FOUS30 KWBC 031547 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1047 AM EST Tue Mar 3 2026 Day 1 Valid 16Z Tue Mar 03 2026 - 12Z Wed Mar 04 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MIDWEST AND OHIO VALLEY... 16Z Update... The 12Z HREF guidance has trended just a tad wetter across especially the OH Valley for the period ending 12Z/Wednesday. Ongoing moderate to locally heavy rains this morning are very gradually moistening up the soils across areas of central/southern IL through the southern half of IN, however, much of the rainfall continues to be stratiform in nature. A new surge of stronger warm air advection associated with a southwest low-level jet of 30 to 40 kts interacting with a frontal zone should favor additional rounds of heavy rainfall potential this evening and overnight. MUCAPE values are forecast to rise to near or slightly above 500 J/kg. This will help support some elevated convection near and poleward of the front that should remain draped across the OH Valley going through tonight. Some rainfall rates may reach a 0.50" to 1"/hour with the stronger cells, and these rates are supported by the 12Z HREF guidance. Multiple CAMs do suggest some localized cell- training concerns that may yield some additional 1 to 2+ inch totals. However, the antecedent conditions for most areas (minus areas closer to the central Appalachians/WV) are rather dry. This coupled with the relatively modest rates suggest any runoff concerns would tend to be more urbanized in nature and certainly isolated. The threat farther east into the central Appalachians (notably central and northern WV) could end up being a bit higher given the wetter antecedent conditions here, but the guidance overall generally pegs the heaviest totals occurring farther west across areas of central IL eastward through southwest OH. As such, the Marginal Risk is maintained for this update. Orrison Previous discussion... Models have solidified their agreement in an axis of 1-2 inch rainfall totals generally from northeastern Missouri eastward through southern Ohio. These totals will coincide with an east-west oriented front across the region, with point forecast soundings suggesting fairly fast cellular motions and minimal surface-based instability. The main contributor for flash flood potential with this axis is repeating/training rainfall, though dry antecedent conditions remain a mitigating factor for a larger-scale flash flood risk. One exception to this is West Virginia - soil moistures are relatively wet there compared to points west. Rainfall totals may be somewhat lighter there too though (0.5-1.5 inches), also keeping any flash flood potential isolated. Cook Day 2 Valid 12Z Thu Mar 05 2026 - 12Z Fri Mar 06 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM NORTH TEXAS NORTHEASTWARD INTO THE OHIO VALLEY... Minimal changes are made to the inherited outlook. At the mid- levels, an approaching trough will reach the central Plains during the forecast period. As this occurs, strengthening, confluent low- level flow from north Texas into the Missouri Ozarks will aid in moisture transport and eventually deep convective development especially during the afternoon/evening hours. That convective development will migrate from southwest to northeast within the aforementioned warm conveyor, with areas of training/repeating possible along with local rainfall totals exceeding 3 inches through 12Z Thursday. The collocation of these rainfall totals with varied/sensitive terrain over southwest Missouri/northwest Arkansas suggests that higher probabilities and a Slight Risk may need to be introduced at some point. Lingering concerns regarding antecedent conditions (very dry soils) and eventual convective evolution (models exhibiting a slight westward trend over the past 24 hours) gives pause on introducing an upgrade at this time, however. Current trends suggest that the greatest risk of flash flooding will exist along an axis from Fayetteville, AR to Rolla, MO, though this axis may change between now and Wednesday afternoon/evening. Farther northeast, areas of rain (approaching 1-1.5 inch total in spots) will develop from southern Illinois eastward through West Virginia in similar locations that are expected to receive 1-2 inches of rain during the D1 forecast period (Tuesday into Tuesday night). Soils should continue to moisten during this period, with isolated instances of flash flooding remaining possible. Cook Day 3 Valid 12Z Thu Mar 05 2026 - 12Z Fri Mar 06 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Models are in general agreement that longwave trough will deepen across the Intermountain West, spreading southwesterly flow aloft over a large part of the Great Plains. Meanwhile, low-level moisture advection will aid in an airmass characterized by 1.25-1.5 inch PW values along and just east of a dryline generally extending from near Goodland to near Amarillo. Models depict scattered convection developing amid supercellular wind fields Thursday afternoon, with a mix of cells and linear segments possible along parts of the dryline. Local cell mergers may result in a couple spots of 2-3 inch rainfall totals in this regime, though the overall footprint of heavier rainfall should be too small to even delineate a Marginal Risk area at this timeframe. Antecedent dry conditions/drought are also mitigating factors for flash flood potential. This scenario will need to be monitored for any potential increase in convective coverage that might necessitate a Marginal in later outlooks. Cook 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