Ag Weather Forum

The jet stream can generally be thought of as the storm track. It is where the majority of storm systems originate, and the movement of the jet stream can give you the basic idea on where those storms are going to track. However, under certain conditions, storm systems can either get cut off from the jet stream or develop from other means. Without a jet stream affecting their development and movement, their track can be erratic or wobbly and their speed is usually very slow.

Such has occurred during this past weekend as two jet streams have split across North America. The stronger, northern one has found itself largely over northern Canada, while the weaker, southern one stretches from southern California through the Gulf. In the area in-between, several disturbances have found themselves, seemingly drifting slowly through weak steering currents.

During the Sept. 12-15 period, one of those disturbances moved from the central Rockies into the Northern Plains and up through central Canada. Showers and thunderstorms were widespread as the system was able to tap into the abnormal heat and humidity in the driftless area between the two jet streams. The multi-day rain period produced some heavy amounts over 3 inches in some cases in the general region.

But this isn't the only meandering disturbance out there. There is another that is currently found in the central Rockies. This one is forecast to move into the Plains today, Sept. 16. Like its predecessor, it should be a slow mover. These types of systems are not forecast as well as those tied to a jet stream, but the general forecast is for it to drift eastward into the Midwest during the weekend before getting pushed eastward early next week.

Some areas will have four or more days of shower chances that could mean heavy rain. However, these types of systems are also ones that cause more sporadic showers and thunderstorms and are less organized than their jet stream counterparts. This makes the forecast difficult to pin down the "where, when, and how much" questions that are the most important for those of us on the ground.

With that in mind, a general 1 to 2 inches of rain with pockets of heavier amounts are in the forecast for much of the Plains and Midwest west of the Mississippi River. The system moves a little quicker as it gets eastward during the weekend into early next week, and rainfall amounts drop down to more like an inch or less east of the Mississippi River.

But with the multiple-day rainfall event, there are bound to be some areas that see much more precipitation than forecast. And similarly, the sporadic nature to the rainfall could mean some areas get completely left out.

Those from Arkansas and Mississippi up through the Northeast, which have been on the drier side for the last six weeks or longer, have seen drought conditions rapidly increasing, bringing a poor end to the growing season for agriculture, and causing the water on rivers to fall to very low levels.

That includes both the Ohio and Mississippi Rivers -- major transportation routes for the country. Some of this rainfall will undoubtedly help, especially for the Mississippi River, but it will not be enough to reverse the dryness and drought conditions that have quickly built up in the region. Much more rain will be necessary here, but the long-range forecast is not promising.

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

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