FOUS30 KWBC 061559 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1159 AM EDT Sat Jun 6 2026 Day 1 Valid 16Z Sat Jun 06 2026 - 12Z Sun Jun 07 2026 ...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHERN PLAINS, OHIO VALLEY, UPPER TEXAS COAST, AND CENTRAL GULF COAST... ...Southern Plains... A plume of deep tropical moisture will surge northward across the Southern Plains Saturday. The low level jet advecting this moisture north will run into an area of enhanced lift due to a nearby lingering upper-low, which will be lifting northeast to rejoin the jet. The result will be a series of rounds of storms moving north- northeast across portions of north/northwest Texas, Oklahoma, and western Arkansas. Highly efficient warm rain processes will dominate due to the presence of such abundant amounts of moisture, with PWATs close to 2 inches. For eastern Oklahoma/western Arkansas, rainfall is already ongoing and will persist for much of the day in the form of training lines of storms. To the west, another round of storms is expected to develop with daytime heating along the eastern periphery of the upper-low, with the expectation that repeated rounds of storm development and storm clustering/merging cold pools may eventually lead to a more organized convective system that will progress slowly to the east- southeast through the evening and overnight hours. An internal higher- end Slight covers from southwest of the Metroplex through it, and continuing into much of eastern Oklahoma and western Arkansas for the combination of two areas of persistent heavy rain. The latest convection allowing guidance (CAMs) show peak rain rates reaching upwards of 2-3 inches per hour with locally heavy totals into the 5-6+ inch range, more than sufficient for at least scattered instances of flash flooding despite some locally drier antecedent conditions. ...Ohio Valley... A very-slow moving cold front drifting south across the Midwest/Ohio Valley on Saturday will be the animus for multiple rounds of storms which will track east-southeast within the Slight Risk area roughly from central Indiana east to the central Appalachians. The front will form the leading nose of a plume of deep Gulf moisture tracking northward up the Mississippi Valley. The front will "shear" the moisture eastward in a narrow corridor, along which the storms will form and move. There is some uncertainty as to how persistent an ongoing complex of storms moving into central Ohio will be as they progress east- southeastward through the afternoon. However, even if storms do not maintain quite the same strength/organization as they move into the Mountains of western Pennsylvania and West Virginia, these areas have lower FFG thresholds and the risk for scattered flash flooding will remain a concern. Uplift along the western face of the Appalachians may also locally enhance rainfall rates. Another round of storms is expected along the boundary further west within the Slight Risk over central Indiana where the CAMS/HREF suggest heavier totals into the 3-5 inch range are possible. Additional storms are also forecast to develop further west along the boundary stretching through central Illinois and along the Iowa/Missouri border. However, these storms are forecast to remain more scattered/less organized with generally lower rain totals in the CAMS, keeping the flash flood threat more isolated compared to further east. ...Upper Texas Coast... A Slight Risk remains in effect for the greater Houston area/Upper Texas Gulf Coast. Extreme amounts of moisture will be in place throughout the atmosphere of southeast Texas Saturday afternoon. PWATs between 2 and 2.25 inches are 3 sigma above normal for this time of year, an impressive threshold to meet for June. With peak heating this afternoon, scattered showers and thunderstorms are expected to form, likely 20-50 miles inland from the coast. Cold pools from Friday's storms and new ones from the storms that form Saturday afternoon will likely drive new storm development along the I-10 corridor from southwest of Houston east into southwestern Louisiana. With plenty of new moisture streaming north off the Gulf, the storms will have no trouble reforming and training over the same areas for the duration of the long afternoon. Nightfall should end the storms in the area due to lack of other forcing and the loss of instability. Friday's storms have knocked down FFGs in this region significantly, and with good capability of efficient warm rain processes, urban concerns in Houston, and slow storm movement were all reasons contributing to the Slight Risk. ...Central Gulf Coast... No changes were needed to the Slight Risk area from New Orleans east to Pensacola. A strong front is in place across the eastern Gulf, characterized by very dry air to its east, rather than any significant temperature gradient. The dry air is 2 sigma below normal over portions of central Florida...under 1 inch PWATs. Meanwhile to the west from Louisiana through Texas, an abnormally moist air mass will be streaming north to the west of the