Sunday, December 14, 2008

Can You Find The Low Pressure?

Click the image below and it will open a bit bigger.

That is the "tightly wound" area of low pressure responsible for sucking down sub-zero air from the heart of northern Canada.

Good morning from Denver where the temperature is hovering from 0 to -2°F. It was 58°F above zero here in the Mile High City just about 18 hours ago.

We picked up a fresh blanket of white overnight, enough that I'll be heading out to shovel in a little while -- perhaps when we hit 5 above!

Back to the surface map I attached to this blog -- so it was pretty darn easy to find the low, right?

Now here is a challenge -- click on the picture again and this time draw the cold front. It is somewhere between Minneapolis and Fargo.

That short 3 hour ride up I-94 takes you from 36 above to 7 below zero!

Isn't weather exciting -- and so powerful.

North Dakota is all but closed for business today as I-94 is nearly shut down border to border, and I-29 IS shut down border to border.

And can you see why? As I type, the report coming out of Fargo is a balmy -8°F, heavy snow, and a sustained wind of 33 MPH gusting to 44 MPH out of the north.

There are some pretty good snow totals coming in from that region, with nearly a foot of new snow between Williston and Bismarck.

If you are a weather nerd like myself, and read some of the storm reports from that part of the world, you will notice sometimes the snow reports are estimated.

And that is ok -- in areas where wind blows the snow all over, including here at my house in the eastern suburbs of Denver where either there are no trees OR all the trees are new and offer no protection, sometimes you just gotta do your best to put the pieces of the storm puzzle the wind blew around back together.

In the Pacific Northwest, 38" of snow has been reported at June Lake on Mt. St. Helens.

And 1-3" is on the ground now in the greater Seattle metro area.

I was asked what kind of weather is associated with the occluded front in Friday's blog?

Typically along or ahead of the occlusion the weather is unsettled, cloudy and often wet. Overcast may be a good way to describe it.

Behind it things improve.

Because this is where one air mass overtakes another in a storm system, the weather can be extremely variable over a short distance.

So in the picture below, you can see the storm --- a cold and warm front associated with a low pressure.

At the top, where all the weather wraps back into the low pressure system (counter-clockwise circulation here in the northern hemisphere) the two air masses blend into one and form an occlusion.


  1. Indeed Chris! It's warm here in Oshkosh, WI right now as the temp stands at 37.4°. We are preparing for a quick turn around back to Winter though, thankfully. Any warm up during the Winter around here is a bummer. Enjoy shoveling!

  2. What a drop in temperature this system brought to Missouri! Although the precip amounts weren't impressive, the tight temperature gradient was fun to watch move across the state yesterday evening. One local tv station in Columbia noted a 13 deg. drop in 15 minutes, and Kansas City reported a 23 deg. drop in one hour! Currently, we sit at 9 with a wind chill of -11. It's going to be a cold walk to the gauge this morning!