Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jan 07 2023 08:19:39 FOUS30 KWBC 070819 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 319 AM EST Sat Jan 07 2023 Day 1 Valid 12Z Sat Jan 07 2023 - 12Z Sun Jan 08 2023 ....THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL ACROSS PARTS OF NORTHERN AND CENTRAL CALIFORNIA, INCLUDING NAPA VALLEY AND NORTHERN PORTIONS OF THE BAY AREA... ....Southwest Oregon into Northern and Central California... The models continue to depict robust QPF totals with this latest AR, especially within the Moderate Risk area, where most CAMs have an additional 3-6". The activity begins to taper a bit by Sat afternoon behind the initial shortwave, only to pick up once again in earnest late Sat afternoon through overnight with renewed robust low-mid layer moisture transport directed toward the Central CA Coast. Current high-res CAM guidance show hourly rainfall rates peaking between 0.50-0.75+ inch after 00Z Sun, aided by some elevated instability (MUCAPEs 400-600 J/kg), which would pose a flash flood threat over several 2020-2022 burn scars west of the Sierra and south of the Shasta/Siskiyous mountains. Have expanded the Moderate Risk area a bit farther south to include the 2020 Hennessey, Glass, and Woodward burn scars north of the Bay area. The ARI of the 90th percentile WPC PQPF is currently running at 1-2 years within the Moderate Risk area. Recent excessive rains along with several additional inches forecast, there will likely be widespread areas of flooding and if in proximity of recent burn scars, the threat for landslides, debris flows and road damage will elevate. ....Western Gulf Coast into portions of the Lower Mississippi and Tennessee Valleys... Continued with the Marginal Risk of excessive rainfall over this region, as with yesterday's Day 2 ERO. Strengthening right-entrance region upper forcing (low-mid layer frontogenesis) along with a slow moving front may be able to draw sufficient moisture flux off the western Gulf to result in a small area of training thunderstorms across this region. The models have come into better alignment with the QPF; however there area still some areal spread with respect to the areas of heaviest rainfall. Considering the spread in the guidance, will loosely organized convection implied in the splotchy QPF pattern, along with the relatively dry conditions over the past few days, have continued with the Marginal Risk with the expectation that any flash flooding will be isolated/localized. Instability is meager as well, at least outside of the Middle and Upper TX Coast, which will tend to impede convective upscale growth. Hurley Day 2 The Day 2 outlook will be updated by 0830Z. Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!9JeJ6jSk5TRQzCRXr1R0uidS_DoBg9YQ0cHlsUHQg5ai= Okk3CAxvy3L47vmLYrHjhCP_MrYjL82rFpROqsdBXbLrP0w$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!9JeJ6jSk5TRQzCRXr1R0uidS_DoBg9YQ0cHlsUHQg5ai= Okk3CAxvy3L47vmLYrHjhCP_MrYjL82rFpROqsdBJ7j3qyQ$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!9JeJ6jSk5TRQzCRXr1R0uidS_DoBg9YQ0cHlsUHQg5ai= Okk3CAxvy3L47vmLYrHjhCP_MrYjL82rFpROqsdBYe8Bllc$=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) .