Some states will go from record heat to a freeze — thanks to Alaska
Throughout March in the West, temperatures surged to unprecedented levels for this time of year, due to a remarkable heat dome.
Then in April, that record-breaking heat shifted east. In D.C., temperatures reached 92 degrees on Thursday, based on temperatures recorded at Dulles International Airport, and the 90s in Baltimore, Philadelphia and near New York.
Now states that have had such record-breaking heat will experience some whiplash, as freezing temperatures hit some of those spots within days.
Those conditions are emerging from one place that’s been a starkly cold and snowy exception: Alaska.
Some of that chilly air is sweeping southward. First, a little snow is expected in Denver on Friday. It was 77 degrees there Thursday. Then, temperatures are forecast to dip into the 20s in parts of the Plains, Midwest and Northeast this weekend into next week - with a chance for snow flurries. Widespread blossom loss is also possible near Salt Lake City, warned the National Weather Service, following an early bloom because of record-breaking winter warmth. It snowed there on Thursday.
Nearly 100 million people can expect freezing temperatures across a wide swath from Boise, Idaho, to Boston and southward to near Philadelphia.
Very few low-temperature records are forecast to be broken - and data shows that the recent exceptional warmth in the contiguous United States has not been balanced by unusual cold farther north, considering average temperatures since the start of March.
Since March, about 76% of the planet has experienced above-average temperatures. Meanwhile, it’s been colder than average for the remaining 24 percent - including across Alaska and Canada.
That highlights how the unusual warmth has been disproportionate.
“It was definitely a cold winter up here. Statewide, it was the coldest December to March in 50 years,” said Alaska-based climate scientist Brian Brettschneider.
In his experience, Alaskans typically don’t complain about extended periods of cold.
However, Brettschneider said he “heard more grumbling than typical” during March due to the extended cold. He said it was the snowiest March in Juneau, Alaska, by a wide margin - their fourth-snowiest month on record, which followed the second-snowiest month on record last December.
“People in Juneau were definitely tired of the snow by the end of the month,” he added.
The cause of unusual Alaskan cold was linked to an area of strong high-pressure in eastern Russia. Because air flows clockwise around high-pressure systems, Alaska frequently experienced frigid, northerly wind flows from the Arctic Ocean.
As for whether the icy cold in Alaska balances out the unseasonable warmth in the contiguous U.S., Brettschneider added that if you combine the two regions, it was still the second-warmest March on record, behind 2016.
The coverage of above-average warmth greatly exceeded that of below-average temperatures.
“This is not at all equalizing,” he said.
After a warm start, there are signs that there will be a hiatus on widespread record-breaking warmth in the U.S. during the second half of April.
That’s because an area of high pressure will form near Greenland next week, probably lingering there for a few weeks.
This will cause the jet stream to dip down over the East, escorting unusually chilly, Arctic air masses into the region from time to time.
This wider pattern is known as the North Atlantic Oscillation (NAO). When the NAO is in a negative phase - which is expected next week - there are increased chances for cooler-than-average conditions in Central and Eastern states. During the positive phase of that oscillation, which has been occurring since late February, above-average temperatures are favored in the same regions.
These cooler conditions could help to somewhat suppress severe thunderstorm activity in the Plains and Midwest - but not before significant severe weather risks on Friday - and may be associated with some beneficial precipitation for the drought-stricken Intermountain West.