Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jul 07 2023 02:25:54 AWUS01 KWNH 070225 FFGMPD TNZ000-MSZ000-MOZ000-ARZ000-070800- Mesoscale Precipitation Discussion 0648 NWS Weather Prediction Center College Park MD 1025 PM EDT Thu Jul 06 2023 Areas affected...Northeast Arkansas, Western Tennessee, Northwest Mississippi Concerning...Heavy rainfall...Flash flooding possible Valid 070223Z - 070800Z Summary...Showers and thunderstorms developing along a stationary front will expand through the evening with rainfall rates above 2"/hr. Slow motion of this convection could result in 2-3" of rain with locally higher amounts. Flash flooding is possible. Discussion...The regional radar mosaic this evening shows showers and thunderstorms expanding across northeast AR downstream of a shortwave noted on the GOES-E WV imagery near the AR/OK border. As this shortwave drifts eastward with mid-level W/NW flow, it will drive additional ascent atop a convergence of mass and moisture along a stationary boundary analyzed by WPC over Arkansas. PWs within this environment are exceedingly high, over 2 inches, which is above the 90th percentile and near the daily record. The 00Z U/A sounding at LZK also indicated nearly 11,000 ft of warm cloud depth, 3000 J/kg of CAPE, and moist-adiabatic lapse rates through a deep portion of the column, indicating efficient warm rain processes. Thunderstorms developing in this environment have produced radar-estimated rain rates of 1.5 to 2 inches per hour. The slow eastward motion of this shortwave atop the surface convergence should drive increasing convective coverage during the next few hours which is reflected by available high-res simulated reflectivity. This shortwave may also locally back the 850mb inflow so that it, while remaining modest, will resupply more favorable moisture and instability to persist thunderstorms with impressive rain rates. The HREF neighborhood probabilities indicate that rain rates will exceed 2"/hr, with 15-min rainfall accumulation possibly reaching 1" in some places according to the HRRR. Storms will generally be of the pulse variety in a region of minimal bulk shear, but will likely redevelop on outflows and residual boundaries into the overnight. Where these outflow boundaries move against the mean 0-6km wind, which will be from the west at just 10 kts, storm motions may at times fall to near 0, lengthening the duration of intense rainfall. Where this occurs, rain amounts of more than 3" are possible as reflected by HREF probabilities. 14-day rainfall from AR into TN/MS has been generally below 50% of normal which has resulted in soils that should be able to handle heavy rainfall except in the most intense rates. With rain rates possibly exceeding 2"/hr, even the relatively high FFG has a 20-30% chance of exceedance, especially where a storm can stall or move over an urban area. This suggests that at least isolated instances of flash flooding are possible tonight. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-FltzTC77P-ksNbVuGYGfeXV-ZGimT5nGCqVGH_ACJHPilqSRyRVQpmowGjDfySCn6fu= pUfTXy01ARmyEMu5w7llz6s$ for graphic product... ATTN...WFO...LZK...MEG...PAH...SGF...TSA... ATTN...RFC...ABRFC...LMRFC...NWC... LAT...LON 36929131 36639014 35958932 34928903 34408923=20 34178958 34219005 34509055 34759114 35229200=20 35599258 35919303 36329335 36689318 36919236=20 =20=20=20=20=20=20=20=20=20=20=20=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) .