Subj : HVYRAIN: Excessive Rainfall Discussion...updated To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Feb 06 2025 22:19:45 FOUS30 KWBC 062219 AAA QPFERD Excessive Rainfall Discussion...UPDATED NWS Weather Prediction Center College Park MD 519 PM EST Thu Feb 6 2025 Day 1 Valid 2218Z Thu Feb 06 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 Precipitation Discussion (MPD) 23 that is valid until 03z this evening. After a one day break another system is forecast to move into CA today and Thursday night. Not an AR but rather a compact, dynamic system with a vigorous mid level shortwave and strong left exit region upper level jet forcing. These dynamics should support a short duration period of enhanced rainfall rates, although the quick forward motion of the system will limit overall rainfall magnitudes. Given the low-level ageostrophic response ahead of the upper level jet streak, the latest (00Z) GEFS output shows a quick uptick in southwesterly 850-700 mb moisture transport, peaking between 3-4 standard deviations above normal across the central 2/3 of CA Thursday afternoon and evening. Recent model runs continue to show 1-2+ inches falling mostly within 12 hours, with localized amounts of 3+ inches over the coastal ranges and Sierra foothills per the latest high-res guidance. Given the saturated conditions 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 localized runoff issues, especially over burn scars across Santa 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 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 run of the mill -- 0.75-1.25" -- the coolness of the atmosphere is leading to significant saturation, which is aiding precipitation efficiency. MU CAPE of 500-1000 J/Kg is being tapped by elevated activity across west- central KY while similar values of ML CAPE are being utilized by more surface based convection closer to the front. The expectation given the above is for hourly rain totals to 1.5" and local amounts of 3" being possible, which is problematic given the flash flood guidance values being depressed, roughly in the 1-1.5" in 3 hour range. Some of this region is still likely more sensitive than normal to additional heavy rainfall given the 1-3" that fell over the past 24 hours. Overall, a widely scattered to scattered flash flood risk appears to exist. Mesoscale Precipitation Discussion #24 covers the expectations through 04z 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!5SE4mgNYYbuYPOXYezE6X0oxfMIlpZ-SsPD3EGy7vXQG= qR9EnQTEA38qR_zvHt6KUKkDcFVsb5QY5gsmnjddvsPO1iA$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5SE4mgNYYbuYPOXYezE6X0oxfMIlpZ-SsPD3EGy7vXQG= qR9EnQTEA38qR_zvHt6KUKkDcFVsb5QY5gsmnjdd_IC4vrs$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5SE4mgNYYbuYPOXYezE6X0oxfMIlpZ-SsPD3EGy7vXQG= qR9EnQTEA38qR_zvHt6KUKkDcFVsb5QY5gsmnjddkmNcFdM$=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) .