Derecho potential? ‘Widespread damaging wind event’ possible

Over a 30-year weather career, I can probably count on one hand the number of days I've forecast a derecho.  Today is one of them.

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The National Oceanic and Atmospheric Administration's Storm Prediction Center used the phrase "widespread damaging wind event" to describe the potential storms expected to race southeast across Minnesota today.

Forecasting severe weather is always tricky, but I concur with that description of what is possible today.

'Enhanced' risk

Let's start with the risk zone. NOAA's SPC has upgraded the risk zone over southern Minnesota from slight, to a higher "enhanced" level today.

There are still questions as to the precise timing and track, but NOAA's SPC singles out the Twin Cities metro as being in the possible path of a damaging wind event this evening. Here's the wording from today's convective outlook product.

The more intense supercells will be capable of producing at least isolated significant hail and a few tornadoes, while the more widespread and significant threat will be damaging winds with the embedded supercells/bows as the convection grows upscale (acknowledging the aforementioned convective evolution uncertainty).

The severe MCS is expected to pass near or a little south of Minneapolis this evening along the warm front/buoyancy gradient, and then continue into southwestern WI by early tonight.

Storm timing

Storms that formed in Montana last night are already severe and sweeping through North Dakota. They will likely turn southeast and race across Minnesota late this afternoon into this evening.

NOAA's mesoscale models still differ on precise location and timing of a potential bow echo packing damaging winds tonight. To my eye the highest probability window for damaging wind potential in the Twin Cities is between 6 p.m. and 9 p.m. tonight. A bow echo with damaging winds may be on the doorstep of the Twin Cities by 6 p.m., and race at 50 mph into the central metro core around 7 p.m. tonight.

NOAA's High-Resolution Rapid Refresh model has favored a bow echo racing from near Fargo, N.D., along Interstate 94 in Minnesota through Alexandria, St. Cloud to the Twin Cities by around 7 p.m. tonight.

30 percent chance of wind damage

It's rare for NOAA to issue a 30 percent chance of damaging winds for Minnesota. But that's what they did today. NOAA cites the Twin Cities as being in the zone for a potential "significant severe" event tonight.

Bottom Line: There is a significant risk of severe weather across central and southern Minnesota today and tonight. Details on timing and precise location are still uncertain, but a damaging wind event is possible, even likely. Expect severe weather watches and warnings, and stay situationally aware.