FOUS30 KWBC 010825 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 425 AM EDT Thu Oct 1 2026 Day 1 Valid 12Z Thu Oct 01 2026 - 12Z Fri Oct 02 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHERN PLAINS... Latest trends in guidance signal a reputable chance for significant rainfall over much of the more flash flood prone areas of south-central Texas, including the I-35 corridor from Dallas- Fort Wort to Austin-San Antonio with a secondary max situated along the southern Rio Grande Village. Widespread 3+" rainfall opportunities with a swath of 50-90% probabilities for the 3-inch threshold. Rainfall potential over the Hill Country is the most notable area for appreciable impacts as another period where 2-4", locally higher totals are plausible leading to locally significant flash flood prospects given the sensitivity of the area in general. Hourly rates likely between 1-2"/hr with as high as 3-4"/hr for intra- hour rate potential, a signature notorious for elevated flash flood concerns within the Hill Country and the I-35 corridor. Greater than 5" probs are very high over that area in Deep South Texas with a large areal coverage of 60-90% situated just south of San Antonio into the Rio Grande Village. The front will be slow to progress through the state, so the convergence pattern along and just ahead of the front will be long- lasting, creating an extended period for potential training before the frontal passage occurs. The Moderate Risk was maintained from South Texas to southeast Oklahoma. Prolonged diffluent flow over the Plains into the Midwest sets the stage for heavy rainfall over a broad area of uncharacteristically high PW values thanks to an airmass coincident with the remnants of Tropical Cyclone Polo. PW values between 2-2.25" over the Midwest and Mid- Mississippi Valley will be upwards of 3-4 standard deviations above normal, an anomaly that will likely flirt with some of the daily and even monthly maxima for PWs over this general area. A broad Slight Risk covers Texas to Wisconsin and northeast Indiana for scattered to potentially widespread flash flooding. Models are consistent in the heaviest precipitation footprint occurring over the first half of the forecast period over Iowa into southern Illinois as the remnant energy and anomalous moisture from Polo will still be present with widespread thunderstorm activity likely to occur over the course of Thursday morning before the front from the northwest finally pushes through the region. This will end the threat over Iowa/Wisconsin/northern Illinois, but not before scattered flash flood concerns over the population centers based in the area from eastern Iowa into adjacent Illinois. Widespread 1-3" of additional rainfall is forecast for these areas. Priming today will set the stage for more flash flood prospects the first part of the D2 with the heaviest rainfall. Campbell/Kleebauer Day 2 Valid 12Z Fri Oct 02 2026 - 12Z Sat Oct 03 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHERN/EAST-CENTRAL TEXAS... The frontal boundary will be lingering in the region to provide one last round of appreciable rainfall before conditions improve moving into the weekend. An Additional 2-4" of rainfall possible from Laredo to McAllen and areas just inland with a secondary max possible over east-central Texas, mainly just east of the I-35 as the front finally moves through on Friday morning. A Slight Risk area cover much of South Texas, eastern portions of the Hill Country and parts of eastern Texas. Farther north and east, the cold front will continue to advance southeast through the Ohio Valley, with some potential for heavy rain along and ahead of the boundary. Supported by deep southerly flow along the western extent of the subtropical ridge, guidance continues to show a broadening pool of anomalous moisture spreading from the Gulf Coast into this boundary. Mid- level energy embedded within the flow may help produce areas of heavy rain, with some guidance indicating heavy amounts along the Gulf Coast from Mississippi to the Florida Panhandle this period. A broad Marginal spans from Texas across the Gulf to western Florida and then northeast to Ohio and Kentucky. These areas will likely see some heavier rainfall rates >2"/hr considering the environment and available instability in the area, however the FFG's are much higher in these zones with the most notable areas of impact in the more urbanized areas along the Gulf coast from Panama City over to Galveston. Campbell/Kleebauer Day 3 Valid 12Z Sat Oct 03 2026 - 12Z Sun Oct 04 2026 ..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE CENTRAL GULF COAST NORTHWARD INTO THE TENNESSEE VALLEY... During this period the upper level trough will continue to track toward the east while slowly amplifying along the way to the eastern U.S. Deep, anomalous moisture (2-2.5+ std dev above normal) will be drawn along and ahead of a wavy front that is forecast to extend southwestward from the southern Appalachians back into the western Gulf early in the period. Mid- to-upper level energy moving along the base of the broader scale trough will have the potential to produce organized, highly- efficient storms, resulting in areas of heavy amounts. Heavy rainfall is expected to align along and ahead of the frontal boundary where the axis of deepest moisture will be present. A Slight Risk for excessive rainfall and potential flash flooding was maintained for much of the central Gulf Coast and northward across Mississippi, northern Alabama and northern Georgia. Campbell/Pereira Day 4 and Day 5 Valid 12Z Sun Oct 04 2026 - 12Z Tue Oct 06 2026 ...THERE IS A SLIGHT RISK OVER PARTS OF THE CENTRAL GULF COAST... For Day 4 (12Z Sun-12Z Mon) -- The one meaningful change compared to yesterday's Day 5 ERO was to extend the Marginal all the way to the Mid Atlantic and Southeast Coast. There is a handful of guidance (including the 00Z ECMWF, EC ensemble mean, and EC-AIFS) that are a bit more progressive with the southward extent of the broad frontal zone, thus implying any outlook areas would be shifted farther south toward the Gulf Coast. For now, have maintained the Slight Risk across parts of the Central Gulf Coast, though if the trends in the global guidance continue (amplifying upper trough over the Great Lakes), later shifts may start peeling away at the northern extent of the Slight (as well as Marginal) with the faster surface cold frontal passage. On Day 5, the only area of concern at this point is the Lower TX Coast. This is where the surface front would more likely get hung up, as both the 00Z ECMWF and GFS show stretched mid-level vort lobes lingering across South TX. At this time, the guidance shows a very compact area of heavier rain (higher deterministic and probabilistic QPF) onshore from the Gulf, basically along the Lower TX Coast and into eastern portions of the Rio Grande Valley. Hurley 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 $$