771
FXUS63 KARX 120254
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
954 PM CDT Tue Mar 11 2025

.KEY MESSAGES...

- Cooler temperatures today with a warming trend expected for the
  latter half of the work week. Near record high temperatures
  currently forecast on Friday.

- Unsettled weather expected this weekend with a strong storm
  system moving in from the Plains into the Upper Midwest and
  Great Lakes region. Rain with embedded thunderstorms is likely
  (70-100%). Uncertainty remains in whether severe storms will
  be possible as far north as the Upper Mississippi Valley.

&&

.DISCUSSION...
Issued at 202 PM CDT Tue Mar 11 2025

- Cooler Today with Warming Temperatures Through Friday

Temperatures today are noticeably colder than this time yesterday
with highs today still expected to be around 20-25 degrees
colder than Monday. While a drier airmass has worked into the
area behind last nights cold front making RH values similar to
where they were yesterday in the 30-50% range around 1 PM, winds
are much lower out of the northeast at 10 mph or less. Min RHs
are still expected to bottom out in the 20-30 percent range east
of the Mississippi with 30-40 percent expected west of the
river but overall fire weather concerns should remain low for
today.

As the surface high begins to drift east out of the region tonight,
surface winds will again veer to the south, allowing for the return
of WAA into the area. Highs by Wednesday will be back into the 50s
areawide with upper 50s to mid 60s expected on Thursday. Friday is
when we`re expecting the big jump up for most of the area south of
the Chimney. With a warm front expected to lift north through the
area during the day ahead of the next storm system, along with
strong south/southeasterly winds in the lowest levels, temperatures
will be able to warm dramatically - even with a lack of insolation.
NBM probabilities of max temperatures greater than 70 degrees are in
the 70-100% range along and south of I-94. The chance for abnormally
warm temperatures is also highlighted in the EFI with a .8-.9 across
our area and a non-zero SOT. Current forecast highs for La Crosse
and Rochester are 73 and 72 respectively.  These are both 2 degrees
lower than their record highs for March 14 (75 and 74 degrees, both
set in 2012).

System This Weekend to Bring Storms (Severe?) and Wind

Our main focus for the forecast continues to be the storm system
expected to move through the area this weekend. The track of the
upper low remains generally the same from yesterday with the trough
moving onto the California coast Thursday before ejecting north and
east through the southern/central Plains and into the Upper
Midwest/Great Lakes. The upper low is generally progged to move
across Southeastern Minnesota and Northeastern Iowa by Saturday. The
subtle timing differences between the EFS and GEFS from previous
forecasts has decreased in this past cycle, though the GFS continues
to take a very slightly faster track overall. The timing differences
are largely ahead of our area though as they come into line quite
well from 00Z Saturday onwards. The corresponding surface low is
expected to be a strong one as it moves out of the Plains and into
the Upper Midwest with strengthening still expected not long before
it moves into our area. Both the NAEFS and EFS show a mean 980 mb
low passing over our area with the deterministic models showing even
lower minimums in the 973-976 mb range. Current forecasts keep this
lowest pressure out of our area but slight deviations in this path
could be significant. Of note, the low pressure records for LSE and
RST could be under threat with this system. LSE`s low pressure
record is 977.0 mb set on March 27, 1950 and RST`s is 980.4 mb also
set on March 27, 1950.

With this system, we`re watching the potential for severe weather
along with the chances for showers and storms. As the upper low
rotates northeast into our area between 18Z Friday and 06Z Saturday,
we will be sitting on the edge of the mid level jet, generally
around 50-60 kts at 500-700 mb. We look to be in an area of more
speed shear than directional shear but nonetheless effective shear
values will be in the 30-45kt range. This looks to be more front-
parallel shear which would lead to more rapid upscale growth of the
storms into more of a QLCS storm mode, which is what we are
expecting by the time the storms get to our area. Instability has
increased across guidance from yesterday but still looks meager with
MLCAPE values generally between 500-1000 J/kg. Looking at soundings,
the CAPE profile is very long and skinny and the atmosphere will be
capped into the early evening. It doesn`t look like we could see any
storms ahead of the front with the capping hanging on until the
frontal passage can overcome the CIN. There will be a narrow window
for the storms along the front to tap into the narrow CAPE and
strong low level helicity with SRH values generally between 200-300
m2/s2. While the primary threat will be damaging wind gusts along
the line of storms, the abundance of synoptic forcing and low level
shear means the threat for QLCS tornadoes cannot be ruled out. As we
get closer in time and into a period where high-resolution guidance
can cover this system, we will keep an eye on trends in the
mesoscale environment and if the potential for severe weather
continues to look favorable. While the robust moisture return seems
to favor at least enough instability for storms to potentially tap
into given the impressive shear, subtle changes can play a large
role in how the ingredients pan out.

As the storm continues north and east during the day on Saturday,
wrap around moisture will work into our area, keeping PoPs elevated
through the day. This should stay in the form of rain for most of
the day but will gradually transition into a rain/snow mix as the
colder air begins to funnel in on the back side of the low. We are
also expecting strong winds out of the west behind the low, largely
due to the signficiant pressure gradient. The system, at this point,
will start to weaken due to occlusion but should nevertheless remain
strong enough and close enough to our area to create some gusty
winds. Eventually, precipitation will transition completely over to
snow late Saturday evening with some minor accumulations possible.
None of the ensembles seem bullish on the idea of our area seeing
any significant snowfall on the back side of this system. The
track of the low will be important but it looks like that by the
time we get cold enough to see snow, the system will be too far
removed to the north and east. Temperatures Sunday will be cold
in the 30s to low 40s before we start to warm back up to near
normal into the upper 40s to 50s by Monday.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1000 PM CDT Tue Mar 11 2025

VFR expected across the forecast area from northeast Iowa,
southeast Minnesota, and western into central Wisconsin.

Southeast winds at 12.06Z TAF issuance turn clockwise through
Wednesday morning becoming near westerly Wednesday evening
before dropping off to variable Wednesday night.

&&

.CLIMATE...
Issued at 619 PM CDT Tue Mar 11 2025

- Possible Record Warmth (Record / Forecast):

                           Maximum                Minimum
Thursday (03/13)
Rochester, MN          68 (2024) / 65              N/A
La Crosse, WI          71 (2015) / 66              N/A

Friday (03/14)
Rochester, MN          74 (2012) / 72        49 (2012) / 51
La Crosse, WI          75 (2012) / 73        49 (1990) / 50

&&

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

&&

$$

DISCUSSION...Barendse
AVIATION...JAR
CLIMATE...JAR