Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Dec 05 2023 07:35:49 FOUS30 KWBC 050735 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 234 AM EST Tue Dec 05 2023 Day 1 Valid 12Z Tue Dec 05 2023 - 12Z Wed Dec 06 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE OREGON COASTAL RANGES INTO PORTIONS OF THE WASHINGTON AND NORTHERN OREGON CASCADES... ....Washington and northern Oregon Cascades, Central to Northern Oregon coast,,, No significant changes made to the previous Excessive Rainfall outlook areas across portions of the Pacific Northwest for the ongoing atmospheric river event. The surface frontal boundary emanating from the deep low across the North Pacific will begin to slow day 1 as it pushes into western Washington and far northwest Oregon. Strong onshore southwesterly to west southwesterly flow in an axis of anomalous PW values, 2 to 3+ standard deviations above the mean, along this boundary will continue to impact the Washington and far northern Oregon Cascades and nearly all of the Oregon coast range for most of the upcoming day 1 period. There is very good agreement in the latest model suite for additional rainfall amounts of 2-5" along the central to northern Oregon coast into the northern Oregon Cascades and Washington Cascades.=20 The heavy rainfall over the past few days has resulted in much above to high stream flows along with high soil saturation levels across the slight risk area, with the expected additional amounts likely to continue a flooding risk. The slight risk area corresponds well with where HREF neighborhood probabilities are high for 1, 2 and 3"+ amounts day 1. The central to northern Oregon coast range and the southern Washington Cascades are areas where the HREF EAS probabilities are also high for 1, 2 and 3"+ amounts, albeit over a smaller region than the neighborhood probabilities.=20 ....Northern Idaho Panhandle, far northeast Washington and far northwest Montana... No changes made to the previous marginal risk area across the northern Idaho Panhandle, including surrounding areas of far=20 northeast Washington and far northwest Montana. This region has not seen as much precipitation over the past few days as areas closer to the Pac Northwest coast have. Latest model guidance, however, does show strengthening southwesterly low level flow impacting this region with overall good agreement on precipitation potential. Areal average 1 to 2"+ amounts expected day 1 with isolated totals of 3-4"+ totals possible. With snow levels expected to remain very high, most precip will fall as rain. This along with snow melt will continue the threat for runoff issues.=20 Stream flow as per the National Water Model are a mixed bag across this area with below normal to normal flow levels intermixed with above to much above normal flow levels. This and soil saturation levels that are relatively low, under 50% across far northern Idaho, may mitigate some of the runoff threat. For these reasons the threat level was maintained at marginal. Oravec 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!5TcGkG_MUSBxvULtnalilQ_O05vifCyx0ddRPHuyTpM2= 3sNAFHHORYNxVVZy5T1xQzDYdiA9sm6BL6cusjPInA24ndM$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5TcGkG_MUSBxvULtnalilQ_O05vifCyx0ddRPHuyTpM2= 3sNAFHHORYNxVVZy5T1xQzDYdiA9sm6BL6cusjPIShgVse0$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5TcGkG_MUSBxvULtnalilQ_O05vifCyx0ddRPHuyTpM2= 3sNAFHHORYNxVVZy5T1xQzDYdiA9sm6BL6cusjPI6Vloz4E$=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) .