Flash Flood in Wisconsin, July 15, 2022

Area Forecast Discussion
National Weather Service La Crosse WI
227 AM CDT Fri Jul 15 2022

.DISCUSSION...(Today through Thursday)
Issued at 226 AM CDT Fri Jul 15 2022

Key Messages:

 - Showers and storms continuing into today, heavy rainfall mainly
   east of the Mississippi

 - Periodic rain chances over the weekend

 - Warmer for next week

Overnight Showers and Storms Continuing Today:

As of 15.07 Z, showers and storms are developing and moving
southeast through the area. Storms currently in northwestern
Wisconsin appear to be forming along a max DCAPE axis, contributing
to efficient rainfall. MRMS data as of 15.06 shows rain amounts
ranging from a couple tenths to about 1.1 inches in eastern
Minnesota. More rainfall is on the way so we can only expect those
numbers to climb overnight and into the day. CAMs solutions are
beginning to come together and become more clear, with the HRRR
performing well at the moment. This round of precipitation will
continue from the overnight through around noon today. The primary
threat is still heavy rain, which could cause street flooding or
flash flooding if one location gets impacted by the expected
training storms.

Warm cloud depths are around 3500-4000 meters, depending on the
model; but not very impressive overall. PWATs up to 2 inches are
also not terribly impressive. CAPE also barely reaches 1000 J/kg in
some models mainly west of the Mississippi. Because these values are
on the lower end, high rainfall totals should be due to the expected
training pattern of the storms. However, stronger storms could be
capable of producing sporadic damaging wind gusts.

HREF 24 hour QPF has increased from yesterday and suggests that rain
amounts of 7+ inches are possible in a corridor through central
Wisconsin. This area of highest rainfall has shifted a bit to the
east compared to previous runs. In areas on the periphery of the
corridor, HREFv3 suggests at least a 40% chance of 2+ inches over
the 24 hour period in most areas east of the Mississippi River, with
the range mostly being 2-5 inches. West of the Mississippi, 2-3
inches of rain is possible.

Periodic Rain Chances This Weekend:

Still looking at intermittent rain chances for the weekend, though
they slightly decreased again compared to yesterday. Should be light
rain with weekend totals of a couple hundredths to tenths of an
inch. Thunder could be mixed in with the showers at times, but those
storms are not expected to be severe. Models favor a rain event of
*some* kind this weekend. There continue to be differences between
models on the placement and timing of weekend showers, so lower
confidence on those details of rain. Higher rain amounts should stay
south of the area, with chances decreasing into northern Wisconsin,
and some models suggesting northern areas would get no rain at all.
Can't rule out the possibility of rain with a couple shortwaves
passing over the area, so will continue to keep pops in.

Warm Up Next Week:

Next week will begin with above normal temperatures and muggy
conditions. Highs could reach the lower 90s and dewpoints 70 on
Monday and Tuesday. Heat indices in the upper 90s are suggested for
some locations, particularly in valleys, NE Iowa, and SW Wisconsin.
But otherwise should be relatively quiet weather, save for a chance
for rain Monday night into Tuesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1030 PM CDT Thu Jul 14 2022

CIGS: cigs still look on track to drop to MVFR toward 12z-ish,
hanging around into the afternoon. Could see a drop into IFR for a
short period later this morning. Latest RAP/NAM suggest the low cigs
could linger well into the evening (NAM most aggressive) while the
GFS favors scattering out. Will push back the scattering...but there
is the potential skies won't clear until later Sat with sfc
low/trough just to the south.

WX/VSBY: Showers and storms will track southeast across the area
overnight/friday morning. While CAMS/Meso models continue to show
some differences in where the main slug of heavier rain will track,
there is some consensus with favoring impacts for the TAF sites
between 09-15z. That is the most likely period for storms, heavier
rain, and IFR/MVFR vsbys. Will add a tempo group near 12z to
highlight a more likely period for greater impacts.

WINDS: Winds will be out of the southeast and will stay around 10
knots...becoming more easterly Fri night (and lightening up a tad).

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&

DISCUSSION...Dahl
AVIATION.....Rieck