Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jan 16 2024 20:43:28 FOUS30 KWBC 162043 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 342 PM EST Tue Jan 16 2024 Day 1 Valid 16Z Tue Jan 16 2024 - 12Z Wed Jan 17 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Kebede Day 2 Valid 12Z Wed Jan 17 2024 - 12Z Thu Jan 18 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF FAR NORTHWEST CALIFORNIA INTO SOUTHWEST OREGON... ....2030z update... The Marginal Risk are for day 2 (12z Wednesday -- 12z Thursday) remains mostly the same with only minor changes around the periphery. The timing of the mid-level trough's arrival continue to be on track for tonight into Wednesday morning across the Northwest coast. The GFS/ECMWF/CMC/CMCR have all trended higher with QPF totals over this 24 hour period while the NAM and UKMET have trended lower. Kebede ....Previous discussion... We opted to introduce a small Marginal risk across portions of far northwest CA and southwest OR with this update. A strong mid level shortwave will move across western OR between 06z-12z Wednesday which will result in an uptick in rainfall intensity. After 12z onshore upslope flow will continue to be directed into this region to the south of a surface low expected to be positioned off the WA coast. This is not the strongest core of IVT, but it is persistent enough to result in up to a 12 hr period where 0.25"-0.5" rainfall will be possible within the favorable western facing terrain. The consensus of current guidance would suggest 09z-21z Wed as the most favored time for these heaver rainfall rates. The 18z experimental RRFS ensemble supports 20-50% chance of 0.5"/hr rainfall during that window, with the 00z ECMWF depicting 1"/3hr rainfall. There remains some model spread with regards to the axis and magnitude of heaviest rainfall amounts. The GFS remains a bit lighter, but the 00z ECMWF/NAM/UKMET/HRRR all support some heavier totals into this region. There are several pieces of guidance that suggest 2 day rainfall amounts upwards of 4-7" over this area, which may begin to cause some mainly minor runoff concerns. Chenard Day 3 The Day 3 outlook will be updated by 2030Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7IaJSOyl_r6rUrWxX2lEXXN4S8AK57fspTAbtIr91aWv= gBDGMNwavGeruTL-mwxiVYomggoqUWoBCMcHXQ-MSa3k7ls$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7IaJSOyl_r6rUrWxX2lEXXN4S8AK57fspTAbtIr91aWv= gBDGMNwavGeruTL-mwxiVYomggoqUWoBCMcHXQ-MYQR1h-U$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7IaJSOyl_r6rUrWxX2lEXXN4S8AK57fspTAbtIr91aWv= gBDGMNwavGeruTL-mwxiVYomggoqUWoBCMcHXQ-Ma1F7w90$=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) .