Special Weather Statement, NWS La Crosse, WI

Area Forecast Discussion
National Weather Service La Crosse WI
230 PM CDT Fri Jul 21 2017

.SHORT TERM...(Tonight through Saturday Night)
Issued at 230 PM CDT Fri Jul 21 2017

Current trends show a large shield of showers and embedded
thunderstorms basically along and south of I-94. Some spotty heavier
rains occurred this morning across southeast MN/northeast IA with
amounts in the 3-4 inch range. With that, and expected re-
development this afternoon, expanded the Flash Flood Watch to
include Mitchel, Floyd, Chickasaw, and Fayette counties in northeast
IA.

Existing complex of showers and storms pushed cooler outflow
southward to near I-80 in Iowa. So, previous thinking of return flow
on the backside of this complex reaching up through I-94 has
diminished. Attention more focused now on areas across northeast IA
into far southwest WI this afternoon into this evening where
impressive nose of moisture transport will exist. Moisture transport
is firing additional storms over this outflow boundary as
precipitable water values push near 2.5 inches. In addition, plenty
of CAPE/shear for severe potential. Main threats through this
evening will be torrential/possible flooding rainfall and damaging
winds. All things considered, will lop off northern portions of
Flash Flood Watch and keep it going across northeast IA into far
southwest WI.

Shower/thunderstorm chances will be seen Saturday mainly along and
north of I-94 as a weak mid-level/surface trough ripples southeast
across the area. Farly decent CAPE available along with decent
shear, so cannot rule out a stronger storm or two north of I-94.
Otherwise, warm and still humid with highs topping out in the 80s. A
few showers and isolated storms still possible into Saturday night
northeast of I-94 with mid-level trough and steeper lapse rates.
Look for overnight lows

.LONG TERM...(Sunday through Thursday)
Issued at 230 PM CDT Fri Jul 21 2017

Cooler/drier air filters in on Sunday thanks to Canadian high
pressure sinking southward into the region. Still could see a small
chance of a shower/thunderstorm across north central WI with
lingering steeper lapse rates up that way.

Look for pleasant/dry conditions hang on through Monday as high
pressure drifts overhead. Looks like readings will top off in the
70s with dew points in the upper 50s/lower 60s.

Shower/thunderstorm chances return Tuesday and linger through Friday
as northwest flow aloft bring a couple systems through the region.
Otherwise, seasonably warm.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1242 PM CDT Fri Jul 21 2017

Cloudy (mostly VFR) skies with periodic light to moderate rain
showers will be the rule at KLSE/KRST through the afternoon. Could
see some MVFR reductions in visibility, especially at KLSE. A second
round of thunderstorms is then expected to develop late this
afternoon and into the evening. However, these storms should remain
south of the TAF airfields and removed all thunder from the 18Z
TAFs. Given moist airmass and light winds, ceilings may drop below
3000 ft agl overnight and have introduced this idea at KRST
beginning at 22.08Z and at KLSE beginning at 22.10Z. Some guidance
suggests IFR ceilings are possible and this is something to monitor
over the next 12 to 18 hours. Light south winds this afternoon will
gradually to turn to the southeast, and then to the northeast or
becoming variable overnight.

&&

.HYDROLOGY...
Issued at 230 PM CDT Fri Jul 21 2017

Aerial flood warnings continue for counties impacted by
significant rains and flooding east of the Mississippi River, with
flood crests currently working down the Trempealeau and Kickapoo
Rivers as well as down the La Crosse River. With southward shift of
heavier rain threat, conditions should continue to improve for areas
basically north of I-90. Showers and thunderstorms across northeast
Iowa into far southwest WI will continue flash flood threat into
tonight. Those along waterways really need to pay very close
attention to the weather today, and be prepared to act quickly if
heavy rains again develop.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...

WI...Flash Flood Watch through Saturday morning for WIZ053>055-061.

MN...None.
IA...Flash Flood Watch through Saturday morning for IAZ008>011-018-
     019-029-030.

&&

SHORT TERM...DAS
LONG TERM...DAS
AVIATION...ROGERS
HYDROLOGY...DAS

Hazardous Weather Outlook
National Weather Service La Crosse WI
225 PM CDT Fri Jul 21 2017

IAZ008>011-018-019-029-030-WIZ053>055-061-221200-
Mitchell-Howard-Winneshiek-Allamakee-Floyd-Chickasaw-Fayette-
Clayton-Vernon-Crawford-Richland-Grant-
225 PM CDT Fri Jul 21 2017

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

.DAY ONE...This Afternoon and Tonight

A Flash Flood Watch is in effect through tonight.

Thunderstorms have weakened, but another round of thunderstorms
is expected between 4 and 10 pm. This time period is of greatest
concern for additional flash flooding. Additionally some of the
storms could be severe, mainly along and south of U.S. Highway 18.
Damaging winds are the main hazard, though large hail cannot be
ruled out.

