392
FXUS63 KARX 080829
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
329 AM CDT Mon Jul 8 2024

.KEY MESSAGES...

- Hit or miss showers and storms (20-40% chance) from now
  through the middle of the week. More likely you will remain
  dry than not.

- Temperatures holding steady for much of the week with highs in
  the upper 70s and lower 80s. A warming trend is expected late
  week and this weekend where highs could reach into the 90s for
  some areas.

- Locations along the Mississippi River from Guttenberg, IA on
  northward are observing falling river stages that are expected
  to continue through this week.

&&

.DISCUSSION...
Issued at 329 AM CDT Mon Jul 8 2024

Today - Wednesday: Periods of Showers and Storms

The overall synoptic pattern over the next couple days revolves
around a broad 500mb trough that be seen clearly in the GOES-16
water vapor imagery and RAP 500mb heights. Embedded within this,
there are multiple weak areas of vorticity within this pattern with
one swinging through east/northeastern IA early this morning and
weakening with limited instability currently in place. As we
progress through the early morning, this MCV will make its way
northeast bound with a broad area of weak showers and isolated
storms with it. Additional, weak pieces of energy behind it
through the first half of the week can be noted in the 500mb
flow as well. Consequently, expecting scattered showers and
storms to pop up with increasing diurnal instability (500-1500
J/kg) during the afternoon/evening on Monday. Expecting fairly
limited coverage with these during afternoon/evening so would
anticipate that any given location is more likely to be dry
than wet. Additionally, with limited shear profiles (much of
your stronger synoptic winds are above 400mb in the 08.04z RAP),
would expect very low potential for any severe threat with
these having overall light rainfall amounts with maybe some
pockets of heavier rainfall if storms are slow moving. As
diurnal instability wanes later into the evening, expect
convective coverage to diminish. Tuesday will likely feature a
similar type of setup with marginally lower instability
(500-1000 J/kg) so have trended precipitation chances ever so
slightly lower (15-25% chance) for Tuesday but similar idea with
scattered showers/storms but most locations remaining dry.

As we turn to Tuesday night and Wednesday, the remnants of
Hurricane Beryl will track well southeast of the region with the
current NHC forecast have the system as an post-tropical
cyclone moving through portions of southern MO/IL/IN and into
the Ohio valley. Guidance has generally shifted much of the
heavier precipitation further south east with virtually no
probabilities (under 10% chance) in the 07.00z GEFS of seeing
0.5" or greater in southwestern WI. Regardless, could see some
wrap around showers and isolated storms with the combination of
cyclonic flow around the system and a descending shortwave from
southern Canada. Overall the heavy rain threat from now through
Wednesday seems minimal with precipitable waters in the 1.3" to
1.6" range and marginal warm cloud depths to around 3.5km. As a
result, probablistic guidance paints light amounts for our
local area from now through Wednesday with the 07.00z GEFS/EC
ensemble showing lower probabilities (20-50% chance) for total
QPF of 0.5" during this time. Therefore, would need slow moving
or repeating thunderstorms to get any flooding issues.

Thursday - Sunday: Warming, Drier Trend

Going into late week, a building ridge out west tries to nudge
slightly eastward and with the synoptic trough pushing towards
the eastern US will subject our region to northwesterly flow.
Consequently, expecting a drier but warmer pattern to ensue with
high temperatures beginning to trend warmer than normal by late
week and into the week with the 07.00z grand ensemble (GEFS/EC
ensemble/Canadian ensemble) wants to show an inter-quartile
range for high temperatures at La Crosse of 86 to 93 degrees
with a median of 89 on Sunday. With probabilities for highs of
90 degrees or greater of around 20-60% across the region by
Sunday. Shower/storm chances right now trend lower with the NBM
in the quasi-zonal to northwest flow. However, will want to
monitor for any pieces of shortwave energy that can pivot into
our region during this period. So overall would say this is more
a reflection of lower confidence in any specific features that
can increase our precipitation chances at this time.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1023 PM CDT Sun Jul 7 2024

Showers and storms continue into the overnight hours primarily
from southeast Minnesota through central Wisconsin. Main impact
has been ponding water on roadways and scattered thunder.

Primary aviation concern remains to be the potential for valley
fog. Highest confidence will be in the more prone areas of
Wisconsin River Valley and tributaries. Low to moderate
confidence in Mississippi River Valley and TAF site at KLSE. Low
level winds may remain strong enough to abate or limit temporal
and spatial extent. Have leaned pessimistic with IFR
visibilities given recent rains and overnight lingering humidity
with draped frontal boundary.

&&

.HYDROLOGY...
Issued at 329 AM CDT Mon Jul 8 2024

Falling river stages can be noted from Guttenberg, IA on
northward along on the Mississippi River. Falling river stages
are expected to continue through this week from southwest
WI/northeast IA on northward. Currently, locations at La Crosse,
WI, McGregor, IA and Guttenberg, IA remain at Moderate flood
stage with severeal other locations at minor flood stage. As we
head through this week, expecting scattered showers and storms
during the afternoon/evening hours on Monday and Tuesday to
produce generally light rainfall amounts. Locally heavier
rainfall will be possible with slow moving storms or if storms
repeat over the same locations. Overall though these
showers/storms are not expected to have much impact on the
Mississippi River basin.

&&

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

&&

$$

DISCUSSION...Naylor
AVIATION...JAR
HYDROLOGY...Naylor