high pressure area characterized by the dry air. Over much of Louisiana, PWATs will be over 2.25 inches or 3 sigma above normal. The front makes up the gradient between these extremely contrasting air masses. Through the day, the front will push east as the moist air mass gradually gains ground. However, the front will be the forcing along which numerous showers and thunderstorms pushing north out of the Gulf will form along. The front will be slow to move, allowing repeating rounds of storms to impact the central Gulf Coast. FFGs are high, about 4 inches/hour, but the repeating rounds of storms should rather quickly bring those numbers down, allowing for scattered instances of flash flooding to develop where the rains are most persistent by late afternoon, particularly for urban areas. HREF probabilities for rainfall exceeding 5 inches are also moderate to high (45-70%), with low end probabilities (~15%) of exceeding 8 inches. Storms are also expected west along and just to the north of the I-10 corridor between the Slight Risks covering southeastern and far southwestern Louisiana. However, more persistent forcing/greater storm coverage to the east and lower FFGs to the west suggest there will be a relatively more isolated threat in between. Similar to the Upper Texas Coast, nightfall should see a decrease in shower and storm activity, ending the flooding threat. Putnam/Wegman Day 2 Valid 12Z Sun Jun 07 2026 - 12Z Mon Jun 08 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE MID-MISSISSIPPI VALLEY, OZARKS, AND THE WESTERN TENNESSEE VALLEY... A pair of forcings will work cause renewed rounds of showers and storms across much of the Mississippi Valley on Sunday into Sunday night. A slow moving but still potent upper level low will track northeastward up the Plains and into the Midwest by late Sunday night. Meanwhile a strong front oriented north-south will allow for shower and thunderstorm development further east across portions of the South. For the Mid-Mississippi Valley and Ozarks, the shortwave will be the primary forcing. Deep tropical moisture characterized by PWATs on either side of 2 inches will advect northward up the Mississippi Valley. The shortwave will provide the forcing for storms to form, along with the topography of the Ozarks. Many of these areas, especially from far eastern Oklahoma, northwestern Arkansas, and southwest Missouri have seen repeated rounds of heavy rain in recent days, so FFGs are lower in this area. Thus, a higher-end Slight was introduced for this area depicting an even greater threat for flash flooding, as the topography of the Ozarks works to increase the severity of any flooding. FFGs are also lower from northern Missouri into Iowa. Storms forming in these areas will be closer to the nose of the low level jet, though the upper level shortwave should still be the primary forcing. The Slight Risk area was expanded north up the Mississippi Valley into southern and eastern Iowa and western Illinois with this update. For portions of the western Tennessee Valley, including western Tennessee far northeastern Mississippi, and especially northern Alabama, the aforementioned north-south oriented front will be the primary forcing for the first half of the day. The front will more rapidly retreat east across Georgia by Sunday night, leaving any forcing to weak upper level shortwaves. Thus, most of the storms will be during the afternoon and evening during peak heating and when the front is closer. FFGs are lower across northern Alabama from recent heavy rainfall, around 2.5 in/hour, which due to PWATs occasionally over 2 inches, should be easily attainable by the strongest storms expected Sunday afternoon. Thus, the Slight Risk was expanded southeast for these reasons. Wegman Day 3 Valid 12Z Mon Jun 08 2026 - 12Z Tue Jun 09 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MID-MISSISSIPPI, LOWER OHIO, AND WESTERN TENNESSEE VALLEYS... On Monday, the excessive rainfall risk translates a bit further north and east into the Mid-Mississippi, lower Ohio, and western Tennessee Valleys. A strong front over the Great Lakes will retreat northeastward as the plume of anomalously deep moisture from the Gulf surges northeastward to replace the drier air mass in place over the Northeast. A slow-moving negatively tilted trough will also promote upper divergence and lift throughout the atmosphere over the Slight Risk area throughout the period. PWATs around 2 inches will be 3 sigma above normal for this time of year across the region, so many of the storms that form will consist of highly efficient warm rain processes, which will promote heavy rainfall. FFGs across the region will average around 2-2.5 inches, which will be easily overcome by many of the strongest cells, so long as their forward speed is kept in check. The Slight Risk area was nudged west over more of southeastern Missouri with this update, adjusted for expected heavy rainfall and likely lower FFGs in this region from the Day 2/Sunday period. Wegman 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