FOUS30 KWBC 260104 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 904 PM EDT Sun Oct 25 2026 Day 1 Valid 01Z Mon Oct 26 2026 - 12Z Mon Oct 26 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL AND SOUTHERN HIGH PLAINS... ...01Z update... ...Southern High Plains into the Central Plains... Overall, not much change from the previous outlook, with a Slight Risk maintained from Far West Texas to southeastern Kansas. Expect the greater threat for organized heavy rain through the near-term to focus from northeastern New Mexico through the Panhandle Region into southwestern Kansas. Favorable upper jet and mid-level forcing interacting with persistent southerly low-level inflow/moisture advection will continue to support moderate to heavy rain along this axis, with training storms raising the threat for heavy amounts and flash flooding. Both the HREF and REFS show high neighborhood probabilities for additional amounts of 1-2 inches across this area through the remainder of the evening into the overnight. Farther to the south across southeastern New Mexico and Far West Texas, activity is expected to be generally less organized. But given the greater sensitivity and low FFGs across this area, along with the potential for some additional localized 1-2 inch amounts, the Slight Risk was maintained. The latest HRRR, HREF, and REFS did suggest the threat for heavy rain and flash flooding would be confined farther west than the previous Marginal Risk suggested, so the eastern extent of the Marginal Risk was pulled a little farther west with this update. ...Florida... Onshore flow continues to produce isolated to scattered showers along the eastern shores. While an isolated concern can not be ruled out, these showers are fairly progressive and are moving into a more stable airmass centered over the peninsula. With latest guidance also not indicating a notable signal for anything beyond isolated heavy amounts, the Slight Risk was removed but a Marginal Risk maintained along the coast. Pereira 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... ...21Z update... ...Central and Southern High Plains... The 12Z models showed good agreement on the movement of the upper low to track northeastward from the central High Plains on Monday, and an upper trough axis forecast to advance through AZ/NM. The upper trough will be associated with a a 70-90 kt upper level jet streak which will bring favorable diffluence and divergence aloft over the southern High Plains between 18-00Z, coinciding with peak daytime heating and 1 to 3 standardized anomalies of precipitable water. Brief training/repeating of thunderstorms will be possible among MLCAPE values of roughly 500-1500 J/kg, supporting hourly rainfall of 1-2 inches. ...Southeast Florida... The Marginal Risk was maintained for southeastern FL given the continued potential for isolated excessive rainfall. While the model signal for high QPF has fluctuated over the past 24 hours and the latest models do not indicate very high rainfall totals (40 km neighborhood probabilities from the 12Z HREF/REFS are ~30 percent or less for 2+ inches/24 hr), limited potential remains for mainly urban flash flood impacts across the urban southeastern corridor. Otto ...previous discussion follows... ...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... ...21Z update... The latest models maintained a limited/isolated and likely urban threat for heavy rainfall/flash flooding across southeastern FL on Tuesday into Tuesday night. The threat was driven largely by the QPF placement seen in the 12Z AIGFS and 06Z ECAIFS along with low probabilities for 2+ inches of rain over the 24 hour period from the 12Z CMC and 00Z ECMWF ensembles. Forecast instability profiles show a gradient in CAPE along the southeastern FL coast with higher values (500 to 1000+ J/kg) offshore, and little to no CAPE for inland locations. Additional decals on the forecast can bee seen in the previous discussion below. Otto ...previous discussion follows... ...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... 20Z Update... While there remains a fair amount of spread in the latest deterministic guidance, the Slight Risk introduced overnight still falls near the midst of the guidance envelope, and close to the AI guidance and higher probabilities for heavier amounts. Therefore, the previous outlook was left unchanged. Pereira Previous discussion... 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 $$