Slow Starting Monsoon Season
The monsoon season that usually develops in late June and early July in the Desert Southwest has been off to a late start this year. The natural increase in thunderstorm activity in the Desert Southwest takes place as the hot deserts help to draw moisture from Central America and Mexico into the western United States.
However, the very cool June weather across a large part of the west, keep the deserts from heating up, delaying the onset of the monsoon moisture flow. Therefore, rainfall has been below average over the past several weeks in AZ, NM, NV and UT. With the heat finally beginning to build and high pressure developing over the Rockies and the Desert Southwest, the monsoon thunderstorm pattern will be increasing in the coming weeks.
The graphic below shows the cooler than normal temperatures in the west over the past month. Notice all the blue (cooler than normal temperatures).
However, temperatures are expected to increase over the next two weeks over the western half of the nation. This will help draw moisture northward into the Desert Southwest and Rockies in the coming weeks.
The forecasted precipitation over the next ten days is shown below.
The heavy rains, possible flash flooding that can accompany monsoon driven storms can be expected across AZ, NM, CO, UT and WY in the coming weeks.