716
FXUS63 KARX 172349
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
649 PM CDT Sun Aug 17 2025

.KEY MESSAGES...

- Widespread heavy rain progresses from west to east overnight
  through Monday. An additional 0.5" to 1.5"+ is expected for
  much of the area.

- Cooler and drier conditions return Tuesday and continue into
  next weekend.

&&

.UPDATE...
Issued at 337 PM CDT Sun Aug 17 2025

Additional showers and storms will move into the area late this
evening ahead of an MCV. With high precipitable water values
(ranging from 1.5 to around 2 inches) and warm cloud layer
depths of 4 to 4.3 km, these showers and storms will be highly
efficient rainfall producers. With saturated soils, this
additional rainfall will quickly result in flash flooding. Due
to this, a Flash Flood Watch has been issued for Dodge,
Fillmore, Mower, Olmsted, Wabasha, and Winona counties in
southeast Minnesota and Buffalo and Trempealeau counties in
west-central Wisconsin from 10 PM tonight through 10 AM Monday
morning.

&&

.DISCUSSION...
Issued at 134 PM CDT Sun Aug 17 2025

Today - Monday: Dry this Afternoon, Widespread Chances for Rain
Returning Tonight

The band of precipitation that dropped 5-8 inches overnight in
some locations has finally dissipated with dry conditions
present across the area. Low clouds will erode into the
afternoon with high clouds likely sticking around into this
evening. A surface low and MCV across the Dakotas, along with a
perturbation in the crest of the ridge aloft, are setting off
showers and storms across the Northern Plains this afternoon.
All members of the 17.12Z HREF are indicating that these storms
will grow upscale into a more MCS/linear type feature as they
move east into the evening/overnight hours. The severe threat
overall looks to be limited with a much more stable airmass
overhead and strong capping in the low/mid levels. Some strong
to potentially isolated damaging wind gusts, especially for
areas west of the Mississippi, will be possible with ample DCAPE
(1000+ J/kg) expected to be present. The 850 mb LLJ should keep
the storms going through the overnight hours with plenty of
moisture still available across the region. PWats are still
expected to be in the 1.5-2"+ range into tonight which will
allow for efficient rainfall production with these storms. This
main line of storms looks to move into our area overnight,
potentially continuing into the morning hours east of the
Mississippi.

The aforementioned surface low is expected to be in our
vicinity through the day tomorrow, keeping our area in the warm
sector. Depending on how well our area can destabilize into the
afternoon, scattered thunderstorms would be possible given the
low level synoptic lift near the triple point. Instability will
be better further to the south and west across Iowa but the
shear is expected to be weaker. Overall, nebulous mid level
forcing and no real low level foci preclude an organized severe
threat but enough confidence remains to keep our area in the Day
2 Marginal Risk for Severe Weather.

QPF wise, the 17.12Z HREF grand ensemble is showing a broad
0.5-1.5 inches of rain across our area through 7 AM Tuesday.
Confidence is a little lower on amounts greater than 1 inch
with probabilities in the 20-40% range with some higher pockets.
This seems to be a reasonable estimation though as per usual,
localized higher amounts could be possible in the stronger
storms with higher rainfall rates.

Tuesday - End of the Week: Drier and Cooler

By Tuesday, ridging is expected to become more prominent across
the Rockies, putting our area in northwest flow aloft. The
surface low is finally expected to make some more progress
through the area with the attached cold front finally moving
through late Monday into Tuesday. This will bring a cooler and
drier airmass behind it as a surface high drops into the region.
This should help to keep conditions dry through the end of the
work-week. High temperatures through the week look to remain
seasonable mild in the upper 70s to lower 80s. A dry cold front
attached to a surface low well to our north across Ontario is
expected to move through the area late Friday. Current forecasts
have high temperatures for next weekend in the upper 60s to low
70s, almost a taste of early fall. This is still a ways out and
there is plenty of time for the details to change but overall
after a very soggy week or so, we`ll finally see some reprieve
for the back half of this upcoming work week.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 651 PM CDT Sun Aug 17 2025

Scattered showers and storms will continue to develop along a
boundary near the Interstate 90 corridor and along a warm front
across northeast Iowa tonight. These storms will produce gusty
winds and MVFR ceilings and visibilities. It will then become
VFR on Monday morning and remain that way into the mid-
afternoon. Scattered showers and storms will then return to the
forecast as a cold front moves east through the region.

&&

.HYDROLOGY...
Issued at 134 PM CDT Sun Aug 17 2025

A narrow band of training precipitation set up across our area
overnight, extending from NW Mower County, MN all the way to SE
Grant County, WI. Totals in this area ranged anywhere from 2-8
inches, with the highest totals across portions of Fillmore
County, MN to Allamakee County, IA. This band of precipitation
lasted for much of the night before finally dissipating through
the morning hours as the low level jet tapered off. This comes
in addition to the 2-6 inches that fell across portions of West
Central Wisconsin a couple days ago. Many locations across the
Coulee region are seeing ponding and remain susceptible to
flooding from additional rainfall. With an additional 0.5-1.5+
inches expected from tonight/Mondays activity, this could
exacerbate problems in some areas. Overall, this upcoming system
looks to be more progressive in nature which will limit
residence time over any given area but in some areas where FFGs
are now below 0.5 inches, any rain could create concerns.

Rivers have responded generally as expected across the region.
Sharp rises at locations on the Cedar, Root, Yellow (IA), and
Upper Iowa rivers have been noted from gauge observations.
Overall, rises have stayed within their banks, only making it to
action stage or just barely making it into minor flood stage
before dropping back down. Looking at ensemble river forecasts,
most rivers would need an additional 2+ inches to even break
action stage which doesn`t seem all that likely. The exception
looks to be the Cedar River which could reach minor flood stage
with a little between 1-1.5 inches. This river in particular
will need to be monitored through tomorrow given its flashy
nature and QPF well within reason for potentially reaching flood
stage.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch from 10 PM CDT this evening through Monday morning
     for WIZ032-033.
MN...Flood Watch from 10 PM CDT this evening through Monday morning
     for MNZ079-086>088-094-095.
IA...None.

&&

$$

UPDATE...Boyne
DISCUSSION...Barendse
AVIATION...Boyne
HYDROLOGY...Barendse