048
FXUS63 KARX 260732
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
232 AM CDT Wed Jun 26 2024

.KEY MESSAGES...

- Quieter Today & Thursday With Daytime Highs In The 70s to Low
  80s

- Storm Chances Return Early Friday, Sticking Around Into The
  Overnight Hours

- Cooler Weekend On Tap, Temperatures 5 to 15 Degrees Below
  Normal For This Time Of Year

&&

.DISCUSSION...
Issued at 205 AM CDT Wed Jun 26 2024

Today & Thursday:

Building upper level heights early this morning will usher in
quieter weather for today and Thursday. Disagreement in
specific timing of building heights is resulting in slight
differences for daytime highs today, from low 70s to the low
80s. The slower the high pressure onset, the warmer the
solution. Given overnight observations, have leaned into a
slower solution, keeping higher temperatures aligned with bias
corrected guidance. Eventually, the cooler northerly flow is
expected to settle in for Thursday resulting in slightly below
normal daytime highs in the 70s.

Otherwise, have slightly backed off National Blend dewpoint
temperatures given upstream observations. Short term model
guidance shows a large spread (10+ degrees) between the HRRR
(45 to 50) due to too much mixing the Fv3 (60 to 65) due to
holding onto the departing moisture. Have gone in the middle by
slightly backing off of National Blend.

Rain & Storm Chances Return Friday:

Rain and storm chances shift north-northeast through the
Central into Northern Plains Thursday as a closed upper level
low advects eastward. Best initial synoptic forcing lies off to
our the west, meridionally advecting peak low level moisture
into the Northern Plains. This gives the ridge a slightly longer
residence time, delaying local precipitation and storm chances
into Friday morning. Eventually, the synoptic closed low advects
east, pushing precipitation and storm chances from west to east
across the Upper Mississippi River Valley through the day
Friday.

Potential Impacts:

Narrow southwest to northeast oriented corridors of higher
precipitation take shape through Friday with breaks in peak low
level moisture transport. Long term global ensembles suggest
two main corridors of 1"+, north and south of the local forecast
area. The EPS solution places the highest confidence along our
south from northeast Iowa into far southwest Wisconsin while
the GEFS solution remains to the north, along the International
border.

Best instability (>500 J/kg SBCAPE) pulses diurnally along our
western periphery during the day Friday before shunting south
with the best low level moisture transport. Deterministic
(GFS/ECMWF) sounding solutions show long, skinny, and transient
mixed layer CAPE with the quite variable shear/helicity most in
unison with CAPE in the lowest levels. Much too early to
discern severe threat at this time but will be subsequent
timeframe to keep an eye on.

Cooler Weekend On Tap:

Another break in the recently active pattern expected through the
weekend as upper level heights build and temperatures return to
below normal. Long term global ensemble certainty suggests
temperatures 5 to 15 degrees below normal through the weekend
and into early next week with daytime highs in 70s and overnight
lows in the 50s.


&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1038 PM CDT Tue Jun 25 2024

Weak front will push across the area Wednesday morning. The
front could bring a few light rain showers into the RST/LSE taf
sites. Have introduced VCSH at both taf sites at 12z Wednesday
and the light rain showers should last for a few hours.
Otherwise...VFR conditions will prevail across the region
through the taf period.

&&

.HYDROLOGY...
Issued at 235 PM CDT Tue Jun 25 2024

Several rivers fell below flood stage over the last 12 to 24
hours, but most of this water is still on route to the
Mississippi River. The Mississippi River is expected to keep
rising through the next 5 to 7 days depending on location and
which rivers route into that particular location. Minor to
moderate flood stages are expected from Lake City through
Guttenberg. While official forecasts from the River Forecast
Center do take into consideration all of the water that has
already fallen and is on its way into the Mississippi River, it
only takes the next 24-48 hours of forecast precipitation. Since
the next chance of precipitation for the local area is not until
Friday, this will not be accounted for in the official
forecasts.

The forecast rain on Friday will likely keep the river elevated
beyond the next 7 to 10 days and the river may initially fall
some before beginning to rise again as the additional rainfall
flows downstream this weekend into next week.

&&

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

&&

$$

DISCUSSION...JAR
AVIATION...DTJ
HYDROLOGY...JAW