Thunderstorms developed in the afternoon of Tuesday, July 14th across west central Wisconsin. These storms developed along a cold front with steep lapse rates and modest instability.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS MPX wrote it up.
Thunderstorms developed in the afternoon of Tuesday, July 14th across west central Wisconsin. These storms developed along a cold front with steep lapse rates and modest instability. Several storms merged over Eau Claire County and developed a small bow segment that produced wind damage in Augusta.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Twin Cities, MN wrote its last area forecast discussion before the first event at Jul 14, 2:17 PM CST, 1 hour 1 minute earlier.
Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 317 PM CDT Tue Jul 14 2020 .SHORT TERM...(This evening through Wednesday night) Issued at 304 PM CDT Tue Jul 14 2020 Much more tranquil weather is on tap starting tonight after the active weather the Upper Midwest has experienced the past 24-36 hours. A cold front over central-southwest WI into northeast IA this afternoon will continue to press eastward tonight, nudging any and all remaining rainfall over far eastern portions of the WFO MPX coverage area off to the east. While a few thunderstorms are still possible, any embedded t-storms will be weak and thus there is no longer a threat of severe weather within the WFO MPX coverage area in the short-term period. Clearing skies are already evident in western MN and this trend will continue eastward as the front slides east and high pressure over the Northern Plains expands eastward into the Upper Mississippi River Valley tomorrow. The high pressure will remain in place through the day tomorrow into Thursday morning, resulting in mostly clear skies tonight through tomorrow night. Temperatures will remain comfortable through tomorrow, particularly because noticeably drier air will advect into the region behind the cold front and with the high pressure area. After highs today in the 70s area-wide, lows will drop to the 50s area-wide tonight, which will run roughly 5 or so degrees below normal. With plenty of sunshine tomorrow, highs will run from the upper 70s to lower 80s for much of the area, and potentially the mid 80s in far western MN. The main difference will be the humidity levels, which will be much lower as dewpoints will remain in the 50s area-wide, putting RH values in the 30s to 40s percent, rather comfortable for mid-July. .LONG TERM...(Thursday through Tuesday) Issued at 304 PM CDT Tue Jul 14 2020 No significant changes to the pattern over the next week. The upper Midwest sits atop the expansive ridge with active westerly flow through the region. This pattern will leave us in the track for several shortwave troughs and frontal passages every 2 to 3 days. The main concern for this period will be Saturday into Saturday night with the potential for excessive heat and strong to severe thunderstorms. Heat and humidity will continue to build toward uncomfortable levels on Friday. Precipitation chances will increase Friday evening with a surge of instability associated with a strong warm front. Convection will likely form northeast of the MN river valley. Saturday will be hot and steamy with temperatures in the low 90s and dew points in the low to mid 70s. This would indicate heat indices near the 100 degree mark if we do get that warm. With that level of heat and moisture there will be plenty of instability with SBCAPE values around 5000 J/Kg. A conditional thunderstorm potential develops Saturday afternoon/evening, with models have steep mid-level lapse rates of 8 deg C/KM ahead of a cold front moving through central MN and northern WI. Warm sector model soundings indicate strong capping thanks to warm h7 temperatures of 12-14c, but the arrival of a shortwave out of the North Dakota Saturday evening will cool h7 temperatures and work to weaken the capping inversion. This would allow for some convection to develop across the warm sector ahead of the cold front. Models continue to vary with timing on the surface cold front and location of the shortwave, but given the set up, the potential for severe weather and heavy rain will be a threat with any storms that do develop. The cold front and convection will shift south on Sunday before stalling across northern Iowa. Guidance attempts to bring the boundary back north with the threat of thunderstorm activity across southern MN. After Sunday the pattern remains with another shortwave likely early next week. I've decided to stick with NBM PoPs for the remainder of the period due to the uncertainty past Saturday night. Temperatures will "cool" towards normal after Saturday's threat of dangerous heat. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1250 PM CDT Tue Jul 14 2020 Rain is ongoing across much of the area this afternoon with a handful of TAF sites experiencing MVFR and even brief IFR conditions. This precip will continue to move off to the east, with a few thunderstorms possible as well. Conditions look to improve by late this evening from west to east. Winds will be light overnight with a shift to the southwest for Wednesday with VFR conditions returning. KMSP...Slight chance of thunderstorms near KMSP between 19z-22z, a TEMPO group has been added to account for this activity. Ceilings have been bouncing around for much of the late morning/early afternoon from SCT/BKN013-018 and this will continue through 23z. Conditions improve late this evening as a cold front moves through and winds become southwesterly for Wednesday. /OUTLOOK FOR KMSP/ Wed...VFR. Wind SW 5 kts. Thu...VFR. Wind SW 5-10 kts. Fri...Mainly VFR. Chc SHRA/TSRA/MVFR. Wind S 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && SHORT TERM...JPC LONG TERM...BPH AVIATION...Dye
Hazardous Weather Outlook National Weather Service Twin Cities/Chanhassen MN 203 PM CDT Tue Jul 14 2020 MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028- 151200- Douglas-Todd-Morrison-Mille Lacs-Kanabec-Stevens-Pope-Stearns- Benton-Sherburne-Isanti-Chisago-Lac Qui Parle-Swift-Chippewa- Kandiyohi-Meeker-Wright-Hennepin-Anoka-Ramsey-Washington- Yellow Medicine-Renville-McLeod-Sibley-Carver-Scott-Dakota- Redwood-Brown-Nicollet-Le Sueur-Rice-Goodhue-Watonwan-Blue Earth- Waseca-Steele-Martin-Faribault-Freeborn-Polk-Barron-Rusk- St. Croix-Pierce-Dunn-Pepin-Eau Claire- 203 PM CDT Tue Jul 14 2020 This Hazardous Weather Outlook is for portions of central and southern Minnesota...and west central Wisconsin. .DAY ONE...This Afternoon and Tonight. A few thunderstorms are possible in southeastern Minnesota into west central Wisconsin. No severe weather are expected. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Chances for thunderstorms return Thursday night through Monday. Some severe weather is possible. Heat and humidity will increase Saturday. Heat indices around 100 are becoming likely. .SPOTTER INFORMATION STATEMENT... SKYWARN spotter activation will not be needed through tonight.
