainfall amounts
in excess of 3-4" are certainly possible with GEFS showing
probability of 2" > 50%, and a 10-20% of greater than 4+". This
could lead to areas of areal or river flooding, especially if
the higher end of the rainfall distribution occurs.  More to
come on this in future days.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1035 PM CDT Thu Sep 10 2026

VFR conditions prevail for much of the TAF period. Patchy fog is
possible mainly in southern Iowa on Friday morning with MVFR to
IFR visibility possible at KOTM. South winds become breezy
Friday with gusts of 20-25 kts across northern site
KFOD/KMCW/KALO. Wind at KDSM should be lighter and have not
included gusts at this time.

&&

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

&&

$$

SHORT TERM...Vorst
LONG TERM...Fowle
AVIATION...Hagenhoff