04:18
Omega block leaves weather pattern stubbornly damp on both coasts
Rain remains in the forecast for the East through the end of this week, while it's a soggy weekend forecast in the West.
The U.S. remains in a weather pattern that hasn't varied much this week, with the FOX Forecast Center expecting what is known as an "Omega block" to continue to dominate through the end of the workweek before a pattern change begins to take shape this weekend.
An Omega block is simply a pattern where a ridge of high pressure is sandwiched in between dips in the jet stream, where areas of low pressure are usually found. Its name comes from the pattern's resemblance to the Greek letter Ω.
This pattern means parts of the East and West coasts will remain rather stormy and cool while the central U.S. stays warm and dry.
01:21
What is an 'Omega block' weather pattern?
Named for its resemblance to the Greek letter, an Omega block occurs when two low-pressure systems become cut off from the main flow of the jet stream, sandwiching a high-pressure system between them.
"In the middle part of the country, it translates to nice, warm weather, but out to the East, it means we're going to stay exactly how we were this past weekend: wet, cold, damp and breezy," FOX Weather meteorologist Britta Merwin said.
During this weather pattern, significant severe weather outbreaks tend to be uncommon because the dynamics are not in place for developing areas of low pressure to take advantage of needed ingredients. However, a few severe storms could rumble across parts of the central and southern Plains late this week.
WHAT IS AN OMEGA BLOCK?
An Omega block pattern is expected to dominate the weather across the U.S. throughout the first week of May.
(FOX Weather)
Northeast rainy, cloudy pattern
The FOX Forecast Center expects rounds of rain showers to continue sweeping across the Northeast and mid-Atlantic through Friday.
"We'll see some scattered rain showers across Pittsburgh, Syracuse, as well as Hartford. It's all because of that low here," FOX Weather meteorologist Jason Frazer said. "That low is going to be sticking around at least through (Thursday night). But it's going to be (Friday) that we're going to finally start to see this pattern change."
While the rainfall will not be nearly as heavy as last weekend, cool temperatures, clouds, rain showers and breezy conditions will be ongoing for another day or so.
The FOX Forecast Center said the increased cloud cover will keep temperatures cooler than they should be during the last month of meteorological spring.
For example, Pittsburgh typically sees highs in the upper 60s to 70 degrees in early May, but with the unsettled weather, daytime temperatures only managed 47 degrees on Wednesday. The city should manage the upper 50s on Thursday, but that's still about 10 degrees below average.
IOWA CITY BRACES FOR RISING FLOODWATER FROM MISSISSIPPI RIVER
A low-pressure system associated with the Omega block produced a record-breaking May snowstorm in Michigan’s Upper Peninsula Monday and Tuesday. Marquette picked up 26.2 inches of snow, ranking as the largest two-day snowfall on record in May and vaulting the city to its snowiest May on record. Herman, Michigan, measured an astounding 52 inches of snowfall from the winter storm.
Upper Midwest, Plains dry out
The continued melting of a significant snowpack has sent more than 100 water level gauges near or above flood stage across the Upper Midwest and Plains.
The flooding is impacting major waterways such as the Mississippi, Minnesota, Red and James rivers.
Under a ridge of high pressure, chances of any significant precipitation will be greatly reduced as fair weather remains in control.
The lack of rainfall will aid in some rivers cresting and slowly coming off seasonal highs.
The FOX Forecast Center expects a lack of cloud cover will also mean a warmup for some communities, with temperatures running 10 to 20 degrees above average.
Minneapolis-St. Paul usually sees daytime highs in the mid-60s this time of year, but average readings will be replaced with temperatures in the mid-70s on Thursday.
The warm dome of air is even more impressive in the northern Plains and Rockies.
According to climatological data, Billings, Montana, should only reach the lower 60s in early May, but temperatures are expected to rise into the lower 80s on Thursday.
MONTANA’S EXTREME WEATHER HELPS SHAPE CHARACTER OF ICONIC STATE
West Coast storminess
The West Coast is expecting cool, damp and cloudy weather as an unusually strong storm system remains parked just offshore due to the Omega block pattern.
Periods of rain will continue to sweep across the region through the end of the week before the main storm system finally slides north into Canada.
"Unfortunately, the West Coast kind of on the other end of the bookend that's been dealing with similar conditions to what we've seen on the East Coast, so we've been very gloomy, very cloudy," Merwin said.
The FOX Forecast Center expects precipitation amounts to be light compared to the atmospheric river events that impacted millions during the winter.
Higher elevations will be the recipients of the highest amounts of precipitation, with accumulating snow likely in the Sierra Nevada and Cascades.
The precipitation is likely not welcome news to some in the West enduring flooding from the melting of a historic snowfall season. The threat of flooding even led to extensive closures at Yosemite National Park last week before it began reopening Sunday.
This weather pattern will also keep temperatures relatively cool for early May, with below-average highs expected through the end of the week.
When will the Omega block break down?
Computer forecast models suggest the Omega block pattern will begin to break down this weekend. The FOX Forecast Center said warmer and drier weather should return to the Northeast by Saturday.
The Omega block pattern will begin to break down this weekend.
(FOX Weather)
And more good news: The outlook for next week from NOAA's Climate Prediction Center shows a high likelihood of warmer-than-average temperatures across much of the central and eastern U.S.
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