Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Nov 11 2023 19:51:26 FOUS30 KWBC 111951 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 250 PM EST Sat Nov 11 2023 Day 1 Valid 16Z Sat Nov 11 2023 - 12Z Sun Nov 12 2023 The latest CAM guidance, including the latest HRRR run, is indicating the potential for scattered areas of convection to develop across the central Florida Peninsula Saturday afternoon and early evening, with the potential for some isolated 2+ inch rainfall totals. However, the coverage of this convection does not appear to be widespread enough nor quite heavy enough to merit any risk areas. Also, Deep South Texas may also have some scattered 1+ inch rainfall totals through Saturday night, but here again not enough to warrant any flooding concerns at this time. Hamrick Day 2 Valid 12Z Sun Nov 12 2023 - 12Z Mon Nov 13 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF SOUTHERN TEXAS... A mid-to-upper level trough will drift east across northwestern Mexico and the southwestern U.S. Sunday into Sunday night. Moist southwesterly flow aloft in tandem with strengthening low level easterly winds will enhance an already moist airmass in place across the region. Forecast soundings show a deeply saturated column with PWs near or slightly above 2 inches (more than 2 standard deviations above normal for early-middle November) along the lower Texas Coast back into the Rio Grande Valley. This moisture along with large-scale ascent from right entrance upper jet dynamics will support widespread showers and elevated thunderstorms across the region. While moisture and lift will be abundant, the lack of appreciable instability over land will be a mitigating factor in terms of very high rainfall rates and resulting flash flooding, with the region northwest of the surface frontal boundary. However, a deep warm cloud layer and high lower-middle tropospheric relative humidity will likely support efficient rainfall rates over an extended time period that may cause some nuisance level flooding in poor drainage and urbanized areas.=20 The 12Z model guidance suite indicates the potential for 2 to 4 inch rainfall totals across coastal portions of Deep South Texas, and the CAM guidance suggests the greatest QPF will be near and south of the greater Corpus Christi area. The pool of instability off the coast will support even greater rainfall rates and overall totals, and if any of this heavier offshore convection makes it onshore, the risk of flooding would increase. Therefore, a Slight Risk area for excessive rainfall has been introduced from near Victoria to the greater Brownsville area. Hamrick/Pereira Day 3 The Day 3 outlook will be updated by 2030Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-xbmEvSe2A0doINwZL2fsrxALjf-93kCdNg1Xzdd_TyT= GLjpypDJjp6btxSgmICM75DE2oNQayDfHZ5nypKt0uhbOO8$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-xbmEvSe2A0doINwZL2fsrxALjf-93kCdNg1Xzdd_TyT= GLjpypDJjp6btxSgmICM75DE2oNQayDfHZ5nypKthGkRF-A$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-xbmEvSe2A0doINwZL2fsrxALjf-93kCdNg1Xzdd_TyT= GLjpypDJjp6btxSgmICM75DE2oNQayDfHZ5nypKt8aeUXhg$=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) .