Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 242337
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
537 PM CST Sat Feb 24 2024

.KEY MESSAGES...

- Temperatures held up by the stronger low level winds tonight.
  Warmer with highs in the 40s and 50s Sunday with small
  flurry/sprinkle/light rain chances north of I94 Sunday
  afternoon.

- Near record to record breaking high temperatures on Monday.
  Highs will exceed 60 degrees for most of the region. See
  Climate section for more details. Increased fire weather
  concerns on Monday as well.

- Rain changing to snow is likely (50-70% chance) Tuesday
  afternoon and evening with minor accumulations possible.

&&

.DISCUSSION...
Issued at 222 PM CST Sat Feb 24 2024

Overview:

Latest water vapor satellite imagery, heights, and lightning show a
trough over the New England states and the Ohio River Valley with
ridging for the Upper Mississippi Valley and northwest flow from the
Pacific Northwest through the Plains.  Of note were a couple of
areas of darkening over South Dakota with tight embedded waves.  The
latest surface map high surface high pressure near STL with south
winds locally 5 to 15kts with some stronger gusts.  Temperatures at
19Z were in the 20s and 30s.

Temperatures held up by the stronger low level winds tonight, warmer
with highs in the 40s and 50s Sunday with small
flurry/sprinkle/light rain chances north of I94 Sunday afternoon:

A 110kt jet will push theses wave eastward into the forecast area by
00Z.  Due to the dry atmosphere, precipitation is not expected with
the strong warm advection, but we should see increasing mid and high
level clouds with this quick-moving feature.  Low level 900mb winds
are forecast to strengthen from 15 to 25kts at 21Z to a broad area
of 35 to 45kts across the forecast area; with the strongest winds
aloft pushing east of the area by 09Z. The bulk of the stronger
winds should remain aloft, however some gusts 15 to 30kts possible,
especially for ridgetops.  The thermal ridge and elevated winds
overnight should hold temperatures up into the mid 20s and lower
30s. 25.21z 850mb temperatures Sunday are forecast to be -3 to +3
deg C, so cooling since midnight.  For now, have highs in the lower
40s north central WI to mid 50s south toward DBQ.  Weak
frontogenesis/subtle area of 850-700mb warm air advection may be
enough for some flurries or sprinkles/light patchy rain farther
south.  Sunday afternoon and Sunday night north of I94.  The
HRRR/RAP/NAM are picking up on this, but the signal is on the weak
side.

Monday - Monday night: Near Record to Record Warmth Likely

The big story to start the week will be the absurdly warm
temperatures with southerly surface flow sharply increasing for
Monday. High temperatures on Monday will surge into 60s for much of
the region with the 24.12z grand ensemble (EC ens/GEFS/Canadian
ens) showing an inter-quartile range of 59 to 62 degrees at La
Crosse. This being said, with deterministic guidance suggesting
the potential for higher mixing heights, fairly dry soundings
during the day, and lack of snowpack, we could certainly
overachieve. Consequently, decided to nudge temperatures up from
the national blend to account for this possibility.

Additionally, while there is some moisture advection with this
southerly surface flow, the bulk of the robust moisture remains
to our south and east which when combined with the better mixing
could keep our dewpoints fairly low. As a result, with
increasing surface winds on Monday, there could be elevated fire
weather concerns. More information can be found in the Fire
Weather section.

Tuesday - Friday: Rapidly Changing Temperatures with Precipitation
Chances Returning Tuesday into Wednesday

The middle portion of the week will be dictated by an approaching
upper-level trough sliding off the rockies on Tuesday. As it moves
towards our region, a surface cold front will  push into the region.
The warm southerly flow that will provide the aforementioned warmth
will quickly shift to northwest flow with increasing wind gusts to
around 35-40 mph ushering in much colder air. Exact timing of the
front will be key for how warm you get so there is some more spread
amongst ensembles on Tuesday shown in the 24.12z grand ensemble (EC
ens/GEFS/Canadian ens) with an interquartile range of highs at La
Crosse of 52 to 63. With this in mind, if the front holds back
later into the afternoon more eastern locations could certainly
make another shot at 60 degrees. As the front passes,
temperatures will plummet with guidance painting as high as a 50
degree temperature change in 12 hours with forecast lows
Wednesday morning in the teens and single digits areawide.

