We are seeing weather systems (Mid-latitude cyclones) move through every 3-7 days as upper-level troughs of low pressure move from Eurasia across the Pacific Ocean and into and across the United States with fair weather upper-level high pressure ridges in-between them. The average of this has resulted in a mean trough over the NW and a mean ridge over the Southeast allowing for a clash of temperatures on average in the battle (baroclinic) zone between the two and resultant rain and thunderstorms. See the system from Sunday 1 now in SE Canada and NE U.S. with the next 2-4 systems to our West:

So far Temperatures in April have averaged cooler than normal Northwest and warmer than normal Southeast:

As a result of the location of the warmest and most unstable air being farther South and East than is typical for this time of year most of the severe weather has also been farther South and East compared to normal. Below are the climatology maps showing where most severe weather and tornadoes usually occur this time of year:

Instead THIS April the concentration is not in the Southern Plains and Midwest:

When there is a lack of clashing air masses when either below-normal temperatures or warmer than normal temperatures prevail the number of tornadoes goes down. For example May of 2018 mostly warm and tornado count down, but May of last year a clash in the middle of the nation and the count was up:

And just like magic (just like SCIENCE) the majority of severe weather was in the clash zone:

If we are lucky the pattern will change as we end April and move the severe weather risk farther to our West and North.

IF the ECMWF weeklies are correct it might not happen permanently until the second half of May or June:

In the shorter term the numerical variants are suggesting at least a break in the storminess after Saturday.

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