Look Ahead To Mid-Week

First a bit on morning lows here at the house. While the official TUS low temperatures have been running mostly in upper-40s and low 50s F since I returned from Colorado, it has been considerably cooler here. Morning lows since March 10th have been running from the middle-30s to around 40 F (coldest has been 34 F on the 19th). So chilly mornings continue, with large diurnal swings in temperature.

This week the global models forecast the strongest 500 mb short wave since March 1st to move across the Southwest. The forecasts for 500 mb here are from the operational models initialized at 00 UTC last evening and are valid at 5 pm MST Wednesday, March 26th. The GFS is above and the ECMWF is below. As is often the case, the ECMWF forecasts a short wave that is deeper and further south than does the GFS. The ECMWF heights are about 60 m lower across all of Arizona. The short wave has a negative tilt as it digs from the Pacific toward Arizona and the ECMWF primary vorticity maximum is shifted south and west, relative to that in the GFS forecast.

So, it appears that winds will kick up on Wednesday afternoon and that there will be some precipitation for Arizona. The details will determine how far south the precipitation might reach and the Atmo WRF forecasts will be of interest tomorrow and Tuesday.

The system that will impact the Southwest is currently south of Alaska around 150 W - see CIMSS morphed composite of precipitable water (PW) below. There is a nice pool of moisture northeast of Hawaii and this narrows into a distinct atmospheric river north of 30 N. It will be of interest to follow the evolution of PW as the mid-week system approaches. At least there is finally a bit more weather to follow for this part of the country.