Subj : HVYRAIN: Excessive Rainfa To : All From : Mike Powell Date : Wed Dec 06 2023 09:53:00 FOUS30 KWBC 060733 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 232 AM EST Wed Dec 06 2023 Day 1 Valid 12Z Wed Dec 06 2023 - 12Z Thu Dec 07 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE SOUTHERN WASHINGTON AND OREGON CASCADES INTO THE COASTAL RANGES OF WESTERN OREGON AND FAR NORTHWEST CALIFORNIA AND ACROSS FAR NORTHERN IDAHO... The ongoing atmospheric river event will be diminishing during the upcoming day 1 period as the slow moving frontal boundary currently stretching from far northwest Oregon into western Washington State becomes more progressive inland across the Pacific Northwest. Moderate to locally heavy rains may still be ongoing for the first few hours of the upcoming day 1 period, but they will have mostly shifted to the south and east of where the heavy rains have fallen over the past 24 hours across central to northern Oregon coast into the northern Oregon Cascades and Washington Cascades. The expected increased inland progression of northeast Pacific height falls and the associated frontal boundary will also limit the heavy rainfall potential period, compared to the past 24 hours. This and the farther south qpf axis with little max qpf overlap day 1 and the observed heavy axis over the past 24 hours, has kept the threat level at marginal for the upcoming day 1 period. The marginal risk area continues to fit well where the HREF neighborhood probabilities are high for 1"+ rains day 1. Probabilities for 2"+ amounts day 1 are small and concentrated across far southwest Oregon and far northwest California where no precip has fallen over the past 24hrs, although this region has seen some very heavy precip totals over the weekend resulting in much above normal to high stream flow as per the National Water Model. ....Far Northern Idaho... No changes to the small marginal risk area across far northern Idaho and the immediate adjacent areas of far northeast Washington and far northwest Montana. Model consensus is for additional 1"+ precip totals day 1, with much of this falling as rain before snow levels fall by early Thursday morning. This should continue the threat of runoff issues from the past 24 hours. Oravec Day 2 Valid 12Z Thu Dec 07 2023 - 12Z Fri Dec 08 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Oravec Day 3 Valid 12Z Thu Dec 07 2023 - 12Z Fri Dec 08 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Oravec $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .