Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Nov 11 2023 00:29:33 FOUS30 KWBC 110029 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 728 PM EST Fri Nov 10 2023 Day 1 Valid 01Z Sat Nov 11 2023 - 12Z Sat Nov 11 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Bann Day 2 Valid 12Z Sat Nov 11 2023 - 12Z Sun Nov 12 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Mullinax Day 3 Valid 12Z Sun Nov 12 2023 - 12Z Mon Nov 13 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR SOUTH TEXAS... A potent 250-500mb upper trough over Baja California will track across northern Mexico on Sunday. It will induce vertical ascent atop the atmosphere thanks to healthy positive vorticity advection (PVA) and South Texas' placement beneath the right-entrance region of a 250mb jet streak Sunday night. Meanwhile, two sources of rich tropical Pacific moisture will be directed into South Texas. The first source region is based out of the East Pacific as 700mb moisture flux is channeled northward towards the Rio Grande Valley. The second source of moisture arrives Sunday night as easterly flow strengthens within the 850-700mb layer and an IVT of 400-500 kg/m/s is directed at the Lower Texas Coast. The result is a highly anomalous moisture regime for mid-November. NAEFS between 00-12Z Monday show PWs that are >2" along the Lower Texas Coast, which is above the 99.5th climatological percentile. PWs are not quite as high farther west towards Laredo and south of San Antonio, but PWs could still top 1.8" which is above the 97.5th climatological percentile. While there is ample synoptic scale lift present and no shortage of moisture, there remains a lack of instability. This should help to suppress torrential rainfall rates of 2-3"/hr for example, but area averaged model soundings still depict warm cloud layers could be as deep as 14,000ft AGL and low-mid level RH values >95% Sunday night. These parameters would yield efficient rainfall rates that could cause localized ponding in poor drainage areas and more urbanized settings. The region also does not feature quite as dry of soils thanks to recent heavy rainfall the past couple days. The latest NBM sported 40-50% probabilities for >3" of rainfall from Laredo on east to the central Texas Coast, and the bulk of this rainfall occurring between 00-12Z Monday. Given these factors, a Marginal Risk was introduced for South Texas. Mullinax Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4GOnhbWIeFDXtR3CfUHPntdTJZW7uqZUnbDRv6mnn9Pa= xMpAqSJ8J9izo4bogHPDSUgaG8FEyd_xRcCymJYqHKQSy0o$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4GOnhbWIeFDXtR3CfUHPntdTJZW7uqZUnbDRv6mnn9Pa= xMpAqSJ8J9izo4bogHPDSUgaG8FEyd_xRcCymJYq85bwQAc$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4GOnhbWIeFDXtR3CfUHPntdTJZW7uqZUnbDRv6mnn9Pa= xMpAqSJ8J9izo4bogHPDSUgaG8FEyd_xRcCymJYqqFmeHMU$=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) .