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It can’t be seen with the naked eye, but a curious weather pattern in the upper level atmosphere above the continental United States is forecast to generate unsettled weather and some big temperature contrasts into the weekend.

An “omega block” is expected to form from California eastward into the Ohio Valley, the National Weather Service Weather Prediction Center said on May 2. The blocking pattern is so named because its shape resembles the Greek letter omega.

The unsettled weather will begin with a swath of heavy rain, flooding and potentially severe weather from the Southern Plains into the Ohio Valley on May 2, stretching from Texas into southern Pennsylvania. The greatest risk will exist from southern and eastern Texas into Kentucky and the weather service has posted flooding advisories across southern Oklahoma.

A boundary of moist air along the cold front is forecast to stall in some areas, bringing repeated rounds of rain and storms, with a slight risk of excessive rainfall over portions of the lower Mississippi River Valley and parts of Texas, Arkansas and the southern Plains, the weather prediction center said.

Several rivers that have been flooded in Northern Texas could see a slight bump in water levels over the weekend, according to the National Water Prediction Service. Fortunately for those along the Mississippi River, water levels are forecast to continue dropping despite the predicted rain.

The front will make some progress south and eastward into Saturday, bringing shower and thunderstorm chances to the Northeast, Mid-Atlantic, Appalachians, and Southeast, the weather service said, where moderate to locally heavy rainfall is expected with some additional isolated instances of flash flooding possible.

As the pattern amplifies over the weekend, stretching from west to east, It’s expected to bring big contrasts in high and low temperatures. Parts of the Great Lakes and Midwest may experience cool temperatures well below average, down into the 50s and 60s.

Next week will be a farewell to this recent summer preview in the eastern United States, thanks to a weather pattern known as a cut-off low. That’s a large area of low pressure that gets “cut off” from the main jet stream and just sits and spins for days. It’s forecast to bring a spell of cooler, damper weather to a region that’s in desperate need of rain.

Contributing: Doyle Rice, USA TODAY

Dinah Voyles Pulver, a national correspondent for USA TODAY, covers climate change, weather, the environment and other news. Reach her at dpulver@usatoday.com or @dinahvp on Bluesky or X or dinahvp.77 on Signal.

A vehicle sits in flood debris, Monday, June 16, 2025, in Valley Grove, West Virginia. [AP Photo/Carolyn Kaster]

Six people have been killed, including a 3-year-old child, and two people are still missing after heavy rains and devastating flash flooding struck the northern part of West Virginia on Sunday.

Between 3 and 4 inches of rain fell in less than an hour, drenching the already saturated ground in parts of West Virginia, just west and south of Pittsburgh, Pennsylvania.

The rain caused massive flooding along creeks and into the city of Wheeling, West Virginia, where people were trapped in their cars and homes. Many people were rescued from trees that they had to climb to escape the floodwaters.

Homes were completely destroyed and water could be seen flowing over the tops of cars that were abandoned as people climbed trees or the sides of hills to get out of the water’s way.

Farther south, another storm system devastated Fairmont and much of Marion, causing additional flooding. A three-story apartment building collapsed. Videos posted on Facebook show water gushing out of windows and air conditioning vents and finally pouring like a waterfall over the roof of the building before the wall collapses. Residents of the building have been taken to the nearby university for temporary shelter.

Roads and bridges have been damaged, some completely washed out. Power lines, telephone and gas lines have been knocked out and severely damaged.

West Virginia Governor Patrick Morrisey has declared a state of emergency for Ohio and Marion counties where the flooding occurred.

“As flash floods continue throughout North Central West Virginia, emergency officials are on the scene in Marion County at a partial apartment collapse,” Morrisey said in his emergency declaration. He added, “State resources are being dispatched to the region immediately. Please—stay off the roads. Do not underestimate the strength and speed of these floods.”

The Federal Emergency Management Agency has yet to provide assistance and the Trump administration has not yet declared the region a disaster area.

