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   PID: Synchronet 3.21a-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0   
   TID: SBBSecho 3.28-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0   
   BBSID: CAPCITY2   
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   FOUS30 KWBC 220809   
   QPFERD   
      
   Excessive Rainfall Discussion   
   NWS Weather Prediction Center College Park MD   
   309 AM EST Mon Dec 22 2025   
      
   Day 1   
   Valid 12Z Mon Dec 22 2025 - 12Z Tue Dec 23 2025   
      
   ...THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL IN EFFECT FOR=20   
   PORTIONS OF THE SIERRA NEVADA IN NORTHERN CALIFORNIA...   
      
   Deep moisture continues to surge inland across portions of northern   
   and central California dumping heavy rainfall across the northern=20   
   Sierra Nevada Range. Much of the forecast QPF footprint of 2-3+   
   inches will be where several inches occurred and flooding and=20   
   debris flows were observed yesterday. The Moderate Risk area was=20   
   maintained since accumulations of this magnitude will likely lead   
   to several instances of flooding, sloughing and debris flows,   
   especially near recent burn scars.   
      
   Campbell   
      
      
   Day 2   
   Valid 12Z Tue Dec 23 2025 - 12Z Wed Dec 24 2025   
      
   ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF   
   CALIFORNIA...   
      
   The trajectory of the atmospheric river will become more S/SW to   
   N/NE as it shifts southward during this period as the trough   
   offshore in the Pacific also digs to the south. In contrast to=20   
   the air mass containing the atmospheric river, which will be warm=20   
   and moisture-laden, this contrast will support cyclogenesis along=20   
   the greatest gradient/boundary between the cold air mass within the   
   trough and the much warmer air mass in the ridge/atmospheric=20   
   river. As the low deepens the onshore flow will align parallel to   
   the coastline thus significantly increasing the areal extent heavy   
   rainfall and the higher terrain snow accumulations. The onshore=20   
   flow associated with the low itself will continue very heavy rain=20   
   and mountain snow across northern California, while the trailing=20   
   cold front moves into southern California starting Tuesday night.   
      
   The areas of greatest impact will be into the northern Coastal   
   Ranges and the Transverse Ranges. Both these ranges are   
   sufficiently aligned perpendicular to the south-southwesterly flow   
   to have a significant local upslope contribution to rainfall rates.   
   In the Transverse Ranges, local burn scars will also worsen impacts   
   from resultant flooding over and downstream of any burn scars north   
   and west of the Los Angeles Basin. The renewed round of heavy rain   
   will be in areas getting hard hit by the current atmospheric river   
   and will continue with the deepening low offshore into the=20   
   northern coastal ranges. A Slight Risk was maintained for the=20   
   Oregon border down through Los Angeles.=20   
      
   Campbell/Wegman   
      
      
   Day 3   
   Valid 12Z Wed Dec 24 2025 - 12Z Thu Dec 25 2025   
      
   ...THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL ACROSS SOUTHERN   
   CALIFORNIA...   
      
   Widespread heavy rainfall will ramp up even further across the   
   Transverse Range and surrounding locations of southern California.   
   Areal average of 3 to 5 inches are expected but isolated local=20   
   maximums may reach as much as 9 inches. A Moderate Risk is in   
   effect for a majority of Santa Barbara, Ventura, Los Angeles,   
   range, San Bernardino, Riverside and San Diego Counties. Although=20   
   snow levels will be lowering across the Sierra Nevada and adjacent=20   
   locations and much of the highest elevations will have significant=20   
   snow, some of the lower elevations could receive additional=20   
   rainfall of 1 to 4 inches, which is covered by a sprawling Slight   
   Risk area. Deep-layered moisture will also track eastward across=20   
   eastern California, southern Nevada and into southern Utah and=20   
   western Arizona where areal averages up to 1 to 2+ are forecast. A   
   new Slight Risk area was raised for much of southern Nevada, along   
   the California/Nevada border and for western Arizona. Rainfall   
   rates will easily surpass 0.5-1.0 inch/hr rates, particularly for   
   California.   
      
      
   Campbell   
      
   Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/94epoints.txt__;!!DZ3fjg!9JjHcO3i4DraiMzBjkDzZRGNufIL1YW9X1DCry5fAHGn=   
   Gks-dXKiydPrRtx4INp4yFnqnkEtnp4p7gZBTdwFw0bOn2g$=20   
   Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/98epoints.txt__;!!DZ3fjg!9JjHcO3i4DraiMzBjkDzZRGNufIL1YW9X1DCry5fAHGn=   
   Gks-dXKiydPrRtx4INp4yFnqnkEtnp4p7gZBTdwFhrDPxds$=20   
   Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/99epoints.txt__;!!DZ3fjg!9JjHcO3i4DraiMzBjkDzZRGNufIL1YW9X1DCry5fAHGn=   
   Gks-dXKiydPrRtx4INp4yFnqnkEtnp4p7gZBTdwFMNohQ1o$=20   
      
   =3D =3D =3D   
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   --- SBBSecho 3.28-Linux   
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