Tuesday 12-27-2011

Dec 27, 2011

Greetings and welcome!

Over a decade of doing this has shown me that people like to know by Tuesday what the weekend will hold for riding prospects. Let’s start with that. The chances of a system-wide ride or any distance riding are about zero. There are places where you can find a sheltered forest road to skitch around on a little, but around here it is a layer of ice and a little (1/4″) snow on top. Slug and Gary’s reports last week suggest that you can find that with a little better conditions north and northwest of here. The trails are officially closed in most areas.

When the snowmobile trails are closed, they are closed to ATVs as well. The one exception to this is the Marinette Co year ’round ATV trail system that starts by Jungle Jim’s in Silver Cliff.

Is there any hope at all? Not for the weekend. There is a small clipper for about Wednesday night/Thursday morning that could bring light snow. There is another for the weekend, but that might not be snow. Farther out in the forecast there are more clippers, including some bigger ones.

What about lakes? The warm weather has not been good for making ice. The lake ice is behind where it normally is.  As I mentioned yesterday I haven’t heard an ice measurement over 4-5″ yet. If you go out on the lakes be really sure of what you are riding on, and prepare for the worst. Last week’s paper did confirm that a local man perished after going through the ice on High Falls.

We would much rather have the area full of snowmobilers, but it is what it is. There are a lot of places hawking new year’s eve parties and packages, and the good times will still roll. If you are so inclined, come visit the area anyway.

When I write my reports I frequently speak of the GFS forecast model. Today we will take a little closer look.

The GFS is a 16 day model, and that is one of the main reasons that I use it. Unfortunately it is pretty common to have to look a week or more out for a hope of snow. There are a lot of other forecast models, but the GFS reaches out a little more than most, so it gets the most attention.

I updated the NCEP Forecast model link in the RH column tonight. They took a pretty easy to understand system and made it harder, but again it is what it is.

If you click the NCEP Forecast model link you will come to this page.

On the left side by the red arrow you get to pick your model. The GFS reaches out 16 days. The NAM reaches out 5, and the RUC, or Rapid Update Cycle reaches out about 6 hours and updates hourly. Each are very useful in their own way.

 

Once you pick the GFS link it will take you to this page.

On the top it shows the most recent model run time in white. If the data is not all of the way uploaded for a new version, you can view and earlier model.

Here you want to click the 850_temp_mslp_precip  link. The 850 temp tells us if it will be rain of snow. The MSLP shows us the high and low pressure areas near the surface, and the precip gives and estimate of rainfall equivalent for the frame being viewed.

After clicking the 850_temp_mslp_precip  link the bottom will show a series of time frames. Usually I select loop all on the right side and watch the whole 16 day cartoon. If you want to focus on the frame with the storm at hour 177 out, you can do that too.

 

This frame is looking at Wednesday night’s clipper system. The precip blob is the second level of green, which the chart on the lower left of the page shows is 0.1-0.25″ of precip for that three hour frame.

The 850mb temperature lines showing 0C and -10C are to our north and south. These represent temperatures a few thousand feet up in the atmosphere and provide guidance on rain vs snow. By my observation you generally want -4C or colder 850 temps to expect snow. The red line is my guess where it would be, and subsequently the rain/snow line.

Unfortunately this frame is from Saturday’s clipper system. As you can see the 850mb temperatures are not in our favor. The -10C line is way up in Canada, and the zero C line is right over us. That doesn’t hold much promise for snow. The red line at the bottom is the +10C line, usually meaning a warm day when that comes our way. Seeing the 0C and -10C line so close is bad for snowmobilers.

Put it this way.. 0C is 32 degrees F, plus 10C is 50 degrees F. If it is 5oF a couple of thousand feet up, it will probably mean a warm day. Likewise if you see the -10 or -20 line heading your way get ready for cold weather.

I also talk about QPF a lot. The QPF is the Quantitative Precipitation Forecast , how much rainfall equivalent to expect, indicated by the green area. Around here a 12:1 ratio is a reasonable guess for converting rainfall equivalent to snow. Some mix storms can go 6:1, 9:1, and some really light snow can go 16 or even 30:1 for a conversion factor. Usually a 12:1 is reasonable.

The forecast models are handy guidance when you are trying to get a look at future weather. There are a wide variety of forecast models above and beyond the GFS, NAM and RUC, but frequently the conventions are the same.

As always I encourage you to look into this on your own more. Personally I find weather really fascinating, and with it so important to what we do, a lot of you do too. Hopefully this helps in that direction.

Oh yeah, and there might be a pop quiz later.

Have a good Tuesday and thank you for visiting!

RJB