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JUN 26, 2020 | Severe T-Storms Today Southern Wisconsin

LAST UPDATE : JUN 26, 2020

FRI 10:44 AM - Live forecast update.

FRI 7:20AM - Will need to make some changes later this morning. Give me an hour or two. Getting the kids ready then I'M free. Probably a video update coming. Thanks.

JP


THU 11:22 PM- 00z run has been chaotic to say the least. No changes to this forecast other than to suggest perhaps a slightly southward trend with more focus on the southern 1/3rd of WI? The 00NAM specifically changing from 12/18z runs. Issues mostly related to FRI AM activity along the advancing warm front in SW WI, some models go bonkers with that. Some do not. Can't find a model handling current situation well. I see no reason to deviate from the forecast right now with risk of over-correcting.

THU 10:30AM - Based on 00/12z runs this morning. Timing of the shortwave energy is key. OVERNIGHT 00Z models (GFS, NAM et al) struggled with timing of short wave AND morning convection coming out of MN screwing up the event... but 00 HREF CAMS and 12z NAM are back on track for a potential severe weather event over eastern, central, and/or southern WI + maybe NE WI north of Green Bay? Expect some inconsistencies between models.

The models appear somewhat disjointed but I believe these things will come together. OFTEN ( NOT ALWAYS ) the trigger slows down in the final 36 hrs before event...an hour, maybe two? If so the timing would be perfect for severe weather tying it all together. Very important. It's all there. Just a question of will the short wave be on time? I think so.

Few things stick out...in no particular order:

1. WIND SHEAR - Nice crossovers between 500 & 850mb across the SEVERE zone. Shear magnitude not great but good enough. 700mb jet per 12z NAM is pretty strong and notable, coming in veered from 500 and 850...thus, sufficiently veered sounding despite weaker shear magnitudes. 0-3km shear is very good again(weak in the lowest 0-1km). Enough going on there to organize updrafts. 850mb jet fires up after 21z(5PM) across southern Lake MI - SE WI on the western fringe. If this timed right it will further enhance the event.

12Z NAM sounding cherry picked for the worst case. Nice veering 0-3km. weak 0-1km. Solid sounding all around.
12Z NAM sounding cherry picked for the worst case. Nice veering 0-3km. weak 0-1km. Solid sounding all around.

2. WARM FRONT pushing through eastern WI during the day providing additional vorticity to the lower atmosphere...similar to last Saturday - and many bigger events - we will have a boundary (warm front) crossing roughly NW to SE. Solid instability reservoir develops quickly over southern WI. This is important because 12zNAM does show cells firing on the warm front over central WI moving east during peak heating. If this situation occurs, no question these storms would be supercellular capable of a tornado or two. Tornadoes would probably be weak given weak 0-1km shear magnitudes.

3. AFTER 6PM storms will probably go outflow and supercells will push off into Lake Michigan. Across southern WI with additional development is likely..damaging wind gusts becoming the main threat extending down towards the WI/IL border.

In conclusion: severe t-storms are likely. All modes including large hail, damaging wind gusts, and perhaps a tornado or two.

NE WISCONSIN - I wasn't confident enough to pull the SEVERE zone (see maps) into far NE-WI. I hedged it up a little. It's possible that activity in central/SE-WI will hog the energy? Might depend on how far north the Warm front gets too. I'm not sure. We'll see.

I bumped this event up to 3-MOD again. I added Tornado to possible hazard list. Something about it I find interesting. VIDEO FORECAST (see below). Next update FRI AM. Storm chase is a FULL GO.

-JP


WED 10:00AM - Models today trending weaker, further south with severe t-storm chances for Friday. Can sense run to run retraction of the instability pool back into southern WI. EC the furthest south, GFS furthest north and NAM somewhere in between. Going to pull back for a second to allow this storm to flesh out...despite my optimism yesterday. See maps. Models not done shifting so stay tuned.


TUES 11:30AM - EC, GFS & NAM show 500mb short wave approaching WI by Friday night. Timing and configuration vary. EC showing a threat for t-storms throughout the day with scattered strong storms. The GFS/NAM are flatter/W-E with the 500mb jet, focusing energy into evening round of severe thunderstorms. GFS somewhat consistent.

00EC 500mb flow for FRI. Will wait for models to settle on large scale pattern.
00EC 500mb flow for FRI. Will wait for models to settle on large scale pattern.

Not sure which scenario will occur but the big picture indicates a severe weather event is likely with all parameters present to support all modes. COULD be a widespread event? (NOT saying it will be, just noting the potential) Timing, details, placement uncertain, somewhere between EC & GFS. I've opened with the CAT 3 - MODERATE designation which I usually only do for more notable situations/events. It's early so check back. Not enough confidence to zone in a particular area....gave it a large TARGET.

Forecast falls apart by late next weekend with big disagreements between EC & GFS. Will focus on FRI for now.

Will keep you updated on this thread.

-JP

Forecast Maps

Thunderstorm Outlooks

Thunderstorms
General
Strong
Severe
Significant

Verification


Storm Details

Hazards
Severe T-Storms, Heavy Rain, Tornado
Start
FRI 12:00 AM - Jun 26, 2020
End
FRI 8:00 PM - Jun 26, 2020
Confidence Level
Storm Class

Posts

Choices choices choices. My concern is not committing to either and getting stuck in between. Process of elimination.
Very impressed with dynamic aspect of the approaching low/short wave. Needs to destabilize. Expecting the NAMhres to verify for southern WI.
Updated T-storm Forecast for this afternoon. Video forecast posted on the storm event page. Stay safe and take care! Thanks! https://www.wisconsinwx.com/storm.aspx?s=228
12z short range models show highest threat for severe storms across southern Wisconsin this afternoon. Sim radar img at 6PM.
Plenty of spotty convection throughout the warm sector as the warm front (WF) pushes into WI. The WF will not make it as far north as initially forecast, probably up between Madison and Oshkosh area. Working on more updates stay tuned.

Archives

June 26, 2020

24HR Radar Loop
24HR Radar Loop
Wind Gusts
Storm Reports

Storm Reports

TORNADO & FUNNEL CLOUD (2)
FUNNEL CLOUD
FUNNEL CLOUD
2 NW SHULLSBURG, WI
-
FUNNEL CLOUD
FUNNEL CLOUD
3 SE BENTON, WI
-
WIND GUSTS (5)
TSTM WND GST
TSTM WND GST
4 S WAUNAKEE, WI
54 MPH
TSTM WND GST
TSTM WND GST
LANCASTER, WI
45 MPH
TSTM WND DMG
TSTM WND DMG
1 NNW BLOOMINGTON, WI
-
TSTM WND DMG
TSTM WND DMG
5 NNE PLATTEVILLE, WI
-
TSTM WND DMG
TSTM WND DMG
1 ENE GLEN HAVEN, WI
-
LARGE HAIL (1)
HAIL
HAIL
1 NNE VERONA, WI
0.7"
OTHER (1)
Amish Buggy
AMISH BUGGY
MARKESAN, WI
1
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