2025 Arizona Summer Monsoon Discussions

Synopsis The synoptic scale pattern today is defined by the 500mb anticyclone (Monsoon High) well to the west of Arizona. Moisture and instability is expected to remain relatively modest today as the atmosphere is gradually recovering from several days subsidence. However, thermodynamics will be sufficient for convective initiation over the White Mountains and Sky Islands of Southeast Arizona this afternoon. Strong boundary layer mixing as well as significant dew point depressions will generate DCAPE values greater than 1500 J/kg, so strong outflow boundaries are likely. In fact, t he  Storm Prediction Center (SPC) has issued a slight risk of severe grade wind gusts (> 50 knots) in Southeast Arizona.  Current Conditions 12z 500mb analysis this morning displays a 594 dm anticyclone off the coast of Southern California, a horizontal shear axis extending from Central California into Southwestern AZ, and northeasterly/easterly flow in Southeast Arizona. 12z GFS 500mb...

Synopsis The typical late June extreme heat will continue through Friday as high pressure aloft dominates the Desert Southwest. This weekend into early next week an anomalous synoptic scale pattern is expected with a deep mid latitude trough along the West Coast and a high amplitude subtropical ridge east of the Mississippi River. This will allow high temperatures to cool by a few degrees and below excessive heat criteria, but will delay the onset of the monsoon in Arizona. By late next week, ensembles  show moisture gradually moving northward toward Southeast Arizona. At this time, the onset of our  monsoon could occur as early as the last few days of June. The Pre-Monsoon Heat Tis the season to sit in a pool or in the AC all day. The typical June heat has arrived which is usually a sign the monsoon is knocking on the door of Arizona. As of 2:45PM MST this afternoon, surface observations show temperatures between 105 and 110 degF across the lower deserts with a few ...

Synopsis An upper level cutoff low will remain anchored off the coast of Northern Baja California today before lifting rapidly northward across Arizona tomorrow. This feature is drawing tropical moisture northward from former EastPac TC Alvin into the Southwest CONUS. The majority of shower and storm coverage will remain in Mexico and extreme Southern California through this evening, but by tomorrow precipitation chances will shift into Arizona as the aforementioned low lifts northward across our region. Models forecast impressive precipitable water values near 1.50 inches tomorrow which would be record breaking for June 1st in AZ. A combination of synoptic scale ascent, deep moisture, and modest instability will generate numerous showers with embedded thunderstorms across the state tomorrow afternoon and evening. Total rainfall will be highly variable and dependent on the frequency and intensity of showers and storms. In general, expect 0.1 to 0.5 inches across the lower deserts w...