FOUS30 KWBC 052022 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 322 PM EST Thu Nov 5 2026 Day 1 Valid 16Z Thu Nov 05 2026 - 12Z Fri Nov 06 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Putnam Day 2 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... The prior forecast reasoning for southeastern New England remains on track. Only some minimal edits to the inherited Slight Risk covering portions of Rhode Island into southeastern MA were needed based on the now available hi-res guidance. Both the 12Z HRRR and suite of RRFS guidance support the potential for areal average rainfall over 3" and locally higher totals of 5"+. This guidance trended a bit to the north and east of the inherited Slight Risk leading to an extension further into southeast Massachuesetts to the northern tip of Cape Cod. While FFGs are higher closer to the coast through this region, the locally heavy totals of 5"+ would be more than enough to still lead to scattered flooding concerns. ...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. 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 has been added across southeastern Arizona. A developing upper-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. Putnam ...Previous Discussion... ...Eastern Portions of LI and CT into RI and Eastern MA... Trimmed the western portion of the Marginal Risk area inherited from yesterday's Day 3 ERO across southern New England, based on the guidance trends (continued eastward shift in the rainfall axis). Mid-upper level trough takes on a more neutral tilt, with the large-scale ascent becoming enhanced within the right- entrance region of the 90-110kt upper level jet streak. Low- level flow (1000-850 mb) backs towards the south while increasing to ~30 kts, strengthening the low-level moisture flux/transport off the Gulf Stream. This will bring PWs of 1.5-1.75 across the outlook area, which is 2-2.5 standard deviations above normal for early Nov. Instability, even elevated, is expected to be fairly minimal per the guidance (MUCAPEs ~200-400 J/Kg), however given the axis of favorable deep-layer moisture/theta-e, the bulk of the guidance continues to show peak 24hr rainfall between 3-5+ inches across parts of southeastern New England, particularly from Newport and Providence RI to Plymouth MA. Given the latest REFS exceedance probabilities over this area, including 40-50% of >5"/24hrs, EAS 40-45% probabilities of >3"/24hrs, and 30-40% probs of exceeding 2 year ARI amounts, have opted to include a targeted Slight Risk area in the Day 2 ERO. ...Southeast VA into Northeast NC... Have included a Marginal Risk area across coastal portions of the Mid Atlantic, including Hampton Roads. Degree/duration of favorable dynamics are not as favorable compared to southeastern New England, however the guidance does show a bit more instability to work with (higher probs of at least 750-1500 J/Kg), which translates to higher 1+ in/hr rainfall rates Friday afternoon into early evening. Areal-average QPF within this region is between 1.5-3.0" per a multi-model blend (including the AIGFS and ECMWF AIFS). B Hurley Day 3 Valid 12Z Sat Nov 07 2026 - 12Z Sun Nov 08 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS SOUTH-CENTRAL AND SOUTH TEXAS... ...2030 UTC Update... Only minimal adjustments were needed for the Marginal Risk across south-central/south Texas based on the latest guidance. This included a northwestward extension into portions of the southern Hill Country where there remains a concerning signal from the GFS for heavier rainfall across the more sensitive terrain. As noted below, a Slight Risk may eventually be needed with more confidence in the location of the heaviest rainfall, particularly if it were to focus on portions of the Hill Country or where there would expectedly be more convergence/forcing along the coast. However, there remains too much spread in the guidance to have enough confidence in a risk area for now. Putnam ...Previous Discussion... Model guidance is beginning to converge on a synoptic evolution that would favor areas of heavy rain over southern TX this weekend. A mid-upper low is forecast to dive southeast out of AZ and into northern MX late Friday/Fri night, then gradually progress eastward towards West TX by Sunday. This feature will provide ample ascent for rainfall, with a strong upper level jet providing additional lift. Anomalous moisture will advect northward ahead of this system, and while PWs will likely not be as high as recent events, it is still forecast to exceed the climatological 90th percentile. In the low levels we should have east to northeasterly flow, which will aid in isentropic ascent over the region, but should also act as a stabilizing factor. Thus the degree of instability, which will impact rainfall rates and the flash flood potential, remains a question. In terms of the latest guidance, the ECMWF AIFS continues to be the most persistent model showing the heavy rainfall threat, and is gaining more support from the operational ECMWF, GFS, and CMC. If/where sufficient destabilization is able to occur to drive higher rainfall rates, a future Slight risk upgrade may be necessary. Best chances for this at the moment appear to be along the south TX coast where instability advecting in off the water and coastal convergence could focus higher rainfall magnitudes. B Hurley/Chenard Day 4 and Day 5 Valid 12Z Sun Nov 08 2026 - 12Z Tue Nov 10 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL SUNDAY ACROSS PARTS OF SOUTH TEXAS... Continued with the Marginal Risk area previously issued and valid on Sunday across portions of southern Texas. Models still depict and upper trough and southern stream upper jet support and deep subtropical moisture which gradually shifts east of Texas, but not before another day of potentially heavy rainfall across the region. Both the GEFS and EC Ensemble showed a slight contraction of the areal coverage at the 2 and 3 inch threshold which roughly fit the deterministic GFS QPF solution. We opted to shrink the areal coverage just a bit. Note this does not reflect a fundamental shift in forecast reasoning. It should be pointed out that the narrow corridor of 3-6" amounts persisted in the 12Z numerical guidance run but the spread in placement precluded an upgrade in a region with very high flash flood guidance, Needless to say...this area will continue to be watched in upcoming model cycles. Bann 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 $$