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Pattern Change Bringing Colder Temperatures to West, Snow to Rockies and Heat to South
Published: June 21, 2019
Colder temperatures and even high-mountain snow have pushed into the West for the official start of summer from a weather pattern change that is also heating up the South.
A sharp by late June standards southward plunge of the jet stream is carving out over the West and will inch its way into the Plains over the weekend.
The most noticeable impacts from this change will be in the West, where temperatures will plunge 10 to 20 degrees below average across interior parts of the region through this weekend. Cooler-than-average temperatures will also ooze into the High Plains.
Highs may not get out of the 60s for a day or two in Billings, Montana, Denver and Salt Lake City.
After tying its record-cold high of 56 degrees on Thursday, Missoula, Montana, could again come within a few degrees of its coldest daily high temperature on record Friday, which is also 56 degrees.
Highs in Cheyenne, Wyoming, Friday and Saturday may be more typical of early-mid April, rather than the first days of summer.
It will be cold enough for snow in parts of the northern Rockies above 6,000 feet in elevation late this week, including at Glacier National Park. Snow is not unheard of in the northern Rockies this time of year. In fact, snow fell in this region just days before the Fourth of July last year.
The National Weather Service has issued winter weather advisories for parts of central and western Montana, where snow may make travel difficult, including the Beartooth and Bitterroot mountains.
Elevations as low as 5,700 feet reported a light blanket of snow in Idaho Thursday.
Winter weather advisories have also been issued in the high country of Colorado, where accumulations of up to 10 inches are possible through Saturday night above 10,000 feet elevation, potentially impacting mountain passes such as the Eisenhower Tunnel on Interstate 70 west of Denver.
Snow was already falling above 9,000 feet at Rabbit Ears Pass, southeast of Steamboat Springs, Friday morning.
Those with outdoor activities planned in the lower elevations of the northern and central Rockies where it's not snowing should be prepared for wet and cool conditions into the weekend.
On the opposite side of the spectrum, Oklahoma City recorded its first 90-degree temperature of the year Thursday afternoon, and Kansas City could see its first 90-degree high Friday or Saturday. Oklahoma City typically sees its first 90 in early May, so this was more than a month behind schedule. It was also the muggiest day in Oklahoma's capital city in almost nine years.
Parts of Texas will see temperatures approach or exceed 100 degrees. Record-warm low temperatures are possible into this weekend in parts of Texas and the lower Mississippi Valley.
Southeastern cities such as Atlanta, Tallahassee, Florida, and Columbia, South Carolina, will see summery weather, with highs in the lower to mid-90s this weekend.
It's possible that the general theme of this weather pattern will persist through the final week in June.
Forecast guidance is indicating that another southward plunge of the jet stream could move into the West Coast next week. That may allow temperatures to remain below average in parts of the West. At the same time, portions of the central and eastern states could be favored to see above-average temperatures.
The latest 6- to 10-day temperature outlook from NOAA's Climate Prediction Center generally shows this theme by favoring above-average temperatures next week in parts of the central and eastern states. Most of the West has increased odds of below-average temperatures. There remains some uncertainty with exactly how the large-scale weather pattern will set up, so changes to this forecast are possible.
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