A series of relatively high-percentage rain days in the Valley this week could mark the end of this year’s monsoon season.
While the monsoon has been fruitful in terms of rainfall, a La Nina weather pattern appears to be setting up that will lead to dry conditions in the Valley, according to a National Weather Service meteorologist.
Marvin Percha said Tuesday the chance of rain, which will be as high as 50% Wednesday, tapers off dramatically by this weekend.
“After temps get back over 100 this weekend, we’re looking at warm and dry for the rest of September, and possibly into early October,” Percha said.
So far during 2022, Phoenix has received about 4.08 inches of rain. Percha said the monsoon season has not been as strong for rainfall as 2021, but better than 2020.
“The 2020 monsoon was so dry, it made that year one of the driest on record,” he said.
October is a toss-up in terms of forecast rainfall: there are equal chances of either below or above normal precipitation. However, beyond that, Arizona could be looking at a dry, cool end to fall and start of winter, Percha said.
“October, November and December show they are tilted moderately strong toward below-normal precipitation,” he said. “La Nina conditions tend to be drier than normal.”
La Nina conditions appear to be setting up for the third consecutive year, which is extremely rare, Percha said. Those conditions, as far as Arizona is concerned, tend to involve the jet stream pushing moisture far to the north of the Southwest U.S.
Percha said he hasn’t read about any in-depth studies analyzing possible links between global warming and changes in La Nina conditions or frequency of occurrence.
“There doesn’t seem to be discernible data on that right now,” Percha said.