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JUL 18, 2020 | Severe T-storms Possible Overnight Ending

LAST UPDATE : JUL 19, 2020

11:00AM VIDEO FORECAST (see text below)

SAT 10:30AM - Confidence is LOW for today and overnight. Potential exists for severe t-storms SOMEWHERE over Wisconsin but because of numerous possible scenarios; hard to say exactly who is most at risk. I kept the t-storm forecast broad & vague with STRONG TARGET...will have to take this one into the trenches and tackle it as it evolves. I almost did a broad SEVERE zone instead but don't want to risk overdoing it.

Models are struggling greatly with morning convective complex in southern Wisco. This lowers confidence in all models going forward. I don't think you can rule anything out. Most of the CAMS blow up convection across MUCH OF WI tonight & overnight. I guess this makes sense given available instability returning this afternoon (near 4500 j/kg SB). I still think NORTHERN WI is most at risk tonight relatively speaking. Models generally show severe t-storms moving in from southern MN. With convective complex in southern WI now...I think that will take the edge off?

Looking at wind profiles...shear magnitudes are good but mostly unidirectional (+ thermodynamic dominated environment) which suggests damaging wind threat primarily. Pretty common situation this time of year and TIME OF DAY[NIGHT]. Large hail or even a tornado is possible too.

In conclusion; I won't rule anything out right now. The narrative is "strong to severe storms possible tonight". Spatial risk area is large. Will have to add detail tonight as the situation unfolds.


FRI 10:30PM - quite a variety of solutions on the latest 00z NAM model. Low res showing a totally disjointed setup with supercells firing at 09z SUN over NC WI???..meanwhile high res NAM shoves SE propagating MCS through central WI by that same time? Not sure what to believe yet so let's keep confidence LOW. The pieces are there for a widespread event (low end?). Just not yet convinced it will come together correctly. Watching closely how tonight goes. Will plan for an update tomorrow around mid day.


FRI 1:30PM - Severe t-storms are likely [expected] somewhere across Wisconsin Saturday NIGHT into SUN AM. Confidence LOW because of location uncertainty.

Where the highest risk will be depends on TIMING & LOCATION of morning convective complex. Faster/further north will tend to focus storms north(GFS/NAM). Slower, further south solutions(CAMS) would open door for all of Wisconsin. Damaging wind gusts are the primary concern, large hail and perhaps a tornado possible.

Severe T-storms are likely SOMEWHERE across WI overnight Saturday into Sunday morning.
Severe T-storms are likely SOMEWHERE across WI overnight Saturday into Sunday morning.

On Saturday night; strong instability will be paired with strong upper level flow pushing through WI. Storms most likely during the overnight hours [after sunset]. GFS/NAM try to constrain most of the activity in northern WI. Short range CAMS are further south covering pretty much all of WI with t-storm threat. At least want to blend the two scenarios. Both scenarios are on the table. Looks like a nocturnal MCS event of some form (would like to see a stronger 850mb jet for bigger threat). Given the size and strength of the instability pool, storms could form as far south as the WI/IL overnight Saturday. I'm leaning towards a further south focused solution due to presence of SAT AM convective complex.

So...I will cover Wisconsin with a large STRONG zone for now...add in focused SEVERE zone tomorrow.

Forecast Maps

Thunderstorm Outlooks

Thunderstorms
General
Strong
Severe
Significant

Verification


Storm Details

Hazards
Severe T-Storms, Heavy Rain
Start
SAT 12:00 PM - Jul 18, 2020
End
SUN 8:00 AM - Jul 19, 2020
Confidence Level
Storm Class

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Fewer warnings than before across the state. Keeping a close eye on it yet....not over. Based on reports it could be worse. Think we'll be alright. Strong to severe storms could make it all the way to Lake Michigan...specifically those in central WI which are also trying to get into southern WI.
Cells losing some organization on latest scans. Looked primed to roll not long ago. Told you this event would be hard to pin down. The night is young. I'm taking a break rn, will check back in a couple hours. I will head out locally around 3am if needed...not too far. Just enough to get in on some of the action.
Interesting to watch these three cells. Not warned currently. Heavy rain primarily. Southernmost cell is a right mover that could dive into central WI. Instability gradient in play.
Dealing with supercells west of Eau Claire atm and TOR WARNING near River Falls is legit. I believe this activity will continue eastward along the instability gradient. Busy night? Eyes on
SEVERE TSTORM WATCH for northern WI tonight. Scattered strong tstorms are developing in northwest WI heading east overnight. A few cells could move into central or southern WI. Severe weather possible including damaging winds, hail, and isolated tornadoes.
CAPE gradient NW to SE through WI. Keep an eye on that tonight.
Large supercell set to track near & north of Eau Claire this evening...we'll call it "Big Boy". TOR WARNINGS earlier but weak rotation, since reduced to SVR TSTORM. What about additional development? Strange than were not seeing more cells popping. Suggests Big Boy will be the focal point tonight.
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T-storms expected to develop in the region along the Mississippi River north of Minneapolis late this afternoon. They will push east this evening into the overnight hours. Severe weather is possible. Setting the stage with this update. Will keep you posted!
Overnight storms heading out to sea soon in NE WI. Damaging wind gusts the main threat for Marinette, Door County. Watching the cluster west of La Crosse...not certain it will hold together as it heads east but it looks solid still.
Complex of storms with history of severe weather including damaging wind gusts exceeding 60MPH will enter NW WI within the next few hours. Some weakening as the complex moves through NE WI/UPPER MI early SAT AM.
Wind shear of 20-35kts not strong enough to balance out the 8,000 SBCAPE. Out-of-control outflow on the southern fringe in NODAK. Segment advancing through MN will probably intensify this evening...main event. Heading into NW WI overnight.

