Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Oct 20 2024 19:41:13 FOUS30 KWBC 201940 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 340 PM EDT Sun Oct 20 2024 Day 1 Valid 16Z Sun Oct 20 2024 - 12Z Mon Oct 21 2024 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE SOUTHERN HIGH PLAINS TODAY... 16Z update... The latest observations show that rains have decreased across portions of southeast New Mexico this morning and the HRRR and other CAM guidance shows an additional round of higher rainfall amounts passing through east-central/northeast portions of New Mexico today and into the evening hours. Maintained the Slight and Marginal Risk areas for that part of the state; however with the improving conditions across the southeast part of the state the southern bounds of the Marginal Risk and Slight Risk areas were reduced northward. Campbell Maintained the risk Marginal risk over portions of eastern New Mexico into portions of adjoining states as thunderstorms from the overnight hours should persist beyond 12Z given a highly diffluent upper level flow pattern and a low level jet that keeps convection fed with enough moisture to offset modest instability. The exact placement is a bit in question but was confident enough to largely keep the Slight Risk from Saturday in place into the new Day 1 period due to the expected persistence of the highly diffluent flow aloft helping deep layer ascent over a broad area. In addition...portions of eastern New Mexico were soaked prior to the start of the Day 1 period...which has increased the hydrologic sensitivity to additional rainfall. The low level forcing may not be quite as strong with models showing a modestly weaker low level jet and a correspondingly more modest magnitude of moisture flux convergence. Either way...the potential exists for heavy to excessive rainfall again today before the overall pattern changes enough to lessen the threat. Northwest US... Maintained the Marginal risk area in parts of Washington state with only minor modification. The deepest moisture and heaviest rainfall rates should be shifting southward as a cold front makes its way inland from the eastern North Pacific. However...there looks to be a period in the Olympics and far northern Cascades of Washington that should get additional rainfall associated with the surface and upper low. The additional rainfall amounts only look to be an inch or less...but the combined effect of the rainfall today plus what fell on Saturday may still lead to isolated run- off problems before drier air builds into the region later today/tonight. Bann Day 2 Valid 12Z Mon Oct 21 2024 - 12Z Tue Oct 22 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Campbell Day 3 Valid 12Z Tue Oct 22 2024 - 12Z Wed Oct 23 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Campbell Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6SEae0F7MC26JHdHp0h2j1RYROjzDssX9zvRlkif5PAS= 52PGRWMJNlQ0FcHEiNZHJfVHMCjxp1sV9EcRg__i-Xn_ek0$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6SEae0F7MC26JHdHp0h2j1RYROjzDssX9zvRlkif5PAS= 52PGRWMJNlQ0FcHEiNZHJfVHMCjxp1sV9EcRg__i7VtbSBI$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6SEae0F7MC26JHdHp0h2j1RYROjzDssX9zvRlkif5PAS= 52PGRWMJNlQ0FcHEiNZHJfVHMCjxp1sV9EcRg__iQQyDTQE$=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) .