Ag Weather Forum

Last week in this blog space, I mentioned we need to follow the location of an upper-level ridge to find out where hot conditions were going to be this summer. You can read more about that here: https://www.dtnpf.com/…. Later this week, that ridge is going to park itself in the Southeast U.S. and stick around that area through next week. That feature will cause heat across the southern tier of the country going forward, but its northern edge is usually a good spot to find increased chances for precipitation. For the next week or longer, that northern edge will be near the northern end of the Corn Belt, but most areas in the region will see increased chances for precipitation.

That ridge will shift into the Southeast on Friday, June 28, or Saturday, June 29. Either way, it will anchor itself to that general area or even a touch farther west toward the Southern Plains going through at least July 9. That is the end of the ensemble runs of the American GFS and European ECMWF models. Longer-range versions of those models have that ridge heading farther west after that time. So, for the next two weeks the southern ridge will bring consistent heat from Texas to Kansas eastward through the Mid-Atlantic. Between storm systems, it will reach farther north.

And there will be a steady supply of storm systems. System after system, trough after trough will move from the North Pacific through Canada, going over the top of the ridge throughout the next two weeks. While they come in rapid succession, there will still be a couple of days between storms. While the steady stream of storm systems should pass mostly through Canada, the cold fronts to each storm are likely to move into and through the Corn Belt on a regular basis as well. Being on the northern edge of a ridge of hot temperatures and at least some access to the Gulf of Mexico moisture pool, showers and thunderstorms that develop in the Corn Belt are likely to be expansive and could be robust, with risks of severe thunderstorms most days. The northern edge of the ridge creates a colloquial "ring of fire" where these sorts of conditions are likely. Instead of the garden-variety type of scattered severe storms, the ring of fire is more notorious for organized severe weather threats, coming in clusters and lines meteorologists refer to as Mesoscale Convective Systems, or MCSs. An MCS can spread large hail and wind damage over larger areas and could sometime result in a derecho. A derecho is a long-duration windstorm that causes hurricane-force winds over long distances. In addition to the increased severe threat, we may also see some heavy rain at times, which may be a blessing or a curse depending on where that occurs.

Mostly, these fronts will be moving, but they should stall somewhat on the northern edge of the ridge. In doing so, thunderstorms can train over an area for long periods of time, resulting in heavy and sometimes flooding rain. Such was the case last week when multiple rounds of heavy rain went through the northwestern Corn Belt across southeastern South Dakota, southern Minnesota, and northwestern Iowa. A wide band of 4 to 8 inches of rain with some spots over 10 inches have caused catastrophic damage in some areas and flooding of local rivers. Risks are not high for that sort of damage to happen again, but flooding may be a good possibility. You can read more about the damage from last week and weekend here: https://www.dtnpf.com/….

But farther south, hot and dry conditions led to concerns over flash drought, or quick-developing drought in areas that were previously wet this spring in the Southern and Eastern Corn Belt. With the new configuration of the ridge developing over the next few days, that should lead to an increased chance for rainfall for these southern areas to get more rain. Models are favoring Kansas into Iowa and east through Ohio as the primary areas to see the heaviest rainfall. And through July 9, have as much as 2 to 4 inches of widespread rainfall. Undoubtedly, there would be areas that see heavier rain than is forecast.

But as we know, models are typically poor at determining where thunderstorms will go, especially more than just a couple of days out. Therefore, we should still be concerned over those northwestern areas that have had the flooding. While models are not as heavy there, they are still insisting on some rain and any precip would be detrimental for the recovery efforts.

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John Baranick can be reached at john.baranick@dtn.com

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