Hit and miss monsoon storms around Phoenix


by Meteorologist Royal Norman

Bio | Email | Follow: @RoyalNorman


Posted on September 2, 2013 at 3:17 PM

Updated Monday, Sep 2 at 9:56 PM

PHOENIX -- There were some afternoon thundershowers around metro Phoenix on Labor Day. There is a slight chance that activity will continue Monday night.

Moisture levels are high and it looks like we'll have an up and down week as far as the monsoon goes.

The forecast is very uncertain. Even with increasing chances on Tuesday, that doesn't mean much this season, does it?

Tuesday we expect only a slight chance for thunderstorms and a high around 105 for metro Phoenix. However, on Tuesday the chance for rain goes up a bit.

Here's part of the discussion from the National Weather Service in Phoenix:

Most of the convective potential Monday will likely be focused over portions of southeast CA and the Colorado River Valley...as accelerating upper level southerly winds flow into an increasing jet max over eastern Nevada. In other words...entrance region dynamics is expected over southeast CA.

The highest rain chances will be in that region. Ditto on Tuesday.  The remainder of the forecast area...southwest and south central AZ will be devoid of any upper level support...therefore a slight chance of heat of the day showers and thunderstorms will exist...with somewhat higher probabilities in the mountains of southern Gila county.

Also on Tuesday...an inverted trough is forecast to move into southeast AZ from west Texas by evening. Therefore we have decided to go with a higher rain chances over portions of south central AZ...including the deserts around Phoenix and Casa Grande.

Models forecast the inverted trough may also support a few nocturnal showers and thunderstorms over south central AZ into Wednesday morning.