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   QPFERD   
      
   Excessive Rainfall Discussion   
   NWS Weather Prediction Center College Park MD   
   759 PM EST Fri Nov 14 2025   
      
   Day 1   
   Valid 01Z Sat Nov 15 2025 - 12Z Sat Nov 15 2025   
      
   ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF   
   SOUTHERN CALIFORNIA...   
      
   ...0100 UTC Update...   
      
   ...Southern California...   
      
   The latest Day 1 ERO update included an expansion of the Slight=20   
   Risk area along the Transverse Ranges to the Central CA Coast,=20   
   while a also nudging the Moderate Risk area Slightly westward to=20   
   include more of the Santa Barbara area. The reasons were two-fold.=20   
   First, they incorporate the heavier rain that has already fallen=20   
   (especially areas west of KSBA). Secondly, the slight westward=20   
   adjustment also aligns with the latest high-res guidance=20   
   expectations from recent HRRRs along with the 18Z HREF and 12Z RRFS   
   ensemble suite. The Moderate Risk area aligns well with the=20   
   highest probability of >0.50"/hr rainfall rates later tonight=20   
   (after 06Z, and especially after 09Z when those probabilities climb   
   to over 60%), along with where the highest probabilities of >3"=20   
   will fall through 12Z (25-30%)=20   
      
   Hurley   
      
      
   Day 2   
   Valid 12Z Sat Nov 15 2025 - 12Z Sun Nov 16 2025   
      
   ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF   
   SOUTHERN CALIFORNIA...   
      
   20Z Update: The overall synoptic evolution remains unchanged in   
   the run-to-run variance within guidance today. The prospect for   
   heavy rainfall will carry forward into Saturday with the low   
   progression allowing a protrusion of heavier rainfall to impact the   
   coast to areas inland over the deserts of southern CA/NV into   
   western AZ and southwest UT. Assessment of the 12z HREF blended   
   mean QPF footprint and associated prob fields, both neighborhood   
   and EAS indicate the eastern Transverse and northern Peninsular   
   Ranges of southern CA will be the beneficiary of the heaviest   
   precip threat due to the added orographic enhancement as flow   
   remains mostly orthogonal to the terrain north and east of the LA   
   metro. HREF neighborhood probs between 40-60% for >5" exist over   
   portions of the San Bernardino and San Jacinto Mountains spanning   
   San Bernardino and Riverside counties.   
      
   As the disturbances moves eastward, IVT plume will shift inland to   
   impact the lower deserts in CA and areas further inland towards   
   NV/AZ and southwest UT generating flash flood concerns with a weak   
   convective pattern anticipated through the storm life cycle. The   
   prospects of significant precip on the order of 1" or more are   
   generally high for the above locations which will be sufficient for   
   at least widely scattered flash flood concerns as we move into   
   Saturday afternoon and evening. Probabilities for >2" a bit more   
   subdued and relegated to the CA/NV border into the Imperial Valley,   
   but that doesn't mean a few areas across southern NV into the   
   Colorado River basin can't approach the 2" threshold in this   
   scenario just given the anomalous airmass involved.   
      
   The previous MDT risk was expanded to include more of the San   
   Jacinto mountains where the highest probabilities for >5" are   
   located. The SLGT risk was also expanded in the interior given the   
   latest trends. The MDT was not trimmed in any one location, leaving   
   the LA metro firmly within the highest risk forecast for the   
   period.   
      
   Kleebauer   
      
   ..Previous Discussion..   
      
   The peak of the heavy rainfall event across southern California   
   will occur on Day 2/Saturday. The upper level low off the coast   
   will barrel inland, drawn eastward by the strong shortwave trough   
   leading it. PWATs are expected to increase to around 1.25 inches,   
   which is as much as 4 sigma above normal for this time of year.   
   Meanwhile MUCAPE values could increase to around 250 J/kg near the   
   coast. As the low moves into central California to near the NV/CA   
   border in central CA/southwest NV, the plume of heaviest rain will   
   push inland and slowly weaken with time. Meanwhile, an additional   
   shortwave will round the low and impact much of southern California   
   into Saturday night.   
      
