FOUS30 KWBC 220909 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 509 AM EDT Fri May 22 2026 Day 1 Valid 12Z Fri May 22 2026 - 12Z Sat May 23 2026 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL OVER THE UPPER OHIO VALLEY AND THE SOUTHERN APPALACHIANS... Shortwave energy embedded in broad southwesterly mid to upper level flow from the western to central Gulf Coast, northeastward through the TN/OH Valleys will persist through the upcoming day 1 period. These height falls/broad diffluent upper flow will enhance uvvs in a large region of much above average PW values/anomalous 850-700 mb moisture flux, 2 to 2.5+/2-3+ standard deviations above the mean respectively from the Gulf Coast northeastward into the Ohio Valley. There is fairly good model consensus for the potential for widespread moderate to heavy rainfall total in this anomalous PW axis day 1. Simulated radars suggest cells will be fairly progressive to the northeast. However, with potential for short term training of cells and/or repeat rounds of convection, there will be potential for runoff issues. Slight risk areas maintained over the Upper OH Valley from northeast KY into southern OH where FFG values are relatively low, and in the upslope region of the Southern Appalachians from far northeast GA into the Upstate of SC and western NC where heavy precip likely to focus in the region of southerly low level flow. The slight risk areas fit well with the axes of the HREF and RRFS means 2 and 3"+ probabilities. Across the Southern Plains, a marginal risk area was introduced for potential for additional convection Friday evening into the early hours of Saturday. Additional shortwave energy expected to push eastward into the Southern High Plains, supporting potential for some organization to the associated convection late Friday into the early hours of Saturday. Low confidence on details, with isolated runoff issues possible where convection become organized. Oravec Day 2 Valid 12Z Sat May 23 2026 - 12Z Sun May 24 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF EASTERN TEXAS AND WESTERN LOUISIANA... Additional shortwave energy expected to move from far northeast Mexico into southern and eastern Texas early Saturday, likely setting the stage for another round of organized convection. Building instability early Saturday, Mucape values reaching 2000-300 j/kg ahead of these height falls, in an axis of PW values 1.5-2.5 standard deviations above the mean, will support potential for an organized line of convection to push across eastern and southern TX Saturday morning into afternoon. The previous risk areas were narrowed to better reflect the latest model qpf output and the max RRFS 2 and 3"+ probability axes for the day 2 time period. No significant changes made to the marginal risk area from the Southern Appalachians into the Southeast. Southwest mid to upper level flow with embedded shortwaves will continue across these areas day 2. With PW values remaining well above average, 2 to 2.5+ standard deviations above the mean, additional widespread scattered convection will likely produce locally heavy rainfall totals. Both the HREF and RRFS show fairly high probabilities for 1"+/hr rainfall totals Saturday afternoon, supporting potential for isolated runoff issues. The marginal risk was also expanded northward from the previous issuance into far eastern KS and large portions of MO to cover areas the RRFS, GEM and FV3LAM are showing heavy rainfall totals day 2. Oravec Day 3 Valid 12Z Sun May 24 2026 - 12Z Mon May 25 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE UPPER TEXAS COAST INTO SOUTHERN LOUISIANA... A slow moving upper trof expected to amplify somewhat day 3 as it pushes from eastern Texas into the Lower MS Valley. Similar to the day 2 and day 3 period, there will continue to be an axis of much above average PW values stretching from the Gulf Coast northeastward into the Southeast/Southern to Central Appalachians. There is a lot of spread day 3 with the QPF details, but still a signal for widespread moderate to heavy rain potential in this anomalous PW axis. A slight risk was maintained from the Upper TX coast into southern LA, close to the WPC and NBM qpf max. This covers the urban areas from Houston to New Orleans. The marginal risk area was extended farther northeast through the Southern to Central Appalachians where scattered convection likely in the anomalous PW axis, supporting locally heavy rainfall amounts and potential for isolated runoff issues. Oravec 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