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A strong storm system has begun its trek across the United States and is delivering widespread hazardous weather. It arrived over the weekend in California where it produced thunderstorms, flooding and heavy mountain snow. <a href="https://www.washingtonpost.com/nation/2024/04/01/highway-1-california-big-sur-landslide/" target=_blank>Heavy rain triggered a landslide</a> in Big Sur, causing chunks of scenic Highway 1 to fall down a cliff, closing the road and stranding 1,600 people.

Now the storm system is charging eastward and will spare few areas.

On Monday and Tuesday, it will sweep through the Central and Eastern states, bringing the threat of severe thunderstorms and tornadoes. Widespread large, destructive hail is likely too. Some areas — especially from the Midwest to the Mid-Atlantic — could also see flooding rain.

The National Weather Service’s Storm Prediction Center upgraded the risk of severe storms to Level 4 out of 5 in central Oklahoma on Monday, and in much of Ohio on Tuesday, because of the possibility of large hail and strong tornadoes. <a href="https://www.spc.noaa.gov/products/watch/" target=_blank>Tornado watches</a> were issued into Monday evening for areas of northern Texas, much of central and eastern Oklahoma, eastern Kansas and western Missouri, including Kansas City.

The storm’s last stop will be in New England midweek, where some areas could see an intense late-season snowstorm.

Spring is known as one of the most chaotic times for seriously disruptive weather in North America. Clashing air masses — stemming from crescendoing seasonal warmth and lingering winter cold — can brew powerful weather systems such as this incipient storm.

NOAA/WPC

After affecting California with flooding and heavy mountain snow, the same parent storm system — a disturbance at the upper altitudes — is working to spawn a new low-pressure system east of the Rocky Mountains. That new low will be key in brewing back-to-back days of severe weather over the Plains and Midwest, with the risk of very large hail and a few tornadoes.

Ahead of this new low-pressure system, high pressure parked over the eastern United States is causing a ribbon of warm, moist air from the Gulf of Mexico to swirl into the central states that will serve as fuel for severe storms.

Meanwhile, a jet stream dip will nudge into that warm, humid air mass. It will kick up storms over the course of several days. The added high-altitude winds associated with the jet stream will induce shear — a change of wind speed and/or direction with height. That could induce rotation and a tornado risk within some of the storms.

Sunday featured an “appetizer” storm of sorts that allowed one lone rotating supercell to track more than 200 miles across southeastern Iowa and Illinois. It prompted over 50 reports of large hail, including a few stones approaching tennis ball size in Macon County, Ill.

Monday’s storms could feature even bigger hail that is likely to approach baseball size in spots.

A pronounced threat of severe weather will develop Monday as the storm system becomes better organized over the central states. A Level 3 out of 5 enhanced risk of severe storms stretches from the Dallas-Fort Worth metro area to Louisville and includes the Missouri cities of Springfield, Joplin and St. Louis.

Within that Level 3 zone, the Storm Prediction Center added a Level 4 out of 5 risk in central Oklahoma, including Oklahoma City, Norman and Tulsa, and a sliver of Texas that includes Wichita Falls, noting the potential for “very large” hail and a couple of strong tornadoes.

A Level 2 out of 5 risk expands to San Antonio, Austin and Waco in Texas; Charleston, W.Va.; Cincinnati; and Indianapolis.

Four zones, in particular, will need to be monitored:

A warm front from central Missouri to Indiana. The warm front could increase spin and the tornado potential starting early in the afternoon. It’s likely that storms in this area could also yield an overnight tornado threat.

The “triple point” in north-central and northeast Oklahoma, mainly between Oklahoma City and Tulsa. That’s where dry air, moist air and cold air will all meet near the center of low pressure. That would boost the risk for a couple of tornadoes. An isolated strong tornado can’t be ruled out.

WeatherBell

In Oklahoma and Texas along/east of Interstate 35 from Oklahoma City to Dallas. That’s where storms will be forming along a dryline — the leading edge of bone-dry desert air from the Southwest as it encroaches into humid air — and could become rotating supercells. If the storms remain isolated and don’t interfere with one another, a couple of tornadoes are possible, along with “isolated extreme hail sizes,” according to the Storm Prediction Center. Storms will eventually merge and the threat will shift to damaging straight-line winds.

A squall line in the southern Plains. Once storms do merge, they’ll become a QLCS — a quasi-linear convective system, or a kinked squall line with transient embedded circulations. That would translate to widespread damaging winds and a few quick-hitting erratic tornadoes. That QLCS would propagate east into the night.