The National Weather Service is warning that widespread thunderstorms early this week may produce excessive rainfall across portions of the Ohio Valley and Mid-Atlantic, which could lead to more flooding in the region.

The flooding in West Virginia follows flash floods that hit the San Antonio, Texas, area this past Thursday, which killed 13 people and injured many, with homes and businesses destroyed.

The flooding took place following a record 6.11 inches of rain, including about 4 inches that fell in a single hour early Thursday morning.

Flash flooding is occurring more frequently as a direct consequence of global warming. Flooding occurs when rainfall overwhelms the capacity of natural or man-made drainage systems to absorb or channel water effectively. Flash floods develop suddenly, within minutes to hours of intense rainfall, leaving little time for preparation or evacuation if proper and timely warnings have not been issued.

As the planet warms, the atmosphere can hold more water vapor. This heightened moisture content fuels more intense and prolonged rainfall, leading to an increased likelihood of flash flooding.

2024 was the hottest year on record and the 10 hottest years since 1850 have all occurred in the past decade.

Prolonged rain in an area also saturates the ground and fills up rivers and streams making it harder for them to absorb or move water from sudden violent storms.

The impact of the flash floods has been exacerbated by the chronically high levels of poverty in West Virginia and environmental devastation wrought by the coal and energy giants over more than a century of exploitation. West Virginia consistently ranks among the US states with the highest rates of poverty, with 16.7 percent of the state’s population living below the official poverty line and far more living on the edge.

More than 500,000 West Virginians rely on Medicaid or Children’s Health Insurance Program, and about 277,000—or one in six—residents rely on food stamps through the Supplemental Nutrition Assistance Program (SNAP). Both vital programs are being targeted by Trump’s so-called “Big, Beautiful Bill.”

Additional budget cuts and layoffs by the Trump administration at the National Weather Service and its parent agency, the National Oceanic and Atmospheric Administration (NOAA), have meant that it has fewer resources to monitor and warn of severe weather.

Furthermore, Trump’s anti-science agenda, which includes the denying of climate change, has canceled billions of dollars in research funding on climate change, how to mitigate it and how to prepare for it.

Further layoffs and budget cuts at the Federal Emergency Management Association (FEMA) and the Army Corps of Engineers—which manages water levels on inland rivers—have made it harder to prevent these disasters and to provide aid when they happen.

Unfortunately, this path will ensure more flash flooding. The unavoidable death and destruction that comes with it will continue.

CINCINNATI – Parts of the Ohio Valley are bracing for rain and the potential for severe weather to kick off Easter week, as a fast-moving cold front pushes through the region on Monday.

Cities across Ohio, Indiana, Kentucky, Pennsylvania and West Virginia are under a heightened risk for severe weather from Monday into early Tuesday.

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This graphic shows the severe weather threat on Monday, April 14, 2025.

(FOX Weather)

NOAA’s Storm Prediction Center (SPC) says more than 28 million people across the region will be at risk of severe thunderstorms on Monday. However, the SPC placed more than 9 million people from Kentucky to Pennsylvania in a Level 2 risk on its 5-point severe thunderstorm risk scale.

Cities in the risk zone include Columbus and Cincinnati in Ohio, Pittsburgh in Pennsylvania, Charleston in West Virginia and Lexington in Kentucky.

Forecasters say the primary threats will be damaging winds and large hail, but some tornadoes are also possible.

This graphic shows the tornado, damaging wind and large hail threat on Monday, April 14, 2025.

(FOX Weather)

In addition to those extreme weather threats, any thunderstorm that develops can produce frequent cloud-to-ground lightning and periods of torrential rainfall.

While the front is expected to move through quickly, limiting total rainfall accumulations, localized totals of 1-2 inches are still possible.

