Wisconsin Weather

Wisconsin Preparing for Disruptive Winter Storm [UPDATED]

Feb 20 2018 9:00 AM CST| 0 Comments | Wisconsin | Weather Forecasting

UPDATE 9:00AM TUES - Winter storm is coming to an end. Here is a loop of the last 24 hours featuring heavy snow in northwest Wisconsin and couple thunderstorms in the south. Freezing rain reports popped between 5-7PM on Monday and again this morning (pink dots). This messy winter weather will end today for most, lingering into tonight in the southeast.

24HR radar loop ending 8AM Tuesday

Here is a look at some of the storm totals so far.

Storm total as of 8:00 Tues. Storm has not finished yet. In between the snow and rain was the freezing rain for central Wisconsin.

UPDATE 9:30PM - A few freezing rain observations rolled in between 5PM & 7PM tonight. Generally 0.01" to 0.20" was reported between Osseo, Red Granite, and Green Bay. This was only half of the event for central Wisconsin with another round expected Tuesday morning. Very slippery on sidewalks around Oshkosh tonight.

Snow reports of 12" in Ashland tonight! Assuming there will be spots that exceed 1 foot but not too many. This was a very successful snow forecast for the northwest and will be interested to see how the COOP observations look like in the morning. North-central Wisconsin on the other hand might be facing a snow bust based on reports. We can talk about that later.

An estimated 0.5-1.0" of rain fell roughly from Janesville to Milwaukee prompting a Flood Advisory for runoff due to frozen ground. This feels like a good move by the NWS with more rain on the way and reports of water on roadways which is hard to see at night. Travel safely!

Overnight there will be a lull in precipitation. There might be a few isolated rain/snow showers, drizzle, or freezing drizzle occurring at times. Tomorrow morning our next and hopefully last round of mixed precipitation will pass through. Expect additional snow, sleet, freezing rain, rain accumulation & perhaps a rumble of thunder(south) between 3AM and noon. Rain/snow/frz rain chances decrease during the afternoon.

NAM forecast. Timing & placement has been all over the board lately so hoping third time is a charm.

UPDATE 3:30PM - Current radar trends are rather unimpressive except for far northwest Wisconsin. Monday may turn out a bust for some but the important thing to remember is that this will be a two-part system. Starting to see interesting developments with surface temps in east-central Wisconsin pretty close to the model forecast. Temperatures have cooled by 4F or more in east-central Wisconsin since noon. 28F currently in Green Bay. Oshkosh dropped from 37F to 31F this afternoon. The surface freezing line is moving slowly south while warm air aloft remains parked overhead.

Temperature change since noon valid 3PM Mon.

NAM forecast for freezing rain accumulation by late morning Tuesday.

Waiting to see what other models show as many short range models have been too biased on present conditions (not handling cooling well). Nothing really to change in my opinion. Everything still shaping up close to forecast just random timing, placement, and coverage that makes it feel a little herky jerky.

UPDATE 12:20PM MON - Radar trends show heavy snow in far northwest Wisconsin. 6.0" of snow reported already in Douglass county. Scattered rain showers moved through the southeast this morning. Freezing rain observed in central Wisconsin not long ago with a small cluster of mixed precip moving through. There is a gap across central Wisconsin where precipitation is either not falling or maybe coming down as freezing drizzle. Strange "stretched-out" looking event where things are all over the place both timing and position-wise. Watching another cluster of precip coming out of Iowa. Precipitation chances will peak statewide this afternoon. Will note that temperatures have risen above 32F generally south of HWY 29 which could lead to less freezing rain Green Bay/Wisconsin Rapids southward? Combination of precip cooling and northeast winds may nullify current trends. Still have Tuesday ahead of us in this blended two-part system so no changes yet. Pretty much everyone with a Winter Weather Advisory right now, the Ice Storm Warning was downgraded. Part II arrives tomorrow.

Radar loops with snow in the north, rain showers in the south. Freezing rain reported in Marshfield

UPDATE 8:00AM MON - Slight shift in storm track and timing since our last update. Timing for peak impact will be this afternoon into early evening. Another batch of precipitation arrives mid-day Tuesday. Around 0.25" of ice central Wisconsin. Snow accumulation of 6"+ in the far northwest. 1-2" of rain southeast. Winter Weather Advisory issued for the northern half of Wisconsin.

Disruptive winter storm starts this afternoon. Icy conditions for central Wisconsin. 6"+ snow northwest. 1-2" rain southeast.

5:30PM SUN - Wisconsin is preparing for a disruptive winter storm starting 6AM Monday, Feb 19 through late Tuesday, Feb 20 that is expected to bring between 0.2"-0.5" of ice accumulation to central and southern Wisconsin. Snow will fly across northwest Wisconsin where 6-12" of snow accumulation is expected for far northwest Wisconsin. This storm will have a significant impact on travel. Tree damage can occur with ice accumulations exceeding 0.25" which could lead to power outages. Wind gusts should remain relatively light. Southeast Wisconsin will see 1-2" of rainfall with a rumble of thunder possible.

Warning map as of 5:00PM on Sun 2/18/2018

The National Weather Service has issued a Winter Storm Watch ahead of the system. We have been forecasting a disruptive winter storm since last Thursday. Rare ice Storm Warning may need to be expanded.

Ice, Freezing Rain, and Sleet

A rare ice storm is expected to bring 0.2"-0.5" of ice accretion and accumulation Monday and Tuesday. Surface temperatures will get colder during the day Monday as a cold front pushes south and stalls across southern Wisconsin. Warmer air aloft will produce liquid precipitation that freezes or becomes supercooled as it falls into a wedge of cold air near the surface. The depth of the cold air will determine how much sleet or freezing rain falls and each forecast model handles it differently right now. Where exactly the stationary front sits will have also have a big impact on the forecast.

GFS loop of precipitation type variety Monday through late Tuesday night.

Snow

Long duration snow accumulation event for northwest Wisconsin. 6-12" is possible in far northwest Wisconsin early this week. When you add snow from Sunday a few spots could exceed 1 foot by late Tuesday night. 2-6" of snow accumulation for the Minneapolis, Eau Claire, and Mincoqua areas. Sleet will mix with snow creating icy driving conditions for Rochester, Wausau, to Escanaba.

Rain

1-2" of rainfall is forecast early this week in far southeast Wisconsin. Thunderstorms are possible but severe weather is not expected.

Timing

Precipitation should arrive in two main waves though they may blend together for some places. First comes in Monday morning around and after 12PM. There is a lull overnight before more precipitation moves in Tuesday.

Precip timing and type chart for northern, central, and southern Wisconsin.Best chance for precipitation is between 3PM and 9PM on Monday.

Forecast Discussion

  • Some uncertainty remains in the exact placement of heaviest ice accumulations. Some forecast models are warmer with less ice, others colder with more ice.
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