Heat watch issued through weekend

Yuma County will be under an excessive heat watch later this week and throughout the weekend, with temperatures expected to possibly even reach record levels.

According to the National Weather Service, the forecasted highs for Friday and Saturday are expected to be a stifling 114 degrees. Sunday is expected to hit 115 degrees.

Saturday afternoon could be the hottest day during this time period, with afternoon readings approaching 118 degrees in some places. Nighttime lows are also expected to remain warm, with temperatures in the 90s.

AccuWeather meteorologist Ken Clark said the excessive heat watch will be in effect from 10 a.m. Friday until 8 p.m. Sunday.

"An excessive heat watch is basically the combination of heat, humidity and how it makes you feel," Clark said. "People need to take it easy and be careful during the hottest part of the day."

An excessive heat watch is issued when there are heat indices of 105 degrees during the day combined with nighttime low temperatures of 80 degrees or higher for two or more consecutive days.

The excessive heat watch being issued later this week and weekend is the result of a huge dome of high pressure that has settled over the Southwest, according to Clark.

"Last week it was over the southern Plains. It has been moving ever since and getting stronger."

Although recent temperatures in Yuma on average have been higher than normal, Clark said in the past few days it has been about four degrees cooler than usual here for this time of year.

The National Weather Service and AccuWeather are forecasting Thursday to be partly cloudy and very warm with the high expected to be 111 degrees. Tonight will be mostly clear with a nighttime low of 84 degrees. The heat watch does not apply to Thursday.

The upcoming heat watch has been issued for southwest Arizona, including the cities of Ehrenberg, Parker, Quartzsite, Salome, Buckeye, New River, Wickenburg, Mesa, Phoenix, Fortuna, The Foothills, Yuma, Tacna, Wellton, Dateland, Gila Bend, Apache Junction, Casa Grande and Florence.

Clark said there isn't any type of heat warning or watch in place now because a convective system located over Mexico is moving northward into the Southwest, pushing moisture and cloudiness into the region.

That additional moisture and clouds, Clark said, will help keep temperatures Thursday from reaching as high as they have the past several days.

"The system may cause some monsoon moisture that may provide some cloud cover and possibly even a thunderstorm.'

A convective system is a complex of thunderstorms that form on a large scale, and normally persists for several hours or more during the late afternoon and evening hours.

The National Weather Service also issued "excessive heat warning" earlier this week that included Yuma County. It ended Tuesday at 8 p.m.  

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James Gilbert can be reached at jgilbert@yumasun.com or 539-6854.