July 13th, 2025: First Severe Weather Risk of the Season in Southeast AZ

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, the 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 analysis this morning courtesy of Tropical Tidbits.


The 18z TUS sounding shows modest moisture (1.23 inches of PW) and instability (622 J/kg of MLCAPE). However, there are a couple of inversions measured near 700mb and 500mb as well as -178 J/kg of MLCIN. 


18z TUS sounding courtesy of SPC.



Severe Weather Forecast in SE AZ


Synoptics/Dynamics

As mentioned above, the synoptic scale pattern today is generally unfavorable for monsoon thunderstorms. There appears to be two 500mb anticyclone centers with the major anticyclone center remaining off the coast of Southern California and another over the southern Great Basin. This setup will allow for northeasterly/easterly mid level flow across Southeast Arizona which is favorable for convection over the higher terrain to propagate into the valleys. 


There isn't any synoptic scale mechanism to induce ascent today and in fact the synoptics are relatively hostile, so convective initiation will rely on differential heating of the terrain and then outflow boundaries. 


Thermodynamics

As shown in the observed TUS sounding, moisture and instability are not very impressive with only modest precipitable water and CAPE. CAMs forecast the best instability to remain mainly south and east of Tucson, especially in Cochise County. Below are 18z HRRR model soundings at Sierra Vista (KFHU) and Tucson (KTUS) later this afternoon.


18z HRRR KFHU model sounding valid for 3PM MST this afternoon courtesy of Tropical Tidbits.




18z HRRR KTUS model sounding valid for 5PM MST this afternoon courtesy of Tropical Tidbits.


Notice that there is more CAPE and less CIN in Sierra Vista compared to Tucson which makes sense of course due to the elevation difference. The forecast DCAPE values are quite impressive on the order of 1500 to 2000 J/kg which is why SPC has issued a slight risk of severe wind gusts in Southeast AZ. 


SPC Day 1 Convective Outlook.



Timing, Location, and Impacts


Overall, convection is expected to remain mainly south and east of Tucson today. As mentioned above, a slight risk of severe grade wind gusts is in place for Southeast Arizona. 

As I am finishing up this discussion, storms are beginning to initiate over the White Mountains and a few Sky Island locations in SE AZ. Storms will propagate to the southwest reaching the valleys of Cochise County by late afternoon. Outflow boundaries are expected to be very strong due to the impressive 1500 to 2000 J/kg of DCAPE. The 12z HREF shows 70 to 90% probability of wind speeds in excess of 30 knots in Cochise County late this afternoon and into the early evening hours. 


12z HREF 4-hour max wind speeds and probability of winds in excess of 30 knots where dbz > 20 valid at 7PM MST courtesy of SPC.


I cannot rule out a cell or two in the Tucson vicinity, but CAMs forecast activity to remain mainly south and east of the city. My biggest concern is strong outflow winds and blowing dust moving through the metro this evening. In fact, the 18z HRRR forecast 25 to 35 knot wind gusts in Eastern Pima County later today as shown below.


18z HRRR 10-meter wind gusts valid at 8PM MST this evening courtesy of College of Dupage.


If this verifies, this could generate a significant dust storm (haboob) in Tucson today. 


Traveling conditions will be exceptionally hazardous due to the strong winds and blowing dust, especially along I10 between Tucson and the AZ/NM Border. 


Due to the lack of deep moisture, flash flooding is not likely, but always a possibility especially over the mountains and closer to the International Border.




















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