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   TID: SBBSecho 3.28-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0   
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   FOUS30 KWBC 202039   
   QPFERD   
      
   Excessive Rainfall Discussion   
   NWS Weather Prediction Center College Park MD   
   339 PM EST Sat Dec 20 2025   
      
   Day 1   
   Valid 16Z Sat Dec 20 2025 - 12Z Sun Dec 21 2025   
      
   ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN PORTIONS OF   
   NORTHERN CALIFORNIA|...   
      
   1600 UTC update...no changes made to the previous outlook for this   
   period.   
      
   Oravec   
      
   Previous discussion...   
      
   Still expecting areas within the northern Sierra Nevada to receive   
   the most appreciable precipitation given the trajectory of the IVT   
   pulse and persistent 850-600mb moisture feed with added upslope=20   
   components near the terrain. Greatest flood concerns likely in the=20   
   adjacent foothills on the windward side of the Sierra Nevada.=20   
   Highest probs for >5" are across the I-80 corridor at the=20   
   California/Nevada border with the highest terrain still likely to=20   
   be snow, limiting the threat for flash flooding for the period to=20   
   that of a Marginal.   
      
   Campbell/Kleebauer   
      
      
   Day 2   
   Valid 12Z Sun Dec 21 2025 - 12Z Mon Dec 22 2025   
      
   ...THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL IN EFFECT FOR   
   PORTIONS OF THE SIERRA NEVADA IN NORTHERN CALIFORNIA...   
      
   2030 UTC Update: Expanded the Slight and Moderate Risk areas based   
   on the latest (12Z) guidance QPFs and trends. Within the Moderate   
   Risk area, there are several hours of >50% HREF probabilities of   
   at least 0.50"/hr rates between 12Z Sun and 03Z Mon, while HREF   
   probabilities of >8" within the 24 hour Day 2 period are >60% for   
   much of the area.   
      
   Hurley   
      
   Previous Discussion...   
      
   A significant uptick in moisture will be surging into northern   
   California during this period within the reinforced atmospheric   
   river and will lead to widespread heavy rainfall and greater   
   threat for flash flooding, particularly for portions of the Sierra   
   Nevada foothills where multi-day totals of 5-10" are forecast. A   
   Moderate Risk area was raised for this period given more locations   
   will be at risk for rapid runoff and potential debris flows. The   
   areal extent of the Moderate will continue to be monitored and may   
   be adjusted with future updates.   
      
   Campbell   
      
      
   Day 3   
   Valid 12Z Mon Dec 22 2025 - 12Z Tue Dec 23 2025   
      
   ...THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL IN EFFECT FOR   
   PORTIONS OF THE SIERRA NEVADA IN NORTHERN CALIFORNIA...   
      
   2030 UTC Update: Expanded the Slight and Moderate Risk areas   
   slightly, especially on the southern periphery, based on the=20   
   latest (12Z) guidance QPFs and trends. The Slight Risk area now   
   includes the far northern portions of the San Joaquin Valley and   
   with a little bit more of the central Sierra Foothills.=20   
      
   Hurley   
      
   Previous Discussion...   
      
   The ongoing atmospheric river will persist while sinking a bit southward   
   toward central California, spreading rainfall further down the   
   Sierra Nevada Range and along the coastline. With the reduction of   
   rain on the northern periphery the threat for excessive rainfall   
   will remain at a Marginal level. A Moderate Risk was raised again   
   for much of the area identified during the day 2 period and for   
   locations a touch to the south. This part of the state is expected   
   to pick up another 3+ inches which will tip the 3 day accumulations   
   over 12 inches for some areas. Any additional rainfall will lead to   
   runoff and increase the potential for sloughing and debris flow   
   along the foothills/adjacent locations.   
      
      
   Campbell   
      
      
      
   Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/94epoints.txt__;!!DZ3fjg!-eGz6iZbMpiqPPAQpneN0Xj1A5I3OcTTc3nzMSaPTdBh=   
   YoFW8ChNlOG1N1TyUmEBQ6PKDlJFPzTJvkIhMwFl1UbgsLM$=20   
   Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/98epoints.txt__;!!DZ3fjg!-eGz6iZbMpiqPPAQpneN0Xj1A5I3OcTTc3nzMSaPTdBh=   
   YoFW8ChNlOG1N1TyUmEBQ6PKDlJFPzTJvkIhMwFlWaFX8lg$=20   
   Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/99epoints.txt__;!!DZ3fjg!-eGz6iZbMpiqPPAQpneN0Xj1A5I3OcTTc3nzMSaPTdBh=   
   YoFW8ChNlOG1N1TyUmEBQ6PKDlJFPzTJvkIhMwFloXtyzJ4$=20   
      
   =3D =3D =3D   
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