Flash Flood Guidance
Issued by NWS
Issued by NWS
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286 AWUS01 KWNH 221852 FFGMPD NMZ000-AZZ000-UTZ000-230050- Mesoscale Precipitation Discussion 0490 NWS Weather Prediction Center College Park MD 250 PM EDT Sat Jun 22 2024 Areas affected...Southwest U.S. Concerning...Heavy rainfall...Flash flooding possible Valid 221850Z - 230050Z SUMMARY...An increase in the coverage of showers and thunderstorms this afternoon capable of producing high rainfall rates will once again pose concerns for areas of flash flooding. Any localized slot canyons, burn scars, and the normally dry washes will be the most susceptible to see runoff and flash flooding concerns. DISCUSSION...The midday GOES visible satellite imagery shows a substantial cloud deck extending from central and southern AZ northeastward across northern and central NM in connection with a deep plume of lingering tropical moisture formerly connected to Tropical Storm Alberto which previously came across Mexico. However, there is a fair amount of boundary layer heating taking place, and especially over areas of southeast AZ into west-central NM where there are some areas of showers and thunderstorms developing. SBCAPE values are on the order of 500 to 1000+ J/kg locally, but these magnitudes are expected to increase over the next few hours as additional solar insolation takes place. Meanwhile, the PWs are anomalously very high for this time of the year and as high as 3 to 5+ standard deviations above normal and above the 95th percentile from southern AZ through central NM. An additional uptick in the coverage of showers and thunderstorms can be expected through the afternoon hours that will be capable of producing very heavy rainfall rates that may approach or locally exceed 2 inches/hour from areas of southern AZ through central NM where the CIRA-ALPW data confirms the aforementioned tropical moisture plume extending well into the 500/300 mb layer. Areas adjacent to this across northern AZ and southern UT should have less efficiency where there is drier air near the top of the column, and thus convection here that does initiate near the terrain will tend to have relatively lower rainfall rates. The 12Z HREF guidance overall suggests the Mogollon Rim area and portions of southeast AZ should have the heaviest rainfall potential given a combination of deeper moisture, instability and orographics. Some rainfall totals of 2 to 3 inches, with isolated heavier amounts will be possible. Isolated to scattered instances of flash flooding will once again be possible given the thermodynamic environment and orographic focus of much of the convection this afternoon. The localized slot canyons, areas near burn scars, and the normally dry washes will be particularly sensitive to the high rainfall rate potential and thus at greatest risk for flash flooding. Orrison ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...ABQ...EPZ...FGZ...PSR...SLC...TWC...VEF... ATTN...RFC...ABRFC...CBRFC...WGRFC...NWC... LAT...LON 38541133 36711084 36320918 36750695 36950571 36790460 36210402 35240394 34290452 32980518 32510620 32520779 32200860 31420937 31291082 31361155 31731256 32381296 33961259 35221312 36551325 38511241