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Wisconsin Weather

JAN 17, 2020 | Winter Storm with widespread accumulating snow

LAST UPDATE : JAN 18, 2020

FRI 9:00AM - short update today with more information going on the official forecast coming after this. Will talk about the changes here.

SOUTHERN WI - I still respect the 00/06Z GFS and it's consistency regarding the warmth across southern WI. The issue is that is pretty decent snow surge tonight and short range models are all in agreement on several inches of snow just with that...plus minor additions Saturday morning as the storm pulls away. The biggest change is adding far southern WI and northern IL into the 3-6" including the Milwaukee area. I have to stress accumulations of "THREE TO SIX INCHES". I don't believe Janesville or south-central regions will have any shot at 6"...but should reach 3" before wintry mix, freezing drizzle, or even rain slides through early Sat AM. I debated using a 2-5" zone but it would be the same color as the 3-6" per the mapping logic. Also models have a 3-5" zone across portions of IL and want to put 6" in Milwaukee...which means it would be a 2-5" zone surrounded on all sides by 3-6". In conclusion this was about consistency and simplicity and will need to communicate it well.

The other changes were to trim back the 6-8" SLIGHTLY in central WI. Expanded the 6-8" to cover northern tip of Door County and more area in upper Michigan. Also made changes to 8-10" zones but not paying much attention to that. I feel very good about the 6-8" broad zone across northern WI and will allow locally higher amounts. It's feels like the right thing to do following the last storm.

Added start time map.

Please see discussion below for more!

PREVIOUS

THU 2:47PM - so much to talk about. It's as if we cross that three day mark and everything goes haywire. Pretty confident at this point yesterday. Less confident today. Snow will overspread WI after 3PM Friday night. The initial band could be moderate to heavy with snowfall rates up to 0.5-1.0"/hr between 3PM and midnight. Saturday it will snow across all of Wisconsin ending gradually by 6 PM.

S/E/SE WI - as the GFS hinted yesterday - models today show a warm nose around 8K feet and surface temperatures reaching 32F... pushing into southeast and far eastern WI Saturday morning. This will lead to lower snow accums in this area relative to neighboring regions. A period of rain may develop near the WI/IL border. Snow ratios also decrease significantly right through to the end of the event (including central WI to some extent). NAM is the outlier here still showing 6-10" as far south as Milwaukee. 18Z NAM today wasn't much help. EC at 10:1 is too high and if you account for the snow ratios during the morning Saturday it would look a lot like the GFS. So kind of ignoring the NAM but I respect what it shows Friday night. Then snow returns during the day Saturday but probably won't amount to much. I was purposeful in pulling the 1-3" zone over Milwaukee where the urban environment will further reduce "effective" totals.

REST OF WI(North) & UPPER MICHIGAN - Higher snow ratios throughout the event will lead to higher snow totals more consistently. I like 6-8" zone across northern WI into upper Michigan. Initially had 6-9" but want to stay away from the higher end amounts now. All models show around 6" with pockets of up to 8-9". It'll fall persistently over a 20-24hr period. As for upper Michigan. There was a spot near Ashland that models keeping excluding snow accumulation during the event. Think this is related to warmer air coming off Lake Superior. I will take the risk on being over there.

MINNESOTA - Initially I had 8-12" but didn't want to go all the way to 12" with the challenges we're already facing in WI. Just lobbed off the top to draw less attention. I know the heaviest accumulations will be found in west, southwest, and/or in Minneapolis.

Also I think NWS offices are approaching this as cautiously as possible and probably lower the me. Did see that an advisory was issued for eastern WI.

Forecast Maps

Storm Details

Hazards
Heavy Snow, High Wind
Start
FRI 3:00 PM - Jan 17, 2020
End
SAT 12:00 PM - Jan 18, 2020
Confidence Level
Storm Class

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