Subj : HVYRAIN: Excessive Rainfa To : All From : Mike Powell Date : Fri May 23 2025 07:18:00 FOUS30 KWBC 230821 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 421 AM EDT Fri May 23 2025 Day 1 Valid 12Z Fri May 23 2025 - 12Z Sat May 24 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM SOUTHEASTERN KANSAS AND NORTHEASTERN OKLAHOMA INTO THE OZARKS... ....Southeastern Kansas and northeastern Oklahoma to southern Missouri and northern Arkansas... There remains a good model signal for the development of heavy rainfall later today, in what is expected to be the first of several rounds impacting the region over the next few days. Shortwave energy moving over the top of a broad upper ridge will spur the development of showers and thunderstorms over the Central Plains during the afternoon as they interact with moist southerly, low level flow. While differences in the details persist, most models continue to show increasing organization and heavy rainfall potential as some of these storms move into southeastern Kansas, northeastern Oklahoma and the adjacent Ozark region by the late afternoon. Guidance shows a deepening moisture pool (PWs 1.50-1.75 inches) along a low level warm front supported by increasing southwesterly inflow. In addition to heavy rainfall rates, sustained low level inflow and forcing aloft may support training or backbuilding development, increasing the threat for heavy accumulations. HREF neighborhood probabilities indicate that accumulations exceeding 3 inches are likely, with the potential for amounts reaching over 5 inches across parts of the region. The Slight Risk was drawn for areas where the HREF is showing the greater threat for amounts over 3 inches. ....South Florida... A lingering moisture pool along a weakening boundary will support another day of increased shower and thunderstorm activity. Storms that do develop may pose localized flash flooding concerns, especially over urbanized areas. A Marginal Risk was maintained along the Southeast Florida coast, where the HREF indicates rainfall totals exceeding 3 inches are possible. Pereira Day 2 Valid 12Z Sat May 24 2025 - 12Z Sun May 25 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM SOUTHEASTERN KANSAS and NORTHEASTERN OKLAHOMA INTO THE OZARKS... Expect convection to remain ongoing into the early part of the period, however most of the CAMs show these storms weakening as they move progressively to the south and east Saturday morning. Redevelopment is expected back to the north and west beginning in the afternoon and continuing into the overnight as the low level jet reintensifies across Southern Plains, replenishing the deeper moisture pooling along a boundary as it lingers from eastern Oklahoma and southeastern Kansas through the Ozarks. Additional rounds of heavy precipitation are expected late Saturday into early Sunday as this moisture interacts with low-amplitude shortwave energy moving out of the Plains. Once again, training or backbuilding cells may contribute to heavy rainfall totals. Given the lingering uncertainty regarding how much overlap there will be in the heavy amounts that occur on days 1 and 2, opted to maintain just the Slight Risk for now. However, an upgrade to a Moderate this period may be forthcoming should the models start to show a broader consensus that provides greater confidence. Pereira Day 3 Valid 12Z Sun May 25 2025 - 12Z Mon May 26 2025 ....THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM SOUTHEASTERN KANSAS and NORTHEASTERN OKLAHOMA INTO THE OZARKS... With many of the detail differences typical of a day 3 period, there is general model agreement signaling a widespread moderate to heavy rainfall event that will extend from parts of the Southern Plains into the Tennessee Valley this period. This will likely include those areas impacted by heavy amounts during the previous periods. With some timing and amplitude differences, most models show a fairly well-defined shortwave moving out across the Southern Plains by Sunday night. Similar to the previous days, moisture along the lingering frontal boundary will provide ample fuel for heavy rain. In contrast the previous days, guidance shows moisture deepening a little further to the west, supporting heavy rainfall developing back across northwestern Texas and southwestern Oklahoma as this system moves across the Plains. Heavy rains will spread east late Sunday through the overnight, likely impacting parts of eastern Oklahoma, southeastern Kansas, southern Missouri, and northern Arkansas once again. With some models showing an additional 2-4 inches, pushing three day totals over 6 inches in some locations, the Moderate Risk, which was introduced and centered over the region in the previous Day 4, was maintained for the new Day 3. Also maintained was the Slight Risk extending back through southwestern Oklahoma into northwestern Texas. Part of the previously noted detail differences contributed to an uncertainty as to how far south to extend the Slight Risk across eastern Texas. Some of the models, most notably the ECMWF, show heavy amounts progressing well to the south over East Texas. For now, kept the Slight Risk closer to the broader consensus centered farther north. Pereira $$ --- SBBSecho 3.20-Linux * Origin: ILink: CCO - capitolcityonline.net (454:3/105) .