Winter Storm UpdateDecember 20th, 2012 at 11:44 am by Greg Shoup under Weather
Our forecast models have been consistent in putting the heaviest snowfall north of our area. However, because of the proximity to low pressure we will experience what is termed a ‘tight gradient’ across the area. In layman’s terms gusty winds when lines of equal pressure or ‘isobars’ are very close to each other on a weather map. As a general rule on a map the heaviest snowfall is about 150 to 200 miles north of the main low and that’s exactly how things are setting up with the heaviest snowfall across southern Wisconsin and portions of western and northern Michigan.
The other mitigating factor will be ‘lake effect’ snowfall. The gusty winds will begin Thursday night and Friday Winds will gust up to 60 mph through Indiana and Michigan.
Here is the latest coverage map. Also below is what I’ve been blogging about over the last couple of days. It’s called a ‘trowel’ and it actually warms the atmosphere during a time when snow is occurring. The latest models have confirmed this feature and it should limit most of our area to about 1 to 2 inches. Lake effect snowfall closer to Lake Michigan may bring those totals up around Noble and LaGrange counties.
Here is what a trowel looks like on the weather map. Actually turning into rain for a brief period of time
Here are the warnings and advisories issued across the region for the upcoming storm. The red area across Wisconsin is a blizzard warning. This area includes the city of Madison. The pink areas are winter storm warnings issued for heavy snowfall and gusty winds. There is a winter storm warning issued for areas around Lake Michigan in Indiana. The beige area is for winter weather advisories. These areas don’t meet the criteria for a winter storm warning, which for our area is 6 inches or more of snowfall.