Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Aug 22 2025 00:39:47 AWUS01 KWNH 220038 FFGMPD AZZ000-220600- Mesoscale Precipitation Discussion 0969 NWS Weather Prediction Center College Park MD 838 PM EDT Thu Aug 21 2025 Areas affected...Southern Arizona Concerning...Heavy rainfall...Flash flooding possible Valid 220037Z - 220600Z Summary...Showers and thunderstorms along the Mogollon Rim will drop southwest through this evening while additional storms develop downstream. Rainfall rates of up to 1"/hr are expected, which could result in flash flooding. Discussion...The regional radar mosaic this aftn shows that convection has expanded along the Mogollon Rim, and storms are beginning to shift southwest off of the terrain. Although storm motions have been generally slow and tied to the terrain features thus far, anti-cyclonic flow around the large ridge of high pressure centered near the Four Corners will cause progression of these storms into the lower elevations. At the same time, a weak convergence axis noted in low-level wind fields is collocated with a plume of elevated MUCAPE above 1000 J/kg, which will support additional thunderstorm development. This instability is paired with PWs that were measured via the 00Z U/A sounding at KTUS to be around 1.3 inches, or the 75th percentile for the date. This will support at least brief heavy rain rates through the next several hours. So far, storms have been slow to move off the terrain, but this will change as the 0-6km mean winds increase to 10-15 kts from the E/NE. At the same time, a ribbon of modest but elevated bulk shear of 20-25 kts is progged to surge across southern Arizona, and this will support persistence of these storms as they track SW. At the same time, additional convection is likely to develop as more isolated storms in the lower elevations, and the interaction of these cells could briefly pulse rainfall rates up to above 1"/hr as progged by HREF neighborhood probabilities reaching 10-20% between 01Z-04Z. Additionally, the HRRR forced UA WRF depicts isolated 0.75"/1hr rain accumulations, further indicative of the potential rain intensities within the favorable thermodynamics. A notable inverted-V signature in the KTUS sounding combined with impressive DCAPE and the increasing forward motion of cells from the terrain indicates that wind, rather than rain, may be the primary threat this evening, and explains the modest HREF exceedance probabilities for 1"/6hrs that peak around 30%. However, the intensity of this rainfall could still overwhelm the soils, especially given the general vulnerability of this region due to currently dry soils (NASA SPoRT 0-10cm soil moisture below the 10th percentile). Although the risk appears generally isolated, any heavy rain moving atop sensitive terrain, burn scars, or urban areas could result in flash flood impacts through the evening. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5lroD-MT-SY_gkzlnVM0Wl-qYpTfub53RKfMo1c3-6Z3yX1mKQBrodnkgDDpm_dwH4N-= x-jB_GdEnTAo4GRUt-WPuVc$ for graphic product... ATTN...WFO...FGZ...PSR...TWC... ATTN...RFC...STR...NWC... LAT...LON 34581282 34371178 34011092 33530978 33050940=20 32380960 32151004 31851054 31521101 31461138=20 31461185 31581235 31801277 32111303 32621323=20 33221332 33661324=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) .