Friday, March 5, 2021

Significant Pattern Change Could Bring Severe Weather, Heavy Rain to the Plains, Mississippi Valley, Ohio Valley

 

Jonathan Erdman
Published: March 5, 2021



A significant weather pattern change could ignite severe thunderstorms and heavy rain over parts of the Plains, Mississippi Valley and Ohio Valley next week.

Now that meteorological winter is in the rearview, a somewhat classic stormy spring pattern is expected to set up in the U.S. next week.

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The jet stream is forecast to take a sharp southward plunge over the western U.S. by early next week. That will lead to welcomed mountain snow and rain in California and snow in other parts of the Rockies.

The jet will rise northward into the East downstream from that U-shaped western trough and fuel a dose of spring fever in the Midwest and East.

(MAPS: 10-Day U.S. Forecast Highs and Lows)

When this pattern sets up in spring, it often results in severe thunderstorms and/or flooding rainfall in the nation's mid-section.

This is because warm and more humid air is drawn north from the Gulf of Mexico, topped by colder, drier air several thousand feet above the ground. Strong jet-stream winds increase wind shear - the change in wind speed and/or direction with height - that can support severe thunderstorms.

While the overall pattern is suggestive of a risk of severe weather, the key details, including how widespread and numerous the severe thunderstorms will be, the most at-risk areas, the magnitude of the tornado threat and the exact timing aren't typically predictable this far out in time.

Still, this is a forecast worth paying attention to over the coming days as this forecast comes into focus.

Here's what the general forecast looks like right now.

First Phase

The first round of active weather in the nation's midsection looks to kick off around the middle of next week.

Low pressure could draw warm and somewhat humid air as far north as the western Great Lakes, fueling at least scattered thunderstorms, some of which could be severe, from the upper Mississippi Valley to Oklahoma and Texas. A few rumbles of thunder may be possible as far north as the Twin Cities.

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Rain falling over areas with lingering snowpack, or areas that just melted their snowpack, may lead to some flooding in parts of the upper Midwest.

Some wet snow is possible in parts of the northern Plains into northern Minnesota, though exactly where that snow could fall and how much remains highly uncertain at this time.

(MORE: U.S. Spring Flood Outlook)

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Conditions might be right for the formation of a few strong to severe thunderstorms in the Central and Southern Plains on Thursday.

Second Phase

After Wednesday, most forecast model guidance suggests a frontal system will eventually stall in an east-to-west fashion from the Ohio Valley to the Plains states.

This could serve as a focus for heavy rain as soon as next Thursday, March 11.

Then a potent lobe of upper-level energy from the western jet stream trough could swing into the Plains next Friday into Saturday, March 12 and 13.

This could lead to another round of severe thunderstorms next Friday into next Saturday depending on how that lobe of energy moves into the Plains and how much warm and humid air is not contaminated by clouds and rain. Heavy rain is also a threat in parts of the Southern Plains into the Ohio Valley.

(MORE: March Begins Ramp Up of U.S. Tornadoes)

With some colder air arriving, there could also be some snow, possibly heavy, in parts of the High Plains into the upper Midwest late in the week.

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The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.


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