Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun May 25 2025 17:00:12 AWUS01 KWNH 251700 FFGMPD TNZ000-MSZ000-MOZ000-ARZ000-OKZ000-252200- Mesoscale Precipitation Discussion 0314 NWS Weather Prediction Center College Park MD 1259 PM EDT Sun May 25 2025 Areas affected...Eastern Oklahoma through much of Arkansas Concerning...Heavy rainfall...Flash flooding possible Valid 251659Z - 252200Z Summary...Showers and thunderstorms will increase in coverage once again this afternoon and move across portions of Oklahoma and Arkansas. Rainfall rates of 1-2"/hr or more are expected, which could produce 2-3" of rain with locally higher amounts by this evening. Flash flooding is possible. Discussion...The combination imagery of the regional radar mosaic and Day-Cloud Phase RGB suggest the environment from the Southern Plains into the Lower MS VLY is becoming favorable for renewed convective growth. Updrafts noted in the RGB coincident with increasing Lightning Cast values suggest the environment is destabilizing, additionally reflected by SPC RAP MLCAPE of 1000-3000 J/kg, and in some areas this is resulting in rapid uptick of reflectivity values associated with thunderstorms. While convection from this morning has primarily decayed, remnant outflow boundaries and the wavering stationary front are providing focus for ascent, which within the increasing instability and overlapped ~1.7 inch PWs, is resulting in renewed convection. This is most clearly evident along a boundary in the vicinity of Fort Smith, AR, but other cells blossoming from eastern AR to nearly the Red River Valley indicate the flash flood risk is steadily increasing this aftn. The high res CAMs, despite latitudinal differences in their simulated reflectivity, are all in agreement that coverage will expand quickly in the next few hours. This is supported by current observations, with more rapid growth likely as a shortwave tracks west to east overhead from OK. The latitudinal uncertainty reflected in the CAMs provides some challenge for the greatest flash flood risk location, but the HRRR, ARW2, and RRFS are more closely aligned, and south, of the other guidance, which is tied better to the current instability gradient. This is also supported by what should be a slight jog south of the stationary front as it gets pushed by remnant outflow boundaries. As thunderstorms develop, they should track progressively to the east on 0-6km mean winds of around 20 kts, but as they deepen and organize thanks to bulk shear of 30-40 kts, clusters will begin to track E/SE and repeat/train over the same areas. With rain rates progged by both HREF and REFS probabilities to exceed 2"/hr (20-40% chance), this will result in stripes of 2-3" of rain with locally higher amounts possible (20-30% chance). This region has been saturated by heavy rainfall. 48-hr rainfall from MRMS has been anywhere from 2 to 6 inches, leading to extremely compromised FFG as low as 0.5-1.5"/3hrs. This suggests that any of these heavy rates will quickly yield runoff, leading to potential instances of flash flooding through the aftn. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_v_l5HEX3go-cZVenFMuvBvN9Og1R9Q8um1oN-feJn-AiwUD5ZDpGK5OS8a4cVjhvr9g= No6safGxp7Kf7pxsWlOFKvg$ for graphic product... ATTN...WFO...LZK...MEG...OUN...PAH...SGF...SHV...TSA... ATTN...RFC...ORN...TUA...NWC... LAT...LON 36609089 36539035 36358994 36118963 35568958=20 34679039 34099205 33959377 34069530 34169611=20 34399644 34789655 35809605 36379524 36489359=20 36539179=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) .