Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Dec 02 2023 12:35:09 AWUS01 KWNH 021235 FFGMPD FLZ000-GAZ000-ALZ000-MSZ000-LAZ000-021833- Mesoscale Precipitation Discussion 1186 NWS Weather Prediction Center College Park MD 733 AM EST Sat Dec 02 2023 Areas affected...Central Gulf Coast into the Florida Panhandle Concerning...Heavy rainfall...Flash flooding possible Valid 021233Z - 021833Z SUMMARY...Showers and thunderstorms will generally be on the increase in coverage and intensity going through the midday hours. A combination of heavy rainfall rates and localized training cell activity may result in scattered instances of flash flooding. DISCUSSION...The latest surface analysis shows a west/east oriented low-level trough axis/mesoscale boundary lingering over the far northern Gulf of Mexico south of the FL Panhandle and extending westward into the coastal parishes of south-central to southeast LA. Strengthening deep layer warm air advection and moisture transport over this boundary in response to a weak low-amplitude shortwave perturbation advancing northeast across the central Gulf Coast has resulted in a general uptick in the coverage of heavy shower and thunderstorm activity. MUCAPE values of as much as 1000 to 1500 J/kg are noted across southeast LA and into the immediate offshore waters of southern MS and southern AL. The 3-hour MUCAPE differentials across this region are as much as +250 to +500 J/kg, and suggestive of the northeast transport of greater instability albeit a bit elevated. The PW values are gradually increasing with time with the NESDIS Blended TPW imagery showing a well-defined northward transport of tropical moisture with 2.0 to 2.25 inch PWs lifting north from the Gulf of Mexico toward the central Gulf Coast. The aforementioned low-amplitude shortwave perturbation shows up quite well in the 850/700mb and 700/500mb CIRA-ALPW datasets approaching southwest to south-central LA, and there is evidence in surface observations of a low center near the coast. Already there are broken areas of convection with heavy rainfall rates of 1 to 2 inches/hour impacting parts of south-central to southeast LA and coastal areas of southern MS. Even stronger convection with heavier rates are noted offshore of the FL Panhandle to the south and southwest of Panama City as a more organized convective band with very cold cloud tops aligns itself in close proximity to the aforementioned mesoscale boundary/trough. Given the increasingly parallel orientation of the convection to the deeper layer mean flow, there will be concerns for some training convective bands/cell-activity that will favor excessive rainfall totals. The 06Z HREF and recent HRRR guidance may be a bit too far north with their QPF footprint this morning, and the latest radar/satellite trends suggest areas closer to the Gulf Coast itself will tend to be at risk for the heaviest amounts. Additional rainfall amounts of as much as 3 to 5 inches will be=20 possible going through midday, and this may result in scattered instances of flash flooding and especially around the more sensitive urbanized locations. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!79OZIpLZZaNhcMBW4vXmTwNRqj4tMPNVSVvwEPjeScJaPO9fd_OdbFLCFo4ZTqLTlBTA= 4uo3E1sJNVVaUUbJba85ecg$ for graphic product... ATTN...WFO...JAN...LCH...LIX...MOB...TAE... ATTN...RFC...LMRFC...SERFC...NWC... LAT...LON 31398750 31188539 30868451 30328396 29738424=20 29528504 29918577 30188672 30088841 29628958=20 29369064 29309158 29809183 30399105 31138911=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) .