April is a transitional month in Northeast Wisconsin. Winters finally loosens its grip and spring weather kicks in. Yesterday’s blog covered average temperatures and precipitation in April, but what can we really expect? Hopefully the forecast below can provide you with some answers.
The techniques for making the forecast have had success. My March forecast was nearly right on. To predict long-range weather, I use a combination of extended computer models and teleconnections. But more than anything, I also rely on the weather pattern which set up last fall.
That pattern, which is better described as a cycle, has lasted 45-50 days and is separated by a major storm. The list below highlights the major storms and their time apart.
- October 26-27: Major wind storm with gusts reaching 52 mph
- Blizzard Aiden, 45 days later, 11.0” of snow
- Winter Storm Connor, 49 days later, more than 20” of snow in Racine
- Winter Storm Francesca, 47 days later, 17.8” of snow
- If the cycle continues, the next major storm is between May 7th-12th
The best way to analyze the pattern is by viewing long-wave troughs and ridges in the upper atmosphere. Notice how all of the major storms took on similar characteristics at 500 mb in the graph below. For a more detailed explanation of the major storms in each cycle check out this video.
Let’s get to the forecast….
I won’t spend a lot of time here as it falls in our seven day forecast. The period will be highlighted by a storm on April 3-4. We will see a mix of rain and snow on the morning of the 3rd. The mix will primarily be for northern areas, with rain dominating to the south. The storm begins to exit on the 4th but will still provide the opportunity for light rain and possibly flurries.
The average high for this period is 51°-52°. I am expecting temperatures to be near to above this mark on the 9th and 10th. The warmer air will be courtesy of southerly winds ahead of a stronger storm arriving around the 11th. This storm lines up with other notable storms in the cycle. One of those was Winter Storm Dana on February 20-21st which dropped 13.9” of snow on the area. This doesn’t mean we will be hit hard by snow. It is more likely we get rain and a few thundershowers with strong winds.
This has been a relatively quiet period in the cycle. During the same part of the cycle in November, our high temperatures ran 1° above average. However, during the same stage of the cycle in January and February, our highs were below average.
Here’s where it gets difficult. Since November conditions are more like April, I favor the November stats. However, there are other factors to consider. La Nina conditions, which were consistent with cold temperatures this winter, will still be present. Another influence will be the snow pack. Most of our snow should be melted by this point, but a stubborn snow pack to the north could still keep our temperatures cool. With this in mind I am expecting near to below average temperatures.
This period could be our first taste of severe weather on the season. I am expecting a potent storm to move through, with the best severe dynamics to our south. On November 22, which lines up with this part of the cycle, tornadoes hit southeastern Wisconsin. Tornadoes that late in November is extremely rare! These dates also line up with the February 28th severe weather outbreak which produced wind damage from the Southeast to Pennsylvania. This is a period that definitely deserves keeping an eye on…. It will also likely be preceded by a day or two of warmer temperatures.
Another storm will likely move through around this time. Severe weather can’t be ruled out, but I don’t think this storm will have the severe potential of the April 18th -21st storm.
Here’s another time period that bears watching. This time in previous parts of the cycle led to major severe outbreaks. One was November 29th with the other on March 8th. Take a look at the storm reports below.
You might be thinking if all of the reports are to the south, won’t the storm miss us completely? There are two sides to the argument. The March storm did just miss us to the south. However, we did see rain during the November system. Since it was so late in the season, the severe set up was more favorable to the south. With warmer weather kicking in during late April, the area with great severe weather dynamics will move north.
Not completely satisfied with the forecast? Here are a couple other key points for April.
- Aside from warm days around April 9th and 10th, the first half of April will be cool compared to average
- An active weather pattern will produce more above average days for the second half of April
I hope you enjoyed this forecast. If you have any questions, please comment below. Now it’s time to wait and see what happens!
Meteorologist Andrew Thut