124
FXUS63 KARX 251055
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
555 AM CDT Tue Jun 25 2024

.KEY MESSAGES...

- Storm Chances Depart Early This Morning, Primary Area Of
  Storms Today Remain Along & South Of Local Forecast Area In
  Iowa With A Thin Line of Storms Possible Locally

- Storm Chances Return Friday & Into The Weekend. Near 1" Of
  Rain Possible.

&&

.DISCUSSION...
Issued at 237 AM CDT Tue Jun 25 2024

Storms Early This Morning:

Have been monitoring ongoing storms through the early morning hours
from west to east. The associated low was mostly following a
warm front zonally draped from southern Minnesota through
central Wisconsin. Sufficient forcing remained farther north in
northern Minnesota and north-central Wisconsin as the warmer
elevated air lacked a profound opposing boundary locally with a
cap of CIN.

Storm Chances Today:

As the responsible surface low exits to the east early this morning,
the nose of increased low level theta e lingers across much of the
Upper Mississippi River Valley into northern Wisconsin. The
highest confidence storm scenario for today is along and south
of our southern periphery where a pressure saddle sets up a
zonal shrinking/stretching axis across Iowa. The narrow axis
limits exact confidence of initial storm formation, potentially
grazing our far southern counties in northeast Iowa and far
southwest Wisconsin. Local confidence remains low as forecast
soundings keep a stronger, albeit limited cap of CIN in our
southern spots.

There will be exorbitant instability, 4500+ J/kg, within the
warm, moist airmass along our southern periphery. Therefore,
storms that do pop will quickly turn into towering cumulus.
Given initial forcing along a narrow axis, storms expected to
remain quasi-stationary at first, further firing along the
southerly advecting cold pool. Some models do suggest another
scenario with a quick perturbation lifting storms from
northwest to east-central Iowa around the same time, even less
involved with the local area. Regardless, this perturbation will
eventually pick up much of the storm activity and progress
everything east-southeast late in the evening into the
overnight.

During this time, a secondary small, limited strength line of
storms expected to initiate farther north, zonally across the
forecast area. A narrow dry punch of air associated with the
main cold/dry frontal boundary would be the responsible forcing
mechanism. Instability expected to remain meager, while there
is some adequate shear to persist some small storms. Lightning
appears to be the primary hazard at this time.

Storm & Rain Chances Friday & Into The Weekend:

Storm chances return Friday morning on the cusp of a low pressure
system lifting to the northeast through the Central Plains. A well-
phased closed area of lower heights remains well to the northwest,
limiting initial confidence in storm/precipitation extent. An upper
level ridge also remains parked over the Upper Mississippi
River Valley during this time, preventing the initial farther
east push. Eventually, more zonal flow builds in, allowing the
synoptic trough that joins its main flow advect storm chances
locally into the weekend. Current long term global ensemble
confidence suggests 0.5" to 1" primarily along our southern
counties in northeast Iowa and southwest Wisconsin.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 555 AM CDT Tue Jun 25 2024

VFR conditions are expected through the period with northwest
winds in the wake of a weak front passing southward this
morning. Areas of mostly mid/high clouds will stream across the
region with a small chances for a shower this afternoon and
tonight at KRST/KLSE, but higher thunder chances are likely to
remain farther south.

&&

.HYDROLOGY...
Issued at 501 AM CDT Tue Jun 25 2024

Recent heavy rainfall has resulted in river flooding along many
area rivers and streams in northeast Iowa, southeast Minnesota,
and western into central Wisconsin. Ongoing flooding concerns
will last into next week for the largest rivers such as the
Mississippi. Minimal impacts are expected from shower and storm
chances this afternoon and evening, primarily remaining south of
Interstate 90. Drier days are on tap through Thursday, assisting
the downward trend in river levels seen primarily in
tributaries and smaller rivers. Rain and storm chances return
early Friday morning. Soils will remain well saturated by this
time, therefore precipitation amounts will be important to keep
an eye on as forecast hour nears. Continue to reference the
latest flood statements for additional updates and details.

&&

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

&&

$$

DISCUSSION...JAR
AVIATION...JM
HYDROLOGY...JAR