By Renee Duff, AccuWeather meteorologist
July 16,2017, 10:50:48PM,EDT
An increase in moisture has eased the wildfire danger across the Desert Southwest but is being blamed for the deadly flash flooding that claimed seven lives in Arizona on Saturday.Thunderstorm coverage has increased across the Intermountain West as moisture and higher humidity spread northward in response to the North American monsoon.
Thunderstorms in this type of pattern tend to blossom over the mountainous areas during the afternoon hours before drifting over valley locations toward the evening.
"While higher humidity has surged into the Desert Southwest and slows the rate at which fires burn, there is enough moisture for some of the thunderstorms to unleash flooding downpours," AccuWeather Senior Meteorologist Kristina Pydynowski said.
Tucson, Arizona, was inundated with 1.45 inches of rain in roughly two hours on Saturday night. The city averages 2.25 inches in all of July.
Other instances of such heavy and persistent rain in parts of Arizona and New Mexico can trigger localized flooding and road washouts. Use caution near arroyos which can quickly turn into raging rivers.
Flash flooding turned deadly in central Arizona on Saturday afternoon, near the Cold Springs Swimming Hole, located just north of Payson. CNN reports that nine people were killed, including six children. One other person remains missing.
A few of the thunderstorms can also kick up strong, gusty winds and kick up dust storms, known as haboobs, ahead of the soaking rain.
Humidity and the number of drenching thunderstorms will increase across the central Rockies as the week progresses.
The northern Rockies, which will be far removed from the greatest source of moisture, will also be at a greater risk of dry lightning igniting new blazes. Local afternoon breezes will add to the wildfire danger across this region and the Great Basin.
“Anytime lightning strikes parched and arid vegetation in the absence of meaningful rainfall, the possibility that a new wildfire will erupt is greatly enhanced,” AccuWeather Meteorologist Kyle Elliott said.
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Gusty winds triggered by the thunderstorms will pose further hazards by causing blowing dust, reduced visibility and erratic wildfire behavior. Localized damage can occur should the winds be strong enough.
Valley locations will likely miss out on meaningful rainfall as the precipitation may not survive the long trip to the ground.
The storms will stay away from the Whittier Fire over the Santa Ynez Mountains northwest of Santa Barbara, California, which has burned over 18,000 acres and 50 buildings since beginning on July 8. Mandatory evacuations remain in effect.
Fire crews have finally gotten the upper hand on the Frye Fire in southeastern Arizona, where more meaningful rain and higher humidity will remain present this week.
The blaze, which has charred nearly 50,000 acres since being started by lightning on June 7, has been contained enough to the point that the number of resources is down to 50 people, according to the final report from InciWeb. The last helicopter assigned to the fire has been released.
Firefighters will not have to contend with extreme heat like earlier in the summer.
“Increasing amounts of cloud cover and moisture in the southwestern U.S. should put a cap on how high temperatures can climb,” AccuWeather Meteorologist Kyle Elliott said.
Temperatures will trend downward in Phoenix from a high of 109 degrees Fahrenheit on Saturday to the upper 90s early this week.
Even away from the bulk of storm activity, temperatures will be at seasonable levels in the interior Northwest through Monday, prior to a resurgence in heat later in the week.
The hottest conditions in comparison to normal will remain entrenched across central California, the Great Basin and Idaho’s Snake River Valley through early week.
Temperatures at the Salt Lake City International Airport dropped to only 73 F on Saturday morning, which led to the record for the longest consecutive days of lows at or above 70 F being tied.
"With temperatures expected to remain above that mark well into this week, that record will be shattered," Pydynowski said.