Subj : Flood potential Four Corn To : All From : Mike Powell Date : Fri Sep 12 2025 13:15:56 AWUS01 KWNH 121807 FFGMPD COZ000-NMZ000-AZZ000-UTZ000-122330- Mesoscale Precipitation Discussion 1074 NWS Weather Prediction Center College Park MD 206 PM EDT Fri Sep 12 2025 Areas affected...Western CO...Eastern UT...Northwest NM...Far Northeast AZ... Concerning...Heavy rainfall...Flash flooding possible Valid 121805Z - 122330Z SUMMARY...Quick bursts of sub-hourly .5-.75" totals and isolated repeating spots that may have localized maxima to 1.5" through the afternoon will push naturally low FFG values, especially near burn scars and steep gulleys. A few spots of flash flooding are possible through the evening hours. DISCUSSION...GOES-East WV suite depicts a global scale meridional trough between 117W and 114W slowly shifting eastward, with strong core of energy just west of the base of the overall trough across the Lower Colorado Valley providing a favorable downstream environment to draw remaining enhanced sub-tropical moisture out of the Sea of Cortez northward across the Four Corners region into western CO. CIRA LPW, denotes core of the best moisture remains along and just west of the NM/AZ line through the lowest levels though surface Tds across the Four Corners into Western CO still above normal with mid-50s in AZ/NM and upper 40s to low 50s in the higher altitudes of the San Juans and further north. Additionally, WV suite shows a kink in the upper level jet pattern with expanding right entrance region across S UT into CO as the upstrem jet core rounds the base over the Lower Colorado. This will further enhanced surface to 700mb southwesterly flow while also providing solid larger scale UVVs and outflow to maintain convective clusters. Currently best convergent clusters reside on the northwest nose of the deeper level moisture across East central UT starting to spread across west-central to NW CO. Total Pwats of .75-1" are at 1.5 standard anomalies and with strength of deep layer flux convergence is supporting some above average efficiency thunderstorm activity (including some that induced flash flooding further west in E UT). This includes increasing agitation/TCU field across SE UT, though larger clusters capable of .5"/hr totals continue to expand over SW CO. Cells are fairly progressive, but also have a weak training/repeating orientation as the overall height-fall axis presses eastward very slowly over the next few hours. Scattered to numerous spots of .25-.5" totals are probable, though isolated sub-hourly totals up to .75" and a random potential for repeats may result in a spot or two of 1-1.5". The sheer rate within complex terrain and natural low FFG values in that .5-1"/hr range, along with noted burn scars suggested widely scattered incidents of flash flooding remain possible this afternoon into evening. Further south, the speed max rounding the base of the trof and overall slow eastward motions further increased DPVA and favorable enhancement of weak shortwave feature lifting out of Northern Old Mexico into SE AZ. Stronger thunderstorms are developing at the intersection of the SSWly enhanced LLJ flow and the Mogollon Rim/San Francisco Mtns. Redevelopment along those ridges is likely to continue and support downstream repeating clusters across W and NW NM and far eastern AZ. Deeper layer moisture of 1.25 to 1.4", especially loaded below 700mb suggest slightly higher efficiency than further north and spots of 1" are probable and possible to induce localized flash flooding in prone arroyos. Gallina ATTN...WFO...ABQ...BOU...FGZ...GJT...PUB...SLC... ATTN...RFC...FWR...KRF...STR...TUA...NWC... LAT...LON 40810709 40570572 39460533 36370664 35080728 34280778 33850854 33900944 34340996 34831000 35950987 36970970 37620997 38471034 39690972 40650849 $$ --- SBBSecho 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (618:250/1) .