Stormy weekend in Southeast Arizona

Tucson residents should prepare for a weekend of sudden wind, dust and heavy rain, followed by another stretch of dangerous heat. Thunderstorms are expected across the region tonight, Sunday and Monday, with the potential for 50 to 60 mph or stronger outflow winds, downpours and flash flooding. The combination could affect commutes, outdoor plans, high profile vehicles, neighborhoods near washes and anyone working or exercising outside.

A Flash Flood Warning began at 11 a.m. and is expected to remain in effect through tomorrow, according to the latest local forecast. A Blowing Dust Advisory is also scheduled from 4 to 8 p.m. tonight. Forecasters said storms may produce strong winds that race outward from thunderstorm cells, including in areas that receive little or no rain. Those winds can quickly reduce visibility, spread dust across roads and create hazardous travel conditions.

Tonight brings a 60 percent chance of showers and thunderstorms, with partly cloudy skies and a low near 76 degrees. Storms may contain substantial moisture, raising the risk of intense rainfall and localized flooding. At the same time, gusty outflow winds could reach severe levels, with the strongest gusts expected to stir dust and potentially affect a broad area around Tucson. People heading out should check conditions before traveling, secure loose items outdoors and avoid assuming that a storm is harmless simply because rain is not falling nearby.

The unsettled pattern is expected to continue Sunday and Monday. Sunday has a 60 percent chance of thunderstorms, a high near 99 and a low around 73 Sunday night, when the storm chance rises to 70 percent. Monday is forecast to reach about 94 degrees, with a 60 percent chance of thunderstorms during the day and a 50 percent chance Monday night. Forecasters emphasize that monsoon storms depend heavily on what happens the previous day. A particularly active night can leave the atmosphere less favorable for storms the following day, while a quieter night can allow conditions to rebuild.

The heat threat will not disappear when clouds and storms arrive. The National Weather Service has issued an Extreme Heat Warning from 10 a.m. Monday through 8 p.m. Friday for Western Pima County, the Tohono O'odham Nation, the Tucson metropolitan area, south central and southeast Pinal County and the Upper Gila River Valley. Communities included in the warning area include Tucson, Marana, Oracle, Green Valley, Vail, Ajo, Sells, Mammoth, Safford and Clifton.

Temperatures in the warning area are expected to reach 103 to 110 degrees, while overnight lows may only fall to 79 to 85 degrees. The National Weather Service describes the expected conditions as Major HeatRisk, meaning the heat could significantly affect people spending time outdoors and those more vulnerable to high temperatures. A strong area of high pressure building over the Southwest is expected to push temperatures 5 to 7 degrees above normal across Southeast Arizona. Locations west and northwest of Tucson could run 6 to 10 degrees above normal and become several degrees hotter than Sunday.

Monday's storms may bring more wind than rain in some locations because dry air will limit rainfall. Storms moving into Graham and Cochise counties between roughly 2 and 5 p.m. could generate gusts from 45 to 50 mph. Central and eastern Pima County and Santa Cruz County could see gusts as high as 45 mph during the late afternoon and early evening. The Gila River and San Simon valleys may experience some of the strongest winds. Aviation forecasters are also warning of erratic thunderstorm winds from 40 to 45 knots near southern Graham and northern Cochise counties.

Storm activity may ease Tuesday as high pressure settles over central Arizona, but the break could be temporary. Deeper moisture is expected to move north into the lower deserts of southwest Arizona Tuesday night into Wednesday, potentially making storms more widespread across Southeast Arizona later in the week. Forecast coverage is expected to increase Wednesday and Thursday, with Friday and Saturday also appearing active in current projections. Conditions can change quickly during monsoon season, so residents should continue checking updated forecasts rather than relying on a single outlook.

The forecast calls for a mostly sunny Tuesday with a high near 97 and only a 10 percent storm chance Tuesday night. Wednesday night should be mostly clear, with a low near 75. Storm chances return Thursday night at 20 percent, followed by sunny conditions Friday and Saturday with highs near 101 and a 10 percent chance of thunderstorms each afternoon. Overnight lows during that later period are expected to remain in the mid 70s.

Health officials recommend moving strenuous outdoor work and exercise to early morning or evening, wearing loose, lightweight clothing and drinking water regularly. People working outside should take frequent breaks in shade or air conditioning, and residents are encouraged to check on neighbors, family members and others who may be more vulnerable to heat. Anyone showing signs of heat illness should be moved to a cool, shaded place immediately. Heat stroke is a medical emergency and requires a call to 911. During storms, residents should stay alert for sudden wind and dust, even when skies overhead appear dry.