FOUS30 KWBC 191545 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1145 AM EDT Fri Jun 19 2026 Day 1 Valid 16Z Fri Jun 19 2026 - 12Z Sat Jun 20 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL IN EFFECT FOR PORTIONS OF THE CENTRAL GULF COAST REGION... ...16Z Update... No major changes were needed for the risk areas with this update. Much of the expected rainfall is ongoing in the defined risk areas across Texas, and for the MDT risk region, more widespread scattered convection is expected to develop over the next few hours with daytime heating. The convection appears unlikely to become very organized, instead favoring pulse thunderstorms or small clusters. Cell mergers appear to be the biggest threat when it comes to localized renewed flash flooding this afternoon in the Moderate Risk area across southern Alabama and Mississippi. Elsewhere, a higher-end Slight has been issued for northern Louisiana into northeast Texas for the ongoing very slow-moving storms that are approaching Texarkana. These storms are expected to continue building eastward into the afternoon, followed by a break in the area for much of the overnight. Additional convection could develop in the early morning hours. The Slight over Georgia was expanded to near the coast for the ongoing training storms in that area, which could persist into the afternoon. Finally, the Marginal Risk across the eastern Carolinas was dropped with this update as the rain ongoing there pushes offshore and much drier air replaces them, ending even a Marginal flooding threat there. Wegman ...Previous Discussion... ...Central Gulf Coast States... Lingering flood impacts following the deluge over the last 24 hours will be exacerbated by additional rounds of slow-moving convection today from central MS and eastern LA to the FL Panhandle and far southwest GA. Low-to-mid level convergence will extend in a west-east orientation just to the north of the Gulf Coast and remain a focus for broken areas of showers and thunderstorms throughout the day. These storms will tap into PWs above 2" and remain relatively slow-moving with westerly convergent 850mb flow less than 15 kts, leading to hourly rates of 2-3"/hr. Activity will likely be ongoing across the region at 12z and pulse throughout the day and into the overnight period. 00z HREF probabilities for at least 3" per 6-hrs start the day 1 period as high as 60% across southern AL and the FL Panhandle before becoming more scattered in nature and lowering to around 30% for the overnight period. The primary factor for maintaining the MDT risk is the fact that these storms are likely to overlap with an area that recently received widespread 4-8" rainfall totals (locally over 12") and soils are easily overcome when rainfall rates exceed 2"/hr. This will lead to additional scattered flash flood concerns on top of ongoing flood impacts and recovery efforts. ...Southern Plains to the Upper Texas Coast... Scattered flash flooding is also a concern from southern OK into much of central and eastern TX today as thunderstorm activity begins early this morning and gradually meanders east with time through tonight. Vast amounts of uncertainty exist with the mesoscale details surrounding the excessive rainfall forecast in this area, particularly for being a day 1 forecast, but PWs near/slightly above 2" and widespread dew points into the upper 70s and low 80s point to an environment ripe for intense rainfall rates. As convection develops early this morning the expectation is for an MCV or multiple MCVs to spawn ahead of an approaching weak shortwave and within a building ridge over the south-central U.S.. This weak steering pattern will lead to conditions where MCV location and outflow boundaries could drive the convective mode. Even if thunderstorms remain mostly progressive after cold pools develop, intense rainfall rates of 2-3" are possible throughout the Southern Plains into eastern TX and the ArkLaTex. One area of focus to monitor into the overnight period into Saturday morning will be across eastern TX into central LA where a frontal boundary is forecast to drape and potential interact with a weak surface low or remnant MCV. Several CAMs indicate more widespread thunderstorm activity around 12z Sat. here or just to the south across southeast TX as the nocturnal low-level flow increases towards the frontal boundary. 