Damaging Winds in Iowa, July 9, 2020

Area Forecast Discussion
National Weather Service La Crosse WI
1215 PM CDT Thu Jul 9 2020

.SHORT TERM...(Today and tonight)
Issued at 253 AM CDT Thu Jul 9 2020

Water vapor imagery early this morning depicts a closed low located
over Saskatchewan/Manitoba and a few shortwave troughs out ahead of
it across the Upper Midwest and central Plains. Some scattered
showers and storms associated with one of the shortwaves were
observed across north-central Wisconsin early this morning, though
activity continues to push east. At the surface, a cold front is
draped from northern Minnesota southwestward into western Nebraska,
with it expected to progress eastward across the area today. Models
continue to depict that a MCV associated with remnant convection
over South Dakota/Nebraska will drift eastward across Iowa and merge
with the surface cold front by this afternoon, allowing convection
to develop into along these features. With moisture remaining high
across the area (dewpoints in the upper 60s to low 70s), there will
be the potential for a few strong storms at times this afternoon
into this evening. Models depict pretty good instability across the
area this afternoon, with CAPE values generally 2000+ J/kg, though
there looks to be little shear present - at most maybe 20 kts in the
0-3 km layer. Any thunderstorms that do develop will be efficient
rain producers with warm cloud depths between 3-4 km and
precipitable waters nearing 2 inches for some. Because of this, the
primary threats with any stronger storms look to be locally heavy
rain and gusty winds. Mid-level lapse rates will be around 7-8 C/km,
so hail development will also be possible in any stronger storms.
Cannot completely rule out a few severe storms, though with weak
shear, they would be more pulsey in nature. Primary severe weather
hazards would be strong wind gusts and possibly some hail with
collapsing cores.

High temperatures today will be in the 80s, with overnight lows in
the 60s.

.LONG TERM...(Friday through Wednesday)
Issued at 253 AM CDT Thu Jul 9 2020

After a brief break from the rain chances Friday, these will
quickly return for the weekend. A short wave trough coming across
the upper level ridge is expected to drop across the region
Saturday and Saturday night in a developing northwest flow regime.
This has been a consistent signal from the models for a several
runs now, along with the differences in how strong this wave will
be. Both the 09.00Z NAM and GFS begin to strengthen this wave once
it gets past the ridge axis over the northern Rockies Friday
afternoon and then continue to strengthen it with an open upper
level low forming as it moves across the Upper Midwest. The 09.00Z
ECMWF does not show near the strengthening of the other two models
and tracks the wave more across the Great Lakes. While the 09.00Z
GEM has the short wave trough farther southwest than any of the
other models, it does lend support to the ECMWF solution of not
showing nearly as much strengthening of the wave. As a result,
will trend toward the less amplified solutions for now and keep
the rain chances in the 30 to 50 percent range. The potential for
severe weather looks to relatively low with this system. Clouds
should spread over the area limiting the amount of heating and
keeping the ML CAPE at or below 1000 J/kg. Deep layer shear looks
to be lacking as well with maybe around 20 knots in the 0-3km
layer to work with.

The upper level ridge should briefly build back over the region
for another short period of dry weather Sunday night into Monday.
The ridge should then get flattened as a large upper level low
moves across central Canada and re-establishes the westerlies over
the northern part of the country with the flow turning to the
southwest by early next week. This should bring a short wave
trough across the region Monday night followed by a potentially
stronger wave for Tuesday night into Wednesday. These wave will
return the chance for rain to the area for the first part of next
week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1215 PM CDT Thu Jul 9 2020

Scattered storms will be ongoing this afternoon but are expected
to push east this evening. Very heavy downpours/temporary severe
reductions in visibility can be expected under these storms.
Otherwise, expecting prevailing VFR conditions. Also plan on
variable winds, gusty in any storms, becoming northwest 10kt or
less toward Friday morning.

&&

.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
507 AM CDT Thu Jul 9 2020

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-
032>034-041>044-053>055-061-101100-
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-
507 AM CDT Thu Jul 9 2020

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

.DAY ONE...Today and Tonight

Thunderstorms are expected across the area today and tonight. Some
of these could be strong to locally severe with heavy rain,
damaging winds, and hail.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Additional chances for storms are possible this weekend and again
from Monday night into the middle of next week. Organized severe
weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated. Rainfall reports would be
appreciated.

.EMERGENCY MANAGEMENT COORDINATION...

No webinar is scheduled.

