The last two weeks have brought monsoonal moisture to much of the Four Corners region. Last week alone much of Arizona received at least 2″ of rain with some spots picking up more than 7″ of rain. Even parts of southern Nevada received heavy rain!
And in Phoenix, it rained, and rained, and rained all day Friday. As a result, area-wide flooding occurred. More rain is expected today in Arizona before some of the moisture surges into parts of California and Nevada on Monday.
Last year was referred to as a “non-soon” because the typical monsoon rains never really fulfilled. Monsoon rains are related to wind shifts in the Desert Southwest which draw in moist air and produce the rainy season for the desert.
In fact, it rained so much from Thursday to Friday in Phoenix that the Sky Harbor Airport 24-hour rainfall total *beat* **all** of last year’s 2020 monsoon season rainfall!
Flash flooding will continue to threaten the Four Corners region again today. Grounds are not equipped to hold as much rain as some places have seen along with the intensity of each passing storm. Flood alerts are in place today through Monday for the potential of heavy rain to cause flash flooding and debris flows. Never drive through flooded washes or water-covered roads!
Flood Outlook
As moisture evaporates and returns to the atmosphere then teams up with the moisture streaming in from the Pacific and Gulf of California, we see more storms across the Four Corners region. Heavy rain and flooding will be most likely in Arizona, southern Nevada and parts of southern California on Sunday.
The flood threat shifts into southern California and Nevada on Monday as a mid-level low-pressure system drifts west and pulls some of the monsoon moisture with it. These areas are in exceptional drought, the highest category, and desperately need rain.
Thunderstorms with strong downdraft winds are possible this afternoon near Las Vegas and Kingman. Strong storms will be isolated but could produce damage or power outages.
Timeline
More storms will develop Sunday afternoon. Pockets of heavy rain leading to flooding and gusty downdraft winds will be the main threats.
Rain will be heavy at times Sunday afternoon and evening. Some of the moisture will move into California and Nevada as well.
Moisture continues to work into Nevada and California Monday as energy from the mid-level low moves west.
Bursts of heavy rain will continue through Monday evening. Brief flooding and pockets of gusty winds will be possible.
Forecast Rainfall
Into this weekend, we can expect an additional one to two inches of rainfall across the Four Corners. However, isolated amounts may reach up to three to four inches locally. This will be very beneficial to the ongoing drought conditions across the Desert Southwest, however, it could trigger pockets of rushing/standing water or flash floods.
