Caly: An Imperfect Storm (Updated)

Yes, of course the Weather Channel has given it a name.  Because Weather Channel.

Winter storm "Caly" is churning up in the west and will impact Wisconsin's weather for a prolonged period of time this weekend -- probably for about 36 hours, from 6pm Saturday to 6am Monday.

When it's all said and done, most of south-central Wisconsin will have 8-11 inches of snow to deal with.  Isolated areas in southwestern Wisconsin could be more in the 11-14 inch range.

Let's get to the pretty maps, and then we'll discuss some forecast details.

Here's how GFS sees snow totals through Monday morning.  Remember, you can click on any picture to enlarge.

And here's the wider view.  Totals in maroon are 10-12".

The National Weather Service agrees with those totals:

Because most models are in good agreement with this prolonged storm, NWS gives us a better than 50/50 chance of 8 or more inches before it all ends Monday morning.

Caly is actually two phases of one storm that will hit our area without much pause in between the two.  Here's how it sets up:

Saturday evening: light snow starts to overspread the area from west to east, and steadily increases in intensity throughout the night.  Look for about 3-5" by sunrise Sunday.  This is the flare-out snow area before the actual low approaches Wisconsin.

Sunday: the main low pressure begins a track through Iowa and northern Illinois, keeping us in moderate snow much of the day.  This adds another 4-6" by dinnertime on Sunday.  A good stiff breeze will cause blowing and drifting with this drier, fluffier snow, which is sure to piss you off as you attempt to clean off your driveway.

Here's how GFS sees low position at 6:00pm Sunday.

Sunday night: the low pulls off to the east, but light snow remains on the backside (probably an additional 1-2") -- as does the wind.  Whatever snow you cleared during the day on Sunday may relocate itself back to its original spot.  Not my fault.

Madison's average December snowfall is around 13 inches.  This storm, combined with last weekend's official 5.7", will put us over our average snowfall for December with only a third of the month in the books.  Gee, do you know any amateur forecasters that predicted above average snow this winter?  Like, on Labor Day?

So why does the headline call Caly an "imperfect storm"?  Mostly, because of its lack of organization.  This is not a classic Wisconsin winter storm that races through in 12 hours and dumps heavy snow.  Nope, it's gonna just hang around for a day and a half and annoy you like the guest that won't leave.

It's also likely that the prolonged nature of the storm is what has so far prevented the National Weather Service from issuing a Winter Storm Watch for our area.  It would be unusual to issue a 36-hour Watch.  But they'll have to issue something.

UPDATE: At 11:00am, the National Weather Service finally issued a Winter Storm Watch for south-central and southeast Wisconsin.  Area in blue is the Watch; area in purple is a very non-committal Winter Weather Advisory:

Here's the text of the Watch statement:

Note that this watch may be extended past Sunday evening, depending on backside snow rate and blowing/drifting.

(END UPDATE)

Some schools will likely be on 2-hour delay Monday morning.  Some will close.  It's too soon to pinpoint those cancellations.

Looking ahead, the fresh snow cover, along with a significant Arctic blast, will make it very cold by the middle of next week.  Wednesday and Thursday will make you curse your decision to live in Wisconsin.  Look for highs both days to hover between 0 and 10 degrees, with wind chills in the -25 neighborhood.  Check out these temps:

Looking farther ahead, models are suggesting yet another storm next weekend.  But let's get through this one first.

Over the next few days, I'll be prepping a Christmas travel forecast in diary-style, updating it frequently as we get closer to that holiday weekend.

What questions can I answer for you?

~Scott