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   FOUS30 KWBC 130824   
   QPFERD   
      
   Excessive Rainfall Discussion   
   NWS Weather Prediction Center College Park MD   
   324 AM EST Sat Dec 13 2025   
      
   Day 1   
   Valid 12Z Sat Dec 13 2025 - 12Z Sun Dec 14 2025   
      
   The probability of rainfall exceeding flash flood guidance is less   
   than 5 percent.=20   
      
   Bann   
      
      
   Day 2   
   Valid 12Z Sun Dec 14 2025 - 12Z Mon Dec 15 2025   
      
   ..THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF=20   
   WESTERN WASHINGTON STATE LATE SUNDAY NIGHT/EARLY MONDAY MORNING...   
      
   Maintained the Marginal Risk area over parts of the Olympic and=20   
   northern Cascade Ranges in Washington as the next push of moisture=20   
   approaches late Sunday night into the early morning hours of=20   
   Monday. The models have shown some run to run differences with QPF=20   
   but no real clear trend. One consistent signal is that the=20   
   orientation of the moisture plume remained more southwest-northeast   
   than the event that just ended a couple of days ago. That still=20   
   points to the idea that rainfall may not increase in coverage or=20   
   intensity until late in the Day 2 period. Based on the expected IVT   
   plume increasing to over 600 at about the time that the flow=20   
   reaches the coast and begins to take on more of an on- shore=20   
   component...am inclined to follow the ensemble idea of 0.75 inches=20   
   to locally 1.5 inches of precipitation focused in the terrain. The=20   
   area is sensitive given the nearly week-long excessive rainfall=20   
   event...so any additional rainfall is expected to bring renewed=20   
   hydrologic concerns. Given a fairly tight window of opportunity for   
   rainfall during the outlook period...and at least some questions=20   
   about timing of the onset....still think a Marginal Risk is=20   
   sufficient for now although later shifts can adjust if needed.   
      
   Bann   
      
   Day 3   
   Valid 12Z Mon Dec 15 2025 - 12Z Tue Dec 16 2025   
      
   ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF   
   WASHINGTON AND OREGON...   
      
   Areal coverage of rainfall expands and rainrates increase on Monday   
   as a well defined atmospheric river continues to direct abundant   
   moisture into the Washington coastal ranges and Cascades that   
   gradually makes its way southward into Oregon. Given antecedent   
   conditions from the excessive rainfall event from earlier in the   
   week plus whatever falls on Day 2...the concern is for renewed   
   flooding potential in addition to worsening on-going flooding=20   
   especially in the terrain with potential for additional landslides=20   
   or mudslides. Saw little reason to modify the Slight risk area that   
   propagated into the Day 3 period from yesterdays Day 4 outlook=20   
   especially given the magnitude of the IVT and precipitable water=20   
   values forecast by the global models. The focus of the heavy=20   
   rainfall should gradually shift southward into an area that did not   
   receive as much rainfall from the previous atmospheric river.=20   
   Opted to extend a Marginal risk area along the coast as far south=20   
   as northwestern California more in deference to uncertainty of=20   
   timing as to the rainfall amounts.=20   
      
   Bann   
      
      
   Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/94epoints.txt__;!!DZ3fjg!68aCra7KzTwu5f99YQRkb4cpHCppbxCCpUto982064dk=   
   nbXyGawvgicsKtRcPjWVSq14iL7lRekFYm2LAOD9YB5A69Q$=20   
   Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/98epoints.txt__;!!DZ3fjg!68aCra7KzTwu5f99YQRkb4cpHCppbxCCpUto982064dk=   
   nbXyGawvgicsKtRcPjWVSq14iL7lRekFYm2LAOD959R9D5E$=20   
   Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/99epoints.txt__;!!DZ3fjg!68aCra7KzTwu5f99YQRkb4cpHCppbxCCpUto982064dk=   
   nbXyGawvgicsKtRcPjWVSq14iL7lRekFYm2LAOD94ZveedA$=20   
      
   =3D =3D =3D   
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