00z HREF neighborhood probs for at least 3" per 6-hrs are generally around 30% here, but REFS probs are much higher (60%) and farther south along the upper TX coastline. Thus, a large SLGT risk is in effect for this region to highlight the widely scattered/uncertain nature of thunderstorms, but while also likely containing intense rainfall rates capable of flash flood impacts. Snell Day 2 Valid 12Z Sat Jun 20 2026 - 12Z Sun Jun 21 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF THE CENTRAL PLAINS AND MISSOURI VALLEY... ...Central Plains and Missouri Valley... A large area of heavy rain associated with a developing MCS starting Saturday afternoon and continuing into Saturday night is expected to bring widespread heavy rainfall across portions of the central Plains into the Missouri Valley with the greatest threat currently expected across southeastern Nebraska, northeastern Kansas, and far northwestern Missouri/southwestern Iowa. Storms are expected to initiate Saturday afternoon with peak heating over the central High Plains and ahead of a racing shortwave crossing the Rockies. Meanwhile, a LLJ of southeasterly flow will pump deep Gulf moisture up the Plains through the day. This will force the dryline to race eastward in response. The warm front associated with the low and the dry line will uplift the deep moisture, resulting in widespread shower and thunderstorm development. These storms are expected to grow upscale into an expansive, organized convective system into the evening and overnight hours that will then track southeasterly across the risk area. The latest deterministic guidance shows areal average rainfall totals along the expected path of the MCS in the 2-3" range with locally higher amounts of 4-6", more than sufficient to lead to scattered and potentially widespread flash flooding, which has prompted the level 3/4 Moderate Risk. As is usually the case with convective systems the exact path and duration will be determined by more mesoscale details than the guidance can typically pin down at this time frame, so some areal modification and possible expansion of the Moderate Risk will be likely over the next couple of days. The most likely area for expansion would be further to southeast into more of western Missouri and east- central/southeastern Kansas. However, given the noted uncertainty with the evolution of these types of systems at this timeframe, have limited the extent of the risk area to also overlap where the greatest support/confidence is shown by the ensemble mean/probabilistic guidance. ...Eastern Texas through the Central Gulf Coast... One more day of scattered slow-moving storms is expected on Saturday across the Deep South between eastern TX and southern AL/FL Panhandle. The lingering frontal boundary draped north of the Gulf Coast will begin to lift north during the day and leave convection widely scattered, but more focused activity is likely during the morning hours as high pressure over the Tennessee Valley keeps the thermal/moisture gradient rather sharp and focuses ongoing thunderstorm activity within PWs above 2". Lingering MCV(s) from the day 1 period across eastern TX and the Lower Mississippi Valley could also add locations for more organized thunderstorm activity. The soils in this region also remain extremely saturated and sensitive to additional intense rainfall rates, leading to the potential for scattered instances of flash flooding on Saturday and the SLGT risk of excessive rainfall. Snell Day 3 Valid 12Z Sun Jun 21 2026 - 12Z Mon Jun 22 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EASTERN OKLAHOMA AND THE OZARKS THROUGH MUCH OF THE MIDWEST AND OHIO VALLEY... ...Midwest... By the start of the day 3 forecast period a potent shortwave and related surface low are expected to eject eastward out of the central Plains into the Midwest. There remains some uncertainty regarding the speed and latitude of these features, but PWs above the 90th climatological percentile (per the 00z GEFS) overlapping with soils likely still recovering from recent heavy rain in the Midwest will lead to at least scattered flash flooding concerns. NBM probabilities for at least 2" are very high (between 60-80%) and cover much of the northern SLGT risk area from MO/IA to OH. Locally higher totals are likely given the convective environment. The progressive nature of these storms may end up limiting the severity of flash flood impacts, but a MDT risk upgrade is possible should training/back- building elements become more obvious in the short range updates, particularly along the leading warm front ahead of the primary surface low. ...Southern Plains, Ozarks, and Lower Ohio Valley... The setup on Sunday could lead to a southern secondary axis of heaviest QPF and flash flooding impacts. The southern end of the Saturday night thunderstorm