WSAW - Blogs - Chad Franzen

Big Snowstorm this week -- Updated Wednesday

Allright everyone... after not necessarily "buying" in to the much farther northern track from yesterday's computer model run... today it is even farther north, so now I'm a believer in the heavy snow potential for ALL areas, as opposed to a few select ones listed below.

Here's my forecast for Thursday afternoon and evening from Wednesday's Noon Show:

 

Here's the forecast from the National Weather Service Green Bay:

 

Here's the new forecast for the National Weather Service La Crosse

 

 

Few things here... notice how all of our forecasts now look more in line with each other's compared to yesterday's forecast?  Green Bay has been rather consistent with their heavy snow band, I have pushed mine 20 to 30 miles farther north... and LaCrosse moved theirs a good 75 miles farther north.   As I mentioned yesterday, there's a lot that goes into these forecasts.

Here's my new predicted amounts for :

Phillips: 4.5" ... as opposed to 1.5" from yesterday

Rhinelander: 4.0" ... as opposed to 1.5" from yesterday

Wausau: 5.0" ... as opposed to 3.0" from yesterday

Stevens Point: 6.5" ... as opposed to 3.5" from yesterday

Wisconsin Rapids: 7.0" ... as opposed to 4.0" from yesterday

Adams-Friendship: 7.0" ... as opposed to  5.0" from yesterday

 

Allright... for those true diehard weather nerds out there... here's how I came up with my narrow heavy snow band forecast as opposed to just a general swath of 6" to 10" that the Green Bay National Weather Service Office shows on their forecast...

Here's a map of something called critical thicknesses...

There are a lot of colored lines on this map,,,, but the one I'm looking at is the red line, which is the 1000mb-700mb (2840m) thickness line.  I'm using the 850mb low track and this critical thickness to forecast the heavy snow line and where it will set up.  Right now, most of the computer models have the 850 low tracking through northern Illinois and using the 2840m thickness line, compared to the low track, there's a few general rules of thumb to follow.

1)  The 850mb low is tracking approximately 150 to 175 miles SOUTH of the 2840m thickness line

2)  This then points to a Moderate to Heavy snow band that will run 50 miles to 75 miles NORTH of the 2840m thickness line and will be likely to be 75 miles or less in width.   The 2840m line is in Green Lake county... so eyeball and push that north 50-75 miles which roughly puts that in northern Juneau and Adams counties.... and again, the heavy snow line is about 75 miles wide. 

Now, why did I not put a very heavy snow band in southern Juneau and Adams counties?  Well, I think with the surge of moisture and transport of warmer air (low 30's)... it will be a heavy wet snow that will melt a little bit and heavy wet snow compacts very quickly.

I think in my forecast above, the 5"-7" line should probably be more of a 5.5" to 8" line, maybe shift a little bit farther north, and depending on how the upper level support moves through, we may have a few areas with up to 9" by early Friday morning.

 

Bottom line:  driving Thursday afternoon through Friday morning is NOT recommended for most of Wisconsin.  Please do NOT travel if at all possible.   I'll post totals in a new blog Friday.

 

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I've been getting a lot of questions and calls about this storm system coming up for Thursday ... and to be honest with you, I'm not totally sold on it being a huge heavy snow event for our area.   I will explain a little about my forecasting theory, and then you can see the forecasts from the 2 National Weather Service Offices in our area that are forecast completely different things as well.

 

First off, it was only today that it looked like we were going to have the possibility of a heavy snow event.  As I mentioned to Jona on Monday's Noon Show, this was going to be a very heavy snow event for northern Illinois (hello my Stateline friends) and far southern Wisconsin.  I did mention if it tracked a little farther north, it would be a "good" snow event for our area.. and it was this morning that some of the computer models brought it farther north.

 

My theory of forecast (thanks Dr. Arnold) is one that you remain consistent in what you do, methodical in how you analyze everything, and always look at the intialization of the computer models.  If the computer model intializes and starts with a horrendously wrong forecast, chances are that's what you're gonna end up with.  In addition, computer models have bias', in which one may track a storm system farther north compared to another.  This a huge problem this time of year east of the Rockies and with the Global Forecasting System Model (GFS formerly AVN) and the North American Model (NAM, formerly Eta).

 

The first thing I noticed is the track of this storm is now pointed more at central-southcentral Wisconsin, as opposed to the WI/IL stateline border.   When I see a storm track change that much... I have immediate red flags that come up in my forecasting.... the first of which is, "Do I believe this big change in the storm's track?"   "Is it plausible?"  (big word that I "stole" from MythBusters!)  "Why is it only doing this now, as opposed to yesterday, etc?"   The next thing is, if the track has changed, that will obviously change the amount of moisture that this storm system will have to work with, especially if it comes up from the southwest and grabs and drags up some Gulf of Mexico moisture to work with.   

 

So, do I believe this is a major snow for our area?  Yes.

Will everyone get snow (3" or more)?  No.

 

So, here's my forecast for snowfall valid Tuesday Feb. 24.   My forecast track and snowfall will probably change somewhat for tomorrow's forecasting round of fun.

 

 

Notice that I expect the heaviest snow to fall in our southern viewing area of Juneau, Adams, Waushara, southeastern Portage and southern Waushara Counties.

 

Now, here's the forecast from the National Weather Service Office in Green Bay for the same time frame:

 

Notice where their heavy snow track is... relatively close to mine.... and finally -

 

here's the forecast from the National Weather Service in La Crosse...

Notice how their heavy snow band stays farther south... as my forecast did from Monday, but not today.

 

 

Now, who is correct?  Who knows?  Ask me on Thursday and I will post the snowfall totals.   LOL

Here's my forecast for local communities: (from Tuesday's Forecast)- I will update tomorrow (Wednesday)

Phillips: 1.5"

Rhinelander: 1.5"

Wausau: 3.0"

Stevens Point: 3.5"

Wisconsin Rapids: 4.0"

Adams-Friendship: 5.0"

 

 

 

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