Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Sep 06 2025 18:27:34 AWUS01 KWNH 061827 FFGMPD TXZ000-NMZ000-AZZ000-070030- Mesoscale Precipitation Discussion 1055 NWS Weather Prediction Center College Park MD 227 PM EDT Sat Sep 06 2025 Areas affected...Southeast Arizona, Southwest New Mexico Concerning...Heavy rainfall...Flash flooding possible Valid 061830Z - 070030Z Summary...Showers and thunderstorms will expand across portions of New Mexico and Arizona this afternoon and evening. As convection intensifies, brief rainfall rates t0 3"/hr are possible resulting on 0.5-0.75 inches of rain in 15 minutes. This may cause flash flooding. Discussion...The GOES-E day-cloud phase micro-physics RGB this afternoon shows a slow expansion of ice-clouds associated with strengthening updrafts driving deepening Cb. At this time these are mostly positioned across southwest NM and focused in higher terrain, but should expand and move into lower elevations during the next few hours. Despite some drier air encroaching from the west noted in the LPW fields, PWs remain 1.25 to 1.5 inches as measured by GPS, above the 90th percentile for the date, which is overlapping SBCAPE that is climbing to 1500 J/kg within regions of clearing. These thermodynamics are supporting the increasing updrafts, with additional lift being provided by a weak surface trough analyzed by WPC and a shortwave that will slowly dig southeast into the evening. Despite the relatively fresh convection, these storms have already produced 15-min rainfall as measured by MRMS of 0.3 to 0.4 inches in the deeper cells. As the afternoon progresses to peak heating, surface instability may exceed 2000 J/kg, likely causing these rain rates to become even more intense. Additionally, the shortwave dropping southeast may help focus some organization later this afternoon, especially as storms begin to drop off the terrain and dive E/SE on 0-6km mean winds of around 10 kts. A lack of significant bulk shear will keep storms generally of the pulse variety, but in the presence of the increasing ascent and favorable thermodynamics, residual outflow boundaries will likely lead to additional development. This could reuslt in storm mergers/collisions causing rain rates to perk up to as much as 0.75"/15 min as reflected by the HRRR-forced UA WRF precipitation rate and HRRR 15-min rainfall product. Although total rainfall in most areas will likely remain below 1 inch, a few repeating rounds are possible which could cause locally more than 2 inches. While this will enhance the flash flood risk, it is possible that any of these intense rain rates, even if short lived, could cause rapid runoff as 3-hr FFG is generally only around 1 inch in many areas. The HREF exceedance probabilities for this 3-hr FFG peak as high as 50% in southern AZ, but any of this heavy rain falling atop vulnerable regions such as urban areas or burn scars, could experience impacts from flash flooding into this evening. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!99dzq7IUQKyvn3avb1hIDqbUdram2GDffIWqvWKCNKp6j-HbkSXA4qySCTl48fUZSWL-= -dyElsTl25kwMa3UEBNEa5Y$ for graphic product... ATTN...WFO...ABQ...EPZ...FGZ...PSR...TWC... ATTN...RFC...FWR...STR...NWC... LAT...LON 34830806 34680675 34470615 34080556 33270529=20 32530539 32000602 31770667 31580729 31390809=20 31270897 31281048 31271092 31441158 31791165=20 32221127 32731077 34350905=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) .