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   QPFERD   
      
   Excessive Rainfall Discussion   
   NWS Weather Prediction Center College Park MD   
   357 PM EST Sun Nov 16 2025   
      
   Day 1   
   Valid 16Z Sun Nov 16 2025 - 12Z Mon Nov 17 2025   
      
   ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE SANTA LUCIA   
   RANGE OF CENTRAL CALIFORNIA...   
      
   ...16Z update...   
      
   No significant changes were made to the previous outlook. The   
   initial shortwave responsible for the flooding rainfall across   
   California over the past couple of days has moved inland this   
   morning and is forecast to lose some of its vigor as it moves into   
   a downstream ridge. Moisture anomalies have come down compared to   
   yesterday across the West, and while they remain above average (+1   
   to +3 standardized PW anomalies), a lack of higher instability and   
   progressive storm motions should limit the flash flood threat for   
   most locations. There should be an isolated risk for hourly   
   rainfall in excess of 0.5 inches from portions of northern to   
   southern California today.   
      
   The next shortwave will bring a cold front to California this   
   evening and overnight, and with it, a better chance for 0.5 to 1.0   
   in/hr rainfall rates. The front and heavy rain axis should remain   
   progressive though, limiting total rainfall to an inch or two for   
   most locations, although ground sensitivities due to recent   
   rainfall maintains the Marginal and Slight Risk areas. The greatest   
   24 hour rainfall potential looks to be within the central to   
   northern Sierra Nevada where 2 to 3+ inches of rain could fall.   
      
   Otto   
      
   ...previous discussion follows...   
      
      
   A pair of deep shortwaves will impact much of California through   
   the period today. The one that has been causing heavy rain across   
   much of southern California is pressing inland this morning. Rates   
   have come down a bit overnight due to waning instability, but much   
   of central California and portions of southern California remain in   
   more-or-less steady light to occasionally moderate rainfall. As   
   the upper low departs to the east, the steady rain across much of   
   inland California should diminish through this afternoon. Following   
   this first shortwave, another vigorous, deepening longwave trough   
   will track SSE out of the North Pacific and approach the northern   
   California coast late tonight/early Monday morning. This second   
   shortwave will have much more upper level energy with it by tonight   
   than the first does now. This longwave trough will also have some   
   instability with it. The result will be steady rain associated with   
   the approaching low plowing into the northern California coast   
   this evening, then spreading south in the form of a line of   
   moderate rain with embedded thunderstorms capable of brief periods   
   of heavy rain. It will cross the Bay area late this evening, then   
   push south almost to Point Conception by 12Z Mon. The heaviest rain   
   will push inland, reaching the central Sierra around the same   
   time.   
      
   Much of the Santa Lucia Range in central California have picked up   
   between 5 and 8 inches of rain over the last week. Continued light   
   to moderate rain may add another inch through this morning, but the   
   heavy rains tonight with the cold front will likely drop another   
   1-2 inches. Rock and landslides have been reported from today's   
   rain. Thus with shifting winds and heavy rain tonight, it's   
   probable there may be additional impacts from the storms. In   
   coordination with MTR/Monterey, CA forecast office, a Slight Risk   
   upgrade was introduced with this morning's update. Elsewhere the   
   surrounding Marginal remains unchanged.   
      
   ...Southwest Utah...   
      
   The Marginal Risk area in southwest Utah also remains unchanged.   
   Upslope flow into the Pine Valley Mountains may cause isolated   
   instances of flash flooding as the area of rain currently over   
   southern Nevada pushes east into the region, where enhanced upslope   
   will cause the rain to intensify. The highest elevations above   
   8,000 ft or so may see snow, which will limit the flooding   
   potential at lower elevations.   
      
   Wegman   
      
   Day 2   
   Valid 12Z Mon Nov 17 2025 - 12Z Tue Nov 18 2025   
      
   ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE LOS   
   ANGELES BASIN OF SOUTHERN CALIFORNIA...   
      
   ...20Z update...   
   Some modifications were made to the outlook areas in CA.   
   Specifically, extended the Slight Risk slightly westward to the   
   Central CA Coast based on the latest (12Z) CAM guidance as well as   
   HREF and RRFS 0.50"+/hr and 1.00"+/hr rainfall rate probabilities   
   on Monday. Meanwhile, also largely based on those HREF and RRFS   
   exceedance probabilities, have also hoisted a Marginal Risk across   
   southwest and central portions of AZ.   
      