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE Twin Cities/Chanhassen MN
1021 AM CDT Tue Jul 14 2020
WIC033-035-091-141715-
Pepin-Dunn-Eau Claire-
1021 AM CDT Tue Jul 14 2020
...URBAN AND SMALL STREAM FLOODING EXPECTED...
Thunderstorms with heavy rain will cause minor flooding in the
following counties...
Pepin...Dunn...Eau Claire...
* Until 1215 PM CDT.
* At 1021 AM CDT, Doppler radar and automated rain gauges indicated
heavy rain due to thunderstorms. This will cause urban and small
stream flooding. Overflow of water will result in minor flooding of
poor drainage locations in the area. Up to two inches of rain have
already fallen.
* Some locations that will experience flooding include...
Eau Claire, Altoona, Durand, Augusta, Fall Creek, Pepin, Eau Galle,
Fairchild, Ludington, Rock Falls, Foster and Caryville.
Additional rainfall of one to two inches is expected over the area.
This additional rain will result in minor flooding.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
In hilly terrain there are low water crossings which are potentially
dangerous in heavy rain. Do not attempt to cross flooded roads. Find
an alternate route.
Please report flooding to your local law enforcement agency when you
can do so safely.
&&
LAT...LON 4460 9200 4456 9204 4441 9209 4445 9224
4446 9225 4454 9220 4454 9213 4462 9214
4478 9201 4486 9117 4485 9092 4460 9093
JPCPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
349 PM CDT TUE JUL 14 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0305 PM HEAVY RAIN 1 NNW AUGUSTA 44.70N 91.13W
07/14/2020 M3.49 INCH EAU CLAIRE WI MESONET
RAWS MESONET STATION AFWW3 AUGUSTA 1NW.
RAINFALL DURING PAST 12 HOURS.
&&
MKMSPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE Twin Cities/Chanhassen MN 353 PM CDT Tue Jul 14 2020 WIC017-035-142215- Chippewa-Eau Claire- 353 PM CDT Tue Jul 14 2020 ...URBAN AND SMALL STREAM FLOODING EXPECTED... Thunderstorms with heavy rain will cause minor flooding in the following counties... Chippewa...Eau Claire... * Until 515 PM CDT. * At 351 PM CDT, Doppler radar and automated rain gauges indicated heavy rain due to thunderstorms. This will cause urban and small stream flooding in the area. Up to three inches of rain have already fallen. * Some locations that will experience flooding include... Eau Claire, Altoona, Stanley, Lake Wissota, Augusta, Cadott, Fall Creek, Boyd, Fairchild, Ludington, Foster and Allen. Additional rainfall of 1 TO 2 inches is expected over the area. This additional rain will result in minor flooding. PRECAUTIONARY/PREPAREDNESS ACTIONS... Turn around, don't drown when encountering flooded roads. Most flood deaths occur in vehicles. && LAT...LON 4460 9159 4494 9130 4496 9092 4460 9093 LS
Special Weather Statement National Weather Service Twin Cities/Chanhassen MN 400 PM CDT Tue Jul 14 2020 WIZ028-142130- Eau Claire- 400 PM CDT Tue Jul 14 2020 ...A LINE OF STORMS WILL AFFECT EASTERN EAU CLAIRE COUNTY BETWEEN 4 PM AND 5 PM CDT... At 400 PM CDT, radar indicated strong thunderstorms were located along a line extending from 7 miles northeast of Fall Creek to near Strum. Movement was east at 40 mph. Wind gusts up to 50 mph and dime size hail are possible with these storms. Locations impacted include... Augusta, Fall Creek, Fairchild, Ludington, Foster, Brackett, Lake Eau Claire County Park and Allen. This includes Interstate 94 in Wisconsin between mile markers 76 and 86. Torrential rainfall is also occurring with these storms, and may cause localized flooding. Do not drive your vehicle through flooded roadways. LAT...LON 4460 9147 4486 9123 4485 9092 4460 9093 TIME...MOT...LOC 2100Z 277DEG 36KT 4483 9116 4459 9134 LS
The La Crosse radar (KARX), 97 km away, was scanning. The volume nearest the first event began at 21:19 UTC.
1 thunderstorm wind. Local standard time, as filed.
Several trees and large tree branches were blown down on the northwest part of Augusta. A few trees also landed on power lines elsewhere in Augusta.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2020Every state in 2020This day in weather historyWarnings in Wisconsin, July 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 893526.