Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Nov 17 2023 13:41:08 FOUS30 KWBC 171341 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 840 AM EST Fri Nov 17 2023 Day 1 Valid 1340Z Fri Nov 17 2023 - 12Z Sat Nov 18 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF NORTHEAST FLORIDA AND WESTERN CALIFORNIA... 1340Z update... The Slight Risk was removed from Florida given that the heaviest rain has ended. The Marginal Risk area is being maintained to cover the area with lingering showers that is quite saturated from yesterday's rainfall. Campbell ....Florida Peninsula... Introduced a Slight Risk of excessive rainfall...generally from northeast of Lake Okeechobee where localized rainfall amounts approaching 10 inches was observed on Thursday evening...northward to the Atlantic coast south of Jacksonville. The southern extent was the most uncertain for two reasons...one question being if convection would be lingering past the start of Day 1 at 17/12Z over waterlogged areas from recent rains while the second question revolves around if/how much additional rain falls later today.=20 Most of the operational guidance showed little rainfall as far south as Indian River county...but the 17/00Z HREF showed at least low potential for rainfall that far south and the associated HREF neighborhood probabilities for 2 and 3 inch rainfall amounts in 3 hours were confined to areas around Cape Canaveral shortly after 17/12Z which spreads north through 17/18Z as a meso-scale low hugs the coast on its northward trek. Generally confined the Slight Risk to areas that have recently been soaked...while only maintaining a Marginal in the north assuming the area can better handle the rainfall. ....Coastal Southern California... Increasing rainfall rates are possible from late this evening into the overnight hours from the coastal ranges may lead to isolated problems with run off or flash flooding in the terrain. Rainfall amounts do not look to be blockbuster values but the concern would be if rainfall rates are sustained over 0.50 inches per hour for too long. Given the potential for precipitation to be convective in nature...and with 25 kts or so of on-shore flow and precipitable water in the 0.75 to 1.00 inch range along the coast by 18/09Z as shown by the NCEP models...it would appear the maximum rates suggested by the HREF are in the realm of possibility. As a result...focused a Marginal Risk area mainly in coastal areas of San Luis Obispo and Santa Barbara counties.=20 Bann Day 2 Valid 12Z Sat Nov 18 2023 - 12Z Sun Nov 19 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Bann Day 3 Valid 12Z Sun Nov 19 2023 - 12Z Mon Nov 20 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Bann Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_5R-MRndYYPw9a7D90szF3s-fOH1Dg7Y56g4Gqp0g5QA= 17LgGaGAPS7tKJaHvPcJoY6yz20uXJyjzV967K-knr778Rc$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_5R-MRndYYPw9a7D90szF3s-fOH1Dg7Y56g4Gqp0g5QA= 17LgGaGAPS7tKJaHvPcJoY6yz20uXJyjzV967K-k0cURvt4$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_5R-MRndYYPw9a7D90szF3s-fOH1Dg7Y56g4Gqp0g5QA= 17LgGaGAPS7tKJaHvPcJoY6yz20uXJyjzV967K-k6IiyKqg$=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) .