Dorchester, Iowa Weather Forecast Discussion

393
FXUS63 KARX 090521
AFDARX
Area Forecast Discussion
National Weather Service La Crosse WI
1221 AM CDT Tue Sep 9 2025
.KEY MESSAGES...
- Potential (15-70%) showers and perhaps (10-20%) a rumble of thunder
  early Tuesday morning into the evening hours, mainly north of
  Interstate 90. Neither severe storms nor flash flooding are
  expected.
- Warming through Saturday with above normal temperatures
  expected this weekend.
&&
.DISCUSSION...
Issued at 202 PM CDT Mon Sep 8 2025
Potential showers, storms Tuesday:
18z WV satellite reveals quasi-zonal flow aloft with a series of
disturbances seen upstream over MT/ND/SD. At the surface, expansive
high pressure is present in the eastern CONUS with this feature
having shifted eastward far enough for southerly winds to resume
across our CWA. Despite the cool temperatures last night,
temperatures have rise into the lower 70s in some locations early
this afternoon.
Late tonight, wave currently over ND will advance downstream to Lake
Superior. With available moisture on a slow increasing trend, this
may result in a shower or two north of US-10. Moving ahead to the
afternoon and evening a more potent wave ejects eastward out of SD
following by another disturbance in the evening. These two will
likely (50-70%) result in showers in Clark/Taylor Counties, in
our extreme western areas, and potentially (15-40%) farther
south. However, progged soundings from the 08.12z extended HRRR
run suggest warm temperatures aloft at around 750mb will limit
overall coverage of showers and potential for thunderstorms, an
outcome that comports with the 08.12z HREF, which suggests a
very low (10% or less) chance for supportive CAPE with low CIN
outside of our far west. When expanding the 08.12z HREF joint
probability to include deep shear, the chance for severe storms
is next to zero across the CWA, an outcome also suggested by
08.12z HRRR neural network output and 08.00z ECENS and GEFS ML-
based outlook. As for heavy rain, both 08.00z GEFS/ECENS mean
PWATs remain below the 90th percentile of model climatology, so
am not concerned about this either despite the potential for a
few rounds of light showers in our north.
Warming trend through Saturday:
Medium range guidance across the 08.12z cycle continues to point
toward an upper ridge building over the Plains and shifting eastward
with heights aloft over our CWA favored to be maximized Friday
and/or Saturday. 08.13z NBM probabilistic output suggests highs will
very likely (80%+) return to the 80s both afternoons along and
southwest of I-94 with a very small (10%) chance to reach 90 within
the Mississippi River valley Saturday.
&&
.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1217 AM CDT Tue Sep 9 2025
VFR conditions expected for the next 24 hours. Winds out of the
south will continue to gust through the overnight hours to
between 15-22 kts. Because of the continuation of surface gusts
and the lack of directional shear in the lower levels, have left
out the mention of LLWS for this package. Sustained wind speeds
are expected to stay at or above 10 kts with sporadic gusts to
around 20 kts through the afternoon hours. Chances for showers
and storms will increase from the west later this morning and
continue for much of the day. Overall, rain chances at the
terminals look to stay below 40 percent so have opted for
PROB30s to cover this activity for now. Showers and storms will
generally wane later into the evening before coming to an end
overnight. Winds are expected to finally decrease this evening,
becoming light and variable tonight.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Ferguson
AVIATION...Barendse

NWS ARX Office Area Forecast Discussion