FOUS30 KWBC 040108 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 808 PM EST Tue Nov 3 2026 Day 1 Valid 01Z Wed Nov 04 2026 - 12Z Wed Nov 04 2026 ...THERE IS SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF MISSISSIPPI AND TENNESSEE AND OVER PARTS OF SOUTHEAST FLORIDA... ...Mississippi and Tennessee... Maintained a Slight risk from portions of central MS into central TN where eastward moving convection may pose an isolated to scattered flash flood risk through the overnight hours. The line of convection has generally been progressive, and observed rainfall rates seem to be lower than recent HRRR forecasts. Given these trends it would seem like HRRR rainfall amounts are initially overdone, and the overall flash flood risk is mainly just a localized urban threat. For this reason we considered dropping the Slight risk down to a Marginal. However, with the low level jet and moisture transport forecast to increase over the next several hours, we may see an uptick in convection downstream of the ongoing line, which could result in some training potential over portions of MS into TN overnight. Still consider this a lower end Slight risk, but this possible uptick warrants keeping the risk that is already in place. ...Southeast Florida... Convection for much of the day has been weak and disorganized across southeast FL. However over the past couple hours we have seen an uptick in convection across a narrow corridor of southeast FL. Confidence is low regarding the maintenance and coverage of this activity going forward tonight, but there is at least a conditional risk of flash flooding along the southeast FL urban corridor. The mesoscale environment remains conducive to heavy rainfall rates and potential backbuilding/training along the coastal convergence axis. Chenard Day 2 Valid 12Z Wed Nov 04 2026 - 12Z Thu Nov 05 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHEAST FLORIDA AND FROM THE TENNESSEE VALLEY INTO THE LOWER OHIO VALLEY AND SOUTHERN APPALACHIANS... ...Tennessee Valley to the Lower Ohio Valley and Southern Appalachians... On-going convection at the start of the period will continue to be capable of producing sufficient rainfall rates to produce isolated threat for runoff concerns into the early hours of the Day 2 period. Then by the afternoon, moist southerly flow into the southern Appalachians along with modest mid-to-upper level forcing will contribute to an increasing chance for locally heavy showers and storms. The general consensus of the 12Z guidance indicates that orographically focused amounts of 1-2 inches, with isolated heavier amounts, can be expected across portions of the Tennessee Valley as well as from northern Georgia into the southern Blue Ridge. ...Southeast Florida... The threat for heavy amounts and flooding concerns will continue to diminish during the period. However, isolated heavy amounts with flash flooding especially in the urbanized coastal areas can not be entirely ruled out given some overlap with areas soaked since Saturday. While drier air will continue to spread into the region, especially late in the period, PWs remaining near 2 inches could support some additional afternoon heavy downpours, resulting in additional isolated runoff concerns. Pereira/Bann Day 3 Valid 12Z Thu Nov 05 2026 - 12Z Fri Nov 06 2026 The probability of rainfall exceeding flash flood guidance is less than five percent. Bann Day 4 and Day 5 Valid 12Z Fri Nov 06 2026 - 12Z Sun Nov 08 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR SOUTHERN NEW ENGLAND ON FRIDAY... 20z Update: Marginal risk was maintained from NYC into southern New England. The model consensus supported a minor eastward shift to the western extent of the Marginal, but otherwise a swath of 2-5" still appears probable across the area. While the 12z models show above average agreement on this axis, we are still 4 days out, and thus additional fluctuations in the rainfall axis are likely. Still in the realm of possibilities it shifts east and is mainly offshore...but enough model support and run to run consistency to maintain the Marginal, with the best chances of localized flash flooding appearing to be from Long Island into eastern CT, RI and eastern MA. Chenard ...Previous Discussion... A Marginal risk area was added for southern New England, NYC and Long Island with this update. There remains considerable uncertainty how fast the front over the Northeast sweeps east, especially into the Mid-Atlantic. However, there is better certainty about a corridor of heavier rain getting hung up across southern New England on Friday. Soils all up and down the Eastern Seaboard, with the notable exception of Florida, remain very dry after over 2 weeks without a drop of rain. Thus nearly all of the expected rainfall will be beneficial. However, the plume of moisture with PWATs over 1.5 inches stalling over New England, potential for some limited instability to support some convective elements, upslope, and plentiful urban areas will all support the possible development an isolated instance of flash flooding or two. This will be where the heaviest rains are most persistent. Thus, this is a low-end Marginal as considerable uncertainty remains. On Saturday, lingering rain in eastern Maine, and a weak tropical disturbance approaching the lower Texas coast both have the potential to cause an isolated instance of flash flooding or two in those respective areas. In Maine several pieces of guidance move the heaviest rains east into New Brunswick and Nova Scotia faster. Meanwhile in Texas, a lot of the expected rain may stay offshore where there will be much more instability. These factors precluded a Marginal Risk issuance for now in both areas. Wegman 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 $$