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July 18, 2020

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July 19, 2020

24HR Radar Loop
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Storm Reports

TORNADO & FUNNEL CLOUD (3)
FUNNEL CLOUD
FUNNEL CLOUD
1 N OSSEO, WI
-
TORNADO
TORNADO
3 SW OSSEO, WI
-
TORNADO
TORNADO
5 NNE PRESCOTT, WI
-
WIND GUSTS (35)
MARINE TSTM WIND
MARINE TSTM WIND
5 WNW CORNUCOPIA, WI
63 MPH
TSTM WND GST
TSTM WND GST
ENDEAVOR, WI
60 MPH
NON-TSTM WND GST
NON-TSTM WND GST
ENDEAVOR, WI
60 MPH
TSTM WND GST
TSTM WND GST
12 W DRUMMOND, WI
59 MPH
TSTM WND GST
TSTM WND GST
WAUSAU, WI
55 MPH
TSTM WND GST
TSTM WND GST
WASHINGTON ISLAND, WI
53 MPH
MARINE TSTM WIND
MARINE TSTM WIND
LA POINTE, WI
48 MPH
TSTM WND GST
TSTM WND GST
OCONTO, WI
46 MPH
MARINE TSTM WIND
MARINE TSTM WIND
5 NE CEDAR, WI
45 MPH
TSTM WND GST
TSTM WND GST
1 N DRUMMOND, WI
43 MPH
TSTM WND GST
TSTM WND GST
4 N NEWPORT STATE PARK, WI
41 MPH
TSTM WND GST
TSTM WND GST
1 SW BUTLER, WI
40 MPH
TSTM WND GST
TSTM WND GST
STURGEON BAY, WI
40 MPH
MARINE TSTM WIND
MARINE TSTM WIND
13 NE SAND BAY, WI
40 MPH
TSTM WND DMG
TSTM WND DMG
THREE LAKES, WI
-
TSTM WND DMG
TSTM WND DMG
PHELPS, WI
-
TSTM WND DMG
TSTM WND DMG
PHILLIPS, WI
-
TSTM WND DMG
TSTM WND DMG
GOODNOW, WI
-
TSTM WND DMG
TSTM WND DMG
LAC DU FLAMBEAU, WI
-
TSTM WND DMG
TSTM WND DMG
MARENGO, WI
-
TSTM WND DMG
TSTM WND DMG
NIAGARA, WI
-
TSTM WND DMG
TSTM WND DMG
4 NE ADAMS, WI
-
TSTM WND DMG
TSTM WND DMG
4 S BROOKS, WI
-
TSTM WND DMG
TSTM WND DMG
5 N WAUWATOSA, WI
-
TSTM WND DMG
TSTM WND DMG
CORNUCOPIA, WI
-
TSTM WND DMG
TSTM WND DMG
DENMARK, WI
-
TSTM WND DMG
TSTM WND DMG
6 SW STONE LAKE, WI
-
TSTM WND DMG
TSTM WND DMG
3 N MARENGO, WI
-
TSTM WND DMG
TSTM WND DMG
3 N RED CLIFF, WI
-
TSTM WND DMG
TSTM WND DMG
3 NE CORNUCOPIA, WI
-
TSTM WND DMG
TSTM WND DMG
3 S OSSEO, WI
-
TSTM WND DMG
TSTM WND DMG
3 SE SAND BAY, WI
-
TSTM WND DMG
TSTM WND DMG
1 S THREE LAKES, WI
-
TSTM WND DMG
TSTM WND DMG
1 SW SAND BAY, WI
-
TSTM WND DMG
TSTM WND DMG
2 NNE FRIENDSHIP, WI
-
LARGE HAIL (13)
HAIL
HAIL
1 ENE OSCEOLA, WI
1.25"
HAIL
HAIL
5 SW NYE, WI
1.25"
HAIL
HAIL
6 NE PATZAU, WI
1.0"
HAIL
HAIL
5 NE PATZAU, WI
1.0"
HAIL
HAIL
1 NE NYE, WI
1.0"
HAIL
HAIL
2 NNE RICE LAKE, WI
1.0"
HAIL
HAIL
2 S THORP, WI
1.0"
HAIL
HAIL
RHINELANDER, WI
1.0"
HAIL
HAIL
3 E SIREN, WI
0.88"
HAIL
HAIL
8 WNW TREGO, WI
0.5"
HAIL
HAIL
4 SE OLIVER, WI
0.25"
HAIL
HAIL
3 W EPHRAIM, WI
0.25"
HAIL
HAIL
KRAKOW, WI
0.25"
HEAVY RAIN (5)
HEAVY RAIN
HEAVY RAIN
ATHELSTANE, WI
1.55"
HEAVY RAIN
HEAVY RAIN
WASHINGTON ISLAND, WI
1.55"
HEAVY RAIN
HEAVY RAIN
AMBERG, WI
1.5"
HEAVY RAIN
HEAVY RAIN
FISH CREEK, WI
1.3"
HEAVY RAIN
HEAVY RAIN
FORESTVILLE, WI
1.2"
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