A new round of severe weather will affect portions of the Southern Plains this Wednesday, as an upper-level trough moves into the Southwest while a surface low pressure develops to the east. Over the Southern Plains a new surface low will enter the picture, increasing the risk for scattered strong to severe thunderstorms from central Montana down toward northeastern Nevada and northwestern Utah. It’s this new storm system that will fuel the risk for days of severe weather through midweek for the Northwest and through the weekend for the Northern Plains.
Our main focus this Wednesday will be centered on the weather for the Southern Plains, specifically across southern Kansas into northern Oklahoma. The beginning of the day will be quiet, with very hot and humid conditions, providing a favorable air mass for storms to erupt during the late afternoon. These storms will form across eastern Colorado, some of which may be severe. They will then track to the east, possibly organizing into a Mesoscale Convective System (MCS) Wednesday night as they move along the Kansas/Oklahoma border. Given the nature of the torrential rain with these thunderstorms, flash flooding will be a concern. This convective system will pack a punch, containing damaging winds and possibly large hail. There is the low risk for a tornado, but the risks exists, especially in eastern Colorado. The complex will weaken by sunrise, evolving into scattered storms over the western Ohio River Valley by Thursday morning.
Back toward the Northwest, scattered storms and multiple lines of storms will form late in the day across a large region. Some of these storms are expected to be severe, packing winds of over 58 mph and possibly some hail. These storms will linger into Thursday morning, but they should be sub-severe as they lift to the north and east toward Canada.
Looking ahead to the rest of this week, as the storm over the Northwest tracks east so will the thunderstorms and thus the severe weather threat. Scattered severe thunderstorms will be present through much of the day, especially during the latter half. Damaging winds and hail will be the main risk once again, but isolated tornadoes cannot be ruled.
The other low pressure over the Southern Plains will also track east. A very large area will be at risk for isolated to perhaps severe but scattered thunderstorm activity on Thursday. This includes the Ohio and Tennessee River Valleys, as well as the Appalachian Mountains. Multiple lines of storms will develop late in the day before weakening by early Friday morning. A few lingering showers and storms may be present over the Ohio Valley after daybreak on Friday. There will also be a risk for flash flooding due to the combination of these heavy thunderstorms and saturated ground.
The threat for severe weather will diminish across the East by Friday. Meanwhile over the Northern Plains, due to that second low pressure there is the potential for a severe weather outbreak. A cold front associated with the synoptic scale system will allow for the rapid development of severe thunderstorms, and even a few supercells, late in the day. All threats will be in place, including large hail, damaging winds, and several smaller tornadoes.
That threat will then take a turn to the southeast for the start of the weekend on Saturday, taking aim at the western Ohio River Valley. As this event comes closer, we’ll have more details on the timing.