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Thank you for stopping by the Weather Watch 12 Blog! If you love big swings in the weather, I think you will enjoy the final days of 2010 and the start of 2011!
For snow lovers in our area, this has been a frustrating month. Most areas in December saw anywhere from 8″ to 14″ of snow which doesn’t sound bad. But early snows during the month were erased when rain fell in parts of the area. And recent lake effect snows hit very isolated areas, leaving others with nothing.
That leaves us in the closing days of December with an official snow depth of just 1″ at Milwaukee’s Mitchell Airport, and of all things rain in the forecast!
The big storm will first push mild air our way, and as that begins to fall as patchy drizzle Wednesday Night, it may be freezing drizzle. This will be a close call, as air temperatures at the surface will be right around 32. That is why I think the best chance will be inland, and most icy spots(if they develop) forming on sidewalks, driveways, and secondary roads.
Below is the NAM precipitation forecast valid Wednesday Night at midnight. Notice the little areas of green, which could be patchy freezing drizzle.
By Thursday the warm air will arrive in full force pushing highs into the low 40s, and insuring that all precip. will be in the form of rain or drizzle. The main energy with the storm will not arrive until Friday. This is when the main area of low pressure will track to our west…again.
This will likely keep our temps in the 40s, while another snowstorm will take shape for parts of Minnesota. Below is the 18Z GFS forecast map for Friday at 6pm. The blue line with a zero on it is the 850mb temperature. This is the freezing line 1500 meters above the ground, and essentially the rain/snow line. That line is well west of our viewing area.
This storm fits very well into our cycling weather pattern. It appears that we are just about to complete the 2nd cycle of this years pattern. Let’s check out where we are, and compare it to the November version of the storm.
Below is the 500mb(middle of the atmosphere) forecast map for this Friday. I labeled the important features 1-6 for easy comparison. First check out the map below for Friday. The main features to keep an eye on is the trough that extends from the northern Plains back into the Southwest.
Now let’s rewind back to November when this part of the pattern last occurred. Below is the 500mb archived map from November 11. Now compare the features above, to the numbers 1-6 below. Amazing!
With the main longterm long wave trough located over the Plains and upper Midwest, I think you can now see why storm systems continue to fall into the same place, thus bringing rounds of snow over and over again to many of the same locations.
Now that 2 complete cycles of this years pattern are almost complete, I want to share some observations. Over the past several weeks I have done map comparisons on the pattern and discussed the likely cycle duration. One important point about the LRC that I don’t think I have talked about enough is the variation that can occur from cycle to cycle and season to season. My general thinking about the cycle duration for this years LRC has been around 47 days. The map comparison above you will notice is roughly 50 days.
As the troughs and ridges cycle in the northern hemisphere, blocking or ‘bumps’ in the highway can develop that may slow down the flow or speed it up. Not to mention the jet stream shifting due to seasonal effects. These are several reasons why a range of days should be used. When introducing the LRC over a year ago I was clear in this regard, saying I’ve seen durations of 42-46 days, 48-52 days, 58-62 days, etc.
Now that two cycles are almost complete, and a wealth of information is available, I think putting a cycle range of around 46-52 days on this years pattern is reasonable. When looking back this coming summer at each cycle, it is very likely this will average out to a duration in the upper 40s.
The long range forecast that I did back on December 15 is still valid, and should turn out to be very close. The one thing that will not happen is ‘warm’ weather for the Rose Bowl game in Pasadena. My comparison was off by about 4 days, and the trough is a little farther south, makes sense it’s late December. That means highs in the 50s on gameday. Hopefully Wisconsin can brin home another Rose Bowl Championship! I’ll be at the game and will share some pictures in the blog when I return!
Have a great day!