Ringing in the New Year with an arctic chill!

***Watch WISN 12 News today at 5:30pm and from 10-11pm for the latest on the New Year’s forecast!***

Thank you for stopping by the Weather Watch 12 blog!  This is Milwaukee’s premier source for the inside scoop on the forecast and we will also strive to teach you something new each day!  This blog will focus on the week ahead which should bring a large chunk of arctic air right over southeast Wisconsin.  Also, I will explain how the weather pattern this week is directly tied to late October.  If you are new to the blog, I will go over a weather pattern theory that I use called the ‘LRC’, which helps in making long range forecasts.

Let’s start with a quick overview of Monday and Tuesday’s weather conditions.  On Monday a storm system will dive into the central Great Lakes, Milwaukee will be on the edge, but still close enough to see a few flurries and a glancing shot of cooler air.  The chillier air will not arrive until the afternoon, by then our highs should be in the mid to upper 20s in most spots.  The big story on Monday may be the wind, it will  gusty out of the northwest at 15-25 mph.  This should keep wind chill values in the single digits to teens all day long.

By Monday night the cooler air settles in as skies clear.  Anytime we see clear skies now with snow on the ground, temperatures can drop very quickly.  Inland locations should see single digit lows on Tuesday morning, with low teens next to the lake.

By Wednesday-Friday(30th-1st) another storm system will take shape.  This storm appears that it will just bring some light snow and colder temperatures to our area.  This storm system corresponds to the storm that made its way through the U.S. back on October 30-31.  This is according to the ‘LRC’.  What is the ‘LRC’? 

  • A unique weather pattern sets up every year between October 1st and November 10th
  • The weather pattern cycles, repeats, and continues through winter, spring and into summer.  Identifying the cycle length helps tremendously when making long range weather predictions.
  • Long term long-wave troughs and ridges become established and also repeat at regular times within the cycle.  These dominant repeating features are a clue to where storm systems will reach peak strength, and where they will be their weakest.
  • The LRC is a winter-long pattern!  There is a pattern! It isn’t just one long-wave trough, storm system, or ridge. It is a sequence of troughs and ridges that are cycling across the Northern Hemisphere.

To put this in very simple terms, the weather pattern that occurs in October and November repeats thru the Winter, Spring, and into the Summer. The cycle length will vary each year. I’ve seen cycles of 42-46 days, 48-52 days, etc. The easiest way to view the LRC is to look at maps in the middle of the atmosphere, the 500mb level. The 500mb level is really a good spot to analize the trough(lows) and ridge(highs) positions to help determine the long term longwave ridges and troughs. At the 500mb level you also don’t have to factor in friction or surface moisture. Since the pattern is unique each year you may be wondering what some of the features are this cycle.

Here are the dominant features that are becoming evident for 2009-2010 and where they are likely to set up.

  • A trough near Colorado
  • A ridge across the eastern Pacific Ocean between 135º W and 155º W
  • A ridge from the Gulf of Mexico extending northeast to the Atlantic Ocean east of the southeastern United States

Now that we have gone over the LRC, let’s see how our next storm compares to late October.  The map below is an archived 500mb map from October 30, 2009.  This shows a large trough over the Plains extending into Canada.  There are also ridges or areas of high pressure over the Southeast and off the California coast. 

Now we fast forward to roughly 60 days later, or the cycle length this LRC year.  That takes us to this week.  The map below is a forecast 500mb chart from the 18Z GFS for December 31 at 6pm…or 00Z January 1.  This map clearly shows the large trough from the Plains into Canada.  The little x’s are vort. maxes with one over Texas and another over North Dakota.  When Milwaukee see’s a big winter storm we need the northern branch of the jet stream and the southern branch that contains Gulf moisture to phase or become one.  The map below shows no phasing at this level as the storm moves across the nation’s mid-section.

So what does this mean for New Year’s in Wisconsin?  As the storm finally get its act together after it passes by us, it will pull in arctic air which will pour in on New Year’s Day and likely last for several days.  The map below is a forecast surface map for late New Year’s Day.  Notice our storm that passed by is now more organized along the East Coast producing rain and snow.  For Southeast Wisconsin we will see gusty north winds and falling temperatures.  Highs will be in the teens and lows in the single digits very likely for next Saturday/Sunday 

For this week it looks like temperatures will end up below average.  There will be periods of light snow and flurries, but accumulations look light.  The arctic air should win out this time and keep the storm from getting organized over the Midwest.  If you are traveling to the East Coast around New Year’s that storm may have a bigger impact there.  Things could change since this is days away, but I’m fairly confident in this forecast.

If you want more examples of the LRC, please see previous blogs.  Or if you have questions please post them in the comments section of this blog.  Thank you for stopping by and have a great week!

Jeremy Nelson


2 Responses

  1. Thanks for all the info (very interesting stuff) 🙂

    • Dan,

      The snow pack and arctic air can push storms south this time of year. I think the next week we’ll see a couple of good shots of arctic air, but there will at least be some moderation between cold spells.


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