A follow-up to my post from last Friday.
Moisture continues to increase from the southeast across New Mexico and Arizona, and this is likely to continue through midweek. Not only is the moisture increasing, but a weak upper-level disturbance will also be coming along in the flow and helping to enhance thunderstorm development.
The following is the sequence from the GFS showing precipitable water amounts over the next couple of days.
As you can see moisture increases, not only moving more north and west but also the amount of moisture increases. This will mean that there will be more moisture available to develop thunderstorms and when thunderstorms develop they will bring more rain with them. It looks to be pretty active across Arizona Tuesday night into Thursday with the potential for locally heavy storms causing flash flooding and strong winds gusts that can produce dust storms. A thunderstorm could spread into portions of the lower deserts of California and north to Las Vegas by Wednesday afternoon and Thursday.
It is not out of the question that enough moisture gets as far west as the mountains of San Diego County north to western San Bernardino County, but the richest moisture for now is most likely to stay east.
The moisture may retreat back to the east some Friday and Saturday then may make another surge west again early next week.
As of the end of June there had been no named storms in the Eastern Pacific basin.
This is some serious and dangerous heat. Outdoor activity is just not at all recommended during the daytime.
A strong ridge of high pressure in the West brings the highest heat of the season so far to a large area.
Combine the cold with the wind and some precipitation and there is a real danger of hypothermia.
Any shower and thunderstorm can contain heavy downpours, heavy enough to cause temporary, low-lying ponding.
According to all long-range models, the warmest area in North America compared to average will be over the Northwest.