Isolated to scattered severe thunderstorms will develop around a dome of high pressure reasserting itself over the Southern Plains this week. A parade of mid and upper-level disturbances will make breaches in this dome, resulting in rounds of thunderstorms.
Monday’s storms will be the least threatening. Isolated severe storms may develop in northern and central Texas and south-central Oklahoma late this afternoon ahead of a cold pool at the surface. Later, storms may form clusters in eastern Texas as they approach Louisiana. Meanwhile, scattered thunderstorms, a few of which may become severe, will develop over the Northern Rockies this evening ahead of a broad upper-level low pressure system. Primary threats in both areas of concern will be damaging wind gusts just ahead of the storms with a slight chance for pea to nickel sized hail.
In the Northern Rockies, an incoming upper level trough will generate lift. Isolated thunderstorms will develop this afternoon ahead of it, becoming more scattered throughout the day as it gets closer. A narrow jet streak, a locally strong region of wind in the jet stream, will cross central Montana Monday evening. The strongest storms are most likely to develop in its southeastern vicinity as it travels northeastward. The timing of the best jet stream dynamics will occur after day-time heating so the extent of severe weather here will be limited. But a dry layer and cold temperatures associated with the upper-level low should be sufficient for the development of damaging wind gusts and isolated cells with pea to nickel sized hail.
In the Southern Plains, a mesoscale convective complex (MCC) of thunderstorms dousing the scorched plains of northern and central Texas Sunday night and Monday morning has prompted the development of a strong cold pool at the surface. By early afternoon, the MCC will begin to dissipate, but the boundary of its cold pool will continue to race eastward, generating new thunderstorms in a more unstable environment. This cold pool will be accompanied by a weak shortwave trough of low pressure crossing Kansas, Oklahoma and northern Texas in the mid and upper levels of the atmosphere. The presence of the shortwave will act to enhance lift associated with the cold pool and generate shear in the wind profile. Shear is change in wind direction and speed with height. Isolated thunderstorms may also develop over northern Oklahoma and southern Kansas but being farther from the cold pool, these storms will be less likely to have severe characteristics.
As the night evening progresses, storms may cluster further east in Texas and Oklahoma and impact larger swaths of area. With the loss of day time heating, hail will be less likely with these clusters, but damaging wind gusts will still be possible. With moist inflow from the Gulf of Mexico, these clusters of storms will persist overnight as they cross Louisiana, maintaining an isolated threat for damaging wind gusts into Tuesday morning as far southeast as New Orleans.
Late Tuesday afternoon and early Tuesday evening, the severe weather threat will escalate over the Northern Plains with the development of supercells ahead of a southeastward moving cold front and kinks in the upper-level flow. These supercells will be capable of producing damaging wind gusts, up to quarter sized hail, and perhaps an isolated tornado. Strong thunderstorms are also expected over the Northern Rockies, but the severe threat is not likely to be as widespread.
Later Tuesday evening, thunderstorms will become more scattered and eventually merge into a southeastward propagating squall line. With the development of the squall line, the threat in eastern North Dakota, northeastern South Dakota and northwestern Minnesota will shift to powerful wind gusts ahead of the line, with small hail also possible.
Wednesday, the same cold front will cross the Central Plains, Minnesota and Iowa. A shortwave will develop in part from the cold pool of Tuesday night’s storms and will enhance lift over Iowa and Minnesota. With a hot, humid and highly unstable airmass ahead of the front, scattered to perhaps widespread severe storms are likely across eastern Nebraska, Iowa, and southern Minnesota.
The severe weather threats for Tuesday and Wednesday need to be closely monitored. We will monitor the situation and provide updated information throughout the week as we know more.