Special Weather Statement, NWS La Crosse, WI

Area Forecast Discussion
National Weather Service La Crosse WI
1251 PM CDT Tue Jul 7 2020

.SHORT TERM...(Today and tonight)
Issued at 251 AM CDT Tue Jul 7 2020

Some patchy fog has been observed across parts of central into north-
central Wisconsin early this morning, where recent storms/rain moved
through. Conditions should improve by mid morning at the latest.

Another warm and humid day expected across the local area, with
zonal flow situated aloft. High temperatures will warm into the mid
80s to low 90s, with maximum heat indices in the low to mid 90s. The
remnants of a MCS/MCV located over South Dakota/Nebraska early this
morning will drift east through the area late this morning into
early afternoon. This paired with a stalled out cold front draped
across the region will provide enough lift to spark a few showers
and storms for some by later this morning into this afternoon,
mainly along and south of Interstate 94. Like the last several days,
with the environment we are in, some stronger storms will be
possible. Forecast soundings depict CAPE nearing 2000 J/kg,
precipitable water values of 1.5"+, and warm cloud depths of 2-3 km.
Primary threats within any stronger storm will be brief heavy
downpours, small hail, and gusty winds. Although widespread severe
weather is not expected, some shear looks to be present later this
afternoon mainly along and north of Interstate 90, with 0-3 km of
around 20-25 kts. Because of this, there could be a short window
later this afternoon into early evening where a severe storm or two
may pulse up, though chances are rather low.

Things quiet down tonight as a brief ridging builds over the area.
Overnight lows will once again not provide much relief with both
temperatures and dewpoints expected to be in the mid 60s to low
70s.

.LONG TERM...(Wednesday through Monday)
Issued at 251 AM CDT Tue Jul 7 2020

The next chance for widespread rains looks to be centered on
Thursday. An upper level low will be centered over Manitoba with
general weak troughing extending to the south/southwest from the
low. A short wave trough embedded in the larger scale troughing is
expected to come out of the central Rockies and strengthen as it
moves across the Upper Midwest Thursday. While there is general
agreement in the 07.00Z models on this scenario, there are still
plenty of differences on the overall strength of this wave along
with the timing. The GFS and ECMWF are similar in strength taking
the center of the short wave trough across Iowa into northern
Illinois with some weaker energy to the north that comes across
the local area and produces weak to moderate pv advection in the
500-300 mb layer. The NAM and ECMWF are the closest on the timing
bringing the wave across Thursday afternoon and evening while the
GFS brings it across Thursday morning. A cold front will get
pushed eastward with the short wave trough and should serve as the
focus for showers and storms. A band of weak frontogenesis is
expected to be generated along the baroclinic zone but it does
look to be rather deep existing in the 1000-500 mb layer. The low
level flow ahead of the front is not expected to very strong
resulting in just some very weak moisture transport impinging on
the front and a narrow band of 2 to 3 ubar/s of up glide on the
305K isentropic surface. With the expected amount of forcing,
looking for a broken line of showers and storms to occur ahead of
and along the front and work across the area during the day.
Depending on the exact timing of the front and the amount of cloud
cover, a pool of ML CAPE around 2500 J/kg could be in place ahead
of the front. Deep layer shear will be lacking with at most 20 to
25 knots in the 0-3 km layer. Mid-level lapse rates of 7-8C/km
may develop and this could help to produce some hail with any
stronger cells that form. Locally heavy rains will also be a
threat with precipitable water values of 1.75 to 2 inches and warm
cloud depths around 3.5 km.

A temporary break in the rain chances is expected for most of the
area Friday as an area of high pressure in the low levels builds
in from the northwest. The upper level ridge will also re-
establish itself over the Rockies during this time period with
troughing developing over the eastern part of the country. By the
weekend, this will place the Upper Midwest under northwest flow
regime and the models continue to show a short wave trough
dropping across the region for more rain chances over the weekend.
While there is good consensus on the timing of this wave right
now, there is a wide variety of solutions on how strong it will
be. As a result, will only have a chance of showers and storms in
the forecast for now.