NMB/04

Special Weather Statement
National Weather Service La Crosse WI
956 AM CDT Thu Jul 9 2020

MNZ079-086>088-WIZ032>034-041>044-091700-
Wabasha-Dodge-Olmsted-Winona-Buffalo-Trempealeau-Jackson-
La Crosse-Monroe-Juneau-Adams-
Including the cities of Wabasha, Dodge Center, Rochester, Winona,
Alma, Arcadia, Whitehall, Black River Falls, La Crosse, Sparta,
Tomah, Mauston, and Friendship
956 AM CDT Thu Jul 9 2020

...Scattered Thunderstorms Across Parts of Southeast Minnesota
into Western and Central Wisconsin Into Early Afternoon...

Scattered thunderstorms will continue across portions of southeast
Minnesota into western and central Wisconsin into early Afternoon. A
few stronger storms will be capable of producing wind gusts in
excess of 40 mph along with penny sized hail. Move indoors if
storms approach your location.

In addition, torrential rainfall is occurring with these storms
and may cause poor visibility, ponding of water on roads, or
localized flooding. Take it slow if driving and never drive your
vehicle through flooded roadways.

Lee

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
1133 AM CDT THU JUL 9 2020

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

1120 AM     HEAVY RAIN       3 NW ROCHESTER          44.04N 92.52W
07/09/2020  M2.00 INCH       OLMSTED            MN   PUBLIC

            FELL WITHIN 30 MINUTES NEAR INTERSECTION OF
            HWY 14 AND W CIRCLE DR. NO FLOODING OBSERVED
            AT THIS TIME.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
1134 AM CDT THU JUL 9 2020

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

1130 AM     HEAVY RAIN       LAKE CITY               44.45N 92.27W
07/09/2020  E2.31 INCH       WABASHA            MN   PUBLIC

            CWOP STATION REPORT.

&&

Special Weather Statement
National Weather Service La Crosse WI
1140 AM CDT Thu Jul 9 2020

IAZ008-018-091730-
Floyd-Mitchell-
1140 AM CDT Thu Jul 9 2020

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT MITCHELL AND FLOYD
COUNTIES...

At 1136 AM CDT, radar indicated strong thunderstorms were located
along a line extending from 6 miles north of Mason City to near
Allison, IA. Movement was north at 35 mph.

Wind gusts up to 50 mph and penny size hail are possible with these
storms. Heavy downpours are also possible.

Locations impacted include...
Charles City, Osage, Nashua, St. Ansgar, Rockford, Riceville, Lyle,
Stacyville, Rudd, Floyd, Marble Rock, Mitchell, McIntire, Carpenter,
Colwell, Orchard, Toeterville, County Roads B 60 And T 18, Rock Creek
and Idlewilde State Park.

If outdoors, seek shelter inside a building.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 4350 9303 4350 9255 4291 9255 4291 9302
TIME...MOT...LOC 1636Z 198DEG 30KT 4322 9344 4267 9291

Lee

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
1200 PM CDT THU JUL 9 2020

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

1034 AM     HEAVY RAIN       6 W GOODRICH            45.14N 90.20W
07/09/2020  M1.31 INCH       TAYLOR             WI   PUBLIC

1150 AM     HEAVY RAIN       3 NNE ROCHESTER         44.05N 92.45W
07/09/2020  M1.41 INCH       OLMSTED            MN   MESONET

            MESONET STATION FW2899 ROCHESTER.

1145 AM     HEAVY RAIN       3 NE ROCHESTER          44.04N 92.44W
07/09/2020  M1.34 INCH       OLMSTED            MN   MESONET

            MESONET STATION EW0729 ROCHESTER.

1100 AM     HEAVY RAIN       1 W ORONOCO             44.17N 92.55W
07/09/2020  M1.00 INCH       OLMSTED            MN   MESONET

            MESONET STATION ONOM5 1 W ORONOCO.

&&

Special Weather Statement
National Weather Service La Crosse WI
1213 PM CDT Thu Jul 9 2020

IAZ011-MNZ088-095-096-WIZ032>034-041>044-053>055-091930-
Allamakee-Winona-Fillmore-Houston-Buffalo-Trempealeau-Jackson-
La Crosse-Monroe-Juneau-Adams-Vernon-Crawford-Richland-
Including the cities of Waukon, Winona, Preston, Caledonia, Alma,
Arcadia, Whitehall, Black River Falls, La Crosse, Sparta, Tomah,
Mauston, Friendship, Viroqua, Prairie Du Chien,
and Richland Center
1213 PM CDT Thu Jul 9 2020

...Scattered Strong Thunderstorms in Southeast Minnesota, far
Northeast Iowa, and Southwest into Central Wisconsin...

Scattered thunderstorms will continue across portions of the area
this afternoon. A few stronger storms will be capable of
producing wind gusts in excess of 40 mph along with penny sized
hail. Move indoors if storms approach your location.

In addition, torrential rainfall is occurring with these storms
and may cause poor visibility, ponding of water on roads, or
localized flooding. Take it slow if driving and never drive your
vehicle through flooded roadways.

CA