Cutoffs Over The Southwest - For How Long?

First - lot of cirrus around today but no middle clouds. Low here at house this morning was only a bit warmer than yesterday at 33F (TUS had low of 45F - also a bit warmer).

The strong 500 mb short wave (currently northwest of Seattle) is forecast by all the models to dig into the Southwest during the next two days - this in response to strong, upstream ridging. The cutoff takes a south-southwestward track over land - which is usually not good for extensive precipitation at low elevations. The 72-hour ECMWF (valid 12 UTC 2 Dec 11 - Friday) forecasts the 500 mb low to be nearly over Yuma. The interesting thing in the ECMWF forecasts is that two more short waves drop down the west side of cutoff, keeping an evolving cutoff over the Southwest. Below is ECMWF at 168-hours (12 UTC Tuesday, Dec 6) with a 500 mb cutoff still forecast nearby - now near San Diego. The longer the cutoff(s) have a fetch from over the Pacific, the greater the chances for pulling in better moisture for precipitation - so a very interesting week on tap.

In the shorter term - at 84-hours - the NAM model (above) forecasts the accumulated precipitation mostly over the mountains. In contrast, the GFS forecasts a significant precipitation event to occur over over central and eastern Arizona. Which will prove more accurate? - a tough call with the culprit short wave still a long way away.