   Given the expected very wet Friday across much of southern   
   California, and with the heaviest rains expected to be ongoing at   
   the start of the period, a Moderate Risk upgrade was also   
   introduced on Day 2/Saturday. This is in line and for many of the   
   same areas as on Day 1/Friday. However, unlike Friday's rains,   
   these rains will have Friday's rains to build upon, worsening the   
   number, severity, and duration of the heaviest rains across   
   southern California. Thus, certainty with the Moderate Risk on   
   Saturday is much higher than on Friday.   
      
   As on Friday, as the shortwave and in this case the entire upper   
   low push ashore, expect occasionally heavy rain with embedded   
   thunderstorms to continue north and east to impact the southern   
   Sierras of central California, much of southern Nevada, including   
   Las Vegas, and much of western Arizona. Rainfall rates will remain   
   high as heavy rains impact much of these areas. Thus, in   
   coordination with VEF/Las Vegas, NV forecast office, the inherited   
   Slight Risk was expanded east to include Esmeralda, southern Nye,   
   and Clark counties in southwestern Nevada, as well as Mohave County   
   in Arizona. Urban concerns will be present across the Las Vegas   
   metro area from the heavy rains as well. The desert soils in this   
   area should be rather hydrophobic from recent dry weather, which   
   should support increased runoff, especially early in the day.   
      
   In coordination with LOX/Oxnard, CA and HNX/Hanford, CA forecast   
   offices, a Moderate Risk area was introduced from Point Conception   
   east through L.A. This especially includes the Palisades fire burn   
   scar near Malibu, as well as others in the area. Debris flows and   
   fast moving water are likely as the rainfall drains into the flashy   
   creeks and streams that drain the Transverse Ranges. Expect the   
   heaviest rains to impact the L.A. Basin through Saturday morning,   
   with diminishing rates down to occasional showers and light rain   
   from Saturday afternoon through the overnight.   
      
   Wegman   
      
   Day 3   
   Valid 12Z Sun Nov 16 2025 - 12Z Mon Nov 17 2025   
      
   ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF   
   CENTRAL AND NORTHERN CALIFORNIA...   
      
   20Z Update: Subtle changes were made to the Day 3 ERO, based on the   
   latest guidance trends. Still some timing differences during day 3   
   (Sun-Sun night) as the initial closed mid-level low opens upon   
   lifting through the ridge across the Great Basin-Central Rockies,   
   while the next deepening low drops along the northern CA Coast and   
   Bay Area. One notable trend -- the bulk of the guidance (outside of   
   the GEM and 12Z RRFS) keeps the heavier rainfall north of the   
   Central CA Coast and Transverse Ranges.   
      
   Hurley   
      
   Previous Discussion Below...   
      
   As the cutoff low that impacted southern California on Friday and   
   Saturday moves inland, it will rapidly weaken and quickly become a   
   non-factor as far as heavy rain is concerned. Nonetheless,   
   especially early Sunday morning, light rainfall associated   
   therewith may be ongoing. The bigger event will be a cutoff low   
   that follows a similar pattern to the first, but much further north   
   and with less of a tropical connection than the first. The cutoff   
   low will sag southward from Oregon into northern California. Upper   
   level energy associated therewith will use what moisture it can   
   muster to support a progressive cold front that will sweep west to   
   east across the state. Once again there could be some modest   
   elevated instability of 300 J/kg or less with the front. Thus,   
   expect some convection/thunderstorms to be associated with the   
   front. Those periods of heavy rain when combined with recent heavy   
   rains from today could lead to isolated instances of flash flooding   
   in prone areas. Thus, a Marginal Risk was introduced with this   
   update for much of central and northern California, as well as far   
   southwestern Oregon.   
      
   Wegman   
      
      
   Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/94epoints.txt__;!!DZ3fjg!8nke49MV169WR97XRcAgTEqLxIr_rVCAKts2bua-L4oC=   
   D0s0zM7P4W7BZnC9r5tVPdDeMhQmsycq5qsKApLbKqVS2qQ$=20   
   Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/98epoints.txt__;!!DZ3fjg!8nke49MV169WR97XRcAgTEqLxIr_rVCAKts2bua-L4oC=   
   D0s0zM7P4W7BZnC9r5tVPdDeMhQmsycq5qsKApLbIJ52TT0$=20   
   Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/99epoints.txt__;!!DZ3fjg!8nke49MV169WR97XRcAgTEqLxIr_rVCAKts2bua-L4oC=   
   D0s0zM7P4W7BZnC9r5tVPdDeMhQmsycq5qsKApLbNwBLypQ$=20   
      
   =3D =3D =3D   
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