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   FOUS30 KWBC 081935   
   QPFERD   
      
   Excessive Rainfall Discussion   
   NWS Weather Prediction Center College Park MD   
   235 PM EST Thu Jan 8 2026   
      
   Day 1   
   Valid 16Z Thu Jan 08 2026 - 12Z Fri Jan 09 2026   
      
   ...THERE ARE MARGINAL RISKS FOR EXCESSIVE RAINFALL ACROSS PORTIONS   
   OF THE MIDWEST & LOWER MISSISSIPPI VALLEY...   
      
   ...16Z Outlook Update...   
   The ongoing forecast philosophy is generally on track. Minor   
   changes were made to the central Plains Marginal area to trim   
   behind an ongoing convective complex in that area. This complex is   
   moving quickly northeastward this morning, and flash flood   
   potential behind it has decreased substantially.   
      
   See the previous discussion below for more information.   
      
   Cook   
      
   ...Previous Discussion...   
      
   Midwest/Lower Mississippi Valley...   
   A strong shortwave preceding the incoming upper level trough is   
   expected to bring 500+ J/kg of MU CAPE into portions of the region   
   during the day on Thursday. The 00z NAM's 2000+ J/kg bulls eye in   
   KS/MO right at the beginning of the period appears unrealistic/too   
   high based on recent SPC mesoanalysis MU CAPE trends, though its   
   trailing instability appears more reasonable, reinforced by the 03z   
   RAP. The mesoscale guidance advertises small areas of a low risk   
   of 3"+ across portions of KS, MO, IL, IN, and eventually LA and MS   
   Thursday night/early Friday morning. While precipitable water   
   values are in the 1-1.25" range for northern areas and 1.5"+ range   
   for southern areas, the atmosphere should be well saturated. There   
   appears to be enough instability to realize local hourly amounts of   
   1.5"+ where a sufficient number of organized thunderstorms are   
   able to materialize. Right now, that appears to be the biggest   
   issue. While it has been dry lately, flash flood guidance values   
   are modest across much of the area, with 3 hour guidance closer to   
   3" for the Lower Mississippi Valley, 2.5" for portions of KS/MO,   
   and 2" for IL/IN. The guidance indicates that the heavy rainfall   
   should move through quickly, so local amounts of 2-3" within a   
   couple hours could be enough for isolated to widely scattered   
   issues, particularly in urban areas. This led to the introduction   
   of Marginal Risk areas for the areas mentioned above.   
      
   Roth   
      
      
   Day 2   
   Valid 12Z Fri Jan 09 2026 - 12Z Sat Jan 10 2026   
      
   ..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF   
   THE TENNESSEE VALLEY AND DEEP SOUTH...   
      
   20Z Update...   
   Following the general trend of the 12Z guidance, the outlook areas   
   extending from the lower Mississippi Valley to the southern   
   Appalachians were shifted a little south and east. A Slight Risk   
   was maintained from southeastern Louisiana to the southern   
   Appalachians, where neighborhood probabilities from the 12Z HREF   
   for amounts above 2 inches are 50 percent or greater. Within this   
   area, the HREF suggests the heaviest totals are most likely to   
   center from southeastern Louisiana to central Alabama, where high   
   (greater than 70 percent) probabilities for amounts over 3 inches,   
   and some 30-60 percent probabilities for amounts greater than 5=20   
   inches, are indicated.   
      
   Pereira   
      
   Previous Discussion...   
   ...Lower Mississippi Valley/Southern Appalachians...=20   
   A positively tilted trough with minimal eastward progression due=20   
   to the parent cyclone's progression northeast will generate a broad   
   axis of ascent from the Mississippi Valley to points eastward with   
   a cold frontal progression slowly migrating east. An anomalously=20   
   moisture plume ahead of the trough, noteworthy for January and near   
   summer averages with a range of 1.50-1.75", will be accompanied by   
   500-1500 J/kg of MU CAPE. Ample shear for convective organization=20   
   is expected, with low- level convergence more or less fixed from=20   
   the Atchafalya Basin in LA into the southern Appalachians. The=20   
   guidance is wet, with local 4-7" totals forecast locally. The=20   
   guidance has shifted southwest,. which caused a southwest shift in=20   
   the risk areas.   
      
   This synoptic setup is classic for a flash flood prospect across   
   this region. Deep layer southwest flow should lead to cell   
   training, and enough effective bulk shear exists for mesocyclone   
   formation. Hourly rain amounts up to 2.5" are possible here, which   
   would overwhelm urban environments. The 00z HREF for the first half   
   of the period advertised a 30-35% of 5"+ near Laurel MS, which if   
   it occurred within a few hours would overwhelm non-urban   
   environments as well. At the moment, this appears to be a high end   
   Slight Risk, but it wouldn't be surprising if a Moderate Risk   
   was considered as we get further inside the mesoscale guidance   
   window. The eastern bounds of the Marginal Risk area were   
   coordinated with the RNK/Blacksburg VA, GSP/Greer SC, and   
   FFC/Peachtree City GA forecast offices.   
      
   Roth   
      
      
   Day 3   
   Valid 12Z Sat Jan 10 2026 - 12Z Sun Jan 11 2026   
      
   ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS   
   OF THE SOUTHERN APPALACHIANS...   
      
   20Z Update...   
   No significant changes were made to the Marginal Risk area=20   
   centered over the southern Appalachians.   
      
   Pereira   
      
   Previous Discussion...   
   Heavy rainfall early in the period is expected over what should be   
   at least partially saturated ground across portions of the=20   
   Southern Appalachians before heavy rainfall ejects into the=20   
   southern Mid- Atlantic States. Added a Marginal Risk as a=20   
   precaution for this reason; the threat not expected to persist past   
   18z Saturday.   
      
   Roth   
      
      
   Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/94epoints.txt__;!!DZ3fjg!6fezlj-OjcauVuB605zq_-ZmqNec2mMKfAeWRqIOdmuk=   
   d4v1y9vMOlF_epe0q6euaoNmBehKGIVUHXzxAjfKPgtooVE$=20   
   Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/98epoints.txt__;!!DZ3fjg!6fezlj-OjcauVuB605zq_-ZmqNec2mMKfAeWRqIOdmuk=   
   d4v1y9vMOlF_epe0q6euaoNmBehKGIVUHXzxAjfKeEZW9MU$=20   
   Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/99epoints.txt__;!!DZ3fjg!6fezlj-OjcauVuB605zq_-ZmqNec2mMKfAeWRqIOdmuk=   
   d4v1y9vMOlF_epe0q6euaoNmBehKGIVUHXzxAjfKa8ScvKE$=20   
      
   =3D =3D =3D   
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