039
FXUS63 KARX 300800
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
300 AM CDT Mon Sep 30 2024

.KEY MESSAGES...

- Ending September with well-above normal temperatures.

- Scattered to areas of frost possible in central and north-
  central Wisconsin on Tuesday night.

- There may be some elevated fire weather concerns in southeast
  Minnesota and northeast Iowa on Wednesday.

&&

.DISCUSSION...
Issued at 259 AM CDT Mon Sep 30 2024

Through Tonight...

A Canadian cold front will move southeast through the area from
late this afternoon into this evening. Temperatures ahead of
this front will range from the mid-70s to mid-80s. Winds will
start the day from the south this morning and then become
southwest this afternoon and northwest tonight. Wind speeds will
range from 10 to 20 mph with wind gusts of 20 to 30 mph. These
are much closer to the NBM 90th percentile. Closer to the
Interstate 35 corridor afternoon relative humidities will fall
into the mid- and upper 20s and range from the mid-30s to
mid-40s elsewhere. Like the past couple days, used the NBM 10th
percentile to lower these dew points.

With the soundings continuing to show much of the area will
remain very dry below 800 mb, kept the forecast dry. The only
exception continues north of Wisconsin 29 where there may be
some isolated showers (less than 25% chance).

See the climate section below to see how warm and dry this
September has been for the area.

Tuesday Night...

High pressure will build across the area. With very dry dew
points (upper 20s to mid-30s), a deep layer of light winds, and
clear skies. Some of the MOS in central and north-central
Wisconsin have low temperatures around 30. Used a blend of the
NBM and NBM 10th percentile to lower the low temperatures in
this area. Scattered to areas of frost will be possible in these
areas. In addition to this, there may be some valley fog
elsewhere.

Wednesday...

On Wednesday afternoon and evening, a cold front will move
southeast through the region. Ahead of this front, there will be
dry relative humidities (mainly in the 20s) and the south and
southwest winds and gusts will be increasing. The strongest
winds and gusts will be found west of the Mississippi River.
These areas may end up seeing elevated fire weather conditions.
See the fire weather section below for more details.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1032 PM CDT Sun Sep 29 2024

VFR conditions expected into the early morning hours on Monday
(between 08Z and 10Z). Around this time, valley fog is expected
to form and remain in the valleys until ~14Z. Confidence is not
high on fog impacting the KLSE airport (10 to 15%) as 10 to 15
kt just off the surface are a limiting factor in fog
development. Light southeast winds overnight will turn into
southwesterly winds by Monday mid-morning with gusts up to 20
kts, especially in southeast Minnesota. Heading into Monday
evening/night, a cold front will move through the region and
shift winds to the northwest that could have gusts ranging from
20 to 25 kts.

&&

.FIRE WEATHER...Wednesday
Issued at 259 AM CDT Mon Sep 30 2024

On Wednesday, southwest winds will increase into the 15 to
25 mph range with wind gusts into 30 to 35 mph range west of
the Mississippi River. Relative humidities across the area will
fall into the 20s. The combination of these winds and dry
relative humidities may result in some elevated fire weather
concerns in northeast Iowa and southeast Minnesota.

&&

.CLIMATE...September
Issued at 259 AM CDT Mon Sep 30 2024

It continues to look like both La Crosse and Rochester will
finish among their top ten warmest Septembers. Based on the
forecast temperatures today, it looks like La Crosse will have
its 8th warmest September (average of 68F) and Rochester will
have its 4th warmest September (average 65.5F). Having warm
Septembers have been a common trend this century. For La Crosse,
10 out of the 17 warmest Septembers have occurred since 2004.
For Rochester, 14 out of the 24 warmest Septembers have occurred
since 2002.

In addition to the anomalous warmth this September, it was very
dry too. Rochester only received 0.77 inches of rain. Most of
this rain fell on September 19 (0.72 inches). This will be their
8th driest September and the driest since 1999 (0.56 inches).
Measurable rain only fell of 4 days at both La Crosse and
Rochester. For La Crosse, this tied 1891, 1892, 1893, 1948,
1967, 2009, and 2021 for the 2nd least. Only 1979 had fewer (3
days). For Rochester, this tied 1939, 1952, 1976, 1999, and 2009
for the 3rd least. Only 1908 and 1979 had fewer (2 days).

&&

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

&&

$$

DISCUSSION...Boyne
AVIATION...Cecava
FIRE WEATHER...Boyne
CLIMATE...Boyne