"Omega Block" To Create Some Big U.S. Weather Contrasts By The Weekend

The weather pattern expected to shape up this 
weekend and early next week over the U.S. A big
ridge of high pressure in the middle of the nation
will keep that area very hot, while the Northwest and
Northeast will be unusually cool. 

 The heat wave grinds on today in the South and parts of the Midwest, with temperatures today up to 100 degrees expected as far north as Yankton, South Dakota and as far north as Chicago tomorrow and Wednesday.  

The heat will grind on in the South especially this week, but we'll remain protected from the scorching weather by a northwest wind flow.  

Over the weekend, the weather pattern over the United States will take on a symmetrical form, with two strong upper level low pressure areas over the northwest and northeast corners of the nation, and a strong, wicket hot dome of high pressure smack dab in the middle. 

It's called an Omega block since the jet stream pattern resembles that of Omega. 

This all means that the Pacific Northwest and northern Rockies, and New England will be unseasonably cool while temperatures rocket past 100 degrees in the Plains again late this weekend and early next week.

As this weather pattern gradually takes shape, it's already pretty chilly in the northwest. We even see a winter storm warning of all things in effect for high elevations in and  near Glacier National Park in Montana.

Several inches of snow are forecast above 5,000 feet in elevation, and up to two feet above 7,000 feet. Not a great time to hike through that national park!

I think some highest elevations in the Pacific Northwest and northern Rockies might have some snow issues well into the weekend. 

Eventually, hiking will become no picnic here in Vermont, either. The upcoming weekend cool spell won't feature snow, except perhaps atop Mount Washington. But after some pleasant days through Wednesday and a rain and storm risk Thursday and Friday, things do get chilly, especially in the mountains. 

The weather pattern, with the jet stream 
configuration as described in image above
is called an Omega block because it 
resembles the symbol from the
Greek alphabet 

The weekend if five days away, so the forecast will need to be fine-tuned. But at this point, expect some very nippy weather, and some cold showers, especially on the Green Mountain summits. I picture temperatures near 40, gusty winds causing sub-freezing wind chills and those light, but cold showers by Sunday up there.

Down here in the valleys were most of us live, it won't be that dramatic, but I expect we'll have a fairly long spell of not beach weather. We'll revert back to what is normal May weather, with highs in the 60s and lows in the 40s to around 50 during that spell of chill.

Omega blocks are usually slow to break down, so once the cooler air hits us by Saturday, it could last quite awhile, maybe even a week or more. For what it's worth, NOAA's Climate Prediction Center keeps us cooler than normal pretty much to the end of the month. 

That doesn't mean every day from this weekend onward to the end of the month will be cool.  It just means that chances are that most days will be on the cool side.