297
FXUS63 KARX 062350
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
650 PM CDT Sun Jul 6 2025

.KEY MESSAGES...

- Small chance (20%) for pop-up showers this evening, mainly
  east of Mississippi River.

- Additional small chances (20%) for afternoon pop-up showers
  and storms Monday afternoon. Heading into Monday night, a
  decaying line of storms with areas north of I-90 more likely
  to see rain (60% chance).

- Unsettled pattern to end the week with 60-70% chance of
  showers and storms on Friday.

&&

.DISCUSSION...
Issued at 140 PM CDT Sun Jul 6 2025

This afternoon: Isolated pop-up showers, possibly a weak storm

Recent convective allowing model runs have been showing a fairly
consistent signal for isolated pop up convection this afternoon-
evening. This will be mainly across portions of southwest/central
Wisconsin where RAP analysis shows an axis of weak surface
convergence - northeasterly flow over central/southern Wisconsin
advancing into more northerly flow closer to the Mississippi River.
Diminishing cloud cover and lingering elevated dewpoints have
allowed for increasing instability with SBCAPE up to 1000 J/kg. Have
introduced slight chance (20%) PoPs to account for isolated shower
activity, but given the instability present can`t rule out a few
rumbles of thunder with the activity. Things should diminish quickly
this evening with the loss of daytime heating. Some patchy fog
likely tonight given the abundant humidity.

Monday-Monday night: Afternoon pop-up showers/storms, then a
decaying line of convection

Monday afternoon is looking to bring almost a repeat of today, with
a building axis of daytime instability in the vicinity of the
Mississippi River interacting with a weak inverted trough and
resultant surface convergence. This should again favor some
additional pop up showers and storms in the afternoon hours, so have
added slight chance PoPs to much of the Mississippi River valley and
surrounding areas.

Heading into Monday night, a decaying linear MCS from the Dakotas
will move into the area. Guidance show a wide variance in its
arrival time with the RAP bringing it into our northwest after 8pm,
the HRRR/ARW/FV3 all closer to 10pm, and the NAMNest not until after
midnight. So, timing will need to be refined over the next 12-24
hours. But there is general agreement that the activity should
weaken substantially, if not almost dissipate, as it approaches the
forecast area. Here again, the NAMNest is an outlier as it retains a
weakened but broken bowing line of storms through the area late
night due to its comparably much higher dewpoints near 70. Given the
wide spread, will stick with NBM PoPs for now (wide line of 50-60+%)
but based on current diminishing trends would expect PoPs to have to
be trimmed much further north where forcing is more favorable. Looks
like higher chances north of I-90 and especially north of I-94. Not
expecting anything strong from this activity.

Rest of the week: seasonable with periodic storm chances

An amplifying ridge upstream over the Rockies will put us in a
northwest flow aloft pattern heading into midweek, setting us up
for what looks to be more active weather beyond Wednesday. A
couple shortwaves are progged to move through the region
sometime in the Thursday-Friday period. NCAR AI and machine
learning numerical weather prediction guidance depict the
greatest likelihood of severe weather with these features over
the Dakotas and western Minnesota on Day 5, so will be something
to keep an eye on as we get closer in time. This looks to be
followed by a closed upper low grazing our area on Saturday. All
in all, looks like on and off rain chances to end the week.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 645 PM CDT Sun Jul 6 2025

VFR conditions are forecast for this evening prior to 06Z.
While confidence is increasing that there will be some form of
fog/low ceiling restrictions across much of the area between
06-15Z, the exact coverage and magnitude of these restrictions
is much less certain. Have trended TAFs downward to IFR levels
for a time near sunrise, but there is a 20-30% chance these
fall to LIFR. Conditions quickly improve to VFR after 12-15Z.
Winds will be light from the north tonight and from the south
on Monday with an increasing risk of isolated showers and storms
in the afternoon.

&&

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

&&

$$

DISCUSSION...Kurz
AVIATION...Skow