FOUS30 KWBC 270050 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 850 PM EDT Mon Oct 26 2026 Day 1 Valid 01Z Tue Oct 27 2026 - 12Z Tue Oct 27 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL AND SOUTHERN HIGH PLAINS AND THE MID TO LOWER TEXAS COAST... ...01Z Update... ...Texas Coast... A Marginal Risk was introduced along the mid to lower Texas coast -- from Matagorda Bay to near Baffin Bay. Guidance shows PWs increasing to at or above 1.75 inches as low-level winds turn southerly ahead of a mid-level shortwave. The HRRR has been fairly consistent over the past several runs -- showing very localized heavy amounts developing as slow-moving, backbuilding storms develop along the immediate coast. The HREF and REFS both indicate localized amounts over 3 inches are likely near the immediate coast -- which may cause isolated flooding, especially across any impacted urbanized areas. ....Southern to Central High Plains... Reduced its footprint, but still maintained a Marginal Risk extending from southeastern New Mexico and West Texas to central Kansas. Expect the threat for flash flooding to remain isolated, with widespread heavy amounts not expected. Will likely continue to see some organized precipitation associated with a well-defined shortwave moving northeast of the Texas Panhandle. However, limited instability will likely keep rainfall rates and the threat for flash flooding low. Some upstream energy could ignite some additional isolated to scattered activity back to the south, which could pose a localized threat for flooding, especially in the more sensitive areas of southeastern New Mexico and West Texas. Pereira Day 2 Valid 12Z Tue Oct 27 2026 - 12Z Wed Oct 28 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR SOUTHEAST FLORIDA... ...2030Z Update... No changes were needed with the Marginal Risk area in southeast Florida nor with the blank ERO elsewhere across the country. Most significant precipitation will be in places that handle it well, such as in the Pacific Northwest, or will remain light enough so as to not pose a notable flash flooding risk. In southeast Florida, as on previous days, any rain will be in spotty showers and thunderstorms, which if one persists over a particularly urban or vulnerable area could pose an isolated flash flooding risk, but that is not likely. Wegman ...Previous Discussion... ...Southeast Florida... Low pressure will gradually shift north over the Bahamas on Tuesday, resulting on another day of northeasterly onshore flow and increasing moisture across Southeast Florida. PWATs will increase to around 2 inches by Tuesday afternoon and evening, but instability may be limited. Global models are showing MUCAPE values 500-900 J/kg along the immediate Southeast Florida Coast, with little to no instability across the rest of the peninsula. Scattered showers and storms are expected to form over the Atlantic, some of which should be able to make it onshore in Southeast Florida. With high PWATs and modest instability, locally heavy rainfall may be possible in some showers and storms. Given recent heavy rainfall in Southeast Florida and the sensitivity of urban areas, isolated instances of flash flooding may be possible along the I-95 urban corridor of Southeast Florida and there is a Marginal Risk of excessive rainfall. Dolan Day 3 Valid 12Z Wed Oct 28 2026 - 12Z Thu Oct 29 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR EAST-CENTRAL AND SOUTHEAST FLORIDA... ...2030Z Update... No signficant changes were needed for the ongoing Marginal Risk along portions of the east coast of Florida, nor for the lack of any risk areas across the rest of the country. As on Day 2/Tuesday, any areas seeing notable precipitation will either not get enough, can handle it well, or it will fall as snow. Similarly, along the east coast of Florida, the pattern will remain much the same. Should heavy rain impact the area, it will be with a moving cell or 2, which could only cause flash flooding should it impact a particularly vulnerable area for an extended period of time, which is unlikely. Wegman ...Previous Discussion... A mid/upper low will continue moving north of the Bahamas off the Florida East Coast. The stream of moisture on the northern side of the low circulation will shift north along the Florida coast, with the highest PWATs (around 2 inches) focused between Cape Canaveral and Fort Lauderdale. Instability will increase as shortwave energy moves across Central and South Florida, which could support increased precipitation coverage, but there is some uncertainty in how much instability will increase. The ECMWF and EC-AIFS are much more aggressive, increasing MUCAPE to 1000-1500 J/kg, while the GFS and AI-GFS only increase MUCAPE to 500-700 J/kg. If showers and storms can tap into the elevated instability, there will be sufficient moisture to support locally heavy rainfall rates. The heaviest rainfall totals will once again focus along the coast, impacting the I-95 urban corridor. Given recent heavy rainfall along the Florida East Coast and the sensitivities of the urban areas, isolated instances of flash flooding may be possible and there is a Marginal Risk of excessive rainfall for portions of east-Central and Southeast Florida. Dolan Day 4 and Day 5 Valid 12Z Thu Oct 29 2026 - 12Z Sat Oct 31 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF SOUTH-CENTRAL TEXAS ON THURSDAY AND CENTRAL ARIZONA ON FRIDAY... 20Z Update... The 12Z runs of the preferred guidance continued to align with the previous outlooks. Therefore, made only minor adjustments to the forecast. Pereira Previous discussion... ..Texas into New Mexico... A Slight risk has been maintained on day 4 (Thu) across portions of TX, stretching from the Stockton Plateau through parts of the western Hill Country and into south-central TX. Overall, not much change was needed to the inherited risk area. 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 mid level 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 4 lead time, exact spatial and temporal details will change some as the event nears. However, models continue to converge on a solution, and confidence in a flash flood event continues to increase. The last few runs of the ECMWF, AIFS, AIGFS and GFS are all clustered fairly well with a max rainfall axis over south-central TX. The latest model consensus is for 2-4" of rain, but with some backbuilding/training probable the potential for at least localized swaths of 6"+ seems in play. We will continue to closely monitor trends, as locally significant flood impacts are possible with this event. Will just carry a marginal risk into day 5. The risk of flash flooding over TX will persist as the features responsible for the day 4 risk shift northward. However the signal becomes a bit more muted by day 5 and uncertainty on the details become higher. So will stick with a Marginal for now, but could eventually need an embedded Slight risk. ...Arizona... Synoptic scale model agreement is above average for a day 5 forecast with broad troughing progressing into the western United States. While some timing uncertainty persists regarding individual embedded shortwaves, the overall environmental ingredients are coming together to support a robust convective and heavy rainfall threat centered over AZ on Friday. Dynamic forcing will be impressive, featuring a very strong southern stream upper level jet that will place AZ within its favored left exit region, promoting strong upper level divergence. Mid level shortwave energy ejecting east will interact with a rather strong southerly low level jet resulting in impressive low level moisture transport and PWs across the region. This strong low level flow should help organize and sustain some training/backbuilding convective cells. While thermodynamic details carry inherent uncertainty at this lead time, current model guidance suggests that corridors of 1000+ J/kg of CAPE are probable. Much of the region has been anomalously west of late, which has notably increased the hydrologic sensitivity across the area. While the exact placement and magnitude of the heaviest rainfall axis remains subject to adjustments as we get closer, confidence is high enough in an isolated to scattered flash flood threat to warrant a Slight risk. 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 $$