451
FXUS63 KARX 042313
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
613 PM CDT Thu Sep 4 2025

.KEY MESSAGES...

- Showers move into the region late today, continuing through
  the overnight hours. Highest rainfall totals are expected over
  north-central Wisconsin. Wind gusts around 40mph will exist
  overnight, tapering off to 20-30mph by Friday afternoon.

- Below normal temperatures continue into the weekend. Some
  locations may reach record cold high temperatures Friday with
  highs of 52-61 degrees.

- Temperatures begin to warm next week, with highs in the 70s
  returning by the middle of the week.

&&

.DISCUSSION...
Issued at 137 PM CDT Thu Sep 4 2025

Rain and Winds Tonight

Late this afternoon into this evening, a 500hPa shortwave trough
currently moving into North Dakota as seen on water vapor imagery
and the associated surface low pressure system will quickly pivot
through our area, in and out in roughly 6 hours. High confidence in
rainfall with this system (70-100%) as an axis of strong moisture
transport sets up north to south from Iowa into northern Wisconsin,
but still not expecting a washout with regard to amounts. 04.12z
HREF LPMM highlights a general 0.1 to 0.6 inches with amounts
increasing from south to north as stronger convergence on the nose
of the low-level jet is expected north of I-94. The northward shift
of the location of the surface low remains, so expecting the highest
rainfall amounts slightly north of Taylor County, but if this system
does end up a little further south, amounts towards 0.75 to 1 inch
could be seen in Taylor County.

Along with the rain, breezy winds will accompany this system as it
moves through overnight. Along the cold front and within the
precipitation, winds associated with a low level jet of 40 to 50mph
could be brought down to the surface via ongoing showers, possibly
allowing for gusts above 40mph at times. Behind the cold front,
strong surface wind gusts will continue, owing to steepening low
level lapse rates associated with cold air advection and another
strong low level jet streak. 40-50kt winds at 850hPa are depicted in
the RAP/HRRR soundings which will be able to efficiently mix to the
surface under the aforementioned conditions. The 04.12z HREF remains
the solution with the strongest gusts, indicating a 60-90%
probability of wind gusts greater than 40mph. Probabilities decrease
for gusts above 45mph, with only a brief window of a 20-40% chance
towards south-central Minnesota and north-central Iowa. However, the
HREF does tend to run a little high on winds and there will be a
lack of precipitation cooled downdrafts to aid in greater momentum
transfer behind the front, so thinking gusts topping out around 40
mph into Friday morning are reasonable. Winds will begin to diminish
Friday, but gusts of 20-30mph will remain through the
afternoon, highest across central Wisconsin.

Weekend Shower Potential and Temperatures

In the wake of tonight`s low pressure system, cold air advection
reinforces our already cool temperatures within cold temperatures
and lower heights within the longwave trough over the Great Lakes
region. High temperatures are expected to be lowest on Friday
associated with the tonight`s cooler air with the potential for
record cold highs. Temperatures remain below normal through the
weekend as the Upper Midwest remains influenced by the
aforementioned troughing. Showers are possible Friday and Saturday
afternoon (10-20%) within this cold air regime, most favorable
along and north of I-90 where 850-700hPa lapse rates are expected to
be steepest.

Warming Temperatures Next Week

The longwave pattern begins to shift eastward next week, allowing
the ridge currently over the western United States to build eastward
into the Upper Midwest. This will promote rising heights and warming
temperatures through much of next week with the 04.06z GEFS/ENS/GEPS
all indicating this warming trend. Despite variations in the
ultimate value within the ensemble guidance, high temperatures
should climb back into the 70s by Wednesday.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 613 PM CDT Thu Sep 4 2025

A line of gusty showers will progress through the region this
evening bringing MVFR to IFR vsby reduction in addition to gusts of
30-35 kts. As these showers exit the region, strong winds off the
surface will be transfered to the surface behind a frontal boundary
which will keep sustained winds at 15-20 kts with gusts to 35 kts
throughout the overnight. Additionally, as the surface low pressure
center moves into the region with more ample low-level moisture,
cigs will drop to MVFR heights with high probabilities
(70-100%) in the 04.12z HREF for cigs under 3kft through late
Friday morning. However, as diurnal mixing maximizes towards
noon, these cigs will lift to VFR heights. Winds will remain
elevated throughout much of the afternoon from the northwest at
10-15 kts with occasional gusts to 20-25 kts.

&&

.CLIMATE...
Issued at 258 AM CDT Thu Sep 4 2025

Record cool maximum temperatures and the current forecast.


 La Crosse, WI

Date           Record Cold High       Forecast High
-----           -----------            -----------
9/5              59F(1896)                61F
9/6              60F(1965)                63F

 Rochester, MN

Date           Record Cold High       Forecast High
-----           -----------            -----------
9/5              59F(1956)                58F
9/6              58F(1965)                61F

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.

&&

$$

DISCUSSION...Falkinham
AVIATION...Naylor
CLIMATE...Falkinham