Mesoscale Discussion 2395 NWS Storm Prediction Center Norman OK 0221 AM CDT Thu Oct 22 2026 Areas affected...parts of central Arizona Concerning...Severe Thunderstorm Watch 690... Valid 220721Z - 220915Z The severe weather threat for Severe Thunderstorm Watch 690 continues. SUMMARY...Scattered strong thunderstorm development remains possible overnight. Although the potential for severe weather may currently be at a relative minimum, it appears that this may increase again by 4-6 AM MST. A new severe weather watch may be needed, but it is not certain whether this will be before WW 690 expires at 09Z, or a bit later tonight. DISCUSSION...There has been little change in the large-scale environment through the evening into the overnight hours, downstream of a notable mid-level trough and embedded low slowly migrating inland of the southern California coast. Southerly low-level flow is maintaining a seasonably moist boundary-layer across the lower deserts into Mogollon Rim vicinity, which has been sufficient to contribute to CAPE on the order of 500-1000+ J/kg beneath modestly cool mid-level air. Beneath strong south to southwesterly flow in the 500-300 mb layer, deep-layer shear remains conducive to supercell development. Forcing for ascent near and north of the Greater Phoenix area continues to support renewed thunderstorm initiation, largely aided by low-level warm advection and upslope flow into and across the Mogollon Rim into Colorado Plateau. This is likely to continue through the remainder of the night. With the continued approach of the upstream trough axis and more substantive mid-level height falls, along with perhaps some further strengthening of low-level flow/shear, latest model output (including convection-allowing and related machine learning guidance) suggests that the environment may once again become increasingly conducive to supercells with potential to produce a tornado or two, in addition to large hail, by 11-13Z, if not earlier. ..Kerr.. 10/22/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FGZ...PSR... LAT...LON 35361229 34911088 34031052 33191132 33351201 34431249 35361229 MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
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