An 'omega block' is controlling US weather. It doesn't want to leave
An 'omega block' is controlling US weather. It doesn't want to leave
Doyle Rice and Janet Loehrke, USA TODAYSat, May 30, 2026 at 10:01 AM UTC
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An Omega Block Is Gripping The Country This Week.
A weather pattern named for the Greek letter omega is guiding the United States' weather as May turns to June, forecasters said, and the pattern is forecast to continue.
Indeed, get ready for weather déjà vu these next few days. An "omega block" weather pattern will linger in some form for a while — locking in cool air for some and hot air for others. It could also redirect storms in unusual ways.
This omega block has been locking in a stagnant, split pattern: very warm and dry weather in the north-central U.S., cooler and wetter along the coasts and South, with slow-moving systems raising flood risks in the wet zones, according to the National Weather Service.
"Blocking patterns like this are known to cause wacky weather as high pressure jams the jet stream and displaces storm tracks to the north and south," said ABC 17 meteorologist Nate Splater on his blog in late May.
The pattern could persist for weeks.
A more open, weaker version of the omega block will set up June 4-12, said AccuWeather meteorologist Paul Pastelok.
What is an omega block?
An omega block is essentially a stalled jet stream pattern over the United States that locks the weather in place – keeping the middle of the country warm and dry while stormy, flood‑prone conditions linger along the coasts for days.
According to Pastelok, an omega block is a large, nearly stationary, upper-level high-pressure area that gets caught between two upper-level low-pressure areas.
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This pattern is common in April and May, when upper-level low-pressure areas are "cut off" from the main flow of air.
And what about the name?
According to Weather.com meteorologist Jonathan Erdman, "if you trace the path of the jet stream across the U.S. from the West to the East, you will trace out the Greek letter omega (Ω)."
What does the omega block mean for our weather?
That depends on where you live.
The general pattern will feature troughing over both the West and East, with ridging in between, NOAA's Weather Prediction Center said. This means cooler weather for the two coasts, with very warm weather for the central U.S.
Cool Northeast: Unseasonably cool weather over the East will be reinforced through early to midweek, the Weather Prediction Center said. The relatively cool air mass across the Northeast and east-central U.S. will keep heat and humidity suppressed to the south.
Hot in the northern Plains: Temperatures are expected to be well above average from central and west-central Canada to the northern Plains, Pastelok said. As the pattern settled in, summer heat finally arrived across the northern tier, shattering nearly 50 records, with temperatures up to 20 degrees above average, Fox Weather reported.
Rainy in the South: The blocking pattern will allow for a very warm, humid, and unstable airmass south of a wavy frontal boundary that will keep much of the South and Southeast active with daily rain and thunderstorm chances into early June, the Weather Prediction Center said.
Wet, snowy West: The WPC added that the trough over the West will close off into a broad upper low and spin over the northern Rockies, bringing low-elevation heavy rain and mountain snow on May 31 into June 1.
Moderating temperatures in the Southwest: Moderating temperatures are expected across the Southwest this week after a period of cooler-than-normal temperatures associated with increased cloud cover and precipitation, the WPC said. Phoenix should hit 104 degrees by June 1, the National Weather Service said.
In addition, "this time of the year, drier-than-average conditions and higher temperatures can lead to fires, especially across the northern High Plains and central Canada," Pastelok warned.
Doyle Rice is a national correspondent for USA TODAY, with a focus on weather and climate.
This article originally appeared on USA TODAY: US weather is under the control of an 'omega block.' What is that?
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