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Wisconsin Weather

DEC 12, 2020 | Winter Storm Ends this Afternoon

LAST UPDATE : DEC 12, 2020

FRI 12:56PM CT

No major changes and previous forecast mostly on target. Sticking with 3-6" zone, added another zone to lower Michigan. Short range models lowered from 00z run, 12GFS snowier so they almost met in the middle. Locally higher amounts possible...some models are snowier in the Kettle Moraine area on Saturday as the system deepens. Storm track with SLIGHT northward shift last 24 hours. Warmer air near Lake Michigan in SE Wisconsin & along WI/IL border likely to reduce snow amounts. Snow starts tonight, most of the accumulation comes Saturday AM. Stay tuned for additional forecast information. Click here for blog post. Thanks! -JP

Snow accumulations of 3-6
Snow accumulations of 3-6" in southern Wisconsin by 6PM Saturday

THU 10:36 PM CT

Looking at evening runs (less EC) it appears the GFS/CAN are the weakest. Storm track mostly the same still. NAM & all of the short range are snowier, most of the guidance supports at least a 3-6" zone atm. Hesitant to go any further than that right now, prefer to balance it out. Went ahead and added the 3-6" zone back in....lines up with initial thoughts again so not much of an update. Will post my final forecast FRI afternoon.

THU 12:24PM CT

Taking a small step back today. Models are pretty stable on storm track. They seem to be settling on the weaker, less snowy scenario. I updated the forecast with a narrow 2-5" max snow zone from Dubuque to Milwaukee. Some models do have locally higher amounts but will wait for more model runs before taking things further. Sharp gradient on the northern fringe.

Updated maps and start/end times as all models showing quicker ending...by 6PM SAT PM. No vlog today but will plan for one tomorrow.


VLOG (see below for text discussion)

WEDS 12:13 PM CT

Moderate strength low pressure system will track from Missouri to the southern tip of Lake Michigan on Saturday. Rain/snow mix showers will develop Friday night in southern Wisconsin with the main winter storm event during the day on Saturday.

Model consistency is OK on latest runs. Earlier progs were bouncing around considerably. 12zEC is coldest/furthest south with narrow snow swath through SE WI. NAM (84hr) is warmest/furthest north, considered an outlier. GFS is close to EC but slightly further north. GFS ensembles *appear to favor* northward trend and the last few model runs we've seen a subtle northward creep of the storm track. Three days out but hopefully the track is solidifying. Confidence is typical for this forecast period.

Assuming no major track shifts; the event will begin Friday night in southern Wisconsin starting with a lighter/scattered rain/snow mix...minor impacts. The storm system will better organize on Saturday with a higher likelihood of accumulating snow developing. Snowfall amounts vary between models; some higher and lower. I like the 3-6" snowfall range for starters along a narrow axis in southern WI by EARLY SUN AM. Latest models have been trending snowier. Will see how things evolve and push additional info as needed.

Winds will be on the increase Saturday night but unlikely they will reach blizzard levels.

For the rest of Wisconsin (the northern half), no significant weather aside from increasing winds and falling temperatures. If the system trends north then obviously that would change things.

Forecast Maps



Storm Details

Winter Storm
FRI 12:00 PM - Dec 11, 2020
SAT 6:00 PM - Dec 12, 2020
Confidence Level
Storm Class


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