Busy March for twisters to end with another multi-day event

A dip in the jet stream is blasting toward the central United States and poised to wreak a new round of havoc to close out an active month. It’s part of the same evolving pattern that brought a severe weather risk to the Pacific Northwest earlier this week.

With numbers north of 12 dozen confirmed, March has already witnessed about twice the average for tornadoes. The map above shows the tracks of those which have been entered into the National Weather Service’s damage assessment toolkit.

Perhaps in proper style, we’re staring down a several-day storm threat to end the month Saturday through Monday.

Sufficient moisture should get into Oklahoma and Kansas on Saturday to mix with enough wind shear aloft for rotating supercell thunderstorm development. Large hail may be the primary risk, but tornadoes are also possible in areas that get near or past 60 for dew points.

The afternoon has the early-season semblance of a passable dry line, a wind-shift conduit for thunderstorm formation. It seems like a chase day for those in the region. Several targets exist, with options for “storm of the day” ranging from beautiful mothership lobbing ice chunks to perhaps a sunset type of tornado producer.

Sunday has the largest threat, by available warm sector and overlap of wind shear plus moisture. It should also more squarely center on the climatologically favored Ark-La-Tex to Mississippi Valley region.

There will certainly be strong, long-tracked tornado potential if the event comes together right — always a question mark from this range, but also now somewhat favored with any significant low pressure plowing into warm/humid air.

This storm has a couple things that may help it try to produce, including what looks like more moisture than prior systems and subtler forcing. The latter may promote fewer thunderstorms challenging each other for dominance. The former is a little in question given time of year and remnants of the South Texas rainstorm moving east across the Gulf prior.

It has potential to be the fourth significant tornado event of March and could boost monthly numbers into the upper echelon since 1950. The most active March on record is 2022 with 234 tornadoes.

A top three finish for the month is within reach, all of the current of which have happened in the past decade. The second most is 208 in 2023 and the third most is 192 in 2017.

The mid-month outbreak that focused on the 14th and 15th was particularly intense. It delivered more than 100 tornadoes, including three violent EF4s and 11 deadly twisters that caused 23 deaths in the states of AR, MO, MS and AL.

While tornadoes come in swarms, and the deaths from them tend to group, having 11 separate killer tornadoes is historically notable for one outbreak. The 12 this year to-date is one behind a since-2012 high (through March 31) of 13 in 2023.

The long-term average for killer tornadoes through the end of March is six, according to analysis of Weather Service data.

Coming out of La Niña winter, spring tends to be active in the early season. There are also increasing signs that the cool season — winter and very early spring — is becoming more favorable for severe weather in a warming world. Both could partially explain yet another active March.

While no two years are exactly the same, decaying La Niña springs often feature vigorous and frequent incursions of powerful northern jet stream disturbances, especially through April or May.

The notorious April 2011 followed a La Niña winter.

It would be foolhardy to call for anything like that this year, but the month does look to start on the busy side. And April through June is the heart of tornado season, so big things can happen on short notice.

This analysis also appears in The Weather Retort.