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   FOUS30 KWBC 012254   
   QPFERD   
      
   Excessive Rainfall Discussion   
   NWS Weather Prediction Center College Park MD   
   554 PM EST Mon Dec 1 2025   
      
   Day 1   
   Valid 01Z Tue Dec 02 2025 - 12Z Tue Dec 02 2025   
      
   ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF   
   THE GULF COAST AND DEEP SOUTH...   
      
   A negatively- tilted shortwave trough moving through the Southern=20   
   Plains at the present time is leading to a forming stationary from=20   
   across the Deep South to the north of a wave of low pressure in the   
   Gulf of Mexico. An area of low-level convergence which started as=20   
   a frictional convergence zone near the northwest coast of Cuba is=20   
   curling up towards the MS/AL coast at the present time. Moisture is   
   sufficient for heavy rainfall, but until recently, instability was   
   scant. However, ahead of the shortwave, MU CAPE has risen to 500=20   
   J/kg near the southeast tip of LA, which should further increase=20   
   from there and spread into nearby areas of the Central Gulf Coast=20   
   with time, as far east as the FL Panhandle. MU CAPE could rise   
   towards 1000 J/kg along portions of the Central Gulf Coast through   
   early Tuesday morning. Effective bulk shear of 25-35 kts lurks   
   across the region, which could lead to cell organization.   
      
   A band of heavy rain with embedded thunderstorms has occasionally=20   
   led to hourly rain amounts eclipsing 1" between southeast LA and   
   southernmost AL thus far, but this has appeared more like a longer   
   duration heavy rain event so far. The 18z HREF and 12z RRFS are=20   
   not exactly in agreement regarding the potential for 2"+ by=20   
   12z...their overlap is in a narrow zone between Dauphin Island AL=20   
   and Pensacola where downstream instability and moisture overlap=20   
   would be greatest. The three hour flash flood guidance values=20   
   regionally are quite high and appear unreachable. However, there=20   
   is some chance of 1.5" amounts in an hour with local totals up to=20   
   3", which would be problematic in urban areas, so left much of the=20   
   Marginal Risk area from continuity intact. The Marginal Risk area=20   
   has been constrained on its west side per radar reflectivity trends   
   and trends noted in the 18z HREF/12z RRFS guidance.   
      
   Roth   
      
      
   Day 2   
   Valid 12Z Tue Dec 02 2025 - 12Z Wed Dec 03 2025   
      
   The probability of rainfall exceeding flash flood guidance is less   
   than 5 percent.   
      
   Surface/low level convergence associated with a frontal boundary   
   forecast to translate eastward into the western Atlantic after 18Z   
   may allow for a band of SW to NE training heavy rain/thunderstorms   
   early in the period over eastern North Carolina. Weak instability   
   and precipitable water values increasing to over 1.5 inches along   
   the coast could support rain rates over 2 in/hr, however, recent   
   hires guidance maintains the potential for 3 to 6 inch totals   
   offshore/east of the Outer Banks. While the threat is non-zero, it   
   is low enough to not warrant a risk area at this time.   
      
   Otto   
      
      
   Day 3   
   Valid 12Z Wed Dec 03 2025 - 12Z Thu Dec 04 2025   
      
   The probability of rainfall exceeding flash flood guidance is less   
   than 5 percent.   
      
   The very beginning of a multi-day rainfall event will begin to   
   unfold Wednesday night along portions of the Upper Texas and   
   Louisiana Gulf Coasts. Mainly for the 06-12Z time frame Thursday   
   morning, the 12Z guidance continues to suggest most of the   
   heaviest rainfall from heavy showers/thunderstorms will remain   
   offshore. However, at least some of that rain could make its way   
   inland. The threat remains sub- Marginal, but the area will   
   continue to be evaluated for a later introduction of a Marginal   
   Risk with future updates.   
      
   Otto/Wegman   
      
      
   Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/94epoints.txt__;!!DZ3fjg!5JhtpKZY8hmMIEMjlBD-SLd-BS71DInY9-GywGAOsomn=   
   na9IpQs3e_SxE2g0hk_DIr1l-vh-NirHC8NF4VeC9BYBeb4$=20   
   Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/98epoints.txt__;!!DZ3fjg!5JhtpKZY8hmMIEMjlBD-SLd-BS71DInY9-GywGAOsomn=   
   na9IpQs3e_SxE2g0hk_DIr1l-vh-NirHC8NF4VeCRhz10QI$=20   
   Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/99epoints.txt__;!!DZ3fjg!5JhtpKZY8hmMIEMjlBD-SLd-BS71DInY9-GywGAOsomn=   
   na9IpQs3e_SxE2g0hk_DIr1l-vh-NirHC8NF4VeCxPbbPEo$=20   
      
   =3D =3D =3D   
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