EASTER TRADITION GETS A MAKEOVER WITH DYED POTATOES

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The increased rain threat comes at a time when many rivers in the region are already running high, with some still dealing with lingering impacts from recent flooding, including along the Ohio and Kentucky rivers.

In Cincinnati, the Ohio River rose above 60 feet – its highest level since at least 2018 – prompting temporary closures of riverfront parks and roadways and the activation of floodgates to protect low-lying areas.

Farther west, in Princeton, Indiana, cleanup efforts are still underway following an EF-1 tornado that touched down on Thursday.

The storm damaged dozens of homes, and now the region faces additional showers and storms that could complicate recovery efforts.

“There’s going to be enough heat and instability in the atmosphere, triggered by that cold front, to support strong storms that will intensify through the afternoon and persist into the evening,” FOX Weather Meteorologist Steve Bender said. “That means places like Pittsburgh and Charleston, West Virginia, could face a nighttime severe weather threat, which is always more dangerous.”

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Following the passage of the cold front, the weather pattern remains uncertain for the remainder of the holiday week.

Some computer forecast models suggest additional weak frontal boundaries could approach the region, but they are not currently expected to bring widespread rainfall due to a lack of instability and moisture.

DRONE VIDEO SHOWS FLOODED OHIO RIVER CREEPING TOWARD CINCINNATI REDS’ STADIUM

Temperatures across the Ohio Valley are expected to remain cooler than average through much of the week.

While mid-April typically sees high temperatures in the mid- to upper 60s, many areas will experience highs several degrees below seasonal averages.

While the Upper Ohio Valley is no stranger to heavy rainfall and flooding, the conditions that have been in place over the past couple of days have supercharged the atmosphere to produce some localized deluges in portions of the area.

What makes this latest round of heavy rain and flooding unique is the amount of moisture that has been observed in the atmosphere leading up to and during the height of the worst flooding from Saturday night through Wednesday morning.

(Photo: KDKA Weather Center)

What is precipitable water?

We can measure the vertical depth of moisture in the atmosphere through the launch of weather balloons looking at a value called precipitable water. Precipitable water is a measure of the amount of moisture in the column of air between two different levels in the atmosphere.

While high values of precipitable water don’t guarantee heavy rain will occur at any moment, it does indicate an exceptionally moist atmosphere that is more efficient at producing and packing in more raindrops per unit volume in precipitating clouds. This is especially true if there is a front or low-pressure area moving through that can lift the moisture and cause clouds to form.

(Photo: KDKA Weather Center)

Precipitable water values break records

On Saturday night before the heavy rain that led to deadly West Virginia Panhandle floods, precipitable water values measured in Pittsburgh were within the top 95% of available records. On Sunday morning, before a flash flood emergency was declared south of Morgantown near the Fairmont, West Virginia, area, moisture levels remained anomalously high, although not record-breaking.

The area eventually moved into record-breaking levels of moisture starting the morning of June 17. On June 17 at 8 a.m., 1.83 inches of precipitable water was observed breaking the 1984 8 a.m. record of 1.82 inches.

At 8 p.m. on June 17, Pittsburgh smashed the precipitable water record of 1.77 inches in 1984 (the 8 p.m. record) with 1.89 inches of precipitable water.

This morning, June 18, we broke another precipitable water record with 1.85 inches observed, breaking the old record of 1.83 inches set in 2024.

(Photo: KDKA Weather Center)

A warmer atmosphere has more room to hold moisture

The weather pattern that led to these unusually high levels of moisture involved a strong ridge of high pressure across the southeast U.S. and semi-persistent troughing in the Midwest and Central Plains.

A persistent southwest flow near the surface and aloft led to rich moisture flowing north from the Gulf. Water temperatures in the Gulf are also much warmer than normal, which allows for greater rates of evaporation and more moisture transport inland to the U.S. mainland whenever the weather pattern is favorable.

(Photo: KDKA Weather Center)

As earth’s atmosphere continues to warm thanks to a warming climate, there is growing concern that these exceptionally moist environments will continue to become more frequent.

