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    Western US weather expert

    More Active Weather in the Southwest

    8/01/2012, 6:27:54 AM

    A sprawling upper-level high in Oklahoma and Texas is helping bring a lot of monsoon moisture north into the Southwest, including parts of California, Arizona, Nevada and Utah. This pattern is not likely to change over the next couple of days.

    That is the big picture. The smaller picture of where storms are most numerous and heavy will be determined by two systems. A small upper-level high centered over central California and an upper-level low over far southeastern California that is centered just north of Yuma. It has been around this feature where the most numerous showers and thunderstorms have been so far today and where the heaviest storms have been as well. The map below show watches and warnings out as of early afternoon Tuesday.

    Notice there are a lot of flood watches, flash flood watches or flood advisories out, and one county covered by a flash flood warning. This area will continue to be the focal point for the most widespread and heaviest showers and thunderstorms, over southeastern California and westernmost Arizona north into parts of southern Nevada and also Utah. There is plenty of moisture available with a lot of rain and also movement of showers and thunderstorms will be quite slow adding to the potential for flooding.

    While these two features don’t move much through tomorrow, the agreement in the models diverge after that. One set is saying the low stays near the Colorado River in eastern California and western Arizona. This would continued to bring the deserts of southern California on north into southern Nevada the most amount of showers and storms with more scattered activity farther west into the mountains of southern California and north into Utah. A second set of models has the upper-level low moving north some of the next day or so, then backs that low southwest to near the coast of Southern California. If that were to come true, it is not out of the realm of possibility that it could shower or thunderstorms in southwestern California late Thursday or Friday. With such a sharp boundary between rain and no rain, a slight movement one way or another could make quite the difference in weather.

    As with any rain in the desert regions, proper attention needs to be taken into consideration for flash flooding and the action needed to keep safe. Never cross a flooded road with a car. It only takes a few inches of water to turn that car into a unsafe boat. Stay away from washes as even a storm that is miles away could fill that wash quickly and without warning where you might be relaxing or camping.

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

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    Western US weather expert