La Crosse, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

384
FXUS63 KARX 061154
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
654 AM CDT Sun Oct 6 2024

.KEY MESSAGES...

- Blustery conditions through late this afternoon with northwest
  winds of 20-25 mph, gusting at times to 30-40 mph, especially
  this morning.

- Today will be the coolest day of the week with highs in the
  upper 50s to mid 60s. We could see at frost across for much of
  the region tonight. A steady warming trend ensues during the
  week with highs again approaching 80 degrees by Friday.

- No rain in store for the work week with the next window of
  opportunity for any rainfall coming next weekend.

&&

.DISCUSSION...
Issued at 300 AM CDT Sun Oct 6 2024

Today: Cooler and Blustery

An initial cold front swept through the region yesterday evening and
resulted in scattered storms north of I-94. A secondary cold front
is plowing southeastward out of North Dakota and northwestern
Minnesota early this morning and reaches our doorstep towards
sunrise. Overnight wind gusts in the wake of this front have
peaked between 40-45 kts across central Minnesota; however,
these winds are expected to lessen as the surface low lifts
further to the northeast into western Ontario, pulling the
strongest pressure rises/tightest pressure gradient
fields/lowest PV 1.5 surfaces along with it.

That being said, the surge of cold air advection has ample
momentum when it arrives with boundary layer lapse rates quickly
steepening and allowing stronger gusts to penetrate to the
surface. Gusts of 30-35 kts are likely between 10-12Z along and
north of I-90, with gusts of 25-30 kts spreading southward
between 12-14Z. Blustery conditions last for much of the day,
though winds decline this afternoon with the pressure gradient
relaxing.

Temperatures in the 850-700-mb layer will be 15 C cooler than
yesterday, with surface temperatures reflecting this airmass change
and holding in the upper 50s to low 60s for highs--very close to the
AVERAGE highs for this time of year.

Tonight: Frost Potential

A 1023-mb surface high pressure cell builds into the region for
tonight, setting the stage for the first decent frost/freeze of the
season outside of the Wisconsin sand bogs, which have had periods of
frost for several weeks now. We are running about 1-2 weeks behind
our climatological first frost (< 36 F) dates and in fact are
passing our typical freeze (< 32 F) dates right now, indicative of
how warm our pattern has been over the last month.

Did lower tonight`s temperatures closer to the NBM 10th percentile
and expand the mention of frost in the forecast given the drier
dewpoints and lighter winds, which increases the potential for
temperatures to fall even further in low-lying locales. The best
potential for a widespread freeze will be north of I-90 in Wisconsin
(outside of the Mississippi River Valley) with forecast lows ranging
from the mid-20s to low 30s. The only fly in the ointment for this
forecast may come in the form of mid to high clouds arriving from
the northwest ahead of a subtle upper tropospheric wave, but these
look to move in after 09Z timeframe, with much of the radiational
cooling having already taken place by then.

Tuesday - Saturday: Dry and Warming

Split flow/longwave ridging builds across the central and western
CONUS and Canada for Tuesday through the end of the week. The
mean ridge axis gradually slides east/southeast towards the
region through the week, with lower tropospheric temperatures
gradually warming during this timeframe. By the end of the week,
we should be looking at highs returning to upper 70s to low
80s, near record values for this time of year. It is impressive
to see the NBM already depicting near record highs 5-6 days
out, which reflects the strength of this anomalous warmth in the
various EPS/GEFS ensemble inputs (60-80% of the EPS members are
already around record highs per the Extreme Forecast Index).

The next shot of precipitation comes over the weekend as the
ridge flattens and the next shortwave can finally bust through,
but even right now only a handful (10-20%) of the longer range
solutions have any measurable precipitation.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 654 AM CDT Sun Oct 6 2024

VFR conditions are expected through the TAF period. Satellite
imagery early this morning shows a large area of low VFR stratus
dropping down across Minnesota. Based on latest trends, it
looks more possible that these clouds make it further south
towards the TAF sites for a time this morning. Otherwise,
northwest winds are starting to pick up again this morning,
with gusts of up to around 25 to 35 kts possible. Winds
gradually weakening through the afternoon, eventually becoming
light into the overnight hours.

&&

.FIRE WEATHER...
Issued at 300 AM CDT Sun Oct 6 2024

There may be a period of elevated fire weather conditions this
afternoon with northwesterly winds sustained around 15-20 mph,
gusting to 30-35 mph at times. These winds will be on a slow
decline as we move through the afternoon as RH values reach
their lowest values around 30 to 40 percent (lowest west of the
Mississippi River). Build-Up Indices have also slowly crept up
over the last few days and are between 80-100 west of the
Mississippi River, indicating that vegetation is approaching
dryness levels that favor quick fire growth.

&&

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

&&

$$

DISCUSSION...Skow
AVIATION...EMS
FIRE WEATHER...Skow