A warmer atmosphere expands and has more room to hold more moisture. This means precipitating systems like thunderstorms and landfalling tropical systems will produce more extreme and damaging amounts of precipitation. This raises the risk of damaging and deadly flooding, especially in vulnerable areas with poor or dilapidated infrastructure.

An uncommon atmospheric phenomenon known as an omega block will bring days of rain and thunderstorms to the Eastern Seaboard, starting on Saturday and lasting until Wednesday or Thursday. With more than three inches forecast in about eight northeastern states, the rain could be heavy enough to lead to localized flooding into early next week. The area that includes central and eastern Pennsylvania, southern New York, New Jersey and western parts of New England may be at particular risk, with scattered severe storms on Saturday afternoon and drenching downpours on Monday and Tuesday.

Still, even as the rain could drive hazardous impacts, the Mid-Atlantic and Northeast could use the precipitation. Abnormal dryness to severe drought continues to cover parts of the region.

Another area of intense, potentially flooding rainfall and thunderstorms will cross the Rockies on Monday, then the southern Plains and parts of the Gulf Coast from Tuesday into Wednesday, with eastern Texas and Louisiana at highest risk.

What is an omega block?

An omega block is a slow-moving weather pattern in which two low pressure systems become stalled on either side of a high pressure area, creating a configuration that resembles the Greek letter omega (Ω) on weather maps.

The pattern forms when jet stream winds, around 40,000 feet above the ground, slow down, causing the systems to become nearly stationary. As a result, omega blocks often lead to prolonged periods of adverse weather, including heavy rain and thunderstorms.

Over the next few days in the U.S., the disturbances will stall over the Southwest and Midwest, where rising air ahead of the systems cools and condenses to produce rain and storms.

How much rain may fall

Through Wednesday, more than an inch of rain is forecast across parts of 42 contiguous states, meaning that the omega block will have wide-reaching impacts.

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The heaviest rain is forecast across the Ohio Valley, Mid-Atlantic, Northeast, Rockies, southern Plains and Gulf Coast, where localized areas of flooding may develop in the hardest-hit places.

Ohio Valley, Mid-Atlantic and Northeast

Areas of rain and thunderstorms, some of which could produce damaging winds, will become more widespread and intensify across the Ohio Valley, Mid-Atlantic and Northeast on Saturday, as southerly wind flows add moisture and humidity to the air.

A band of heavy rain will cross Tennessee, Kentucky, Indiana and Ohio — states that were drenched in April — with the potential for isolated flooding.

Showers and storms are expected to develop along or just west of the Interstate 95 corridor on Saturday afternoon, which may put a damper on any evening plans.

The unsettled weather will continue across the region on Sunday, though it will probably be less intense than Saturday.

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A pinwheeling disturbance in the upper atmosphere, forming part of the omega block, will slowly move eastward on Monday and Tuesday, leading to downpours from Virginia to Vermont — heaviest in eastern Pennsylvania, southern New York, New Jersey and western New England on Tuesday, when some flooding is possible.

Rockies, southern Plains and Gulf Coast

The western side of the omega block will bring areas of heavy rain and thunderstorms to the Rocky Mountains on Monday.

This moisture may coalesce into a cluster of heavy rain and thunderstorms in Colorado, Kansas, Oklahoma, Texas, Arkansas, Louisiana and Mississippi on Tuesday, where flooding can’t be ruled out.

NOAA’s Weather Prediction Center has a slight (Level 2 out of 4) to moderate (Level 3 out of 4) risk for excessive rainfall in several of these states.

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Heavy showers and storms will likely continue across the region on Wednesday, heaviest from Texas eastward to Alabama.

When it will end

While the rain will probably ease across the above regions by late next week, the Southeast may become a focal point for more storms.

There’s a remote chance that a second omega block develops during the second week of May, locking in yet more unsettled weather.