Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 31 2024 17:39:33 AWUS01 KWNH 311739 FFGMPD NMZ000-AZZ000-312330- Mesoscale Precipitation Discussion 0768 NWS Weather Prediction Center College Park MD 138 PM EDT Wed Jul 31 2024 Areas affected...southern Arizona, southern New Mexico Concerning...Heavy rainfall...Flash flooding possible Valid 311738Z - 312330Z Summary...Destabilizing atmosphere will support a slow expansion of showers and thunderstorms through the afternoon. Rainfall rates may reach as high as 1"/hr in the deeper convection, which through slow motion could result in 0.75-1.5" of rain in a short period. Flash flooding is possible. Discussion...The GOES-E day cloud phase RGB product and accompanying lightning cast probabilities indicate that updrafts are strengthening within a destabilizing atmosphere across portions of the Southwest. This is concurrently reflected by increasing Cu/TCu noted in the visible imagery. At the same time, a shortwave lifting out of Chihuahua is evident as a weak spin in reflectivity moving towards far SW New Mexico. Downstream of this impulse, MLCAPE as measured by the SPC RAP has surged to 1000-1500 J/kg in far southern NM and AZ, collocated with PWs as measured by GPS as high as 1.1 to 1.3 inches, nearing the 90th percentile for the date. A few showers have already developed in southern NM, and it is likely coverage will continue to expand impressively in the next few hours. Although low-level inflow on 850-700mb winds are just 10 kts, this is sufficient to surge moisture flux above +1.5 sigma into southern AZ since PWs are anomalous. This will occur in tandem with a slow but steady rise in MLCAPE which may reach 2000 J/kg in southern AZ by late this aftn, and still around 1000 J/kg farther east into NM. This robust environment will become increasingly impinged upon by the shortwave lifting northwest, and this will result in rapidly increasing coverage and intensity of convection over southern Arizona. This is reflected both by high-res CAMs and the UA WRF, with rain rates progged by the HREF potentially reaching above 1"/hr at times, leading to accumulations of 0.75-1.5" just 1-2 hours according to the UA WRF precipitation product. Additionally, a slow increase of 0-6km bulk shear will allow for some storm organization northwest of the shortwave, potentially leading to clusters of storms with a longer duration of these heavy rain rates. This could result in several instances of flash flooding across southern AZ this aftn into this evening despite storm motions that may reach 10-15 kts. Farther to the east over southern NM, the iteration of the shortwave is likely to be less robust as it just grazes the region, but slower storm motions and a more favorably placed RRQ of an upper jet streak could result in very slow moving storms of just around 5 kts with equally impressive rain rates. This could cause isolated instances of flash flooding, but impacts will be most likely across any urban areas or sensitive burn scars. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_jgmsjJ8_bn7Ox6sPcPLLQ9YnbADuz3ATJGqGrfhMCaY_YyL7rpeWb7oR6GRFoRkzSHI= daZlnaOJpSqDXRTfOcbBHl4$ for graphic product... ATTN...WFO...ABQ...EPZ...FGZ...PSR...TWC... ATTN...RFC...CBRFC...WGRFC...NWC... LAT...LON 34350930 34340819 34010774 33710717 33580639=20 33600576 33380528 32950511 32550521 32520610=20 32630689 32640765 32360809 31930820 31520816=20 31190829 30980938 31241119 31541210 32341219=20 32761174 33161125 33541087 33961032=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .