Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 070805

Area Forecast Discussion
National Weather Service La Crosse WI
305 AM CDT Fri Oct 7 2022

.DISCUSSION...(Today through Thursday)
Issued at 300 AM CDT Fri Oct 7 2022

Key Messages:

 - Chilly today with isolated showers/sprinkles possible

 - Widespread freezing temperatures tonight: freeze warning in

 - Warming into next week...still limited rainfall potential

Today-tonight: Cold with widespread freeze likely tonight

Early morning water vapor imagery reveals an upper shortwave trough
stretching from the Dakotas to Lake Superior. Strong surface high
pressure (about 3 standard deviations above the mean) also resides
over the Dakotas early this morning, contributing to a fairly tight
pressure gradient in place. That has prevented the boundary layer
from completely decoupling across most of the forecast area
overnight. That little bit of light wind mixing has been enough to
keep temperatures from dropping too dramatically and has likely
prevented frost formation for most of the area, even with limited
cloud cover.

The aforementioned shortwave, combined with favorable sfc-800mb
lapse rates from ongoing cold advection, has been supporting some
isolated shower activity from the Twin Cities metro into south-
central MN early this morning. Nothing notable or impactful, but
various CAMs support that nuisance shower activity eventually
migrating southeastward into our area today. Added small chances of
showers/sprinkles to the forecast. Will feel like a fall day with
highs generally around 50, plus or minus a few degrees. Not as
breezy as Thursday.

Main forecast concern in the near-term will be the high likelihood
of widespread freezing temperatures tonight. The surface high will
slide by to our southwest tonight with an accompanying dry airmass
scouring out any lingering clouds overhead. Winds may not go
completely calm everywhere with the high not passing directly
overhead, but the accompanying -3 to -5C 850mb airmass will be
favorable for quick nighttime cooling. Weak warm air advection will
actually kick in late tonight from the west, but it likely won`t be
enough to prevent freezing temperatures. After coordination with
neighboring forecast offices, went ahead and issued a freeze warning
for the remaining active counties (generally along/south of I-90).
May not be a hard freeze (28F or colder) for everyone, but guidance
lends high confidence to widespread subfreezing temps tonight.

Next week outlook: Warming initially with mid-week rain chances

Temperatures look to rebound fairly quickly over the weekend,
climbing back into the 50s/60s. A few shortwaves will drop through
the area Saturday into Sunday, but the airmass will be too dry to
support anything more than scattered clouds.

Weak ridging aloft slides into the region as the work week gets
underway, culminating in a very mild Tuesday with temperatures
climbing to 65-75. Next rain chances arrive Tuesday night into
Wednesday as a pronounced western Canada trough digs into the Upper
Midwest. While the area would certainly benefit from a soaking rain,
moisture with this system isn`t looking too impressive with only
modest moisture transport directed into the region and precipitable
water values around 150 percent of normal for mid October. The
system looks rather progressive, too, so there likely won`t be any
long-duration rainfall. GEFS/EPS ensemble probabilities both suggest
amounts will be under 1/2 fact, much of the area might be
lucky to see even 1/10 inch. Still time for the forecast to
fluctuate that far out, so we will wait and see. Colder temperatures
will return late next week once this system and its cold front exit.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1045 PM CDT Thu Oct 6 2022

Sct-bkn conditions are expected to continue through the TAF period.
VFR conditions should prevail with cloud heights mostly above fl030,
however there are periods of patchy MVFR ceilings fl015-030. This
first area of patchy MVFR ceilings could hold to the north of
KRST, but another patchy could them 14-18Z and at KLSE at 11-13Z.
In addition, with an upper level trough swinging through, may see
a few instability showers develop during this time as well. North
winds continue 5 to 14kts, becoming southwest Friday evening.


WI...Freeze Warning from 1 AM to 8 AM CDT Saturday for WIZ041-043-044-

MN...Freeze Warning from 1 AM to 8 AM CDT Saturday for MNZ086>088-

IA...Freeze Warning from 1 AM to 8 AM CDT Saturday for IAZ008>011-018-



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