   Hurley   
      
   ...Previous discussion...   
   The deep and energetic trough that will be centered off the=20   
   northern California coast at the start of the period will track=20   
   southeast down the coast to over the San Joaquin Valley by early=20   
   Tuesday morning. The trough will cut off into a second upper level=20   
   low to impact the state by Monday afternoon. The heaviest rains=20   
   will be out ahead of this cutoff low, where the overall flow is=20   
   onshore out of the southwest. A line of heavy showers with embedded   
   thunderstorms will move down the coast starting around Point=20   
   Conception early Monday morning, reaching the L.A. Basin around=20   
   midday. It will take between 2-4 hours for the heavy rain band to=20   
   sweep through. During that time, rainfall rates peaking between a=20   
   half and 3/4 inch per hour in the thunderstorms may cause widely=20   
   scattered instances of flash flooding, especially on the south=20   
   facing slopes of the Transverse Ranges down to the L.A. Basin. For=20   
   this reason, the inherited Slight Risk remains in place with very=20   
   few changes. At least some of the heavy rain will also penetrate=20   
   inland into some of the California Deserts, including around Death=20   
   Valley N.P. Given how recently the area saw heavy rains from=20   
   yesterday, this additional heavy rain may also cause isolated=20   
   instances of flash flooding. Thus, the Marginal Risk was expanded=20   
   north and east to include a small portion of southern Nevada.   
      
   Wegman   
      
   Day 3   
   Valid 12Z Tue Nov 18 2025 - 12Z Wed Nov 19 2025   
      
   ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF   
   THE SOUTHWEST AND LOWER GREAT BASIN...   
      
   ...20Z update...   
   Based on the guidance trends, have expanded the Marginal Risk area   
   to include more areas off the Mogollon Rim and into the deserts in   
   southern and western AZ, southeast CA, and southeast NV. PW values   
   get near 2 standard deviations above normal in southern-western AZ   
   (0.75-1.00"), while MUCAPEs climb between 500-750 J/Kg south of=20   
   the Mogollon Rim and into the deserts and Phoenix Metro. This will=20   
   maintain the risk of elevated (0.50"+) hourly rainfall rates Tue-=20   
   Tue night as noted from the RRFS exceedance probabilities (through=20   
   00Z Wed), while also implied from the 12Z RRFS and RGEM hourly and=20   
   3-hourly QPFs. 24hr guidance QPFs have come up from 12Z Tue-12Z=20   
   Wed, especially from the global models, which is a bit concerning,=20   
   yet understandable considering how the upper trough begins to pivot   
   more slowly as it amplifies from the shortwave energy diving=20   
   southward on its backside. At this point there's still not enough=20   
   confidence from a duration perspective to upgrade to a Slight Risk=20   
   over the lower terrain (all rain) areas south of the Mogollon Rim,=20   
   which would include the Phoenix area, but the potential to do so=20   
   will exist over the next day or so.=20   
      
   Hurley   
      
   ...Previous discussion...   
   A Marginal Risk area across portions of Arizona and southern Utah=20   
   was introduced with this update. The cutoff low that will spread=20   
   heavy rain across the L.A. Basin on Monday will slowly push east=20   
   across southern California through Tuesday. Once again the heaviest   
   rains associated therewith will be out ahead/east of the low=20   
   center, putting Arizona and Utah in the area most likely to see=20   
   heavy rain. Instability will once again be non-zero, peaking=20   
   between 200 and 400 J/kg, which combined with above normal moisture   
   will result in an area of training thunderstorms, likely along the   
   Mogollon north and east of Phoenix. The southerly flow will=20   
   continue across northwest Arizona and into southern Utah, where wet   
   antecedent conditions from today's rains will support additional=20   
   flash flooding developing with heavy rains in the Pine Valley=20   
   Mountains east to Lake Powell.   
      
   Wegman   
      
      
   Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/94epoints.txt__;!!DZ3fjg!9KW81IrxwnKPvh4x0SmJdkaZD6p9LbK9gW4fpVVSEs8T=   
   Yt92mRPLRneQyMD49Ttu06zqmLj4h6kU4oxa_fJD_liTTy4$=20   
   Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/98epoints.txt__;!!DZ3fjg!9KW81IrxwnKPvh4x0SmJdkaZD6p9LbK9gW4fpVVSEs8T=   
   Yt92mRPLRneQyMD49Ttu06zqmLj4h6kU4oxa_fJDuCTAzFw$=20   
   Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/99epoints.txt__;!!DZ3fjg!9KW81IrxwnKPvh4x0SmJdkaZD6p9LbK9gW4fpVVSEs8T=   
   Yt92mRPLRneQyMD49Ttu06zqmLj4h6kU4oxa_fJDUoLErck$=20   
      
   =3D =3D =3D   
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