Precipitation trends with this system appear fairly unclear at this
moment with much of the favorable environment for convection and
severe weather remaining to our south and east (Not to say some
storms can be ruled out with guidance painting some instability into
our south). Overall though, the axis of moisture generally remains
further to our south which turns problematic for precipitation
probabilities (20-40% chance) earlier in the day. Once the front
reaches our region, better saturation may occur allowing for a more
favorable environment for precipitation (50-70% chance) along the
boundary which would likely present as a transitioning band of rain
to snow when considering the cooling temperatures. Snow
accumulations of an inch or more are not out of the question with
the 24.12z GEFS showing modest probabilities (30-60% chance) for
much of our region which could create a window of low visibilities
when combined the increasing surface winds.

Wednesday will feature a much colder day with the cold air mass now
firmly in place. Highs will likely not escape the freezing mark for
most of the region with the upper-level trough in place. Long-range
guidance tends to narrow the trough as it pushes eastward so the
cold air will likely be short lived with a building ridge behind it.
Consequently, expecting temperatures to rapidly rebound above
average by by the end of the week, perpetuating this excessively
warm pattern.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 537 PM CST Sat Feb 24 2024

A couple of shortwave troughs will move southeast through the
area. These will bring in areas of mid and high clouds from time
to time. As the low level jet increase overnight, low level wind
shear will develop this evening and then gradually decrease
toward day break on Sunday.

&&

.FIRE WEATHER...
Issued at 222 PM CST Fri Feb 23 2024

Fire weather concerns diminish this evening. Additional fire weather
concerns possible on Monday.

Currently, a narrow stripe of lower dewpoints can be noted in
surface observations this afternoon with values down in the single
digits and lower teens leading to low RHs from the general
Winona to Decorah line. As we approach evening, hi-res guidance
progresses this dry slot eastward allowing for recovering
dewpoint depressions as sunset approaches with lowering winds
overnight.

Fire weather concerns return on Monday as temperatures are expected
to reach record warmth with highs easily topping the 60 degree mark
across the region. Forecast soundings in the 24.12z GFS and NAM
during the day Monday are somewhat dry through the entire column
with the potential for decent mixing for this time of year. While
not currently forecast, if mixing overachieves our dewpoints could
drop more than expected leading to very low RHs. If this occurs,
increased winds of 15-25 mph and gusts up to 35 mph, with the warmer
temperatures could lead to elevated fire weather conditions.

&&

.CLIMATE...
Issued at 222 PM CST Fri Feb 23 2024

Based on current forecast, daily high records may be challenged at
La Crosse and Rochester this week. Below are the daily temperature
records that could be broken:

* - Near record to record temperature forecasted

 La Crosse

Date   Record High   Record Warm Low   Forecast High   Forecast Low
-----  -----------   ---------------   -------------   -------------
2/26    61F(1976)       45F(1998)           65F*            33F
2/27    62F(2016)       41F(1882)           60F*            28F


 Rochester

Date   Record High   Record Warm Low   Forecast High   Forecast Low
-----  -----------   ---------------   -------------   ------------
2/26    58F(1958)       40F(1958)           63F*            32F
2/27    57F(1976)       36F(1958)           51F             19F

One key point to know going into next week is that the record all-
time highs for the month of February at La Crosse and Rochester is
65 and 63 degrees respectively. The monthly record high of 65 at La
Crosse has occurred on three different dates (February 12th,
1882, February 15th, 1921 and February 19th, 2017). The monthly
record high of 63 at Rochester occurred on February 17th, 1981.

&&

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

&&

$$

DISCUSSION...Boyne
AVIATION...Zapotocny
FIRE WEATHER...Naylor
CLIMATE...Cecava/Naylor


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