465
FXUS63 KARX 011710
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1210 PM CDT Tue Oct 1 2024

.KEY MESSAGES...

- Remaining dry with near to above normal temperatures through
  the forecast period.

- Recent dry weather, increasing winds, and low relative
  humidities will bring elevated fire weather concerns
  Wednesday. See Fire Weather section for details.

&&

.DISCUSSION...
Issued at 248 AM CDT Tue Oct 1 2024

Today into Wednesday: Frost for Some Tonight, Increasing Winds
Wednesday

Temperatures today fall back towards normal, to slightly below
normal, behind a cold front overnight as a surface ridge of high
pressure extends northward from the Central Plains. The stronger
wind gusts overnight will diminish through the day as the
aforementioned ridge of high pressure works into the area. A drier
airmass and deeper mixing will usher in lower relative humidities
setting the stage for brief radiational cooling conditions tonight
ahead of increasing winds on Wednesday. Temperatures tonight will
initially begin cooling with clear skies and light winds; however,
as the ridge of high pressure continues dropping south into the mid-
Mississippi River Valley, the pressure gradient increasing from the
northwest as a trough works through Manitoba and the Dakotas. As the
winds begin to increase from the NW, temperatures will stop cooling
west of the river, with the typical cool spots across parts of
central Wisconsin continuing to cool a few hours longer. The latest
probabilities suggest a 20%, 30%, and 45% chance of temperatures
reaching 32F tonight at Volk Field, Black River Falls, and Sparta
respectively. With these chances, there will be an inherent chance
for frost across portions of west-central WI as long as the stronger
winds hold off long enough for temperatures to cool.

By Wednesday, the pressure gradient tights with SW winds increasing
through the day. Winds across much of the area will be gusting in
the 20 to 30mph range, with higher wind prone areas west of the
Mississippi River gusting upwards of 35 mph. These stronger winds
combined with warm air advection will bring temperatures back into
the mid to upper 70s across the area. Probabilities for wind gusts
in excess of 30mph west of the Mississippi River on Wednesday
afternoon is around 70 to 90%, with probabilities across western and
central Wisconsin around 30 to 40%. When looking at probabilities
for wind gusts in excess of 25mph, these probabilities increase to
near 100% west of the river and around 70 to 90% east of the river
across western and central WI.

Thursday through the Weekend: Remaining Dry, Temps Trending 5
to 10 Degrees Above Normal

For the second half of the week and into the weekend, global models
and their ensembles suggest a more progressive pattern with a series
of weak troughs and ridges to pass through the Upper Midwest. A
zonal flow pattern on Thursday gives way to a weak trough passing
through Thursday night into Friday, bringing slightly above-normal
temperatures back towards normal on Friday. These near-normal
temperatures will be shorter-lived as global ensemble means show
good agreement in another ridge axis moving in Friday night into
Saturday as a stronger low pressure system passes to the north
through Manitoba and Ontario Saturday evening. As this low pressure
system passes well to our north, it will drag a surface trough and
associated cold front through the Upper Midwest Sunday, with yet
again another ridge favored to build in from the west Sunday night
into Monday. Despite the series of passing ridges and troughs,
global ensembles are still showing a very low chance of
precipitation through the forecast period. The trough passage on
Friday and cold front passage on Sunday will both yield just a 10 to
20% chance of receiving 0.01 inches of rain.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1205 PM CDT Tue Oct 1 2024

VFR conditions are forecast for the period with initial NW winds
of 10-15G20kts decreasing this afternoon and backing to the
south at 5kts by midnight. The S/SW winds increase steadily for
the remainder of the night and through the morning hours,
reaching speeds of 15-20G25-30kts by midday Wednesday, highest
west of the Mississippi River. There may be a short-lived
period of LLWS at valley sites like LSE around sunrise before
the stronger winds can mix to the surface.

&&

.FIRE WEATHER...
Issued at 248 AM CDT Tue Oct 1 2024

Winds increase through the day from the southwest Wednesday
with gusts in the 30 to 35 mph range, especially across
northeast IA and southwest MN. Across Wisconsin, these wind
gusts will be closer to 25 to 30 mph from the SW. Although
mixing heights will only be around 3kft, the already dry air
mass and additional mixing will bring minimum RH values into the
low to mid 20 percent range across the region. Daytime high
temperatures on Wednesday will climb into the mid to upper 70s
across the area. Due to the above conditions, elevated fire
weather conditions are expected on Wednesday.

Dry conditions are expected to continue beyond Wednesday and
through the weekend with little to no chances for precipitation. As
a result, will need to monitor fire weather conditions
throughout the upcoming weekend and into next week.

&&

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

&&

$$

DISCUSSION...JAW
AVIATION...Skow
FIRE WEATHER...JAW