The string of warm summer days looks to continue for much of this
period. Wednesday continues to look to be the warmest day with
high temperatures ranging from 90 to 95 for much of the area. Heat
indices will be a concern for that day as well. Most of the area
should top out between 95 and 100 but some locations, especially
in the valleys, could top 100 and edge into advisory criteria.
Right now, not expecting this to be widespread enough for a heat
advisory, but definitely worth messaging in other products. The
passage of the system over the weekend should bring a very brief
reprieve from the heat with highs Sunday expected to be in the
lower to middle 80s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1251 PM CDT Tue Jul 7 2020

An upper level trough and weak surface cold front will be the
trigger for scattered thunderstorms this afternoon. Most of this
activity looks to be east of the Mississippi River. As such, did
not include in the KRST TAF but did include VCTS mention in the
KLSE TAF after 20Z. Look for these scattered storms to diminish
with sunset/loss of surface heating. Otherwise VFR conditions
expected through the period. Winds will be light and variable his
afternoon, except gusty in the vicinity of any storms. Winds are
expected to become southerly Wednesday morning in the 5 to 15 kt
range.

&&

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

SHORT TERM...NMB
LONG TERM...04
AVIATION...DAS

Hazardous Weather Outlook
National Weather Service La Crosse WI
444 AM CDT Tue Jul 7 2020

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-
032>034-041>044-053>055-061-081200-
Mitchell-Howard-Winneshiek-Allamakee-Floyd-Chickasaw-Fayette-
Clayton-Wabasha-Dodge-Olmsted-Winona-Mower-Fillmore-Houston-
Taylor-Clark-Buffalo-Trempealeau-Jackson-La Crosse-Monroe-Juneau-
Adams-Vernon-Crawford-Richland-Grant-
444 AM CDT Tue Jul 7 2020

This Hazardous Weather Outlook is for portions of southeast
Minnesota...northeast Iowa and southwest into central Wisconsin.

.DAY ONE...Today and Tonight

Scattered thunderstorms will be possible through early evening.
Some of these storms could be strong with hail, gusty winds and
locally heavy rain being the main threats.

Heat indices of 90 to 95 are expected this afternoon.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Periodic chances for thunderstorms will through the weekend.
Strong storms will again be possible Wednesday night into Thursday
that could produce some hail, gusty winds and locally heavy rains.

The heat and humidity will continue into the weekend. Wednesday
looks to be the hottest day with heat indices of 95 to 100. The
cumulative effects of the heat and humidity may take a toll on
those with outdoor activities or without air conditioning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.

.EMERGENCY MANAGEMENT COORDINATION...

No webinar is scheduled.

04/NMB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
207 PM CDT TUE JUL 7 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0145 PM     HEAVY RAIN       1 NW ONALASKA           43.90N 91.23W
07/07/2020  E1.95 INCH       LA CROSSE          WI   PUBLIC

&&

TCR

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
211 PM CDT TUE JUL 7 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0200 PM     HEAVY RAIN       1 NW ONALASKA           43.90N 91.23W
07/07/2020  M2.41 INCH       LA CROSSE          WI   PUBLIC

            CORRECTS PREVIOUS HEAVY RAIN REPORT FROM 1
            NW ONALASKA.

&&

TCR

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
219 PM CDT TUE JUL 7 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0210 PM     HEAVY RAIN       2 NW ONALASKA           43.91N 91.23W
07/07/2020  M1.72 INCH       LA CROSSE          WI   PUBLIC

&&

TCR

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
221 PM CDT TUE JUL 7 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0132 PM     HAIL             2 NW ONALASKA           43.91N 91.23W
07/07/2020  E0.75 INCH       LA CROSSE          WI   PUBLIC

&&

TCR

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