Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Sep 12 2023 23:51:27 AWUS01 KWNH 122351 FFGMPD NMZ000-AZZ000-130550- Mesoscale Precipitation Discussion 1061 NWS Weather Prediction Center College Park MD 750 PM EDT Tue Sep 12 2023 Areas affected...central/southern AZ into NM Concerning...Heavy rainfall...Flash flooding likely Valid 122350Z - 130550Z Summary...Thunderstorms are expected to increase in coverage across central/southern AZ into NM through 06Z. A few areas of flash flooding are considered likely with repeating cells/cell training and rates of 1 to 2+ in/hr. Discussion...At 23Z, scattered thunderstorms were noted across central and southeastern AZ into western NM. The region was characterized by 500 to 1500 J/kg MLCAPE (via 23Z SPC mesoanalysis data) and +1.5 to +2.5 standardized anomalies of precipitable water (12Z NAM/GFS). Deeper layer mean flow was oriented from the west at ~20-25 kt along with a zone of stronger 700 mb flow at 10-20 kt, also from the west. The Desert Southwest was located downstream of a longwave and low amplitude mid-upper level trough axis over NV/CA and just ahead of a shortwave impulse and related jet streak moving through southern CA on 6.9 micron imagery from GOES West. Expectations are that thunderstorm coverage will increase over the next 1-3 hours as the upstream shortwave impulse over southern CA approaches, working with the available instability across the region which is expected to maintain for at least another 3-6 hours. Even after the onset of nocturnal cooling and boundary layer stabilization, elevated instability should remain given steep lapse rates in the 850-500 mb layer forecast to hover near 7.5 C/km. While individual cell motions should tend to be progressive toward the east, there will be potential for multiple rounds of thunderstorms as well as localized areas of training where west-east cell alignment occurs or where cells become temporarily anchored on local topography. These situations should support rainfall rates of 1-2 in/hr, but locally above 2 in/hr cannot be ruled out. The high moisture and sufficient CAPE environment may also support localized sub-hourly totals of 1-2 inches in 15-30 minutes. While flash flood coverage is not expected to be widespread, a few areas of flash flooding appear likely heading into the overnight with storm totals of 2-3 inches through 06Z. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8H81e7WkFeYs9JCeZXAFXjLc4C5gXAzycm7CgAlD3UcnKP8ShduN26RBW3gXVaLXRMAG= W_1OLQqLhL-liH-RLMMrd_c$ for graphic product... ATTN...WFO...ABQ...EPZ...FGZ...PSR...TWC... ATTN...RFC...CBRFC...WGRFC...NWC... LAT...LON 34670975 34440684 33710634 33210653 32840650=20 32370656 32040731 31740783 31290813 31100973=20 31241119 31891260 32741334 34371316=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) .