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Update: Due to Jeremy’s extensive and impressive post, I thought we would let this run another day. Our weather is pretty quiet right now. A nice Thursday on the way. A little rain/snow on Friday, but little if any accumulation. The home opener for the Brewers is still looking pretty crummy. Showers, wind, and cold with temps in the low 40s. Dress warmly. Thankfully, we have a roof.
Thank you for stopping by the Weather Watch 12 blog. Hard to believe another month has passed and we are talking about the first full month of spring! After a winter that produced above average snowfall, and slightly below average temperatures, it’s time to look ahead using the LRC, or Lezak’s Recurring Cycle. Remember, this is the only place in southeast Wisconsin that you will find long range forecasts based on the LRC!
The ‘LRC’ which stands for Lezak’s Recurring Cycle is a weather pattern theory based on the following:
- 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 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 analyze 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. The theory can be translated down to the surface(where we live), which we do in this long range forecast.
The cycle length will vary each year. I’ve seen cycles of 42-46 days, 60-62 days, etc. This year’s cycle duration is about 46-52 days. Overall most of the weather events have repeated about 47-51 days apart. After analyzing the pattern and surface results from October through March, I was able to get a very good idea of what should occur this April.
For this long range April forecast I will highlight when the most active weather and biggest temperature swings should occur during April.
Let’s start by looking at what a typical April looks like weatherwise in Milwaukee.
- Average Precipitation 3.78″
- Average Snowfall 2.6″
- Average High/Low (1st 48/32 & 30th 60/41)
Since the first several days of April are covered on the 7 day forecast I will only briefly touch on them.
Rain or snow showers are possible to start the month across the state on the 1st. A more impressive storm system should impact the region around April 3-5 with rain, wind, and colder temperatures on the backside of the storm. Some parts of the state could see wet snow before the storm ends. Certainly not great news for Brewers fans looking for a warm day for tailgating!
This storm lines up very well with the one that moved by the Midwest December 24-25.
If you want warm weather, this will be the timeframe for the first really good chance at seeing above average temperatures in April. This is the part of the pattern that I touched on at the end of the March forecast that was posted here in the blog on February 27. Here is what I stated then:
While many are hoping for an early Spring, I just don’t see it this year for Wisconsin. However, I do think the first good chance at highs in the 70s may be around April 7-11.
This part of the pattern has occurred like clockwork in the 3 previous times through the cycle. Each time producing a stretch of 2-3 days with temperatures at least 10 degrees above average! I think the warmest days should occur somewhere between April 7-11, and the first 70s of the season are possible.
Each time the big warm-up came crashing down as a storm system moved into the region. I expect that storm system to occur again around April 11 give or take a day or two.
Let’s look at the 500mb(middle of the atmosphere) charts for the 3 previous times thru the pattern. Here is the 500mb map from November 13, 2010 when an upper level low was over the upper Midwest. This produced some rain in the area.
Now fast forward 49 days to January 1, 2011. A strong upper low was over the upper Midwest. At the surface a strong cold front pushed through the region ushering in colder temperatures to start the new year. This storm produced a major winter storm in parts of the Plains.
Now jumping ahead 51 days to February 21, 2010. Another upper low was over the Midwest putting an end to a warm stretch of weather from February 14 to 18. The storm system helped to produce over a foot of snow in Green Bay on Feb. 20-21. While in Milwaukee there was over 0.75″ of precipitation!
Not only should April 6-12 bring a period of warmer weather, but also the potential for a wet storm system, likely toward the end of the period. While a majority of the storm should be rain in southeast Wisconsin. I wouldn’t be surprised if enough cold air mixes in on the backside of the storm for a chance of snow. Certainly possible this could produce a late season snowstorm somewhere in the upper Midwest.
Cooler weather is expected to settle in behind this storm, and should prevail until the next period of more active weather.
This time period could bring the first dose of severe weather to or very close to southeast Wisconsin. Previous parts of the pattern have had a southwest flow aloft, and also warmer surface temperatures. The above average surface temperatures in previous cycles have only lasted a coulpe of days.
Back on November 22 a southwest flow existed at the 500mb over the Midwest, with a large trough digging into the West and northern Plains.
On the surface, a storm system was pushing into the Midwest. On November 22, or roughly 150 days or 3 cycles prior to April 21, severe weather occurred over southeast Wisconsin and parts of the Midwest. Below is the SPC storm reports map from 11/22/10.
Now jump ahead 97 days to February 27 when the pattern returned with another favorable set-up for severe weather. This time the severe weather was more extensive and covered areas from the Plains to the Ohio Valley.
When this part of the pattern returns in April, another round of severe weather is possible. Something we will watch closely, especially if warm temperatures and enough moisture are in place over southeast Wisconsin.
Behind this storm system I expect a cooler stretch of weather, with the potential for rain showers around April 23 give or take a day. Hopefully the showers avoid April 23 or 24, the 23rd is the annual spring football game at Camp Randall Stadium in Madison, and April 24 is Easter. At least using the LRC we won’t be surprised if there is rain on either day.
The month should close with a good chance of a storm system in the Midwest. The previous 3 times through the cycle the precipitation from this potential storm has totaled 0.40″(November 29-30), 0.39″(January 17), and 0.64″(March 9). Once the storm passes the month should end with below average temperatures.
Before we look at the overall outlook for April, I want to show you roughly the time period that this month lines up with, and also the overall weather during those 30 days. I found it very fascinating!
November 5 to December 4
- Precipitation 2.04″ (below average)
- Temperatures +2.6
December 22 to January 20
- Precipitation 0.88″ (below average)
- Temperatures +3.0
February 10 to March 11
- Precipitation 2.50″ (above average)
- Temperatures +1.7
Really incredible that the three previous parts of the cycle all had above average temperatures! The precipitation, or lack of may be attributed to this 30 day window missing all the ‘signature’ storm this season.
April 2011 Outlook
- Precipitation – Near Average
- Temperatures – Average to Slightly Above Average
I won’t issue a snowfall forecast because pinning down snow amounts in April is very difficult, but will say I think we do see snow this month. Past the first week, I think the April 11-13 window some snow is possible if enough cold air works into the storm system in southeast Wisconsin.
Please feel free to ask questions about the LRC, the pattern, or anything weather related in the comments section of the blog. This blog is completely interactive and we love talking about the weather with our viewers!
Have a great day!