complex/MCS is likely to sink southeastward near a trailing cold front and impact areas near the Ozarks early Sunday. Then, the expectation is for reforming scattered convection during peak daytime heating and reorganization of thunderstorms overnight Sunday associated with the LLJ to span from OK to the Lower Ohio Valley, including northern AR, southern MO, and western TN/KY. This combines for guidance to currently depict current QPF amounts of 2-4" and an average localized max of 6". There remains obvious mesoscale uncertainties at this stage, but with Pws near the 90th climatological percentile and a favorably oriented west- east frontal boundary, it's possible a MDT risk upgrade may be needed once CAMs come into forecast range. For the Lower Ohio Valley in particular, some guidance also highlights thunderstorms associated with the initial warm front lifting northward, which could add yet another potential for slow-moving repeating thunderstorms. Snell Day 4 and Day 5 Valid 12Z Mon Jun 22 2026 - 12Z Wed Jun 24 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF THE SOUTHERN PLAINS, LOWER MISSISSIPPI AND TENNESSEE VALLEYS, AND CENTRAL APPALACHIANS ON DAY 4... Day 4 continues to an active pattern through a good portion of the CONUS, east of the Mississippi with a progressive trough axis pushing through the Great Lakes and Northeast leading to periods of moderate to heavy rainfall from the Ohio Valley into the Mid Atlantic and Northeast. Areas of the Northeast are subject to thunderstorm prospects with the best chance for flash flooding likely to occur in the urban footprint from Philadelphia up to Boston with an expansion inland to the Hudson Valley down through eastern PA. Current probs off the latest ensembles and National Blend indicate a large zone of 50-80% probs for >1" across the aforementioned area above with deterministic outputs closer to 2-2.5" into parts of Southern New England. MRGL risk inherited remains in effect, but there's potential here for an upgrade as we move closer to the D4 window, but want to see more of the CAMs to make that decision. Across the Southern U.S., heavy precipitation will preclude another round of convection forming along a quasi-stationary front draped from the Southern High Plains to the Southeastern CONUS. Probs for >1" are highest in-of the areas of Eastern OK into the Lower Mississippi and southwestern Tennessee Valleys. Elevated theta_E's and PWAT anomalies +2 dev. or greater indicate a formidable environment capable of continued heavy rain potential that will likely produce rainfall of 2-4", at least in some of the thunderstorm activity that develops. The focal point along the front will likely be where the heaviest rain will occur, or at least be a low-level convergence mechanism that can enhance regional convection. There's high enough confidence in the location of convection for the D4 period to overlap with areas that will have seen several inches the periods prior which led to an upgrade to a SLGT risk positioned over portions of the Southern Plains through parts of the Lower Mississippi and neighboring Tennessee Valleys. The risk extends through the Smokey Mountains up into parts of the Central Appalachians in eastern KY up into WV as the convergence regime follows the frontal positioning over these areas. Day 5 is a transition period into a more typical summer time regime for the CONUS with a longwave trough over the Northern U.S. and a dome of mid and upper ridging positioning itself across the Southwest. This will cause a persistent northwesterly flow pattern across the Central and Southern High Plains over into the Lower Mississippi Valley as progressive shortwave pulses eject out of the Rockies and ride the prevailing northwesteries in place between the ridge and trough. This highlights potential for MCS development and flash flooding scenarios from the Front Range and points southeast as the steering flow orients between the base of the trough and the northeastern flank of the ridge. This is historically projecting a case of thunderstorm maturation and upscale growth over the area between CO/KS down through OK/TX with potentially the Red River Basin as a focus for thunderstorm activity. Eventually this ends up migrating into the ArkLaTex and/or Lower Mississippi area which is showing up in the QPF footprint on ensembles. With this becoming a more stable signal in the global ensembles and aligning with the NBM QPF output, a MRGL risk was added to the new D5 to account for this potential evolution. Kleebauer 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 $$