As the storm system heads east Tuesday, it will form a zone of Level 3 enhanced risk from Huntsville, Ala., to Akron, Ohio. Within the Level 3 risk area, a Level 4 risk was added for much of Ohio, including Columbus, Cincinnati and Dayton.

“A potentially substantial severe weather outbreak — possibly including a few significant/long-track tornadoes — is evident for Tuesday afternoon and evening, with highest probability centered over the Ohio vicinity, and extending southward across the Tennessee Valley,” the Storm Prediction Center wrote.

A Level 2 risk extends from the Gulf Coast to near Cleveland.

Widespread thunderstorms will form and could quickly evolve into messy lines with embedded areas of rotation. That will pose a risk of tornadoes in addition to damaging winds and hail.

Flood watches extend from the southern half of Ohio through much of West Virginia and northeast Kentucky. That’s where thunderstorms may train, or move repeatedly over the same areas, resulting in rain totals of 2 to 4 inches.

While Washington and Baltimore are under a level 1 out of 5 “marginal” risk Tuesday, the primary concern for severe weather should stay west of the Appalachians. A wedge of cooler air east of the mountains should mitigate severe weather risk.

Snowstorm is possible in interior New England midweek

The storm system’s final act could be a late-season snowstorm.

On Tuesday, the same jet stream dip tied to the severe thunderstorms in the central states will become absorbed into an even stronger upper-air disturbance over the Great Lakes. That disturbance will tug cold air south and could flip rain to snow in Wisconsin by late Tuesday, and even Chicago on Tuesday night.

Michigan may see some snow into Wednesday, but the state could also be in the “dry slot,” or a slice of dry air wrapping into the storm system and cutting back on totals.

Then the parent disturbance will help a new coastal storm to develop east of Long Island. While rain is most probable in coastal areas, heavy snow could break out in interior northern New England on Wednesday and Thursday. It is too soon to predict amounts, but some areas could easily see at least 6 to 12 inches, especially in the high elevations.

The storm began Saturday as it swung an atmospheric river into the West Coast. The rains continued Sunday, with flood watches covering Southern California, including San Diego and Los Angeles.

In San Diego, 1.30 inches fell Saturday, <a href="https://twitter.com/eyesonsdskies/status/1774433367481794967" target=_blank>setting a record for March 30</a>. High water flooded several streets. Around Los Angeles, 2 to 3 inches had fallen through Monday morning.<b> </b>Lakewood, in southern Los Angeles, had tallied 4.03 inches, while Harbor City was up to 4.74 inches.

Santa Barbara had received 4.10 inches of rain through Monday morning, and the mountains just to its north have posted up to 6.88 inches. Flooding submerged five vehicles and forced the closure of Highway 101 southbound at San Ysidro Road in Santa Barbara County on Saturday night.

The Bay Area was <a href="https://twitter.com/US_Stormwatch/status/1774249406638030993" target=_blank>hit by thunderstorms</a> late Saturday, which <a href="https://twitter.com/RobMayeda/status/1774224727730708702" target=_blank>prompted a warning</a> in Santa Clara County and <a href="https://twitter.com/hannah_hagemann/status/1774205005115129984" target=_blank>produced hail in Santa Cruz County</a>.

In the Sierra Nevada and mountains east of Los Angeles, cold air banked against the high terrain produced heavy snowfall. The Mammoth Mountain ski area in the central Sierra got 2 feet of snow, and 14 inches fell at Big Bear Lake in the mountains northeast of Los Angeles.

Harvard University, B.A. Atmospheric Sciences

Matthew Cappucci is a meteorologist for Capital Weather Gang. He earned a B.A. in atmospheric sciences from Harvard University in 2019, and has contributed to The Washington Post since he was 18. He is an avid storm chaser and adventurer, and covers all types of weather, climate science, and astronomy.

Matthew Cappucci

National Weather Association, Digital Seal of Approval

University of Virginia, BA in environmental science, 1998

University of Wisconsin, MS in atmospheric science, 2000

Jason Samenow is The Washington Post’s weather editor and Capital Weather Gang's chief meteorologist. He earned a master's degree in atmospheric science and spent 10 years as a climate change science analyst for the U.S. government. He holds the Digital Seal of Approval from the National Weather Association.

Jason Samenow

Major storm to sweep United States with severe weather, snow, flooding

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