Flooding will continue along the Kickapoo river.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Flooding will continue along the Kickapoo river through the
weekend.

Additional thunderstorms are possible area wide Tuesday night
through Thursday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening.

.EMERGENCY MANAGEMENT COORDINATION...

No webinar is scheduled.

MNZ079-086>088-094>096-WIZ017-029-032>034-041>044-221200-
Wabasha-Dodge-Olmsted-Winona-Mower-Fillmore-Houston-Taylor-Clark-
Buffalo-Trempealeau-Jackson-La Crosse-Monroe-Juneau-Adams-
225 PM CDT Fri Jul 21 2017

This Hazardous Weather Outlook is for a portion of north central
Wisconsin.

.DAY ONE...This afternoon and Tonight

Thunderstorms are possible, mainly through this evening.
Lightning and brief heavy rainfall will be the main hazards with
the storms.

Flooding will continue along the Trempealeau and Kickapoo rivers.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Flooding will continue along the Trempealeau and Kickapoo rivers
through the weekend.

A few thunderstorms are possible near and north of Interstate 94
Saturday afternoon. These storms are not expected to be severe.

Additional thunderstorms are possible areawide Tuesday night
through Thursday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.

.EMERGENCY MANAGEMENT COORDINATION...

No webinar is scheduled.

AJ

Special Weather Statement
National Weather Service La Crosse WI
1155 AM CDT FRI JUL 21 2017

WIZ061-211745-
Grant-
1155 AM CDT FRI JUL 21 2017

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT GRANT COUNTY...

At 1154 AM CDT, radar indicated strong thunderstorms were located
along a line extending from 8 miles southeast of Prairie Du Chien to
7 miles southeast of Bloomington to Holy Cross. Movement was east at
35 mph.

Winds in excess of 30 mph and pea size hail are possible with these
storms.

Locations impacted include...
Platteville, Lancaster, Fennimore, Cuba City, Hazel Green,
Dickeyville, Cassville, Bloomington, Preston, Georgetown, Beetown,
Arthur, Montfort, Potosi, Livingston, Mount Ida, Ellenboro, Hickory
Grove, Tennyson and Union.

Torrential rainfall is also occurring with these storms, and may
cause localized flooding. Do not drive your vehicle through flooded
roadways.

If you are on or near the Mississippi River, get out of the water
and move indoors or inside a vehicle. Remember, lightning can strike
out to 10 miles from the parent thunderstorm. If you can hear
thunder, you are close enough to be struck by lightning. Move to
safe shelter now! Do not be caught on the water in a thunderstorm.

LAT...LON 4254 9064 4258 9068 4264 9071 4268 9092
      4269 9095 4272 9102 4279 9097 4300 9111
      4299 9106 4303 9097 4306 9094 4306 9091
      4308 9084 4313 9043 4251 9043 4251 9064
TIME...MOT...LOC 1654Z 268DEG 32KT 4300 9099 4280 9086 4262 9101

DAS

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
107 PM CDT FRI JUL 21 2017

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

0106 PM     HEAVY RAIN       OSAGE                   43.28N 92.81W
07/21/2017  M2.10 INCH       MITCHELL           IA   EMERGENCY MNGR

&&

CJA

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
111 PM CDT FRI JUL 21 2017

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

1138 AM     FLASH FLOOD      6 NW WESTGATE           42.83N 92.06W
07/21/2017                   FAYETTE            IA   LAW ENFORCEMENT

            WATER OVER THE ROAD.

&&

DB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
301 PM CDT FRI JUL 21 2017

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

0256 PM     HEAVY RAIN       FREDERICKSBURG          42.96N 92.20W
07/21/2017  M4.60 INCH       CHICKASAW          IA   FIRE DEPT/RESCUE

            STORM TOTAL SINCE 6 AM.

&&

AJ

Special Weather Statement
National Weather Service La Crosse WI
503 PM CDT FRI JUL 21 2017

IAZ030-WIZ061-212245-
Clayton-Grant-
503 PM CDT FRI JUL 21 2017

...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN CLAYTON AND
SOUTHERN GRANT COUNTIES...

At 502 PM CDT, a strong thunderstorm was located over Cassville, or
near Guttenberg, moving east at 30 mph. Another thunderstorm was
located near Platteville and was also moving east at 30 mph.

Winds of 30 to 40 mph and half inch hail are possible with this
storm.

This storm will be near...
  Lancaster around 530 PM CDT.
  Platteville, Dickeyville and Cuba City around 545 PM CDT.

Other locations impacted by this storm include Georgetown, Beetown,
Arthur, Potosi and Ellenboro.

Persons in campgrounds should consider seeking sturdy shelter until
this storm passes.

LAT...LON 4259 9069 4264 9071 4268 9090 4265 9090
      4265 9104 4266 9113 4284 9110 4288 9043
      4255 9043
TIME...MOT...LOC 2202Z 277DEG 27KT 4275 9101

RRS