Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Mar 15 2025 21:29:17 AWUS01 KWNH 152129 FFGMPD GAZ000-TNZ000-KYZ000-ALZ000-MSZ000-160315- Mesoscale Precipitation Discussion 0066 NWS Weather Prediction Center College Park MD 528 PM EDT Sat Mar 15 2025 Areas affected...Middle & Eastern TN...Northeast MS...Northern AL...Northwest GA...South-Central KY... Concerning...Heavy rainfall...Flash flooding likely Valid 152130Z - 160315Z SUMMARY...Multiple lines of thunderstorms with moderate shield precipitation between crossing already saturated/low FFG soil conditions, likely to continue flash flooding risk through to early overnight period. DISCUSSION...A very complex surface pattern exists across the middle MS Valley due to the back to back strong upper-level shortwaves. This continues through depth with the EML from the prior stronger closed low being modified by earlier convection this morning across E TN/N MS; while a secondary dry slot is starting to manifest across AR in the wake of the secondary shortwave now maturing across S MO. As such, surface moisture though worked over, remains across E TN/W KY/N MS with TDs still in the upper 50s/lower 60s. However, strong LLJ in response to the shortwave has allowed for the western branch of low level moisture and warming at the boundary layer to wash through and with steepening lapse rates from the new EML; an expanding area of MUCAPE is developing across NE MS and W Middle TN in the wake of the stronger cells further east. As such, there is an expectation of the stronger forcing along the cold front and lifting surface low across N MS to expand elevated thunderstorms along the leading edge further into W Middle TN. MUCAPEs of 500-1000 J/kg will increase over the next few hours and feed cells and given strong low level moisture flux convergence allow for increasing rainfall potential with 1-1.5"/hr rates possible. This is going to fall on areas already saturated/flooded by earlier rounds of thunderstorms (see below) and likely to exceed the compromised FFG values at or below 1.5 at 1-3 hour time periods. Ahead of this new development, the initial storms continue to press eastward across E Middle TN into the Cumberland Plateau as well as extending back as a pre-frontal convective line across N AL and NE MS. A broad shield of moderate precipitation is likely to continue between these two lines maintaining flooding conditions through the late evening/early overnight period.=20=20 Cells to the east are starting to weaken a bit, with reducing lightning mainly has area has only received advected higher theta-E air from central AL/NE GA given cloud cover inhibiting insolation throughout the day. Still, there is weak but sufficient MUCAPEs into E TN and far S KY to maintain some. A spot or two of 3-4" remains possible organization over the next few hours. Rates of 1-1.5"/hr are probable given the broad, strong LLJ pumping 1.5-1.75" TPW (mainly below 700mb) on 50+kts of 850mb southerly flow/WAA. As such, rainfall pattern will show broad area of 2-3" across much of the eastern half of TN and northern AL where multiple rounds will cross with embedded weakening but intense showers to overtake those lower FFG values/saturated soils in the region keeping flash flooding likely through much of of the evening into early overnight period; but a spot or two of 3-4" may result in considerable or even significant flash flooding possible. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9BAOaS0GR8qN_Lw5l6zu_8ndMnqMO_QKRe3gr0a_a7eWDmIYEO2pGoZ15D8wpzhZB-H9= YbKfZSHxeuDjH6T-pjLeEpY$ for graphic product... ATTN...WFO...BMX...FFC...HUN...JAN...JKL...LMK...MEG...MRX... OHX... ATTN...RFC...LMRFC...OHRFC...SERFC...NWC... LAT...LON 37158440 36498387 35568421 34458484 33638532=20 33158642 32408895 32688965 33928905 35528824=20 36368765 36728673 37148538=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) .