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Unusual Late-Season Rain, Then Summer in High Gear

Jun 27, 2011; 12:23 PM ET

There will be some wild weather changes over the next week in portions of the West so hang on, it is going to be a wild roller coaster ride.

First, an unseasonably strong, late-season storm is out west of Oregon around 44 north and 134 west.

This cold storm in the upper atmosphere will be dropping southeast tonight and tomorrow then through northern California late tomorrow night and Wednesday. This is likely to bring rain to areas that rarely ever see rain in late June. Rain is likely to spread into all of western Oregon Monday night and northern California and then spread slowly south during the day tomorrow reaching by late-day to south of the Bay Area to near a Stockton-Yosemite line. Along with some rain or showers will also be a few thunderstorms due to the cold nature of the storm. A couple of showers and thunderstorms spread a little farther south tomorrow night and Wednesday to parts of the Central coast into the San Joaquin Valley and southern Sierra. Along with the unusual nature of the precipitation will come unseasonably cool temperatures. By Wednesday, a place like Fresno that is normally in the middle 90s this time of year won't get out of the 70s that day.

Of course, there will be some rain or showers just about anywhere in the Northwest and eventually northern Nevada, northern Utah and Idaho as well, mostly in eastern areas Wednesday/Wednesday night.

After this storm exits the weather pattern in the West undergoes a major shift. A large and warm upper-level high builds west from the Plains and shifts the jet stream by the weekend and next week to the far Northwestern states and western Canada. This is likely to really build the heat over all areas in the Southwest and California as well as the Great Basin. Some of the hottest weather of the year is likely in the deserts and valley locations from California on east and north by Sunday and early next week. Along with that will also come the first true monsoon looking pattern as upper-level winds turn into the east across New Mexico, Arizona and Southern California. This could transport in moisture and cause at least high level heat source afternoon and evening showers and thunderstorms, and in the deserts of southern Arizona and southeast California perhaps a thunderstorm as well.

Here is what the GFS has for the 500 mb pattern by this coming Sunday morning.

As you can tell, the events over the next seven days will bring about huge changes in a lot of areas. By the weekend and early next week rapid snowmelt is likely to take place as there is still plenty of snow in he high country. This is going to put even more stress on the already swollen rivers and streams.

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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More Ken Clark

  • Nothing Big This Week

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  • Huge Temperature Gradient

    Apr 20, 2012; 12:36 PM ET

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  • Summerlike Weather by Weeks End

    Apr 16, 2012; 12:45 PM ET

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  • Two California Late-Season Storms

    Apr 10, 2012; 12:36 PM ET

    some welcomed rainfall levels of between 1/2 to 1 inch over central California with nearly the same amounts around the Los Angeles Basin.

  • Storms Return Next Week

    Apr 6, 2012; 12:42 PM ET

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About This Blog

Ken Clark
Ken Clark's Western U.S. weather blog tackles daily weather events with commentary from one of the most experienced and trusted Western U.S. weather experts.

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