NWS-La Crosse Forecast Discussion

						FXUS63 KARX 301102
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
602 AM CDT Sun Jun 30 2024

.KEY MESSAGES...

- Two rounds of convection are expected Monday night into
  Tuesday, likely bringing a threat for heavy rain. Some severe
  storms could occur Tuesday afternoon and evening.

- Additional rainfall could occur Thursday through Saturday but,
  at this time, heavy rain chances appear to be lower during
  this period.

&&

.DISCUSSION...
Issued at 409 AM CDT Sun Jun 30 2024

* MONDAY NIGHT INTO TUESDAY: Heavy Rain Threat, Potential Severe

Monday, as a surface high, currently located over MN, continues to
shift eastward after bringing us pleasant weather today, next upper
trough advances over the central/northern Rockies and Canadian
Prairies. Expect 850mb moist fetch from the Gulf of Mexico to resume
in earnest as a result. With plenty of moisture returning to the
CWA, widespread convection should occur, with guidance in pretty
good agreement considering the day 2-3 lead time that this will
mainly focus on two rounds: the first with a lead shortwave Monday
night into Tuesday morning and the second Tuesday late afternoon
into the late evening as the main body of the upper trough
approaches. That said, with various shortwaves likely to eject
downstream in the interim, lingering convection could occur through
the day Tuesday.

Little change from the past few forecast updates - the primary
threat during this period will be heavy rain. Both NAEFS and ENS
PWATs continue to approach the 99.5 percentile of their respective
model climatologies in their latest cycles. NBM probabilities
indicate most areas will receive around 0.75" to 2" of rain from
Monday night through Tuesday night with the potential for localized
areas to approach 4", in line with the convective nature of this
event. Given the high amount of antecedent rainfall, flash flooding
and additional river flooding will be concerns.

As for severe thunderstorm potential, the convergence across
guidance toward two primary rounds of convection with the second
beginning late Tuesday afternoon as peak heating occurs suggests
vigilance will continue to be needed. However, while shear profiles
are broadly supportive of an all-hazards severe risk day, convective
debris from Tuesday morning's convection still appears more likely
than not to prevent sufficient destabilization for that threat to be
realized in our CWA.

* THURSDAY THRU SATURDAY: Additional Chances for Rain

Thursday into Saturday, guidance shows increasing agreement that an
upper low will bring potential for additional rainfall. Best
moisture transport is still largely displaced to our south, with
GEFS/ENS PWAT percentiles below the 90th during this period. Thus,
while additional rain is unwelcome, a repeat of the widespread
threat for flash flooding and rises in the non-Mississippi basins
expected Monday/Tuesday does not appear to be in the cards for later
in the week.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 558 AM CDT Sun Jun 30 2024

VFR expected through the 30.12Z TAF. Light north wind become
southeasterly tonight.

&&

.HYDROLOGY...
Issued at 217 PM CDT Sat Jun 29 2024

Minor to moderate flooding continues along the Mississippi River
and will continue into next week. Additional rainfall is
expected Monday night into Tuesday evening. Rainfall amounts of
1 to 3 inches is possible across the area during this time.
River flooding and flash flooding is possible due to antecedent
conditions across the area. Interests along rivers and creeks
should monitor the latest forecast and trends Monday night into
Tuesday.

&&

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

&&

$$

DISCUSSION...Ferguson
AVIATION...JAR
HYDROLOGY...DTJ