FOUS30 KWBC 060743 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 243 AM EST Fri Nov 6 2026 Day 1 Valid 12Z Fri Nov 06 2026 - 12Z Sat Nov 07 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF SOUTHEASTERN NEW ENGLAND... ...Southeast New England... Main edits to the inherited Slight Risk based on the 00Z guidance included pulling the outlook area west around 20-40 miles, while expanding a bit farther to the southwest and north, covering eastern and southeastern parts of CT and far eastern Long Island, along with much of Boston Metro. As the mid/upper trough take on a more neutral to negative tilt, mean low- mid layer flow will back more southerly (parallel to the surface front), thereby prolonging the favorable moisture flux off the Atlantic Gulf Stream and thus axes of heavier rainfall. TPWs approaching 1.75" is close to 3 standard deviations above normal for early November, while IVT values exceed 750 KG/m/s through late afternoon per both the GFS and ECMWF. The 00Z models continue to show an axis of QPF between 2.5 to 5.0+ inches of QPF within the Slight Risk area, while the 00Z REFS probabilities of 12hr QPF exceeding 5" is between 15-25% within that corridor as well. Meanwhile, REFS probs of the QPF exceeding a 5 year ARI tops out between 25-40%. Mixed-layer CAPEs between 500-1000 J/Kg will certainly aid to the potentially excessive short-term rainfall rates. ...Southeast VA into Northeast NC, the DelMarVa, and coastal NJ... Further south, considered introducing a targeted Slight Risk across portions of southeastern VA and northeastern NC based on the hi-res guidance which shows the potential for some locally heavier totals in the 3-5" range. Modest instability (~1000 J/KG CAPE) should lead to some more robust storms with waves along the front potentially helping to slow its progression and allow for at least brief training potential, both contributing to higher totals. This would result in a greater concern for scattered flash flooding particularly for the more urban areas around Norfolk/Virginia Beach. However, given the generally overall progressive nature of the front and drier relative conditions through the region, have left a Marginal Risk for now. This is supported by the relatively high probs of 3+ inches in 12hrs, in contrast to the sharply lower probs of 5+ inches (less than 15%). The Marginal Risk has also been expanded northward to include portions of the southern DelMarVa peninsula as well as coastal New Jersey based on the hi- res guidance. While there is some concern the eastward progression of the front may clear the coast before storms develop/expand in coverage especially with northward extent, there is enough of a signal for the potential of 2-3"+ through the region that at least isolated flooding will be a concern. ...Southeastern AZ... A targeted Marginal Risk added to yesterday's Day 2 ERO was maintained in the Day 1 Outlook across southeastern Arizona. A developing upper-level wave in the southern stream will pass over the region Friday leading to at least isolated to scattered thunderstorm development. While not quite as anomalous as recent events, increasing moisture as well as modest instability could lead to a few more robust downpours producing ~1" or so of rain, which could be enough to lead to some isolated flash flooding concerns. B Hurley/Putnam Day 2 Valid 12Z Sat Nov 07 2026 - 12Z Sun Nov 08 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF SOUTH, CENTRAL, AND WEST TEXAS... Only minimal adjustments were needed for the Marginal Risk across south-central/south Texas based on the latest guidance. This included a north-northwestward extension, now through much of the Hill Country and eastern portions of the Big Bend. Generally followed the more consistent AI QPF guidance per the GFS and ECMWF. At this point, given the spread in the guidance, limited instability (MUCAPEs <500 J/Kg), and 24hr QPF amounts not overly impressive per current guidance (generally 1-2"), have opted to maintain the Marginal Risk area rather than upgrade to a Slight. B Hurley Day 3 Valid 12Z Sun Nov 08 2026 - 12Z Mon Nov 09 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTH- CENTRAL AND SOUTH TEXAS... ...South Texas... A anomalous upper pattern over the Southwest will shift focus to the South-Central Plains with eyes on the southern half of TX as we head into Sunday. Digging mid-level trough out of the Southwestern CONUS will eventually close off over northern MX and drift eastward leading to increasingly diffluent flow over west TX and points south and east. At the surface, modest surface ridging to the north will send a cold front southward, gradually, with eyes on Deep South TX by the end of the period. The synoptic evolution lends to a classic isentropic pattern situated over the Edwards Plateau through Hill Country, sinking southward into South TX as we move into the back half of Sunday. Prevailing southeast between the surface to 850mb will lead to an ushering of low-level moisture that will send PWATs surging between 1.5-2.1" with the highest moisture prevalence located over the Southern RGV over to the Gulf Coast, mainly south of Corpus Christi. Directional shear will entice the potential for mesocyclone development and the ability to sustain convection, even elevated to the north of the front leading to enhanced precipitation rates with longevity due to the persistence in the diffluent flow aloft. This whole setup will materialize and become a fixture for at least 24 hrs with a broad area of moderate to heavy rainfall with embedded convection situated across Southern TX with the core located along and south of I-10. Models are consistent in the presentation of bouts of heavy rainfall throughout the period with some enhancement expected in the afternoon and evening as the ascent pattern is maximized with the mid and upper level evolution, as well as the additional diurnal instability element that will occur south of the cold front. Widespread 2-4" with locally higher totals are already being forecast within the numerical suite, even the ML coming in with a solid 1-3" from northwest to southeast with the max focused over the lower Rio Grande Valley (RGV). Despite some of the higher FFG indices, this type of setup can surprise and offer some sneaky flash flood prospects, especially within more urban settings and locally flashier creeks and arroyos across the region. In coordination with the local WFO's over South TX, a SLGT risk was added for those areas along and south of I-10 down to the lower RGV. Main areas of concern will be that area of South-Central TX near San Antonio and the RGV areas between Eagle Pass down to Brownsville. Kleebauer Day 4 and Day 5 Valid 12Z Mon Nov 09 2026 - 12Z Wed Nov 11 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL SUNDAY ACROSS DEEP SOUTH TEXAS ON DAY 4... D4 will be the period where the pattern breakdown over TX and the threat for heavy rainfall begins to dwindle from north to south with the loss of the primary ascent, along with more stable air advecting into the region post-front. There is some discrepancy in the amount of lingering heavy rain/convection in the region from the deterministic output with some lighter amounts overall in the various ensembles. Leaning towards a MRGL for South TX with mainly areas along and south of a line from Laredo to Corpus Christi. Rainfall totals will vary in terms of magnitude with perhaps even a threat for an additional 1-3" according to some global deterministic outputs. Eventually, this setup will translate into a quieter pattern and limited impacts are anticipated for the back- half of D4 and beyond for TX. Across the Pacific Northwest, our first true atmospheric river of the season will impact the region with a steady stream of heavy precipitation into northwest WA, sinking south into northeast OR and the neighboring Cascades between WA/OR. Current setup is not conducive for flash flood scenarios at this time as the antecedent soils in the area lean dry and capable of the initial intake of heavy rainfall in the region. A nil ERO is forecast for D5, but will keep an eye on trends for this period and beyond as the synoptic pattern unfolds and rainfall continues into the second half of next week. Kleebauer 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 $$