Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Aug 16 2025 03:11:59 AWUS01 KWNH 160311 FFGMPD AZZ000-160830- Mesoscale Precipitation Discussion 0942 NWS Weather Prediction Center College Park MD 1110 PM EDT Fri Aug 15 2025 Areas affected...Western to Central Arizona... Concerning...Heavy rainfall...Flash flooding possible Valid 160310Z - 160830Z SUMMARY...Expanding convective complex to slowly lift north, intersect with older outflow boundary. Cells with rates of 1.5"/hr and slow motions may allow for localized 2"+ totals and possible localized incidents of flash flooding overnight. DISCUSSION...Fading GOES-W Visible and 3.9m SWIR shows a pair of outflow boundaries from earlier evening convective activity, both extending arched from NNW to SE. The northern one remains along or just off the Mogollon Rim across northern Arizona with a second extending from east of Blythe across the Sonoran Desert southwest of Phoenix toward Pima county. GOES-W WV suite along with GOES AMVs show deep layer upper-level trough over Southern California with a weak negative tilt as a subtle shortwave feature rolls eastward into the Cochella Valley toward the Colorado River Valley. This broad southwesterly flow is orthogonal to the orientation of the outflow boundaries, so all convection has been generally developing and back-shearing northeastward reducing forward overall propagation (at least in the short-term period).=20 Recent stronger LLJ through out of the Sea of Cortez has surged north-northwestward across the Sonoran desert (using CIRA LPW and RAP analysis) with 15-20kts, responding to the advancing shortwave feature. Mid-level steeper lapse rates provide solid instability for stronger/deeper thunderstorm activity along the the southern boundary with MUCAPE values of 2500-3000 J/kg analyzed. The slug of moisture is estimated per CIRA LPW and RAP to be around 1.5" with most in the sub-700mb layer to allow for efficient warm cloud processes for stronger cells.=20 Current 10.3um and RADAR mosaic show a few stronger clusters with the broadest up/downdraft along the Mohave/La Paz county line just east of the California border, as well as newer cells downstream along the Yavapai border. Given instability and moisture flux rates of 1.5-1.75"/hr are probable (along with some hail generation). As the shortwave lifts northeast, deeper layer mean southwesterly flow will allow for northeastward motions back toward the western Mogollon Rim, perhaps intersecting with areas affected earlier. Scattered incidents of 1.5" are probable, with an few more isolated totals of 2-2.5" with higher probability across Yavapai county per recent HRRR, WoFS and 00z Hi-Res CAM solutions. A few back-sheared convective columns can be seen north across E Mohave with the northern boundary, but most of those are generally weaker and widely scattered in coverage, but should still slowly propagate southwest eventually intersecting/integrating with the developing clusters moving northeast with the mean short-wave ejection. Similarly, these intersections/mergers will pose the greatest risk for flash flooding in the slopes of the Mogollon Rim throughout the overnight period, resulting in possible widely scattered incidents of flash flooding. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_SuwBf_PKHENhYETvwNv97alIgQuN-ADZKRki_oRwhmMzJ2-VMY8bvA0tr3f6pQPE9e2= a9M0x3cwbw8pt7T2mnLiork$ for graphic product... ATTN...WFO...FGZ...PSR...VEF... ATTN...RFC...STR...NWC... LAT...LON 36341314 35701240 35241150 34721133 34171142=20 33751208 33561283 33591383 33761407 34291410=20 35361417 35981373=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .