Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Feb 06 2025 22:17:59 FOUS30 KWBC 062217 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 517 PM EST Thu Feb 6 2025 Day 1 Valid 2211Z Fri Feb 07 2025 - 12Z Fri Feb 07 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF CALIFORNIA AND THE OHIO VALLEY... ....California... For a more detailed discussion please refer to Mesoscale=20 Precipitation Discussion (MPD) 23 that is valid until 03z this=20 evening. After a one day break another system is forecast to move into CA=20 today and Thursday night. Not an AR but rather a compact, dynamic=20 system with a vigorous mid level shortwave and strong left exit=20 region upper level jet forcing. These dynamics should support a=20 short duration period of enhanced rainfall rates, although the=20 quick forward motion of the system will limit overall rainfall=20 magnitudes. Given the low-level ageostrophic response ahead of the=20 upper level jet streak, the latest (00Z) GEFS output shows a quick=20 uptick in southwesterly 850-700 mb moisture transport, peaking=20 between 3-4 standard deviations above normal across the central 2/3 of CA Thursday afternoon and evening. Recent model runs continue=20 to show 1-2+ inches falling mostly within 12 hours, with localized=20 amounts of 3+ inches over the coastal ranges and Sierra foothills=20 per the latest high-res guidance. Given the saturated conditions=20 and brief potential for higher rates (0.35+ in/hr) beginning around 21Z along the coast and by 00Z farther inland, this may result in=20 localized runoff issues, especially over burn scars across Santa=20 Barbara, Ventura, and Los Angeles counties. Gallina/Hurley ....TN-OH Valleys into the Western Appalachians... Another round of locally heavy rain has begun to occur across=20 portions of KY, TN, WV and far western VA- NC near and ahead of an approaching cold front and near the base of a broad shortwave transiting the Great Lakes. While precipitable water values are=20 run of the mill -- 0.75-1.25" -- the coolness of the atmosphere is leading to significant saturation, which is aiding precipitation=20 efficiency. MU CAPE of 500-1000 J/Kg is being tapped by elevated=20 activity across west- central KY while similar values of ML CAPE=20 are being utilized by more surface based convection closer to the=20 front. The expectation given the above is for hourly rain totals to 1.5" and local amounts of 3" being possible, which is problematic=20 given the flash flood guidance values being depressed, roughly in=20 the 1-1.5" in 3 hour range. Some of this region is still likely=20 more sensitive than normal to additional heavy rainfall given the=20 1-3" that fell over the past 24 hours. Overall, a widely scattered=20 to scattered flash flood risk appears to exist. Mesoscale=20 Precipitation Discussion #24 covers the expectations through 04z=20 for portions of KY, northern TN, and southwest VA. Roth/Hurley Day 2 Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Pereira Day 3 Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Pereira Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7QnxbMt0H_NWok-GLmEOXmy3OOThASpupQTgdH5xbsLy= c2gzNPxW6AhLJgbotuiE6_ewKjrAUDyVgAU7pA8AUFOtotc$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7QnxbMt0H_NWok-GLmEOXmy3OOThASpupQTgdH5xbsLy= c2gzNPxW6AhLJgbotuiE6_ewKjrAUDyVgAU7pA8AfSMVT_0$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7QnxbMt0H_NWok-GLmEOXmy3OOThASpupQTgdH5xbsLy= c2gzNPxW6AhLJgbotuiE6_ewKjrAUDyVgAU7pA8A4wZCO3w$=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) .