FOUS30 KWBC 250812 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 412 AM EDT Sun Oct 25 2026 Day 1 Valid 12Z Sun Oct 25 2026 - 12Z Mon Oct 26 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL AND SOUTHERN HIGH PLAINS AND SOUTHEAST FLORIDA... ...Central and Southern High Plains... An upper level low will track across the Four Corners region and central Rockies today, while shortwave energy moves north across the southern and central High Plains ahead of the low. This setup will bring anomalously moist air into the south-Central U.S., tapping into Pacific and Gulf moisture that will fuel scattered to widespread convection on the leading edge of the system. PWAT values are expected to rise to 1-1.5 inches (2-4 standard deviations above normal) from West Texas through the central High Plains. The highest instability (MUCAPE 1000-1500 J/kg) is expected to focus across portions of West Texas and New Mexico, which will likely support intense rainfall rates up to 1-1.5 inches per hour. Instability will be more limited over the central High Plains, but modest instability (MUCAPE around 500 J/kg) combined with upper level shortwave support should allow for some deeper convection with locally heavy rainfall. Scattered instances of flash flooding will be possible from West Texas through portions of the southern and central High Plains, which is highlighted with a Slight Risk of excessive rainfall for today. Soils are already saturated from recent heavy rainfall over portions of West Texas and eastern New Mexico, and increased runoff may heighten flash flooding concerns. Areas near steep terrain and burn scars will also be vulnerable to flash flooding. A broader Marginal Risk area extends further north into the central Plains where soils are less susceptible to flash flooding but locally heavy rainfall may result in isolated instances of flash flooding. Moisture will spread even further north ahead of the system into the northern Plains, but with little instability to work with, it will be difficult to get rainfall rates heavy enough to pose a risk of flash flooding. ...East Coast of Florida... A mid-level low will gradually move south over the Atlantic parallel to the Florida Peninsula, then stall offshore of Southeast Florida by this afternoon. This will result in a prolonged period of northeasterly onshore flow along the East Coast of Florida, with an emphasis over Southeast Florida. Moisture wrapping around the northern side of the low circulation will bring PWATs across the Peninsula up to 1.5-1.75 inches and up to 1.75-2 inches across Southeast Florida, which will support scattered to widespread showers and storms that will form over the Atlantic and migrate over the coast. Coastal convergence will focus the highest precipitation totals right along the coast, which will create a risk of isolated instances of flash flooding along the I-95 corridor south of Jacksonville. As the system stalls, precipitation will target Southeast Florida, which is where the highest rainfall totals are expected today. Hi-res models show rainfall totals reaching 1-2 inches across Southeast Florida with locally higher amounts possible. Given the sensitivity of urban areas of Southeast Florida, scattered instances of flash flooding will be possible and there is a Slight Risk of excessive rainfall for much of this area. ...Pacific Northwest... A closed upper low will gradually move onshore in the Pacific Northwest today, accompanied by steady rainfall along a leading cold front and scattered to numerous post-frontal showers across western Washington and Oregon. Locally heavy rainfall may be possible, but given the dry antecedent conditions there is not expected to be a flood threat with this system. Dolan Day 2 Valid 12Z Mon Oct 26 2026 - 12Z Tue Oct 27 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL AND SOUTHERN HIGH PLAINS AND SOUTHEAST FLORIDA... ...Central and Southern High Plains... The upper low will push past the Rockies into the Plains, resulting in surface cyclogenesis over the central/northern Plains. Scattered showers and storms are expected in the warm sector of the system over the central and southern High Plains. Similar to Sunday, anomalous moisture streaming ahead of the system will spread along the trailing cold front up into the northern Plains, but the best instability will be limited to the central and southern High Plains, which is where the highest flash flood risk is expected. Precipitation totals are forecast to be modest compared to previous days, but there will likely be a period of enhanced convection Monday afternoon into Monday evening as an upper level shortwave moves north into the region. During this period, the ingredients will be in place to support a threat of at least isolated instances of flash flooding within the Marginal Risk area. Widespread precipitation is also expected over the northern Plains in the vicinity of the surface low, but with little instability, rainfall rates should remain moderate at best. Model guidance is showing rainfall rates and totals remaining well below current FFGs for the area, so there will be little to no flash flood risk for this area. ...Southeast Florida... Northeasterly onshore flow with high PWATs up to 2 inches will continue across Southeast Florida as the mid-level low remains stalled near the Bahamas. Eventually, the low will be absorbed by another wave moving north over Cuba, then move northeast into the Atlantic later this week. Meanwhile, the system will become weaker and less organized and precipitation coverage and intensity should decrease. Even so, scattered showers will move onshore in Southeast Florida throughout the day on Monday, and locally heavy rainfall will be possible. Given heavy rainfall expected on Sunday, a Marginal Risk area was continued for Southeast Florida where there could be isolated instances of flash flooding, especially in urban areas. Dolan Day 3 Valid 12Z Tue Oct 27 2026 - 12Z Wed Oct 28 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR SOUTHEAST FLORIDA... ...Southeast Florida... Northeasterly flow will continue across the Florida Peninsula, with scattered showers and storms forming over the Atlantic and moving onshore in Southeast Florida. Model guidance shows a surge in moisture across Central and South Florida on Tuesday, with PWATs exceeding 2 inches. This will likely support locally heavy rainfall along the Southeast Florida coast as showers move onshore. Isolated flash flooding could be possible in urban areas, especially considering the previous days of heavy rainfall, so a Marginal Risk of excessive rainfall was introduced for portions of Southeast Florida. Dolan Day 4 and Day 5 Valid 12Z Wed Oct 28 2026 - 12Z Fri Oct 30 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF SOUTH-CENTRAL TEXAS... A Slight risk has been introduced on day 5 (Thu) across portions of TX, stretching from the Stockton Plateau through parts of the western Hill Country and into south-central TX. Large scale forcing for ascent will be driven in part by a strong southern stream upper jet providing divergence aloft. Embedded shortwave energy will also eject out of the East Pacific within the deep southwesterly flow aloft, with some potential moisture and vorticity contribution from what is currently tropical cyclone Vance. Mid to upper level moisture sourced from the East Pacific will combine with a strong southeasterly low level jet bringing moisture out of the Gulf. This combination will drive PW values well above the climatological 90th percentile for late October. The environmental ingredients in place will support an organized heavy rainfall event. As expected at a day 5 lead time, exact spatial and temporal details will change some as the event nears. However there is enough run to run consistency and model clustering...both among physics based and AI guidance (with preference given to the AIFS, AIGFS and ECMWF model suites)...to justify going straight to a day 5 Slight risk. While adjustments to the risk area are probable in subsequent updates as model guidance evolves/converges, the currently outlined corridor represents the area of highest probabilities at this time. We will continue to closely monitor trends, as certainly some chance for locally significant flood impacts from this event. Surrounding the Slight risk, a broader Marginal risk extends westward across West TX and into southern NM. While this region is currently forecast to reside west of the primary heavy rainfall axis, elevated hydrologic sensitivity exists over some of this area from recent rainfall. Some uptick in moisture and instability is forecast which should be sufficient for isolated to scattered convection and localized flash flooding. Chenard 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 $$