Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Oct 29 2024 20:16:12 FOUS30 KWBC 292015 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 415 PM EDT Tue Oct 29 2024 Day 1 Valid 16Z Tue Oct 29 2024 - 12Z Wed Oct 30 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Bann Day 2 Valid 12Z Wed Oct 30 2024 - 12Z Thu Oct 31 2024 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE SOUTHERN PLAINS TO THE UPPER MISSISSIPPI VALLEY/UPPER MIDWEST... A deep layered trough is expected to eject into the Plains by=20 Wednesday morning, which in turn results in surface troughing that draws Gulf moisture northward ahead of an approaching cold front.=20 Cooler air filtering in from the west/north will encounter the warm air advection associated with the low- level jet. Convection over=20 the region is expected to increase in both coverage and intensity with the set up becoming more favorable for isolated heavy=20 rainfall amounts/rates and localized flooding concern. The 12Z global and ensemble guidance continues to show two=20 distinct areas swaths of higher QPF. The first remains focused near the juncture of Oklahoma, Texas and Arkansas state borders amid=20 areas of higher instability...on the order of 1500 to 2500 J per kg of surface based CAPE. The second area from northeast Kansas to northern and central Wisconsin still inched westward in this model cycle close the the greatest mid- and upper-level height falls which was roughly co-located near a region of sloped frontogenesis in the 800 mb to 600 mb layer late in the period. At the same time...the 29/12Z NAM accelerates low level flow to the 45 kt to 65 kt range acting to enhance moisture transport into the area as early as 31/03Z in a few spots. The Marginal Risk area needed only a minor nudge after the shape was altered more noticeably in the=20 previous outlook. Antecedent conditions are quite dry...as reflected by the very high flash flood guidance. That should mitigate any widespread threat=20 of excessive rainfall as well as progressive cells. Even so...the=20 Marginal Risk area still seemed appropriate based on what the=20 magnitude of the instability and mesoscale forcing from the coarser numerical guidance with room to adjust with future guidance=20 (including the CAM guidance). Campbell/Bann Day 3 Valid 12Z Thu Oct 31 2024 - 12Z Fri Nov 01 2024 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE LOWER MISSISSIPPI VALLEY... 2030Z Excessive Rainfall Update... Instability remains the highest in portions of the Lower=20 Mississippi Valley while the flow pattern/mesoscale forcing weakens farther north. The previous outlook had that pretty well handled=20 so no change was made. Bann 083-Z Excessive Rainfall Discussion... The upper level trough will continue to advance through the Upper Midwest which will send the cold front through the eastern portions of the Southern Plains and mid-Mississippi Valley. Strong to severe thunderstorms will persist for areas along and ahead of the advancing frontal boundary per SPC (Marginal Risk); which will shift the heavy rain potential to the central Gulf Coast to western Kentucky where there is a Marginal Risk area for excessive rainfall. Areal averages will be in the 1 to 2 inch range with locally higher amounts possible. Campbell Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8OnI8uxOqC5DwU3nruaA8ZccR5Fzb87B2BIvVFprSksJ= XktvWlYB7G9v3K7yAD-STa94j76zBYcGjPluEd2iu7imRTo$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8OnI8uxOqC5DwU3nruaA8ZccR5Fzb87B2BIvVFprSksJ= XktvWlYB7G9v3K7yAD-STa94j76zBYcGjPluEd2i7G8csPA$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8OnI8uxOqC5DwU3nruaA8ZccR5Fzb87B2BIvVFprSksJ= XktvWlYB7G9v3K7yAD-STa94j76zBYcGjPluEd2iqVgimEo$=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) .