Western US to heat up ahead of next surge of tropical moisture
A pattern reversal will first crank up heat and sunshine, then open the door for tropical moisture to return to the Southwest by late next week.
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AccuWeather meteorologists are tracking a potential surge of showers and thunderstorms in the Southwest late next week, fueled by moisture from short-lived Tropical Storm Mario and a possible new tropical entity.
Ahead of the influx of moisture, conditions will trend drier across the Four Corners region, spanning Sunday, Monday and perhaps into Tuesday. The region has been riddled with frequent shower and thunderstorm activity in recent days, including storms on Friday which produced high wind gusts up to 72 mph in New Mexico. A landspout tornado was reported in southeastern Arizona.
Farther north, a quick-hitting storm will bring clouds, showers and cooler air into the Pacific Northwest to end the weekend before the warmer, drier weather settles in.
"A pattern reversal in the West will result in rising temperatures across the region. Ultimately, temperatures will peak near 5-10 degrees above the historical average during the first half of the week," AccuWeather Meteorologist Gwen Fieweger said.
By Tuesday, high temperatures will reach the upper 90s to near 100 degrees Fahrenheit across California's Central Valley, where lower 90s are more typical for the middle of September. So far this month, conditions have been right near 1 or 2 degrees below the historical average, thanks to a recent stretch of cooler weather.
The warmest day across the Pacific Northwest will be on Tuesday, with highs in the middle 80s and lower 90s in store for Seattle and Portland, Oregon, respectively. Portland's daily record of 92 set in 1994 could be jeopardized.
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The warm weather will be accompanied by sunshine for much of the region, offering ample opportunities to get outside and enjoy the summerlike conditions, Fieweger said.
Return of tropical moisture, cooler air by late week
Temperatures will lower later in the week, especially in the Northwest, as the jet stream dips across the western U.S.
The dip in the jet stream may help to direct a stream of tropical moisture from the eastern Pacific Ocean into a portion of the Southwest.
"Extra moisture originating from what was once Tropical Storm Mario could work its way into the Southwest later in the week, especially across areas of higher terrain but even at the coasts," Fieweger said.
Mario was a short-lived tropical storm that first became a tropical depression on Sept. 11. By the early morning hours of Saturday, it had no longer become a trackable storm.
Even with the dissipation of Mario, showers and thunderstorms remain widespread across the eastern Pacific, and any northward or northeastward surge of moisture could raise the risk of downpours reaching parts of the United States.
It's not a slam dunk that an increase in wet weather occurs, however.
"It is also possible that an area of high pressure that develops over the interior West next week may hold off the bulk of the moisture," AccuWeather Senior Meteorologist Alex Sosnowski said. "In that case, there may be little to no rain."
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