Southwest Monsoon Shutting Down for an Extended Time

It’s been a pretty active monsoon season for the Southwest, especially in Arizona, southern Nevada and surrounding areas. However, there is a big pattern change underway, one that will completely shut down any chance of showers and thunderstorms for an extended time period.

Behind an upper-level trough now in the central Great Basin, a west and northwest flow aloft tomorrow into next week will bring in very dry air, aloft and at the surface, to all the Southwest. This drying process can be seen nicely in the modeled precipitable water forecast, which is a measurement of how much moisture is in the entire depth of the air mass. The following are snapshots of the GFS model showing precipitable water values Wednesday morning through Sunday. All models, not just the GFS, are showing the same drying.

Wednesday morning:

Thursday morning:

Friday morning:

Sunday morning:

In this pattern, expect a lot of sunshine in the Southwest and temperatures will become higher. However, for the lower deserts dew points in the 60s to near 70 will be replaced by dew points in the 40s. Even though temperatures will climb some, with much lower humidity levels it will probably feel better than it has for quite some time. Those relying on swamp coolers for cooling their houses will find they will be working a lot better with the lower humidity.

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