Mesoscale Discussion 1537
   NWS Storm Prediction Center Norman OK
   0501 PM CDT Mon Aug 16 2021

   Areas affected...North-central Arizona

   Concerning...Severe potential...Watch possible 

   Valid 162201Z - 162300Z

   Probability of Watch Issuance...40 percent

   SUMMARY...A few high-based storms may pose a risk for damaging wind
   gusts or hail as they develop and move south into this evening.
   Conditions are being monitored for a possible weather watch.

   DISCUSSION...As of 2145 UTC, regional radar and visible imagery
   shows a few strong/severe thunderstorms developing across the
   Mogollon Rim and Grand Canyon areas of north-central Arizona. As
   lift from a back-door trough on the southeastern flank of the strong
   mid-level ridge continues to move into the area, additional storm
   development is likely into this evening. Diurnal warming and
   monsoonal moisture have destabilized the atmosphere as 1500 to 3000
   J/kg of MLCAPE is present from SPC mesoanalyis. Enhanced northerly
   flow on the backside of the ridge will support organized multicell
   storms with between 20 and 30 kts of effective shear.

   As additional storms develop and surface cold pools strengthen late
   this afternoon and into the evening, several clusters of storms may
   evolve as they drift south-southwest away from the higher terrain
   towards central Arizona. DCAPE around 1000-1300 J/kg and T/TD
   spreads of 25-35 degrees F will favor strong downdrafts and outflow
   conducive to strong/severe wind gusts. The magnitude of available
   instability may also support a risk for severe hail with the
   strongest cores. While uncertainty on the coverage of storms and any
   cluster development remains high, conditions are being monitored for
   a possible weather watch.

   ..Lyons/Thompson.. 08/16/2021

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...TWC...FGZ...PSR...VEF...

   LAT...LON   34611392 35391310 35731243 35581121 35001031 34430978
               33740943 32860953 32491065 32671240 33001316 33451397
               33981410 34611392