540 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 inches, are indicated. Pereira Previous Discussion... ...Lower Mississippi Valley/Southern Appalachians... A positively tilted trough with minimal eastward progression due 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 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 is expected, with low- level convergence more or less fixed from the Atchafalya Basin in LA into the southern Appalachians. The guidance is wet, with local 4-7" totals forecast locally. The guidance has shifted southwest,. which caused a southwest shift in 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 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 Southern Appalachians before heavy rainfall ejects into the southern Mid- Atlantic States. Added a Marginal Risk as a precaution for this reason; the threat not expected to persist past 18z Saturday. Roth Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt