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    Rain, Cooler Air Poised for West

    By By Alex Sosnowski, expert senior meteorologist
    April 28, 2012, 12:09:20 AM EDT

    Just as folks were starting to adjust to the sunshine and heat in the West, a change is heading in for the middle of the week.

    A storm system hovering offshore will get a kick from a system over the northern Pacific Ocean.

    Both storm systems will drive inland over the West during the second half of the week.

    According to Western Weather Expert Ken Clark, "While there will be a few pockets that miss out on rainfall, showers and thunderstorms will be rather widely distributed over the Southwest and Northwest."

    Anytime you have a building of heat like we have now over the West and a storm system with cooler air plows into it, there is a risk of strong thunderstorms.


    "Where the leading edge of the cooler air coincides with the heating of the afternoon and early evening, the storms have the greatest potential to be locally severe," Clark said.

    The storm system in the Southwest has a shot at bringing at least sporadic rainfall and thunderstorms to the deserts.

    Rapid cooling of the upper levels of the atmosphere over the West will translate to cooler weather near the ground as well during the latter part of the week.

    The core of the heat was already beginning to shift eastward. High temperatures trended downward over interior locations of California, Oregon and Washington.

    By the second half of the week, much of the West will have shifted away from temperatures of 20 degrees above normal to 5 to 10 degrees below normal for a couple of days.

    As a return of Pacific moisture returns to the Northwest and the flow becomes more westerly aloft, snow levels will gradually lower over the Cascades and northern Rockies. Snow levels could dip to pass levels by the end of the week.

    Temperatures will trend into the 50s in Portland and Seattle later this week. Highs were in the 70s and lower 80s in portions of western Oregon and Washington this past weekend.

    Along the Southern California coast, the temperature change will be less dramatic, due to a flow off the Pacific over the weekend.


    After setting a record high on Saturday with a reading of 107 degrees, Palm Springs, Calif., stopped 1 degree shy of the record mark of 105 degrees on Sunday, set in 1949.

    A comparison of the weather for both weekends of the Coachella Festival at Indio, Calif. was like night and day. The unusual chill the first weekend was followed up by three days of triple-digit heat.

    Festivalgoers apparently heeded advice to remain hydrated with non-alcoholic drinks according to the Mercury News. However, the turnout was lighter along with the clothing for the second and final weekend of the activities.

    Many locations in the West had experienced, or will continue to experience today, their warmest weather of the season so far with the weather pattern that began late last week.

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