Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Dec 22 2023 21:36:13 AWUS01 KWNH 222136 FFGMPD AZZ000-CAZ000-230330- Mesoscale Precipitation Discussion 1215 NWS Weather Prediction Center College Park MD 434 PM EST Fri Dec 22 2023 Areas affected...Southern Arizona Concerning...Heavy rainfall...Flash flooding possible Valid 222134Z - 230330Z SUMMARY...Repeating thunderstorms are developing into southwest Arizona, and could result in isolated flash flooding. An area of heavier rain around Tucson is expected to persist with developing convective elements, which may also result in isolated flash flooding into this evening. DISCUSSION...A strong upper level low moving into the southern California coast is advecting abundant Pacific moisture, instability (to 2,000 J/kg MUCAPE) and rainfall from the Gulf of California into southern Arizona this afternoon. The convective structure of the areas of rain is evolving from a stratiform light rain, which is ongoing north of Tucson and east of Phoenix into one that's more broken up/less widespread, but includes more convection, including strong thunderstorms. Rainfall totals so far today have been generally between a third and two-thirds of an inch over much of southern Arizona. As the pattern evolves into a more convective one, expect more isolated/scattered precipitation pattern of much higher totals where the storms line up and repeat, resulting in possible flash flooding. While the strongest storms are south of the Mexican border near the AZ/CA/Mexico junction, they are expected to advect into southwestern Arizona...but may clip extreme southeastern California. These storms are currently producing rainfall rates of up to 1.5 inches per hour, and those rates are likely to persist as the storms move into southwest Arizona. Several of the CAMs suggest these storms may develop into a slow-moving repeating line of storms near or just east of Yuma into this evening. A few of those are depicting a meso-low forming, causing the storms to locally slow down and persist over southwestern Arizona. Thus, the area of greatest concern highlights southwestern Arizona. Further east, the area of largely stratiform rain near Phoenix and Tucson is also beginning to evolve into a more convective look, particularly from Tucson south and west. Going into this evening, expect additional storms to develop and persist further north and east, potentially impacting the Tucson metro. Phoenix may end up between the two areas of convection and largely miss out on the heaviest rains, though isolated storms can't be ruled out. Wegman ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6XF7ShSEmcA6jqnrn0S-3DxlSNpZEmlHjD6NNJzj5kOsEwql6UD63v2RU5FnMZ6z5Y9P= cIZcWBmOKzyxIUvue1HI0RI$ for graphic product... ATTN...WFO...PSR...TWC... ATTN...RFC...CBRFC...CNRFC...NWC... LAT...LON 34061357 33271245 33371068 31881024 31291085=20 31341133 31351146 31831276 31961330 32151396=20 32441484 32721522 33121522 33901431=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .