Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Nov 11 2024 00:27:49 FOUS30 KWBC 110027 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 727 PM EST Sun Nov 10 2024 Day 1 Valid 01Z Mon Nov 11 2024 - 12Z Mon Nov 11 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS A PORTION OF THE TENNESSEE VALLEY... Satellite and radar trend from the late afternoon and early=20 evening have been for decreasing coverage of convection capable of=20 producing locally heavy rainfall amounts and rates. The 18Z run of=20 the HREF and its associated neighborhood probability of exceedance=20 guidance still suggests some spotty coverage of 10 percent chance=20 of rainfall rates exceeding 1 inch per hour through 11/05Z or=20 11/06Z. So was able to trim much of the Slight and Marginal risk=20 areas. Kept a small portion of the Marginal risk over the=20 southeastern tip of Louisiana given deeper moisture still=20 circulating around Post Tropical Cyclone Rafael and the way the 18Z HREF keeps some 1-inch and 2-inch per hour neighborhood=20 probabilities lurking right near the coastline overnight. Based on=20 radar...can't entirely rule it out while having only a low-end=20 amount of confidence that it will occur. Farther north...MRMS=20 showed maximum rainfall amount around a quarter of an inch per 3=20 hours over an area with dry antecedent conditions. So the Marginal was removed there. Day 2=20 Valid 12Z Mon Nov 11 2024 - 12Z Tue Nov 12 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Chenard Day 3 Valid 12Z Tue Nov 12 2024 - 12Z Wed Nov 13 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS WESTERN WASHINGTON AND NORTHWEST OREGON... 20z Update: No changes to the inherited Marginal risk area over western WA/OR. Still on track for a slightly stronger atmospheric river to begin impacting these areas between 00z-12z Wednesday. Combining this system and the previous one today into Tuesday...and rainfall totals from Sunday through 12z Wed should average 3-5" across terrain areas, with as much as 5-7" over the Olympic Peninsula. Thus the uptick in rainfall rates with this AR Tuesday night should be enough to result in at least minor flood impacts given gradually saturating soil conditions and rising streamflows with time. Chenard ....Previous Discussion... Precipitable water values of 0.75-1" advect in as a cold front approaches, perhaps moves ashore, the Washington and northern Oregon coast Wednesday morning. Inflow from the Pacific rises to 60 kts at 850 hPa out of the south-southwest with limited instability available near and behind the front. The ingredients appear to be there for hourly rain totals of 0.5"+, which would be most problematic in burn scars. Over the full day, local amounts of 3-4" are advertised for much of the guidance, which would be most problematic along the Skokomish river in the Olympic Peninsula. Enough was there in the guidance for the inherited Marginal Risk area to remain from continuity; simplified its shape. Roth Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6n43e14KBmNHkwfy1tlRdtChRpHGBx9ezsqvvKb5K07Z= _9Gus_WSiHXhkvyKGqVV2EqkM1Zv-27YOINz71eRshOc-2U$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6n43e14KBmNHkwfy1tlRdtChRpHGBx9ezsqvvKb5K07Z= _9Gus_WSiHXhkvyKGqVV2EqkM1Zv-27YOINz71eR8mzgaVM$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6n43e14KBmNHkwfy1tlRdtChRpHGBx9ezsqvvKb5K07Z= _9Gus_WSiHXhkvyKGqVV2EqkM1Zv-27YOINz71eRe94e0Tc$=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) .