434 FOUS30 KWBC 040344 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1144 PM EDT Fri Apr 3 2026 Day 1 Valid 12Z Sat Apr 04 2026 - 12Z Sun Apr 05 2026 ...THERE IS SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHERN PLAINS & MIDWEST... ...04Z Outlook Update... Introduced a Slight Risk in portions of central and eastern Ohio for this update. A persistent band of convection continues to train along an east-west oriented warm front bisecting the new Slight Risk area. This band will likely persist for another 2-4 hours or so as the warm front drifts slowly northward due to warm advection processes. 2-5 inches of rain has fallen near the Mansfield area, and hourly rates around 0.5 to 1 inch/hr are expected to continue at times over saturated soils. Ongoing reports of flash flooding have been received, and more are possible through the overnight hours. Cook ...Previous Discussion... A cold low in the Northern & Central Plains is moving eastward, driving a wavy frontal boundary forward through the Southern & Central Plains and luring a warm front north towards the Great Lakes. Precipitable water values are roughly 1.25-1.5" through the region, though lower in IA within the main cyclone's cold sector and higher across central and southern TX. Downslope flow off the Southern Rockies and northern Mexico has sustained a dry line within the warm sector across portions of northwest TX and the Trans Pecos region of TX. A broad area of 1000-2000 J/kg of ML CAPE and effective bulk shear of 25-55 kts exists regionally, which should maintain organized convection well into the overnight hours. The areas for enhanced flash flood potential will exist from southeast OK southwest toward central Texas and the Big Country, as well as from central IL across the southeast portions of Chicagoland into far northwest IN. Thunderstorms are expected to grow in coverage as the low- level inflow from the Gulf ramps up further. Hourly rain amounts are expected to peak around 2.5" with additional local totals to 4" hinted at by the 12z REFS/18z HREF output. This could occur in conjunction with mesocyclones, cell training, or mergers between greater and lesser organized convection. Though less widespread, additional convection should continue to traverse wet ground conditions across portions of Ohio, Pennsylvania, southwest New York, and northern WV, supporting continued Marginal probabilities in that area through at least midnight. Roth Day 2 Valid 12Z Sun Apr 05 2026 - 12Z Mon Apr 06 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE ARKLATEX AND THE LOWER MISSISSIPPI VALLEY... Much of convective evolution during the D2/Sat forecast period will depend on convective details from lingering convection across Arkansas and Texas left over from D1/Fri. East-northeastward progression of a mid-level wave toward the Great Lakes will aid in southeastward movement of a cold front from the Plains through the Ozarks/Mid-Mississippi Valley during the forecast period. This front will gradually become more parallel to weakening flow aloft from Texas to Mississippi, supporting additional opportunities for training convection as storms organize along remnant outflows and backbuild, with the potential for areal average rainfall in the 1-2" range leading to isolated instances of flash flooding. A more focused threat has been identified supporting the introduction of two Slight Risk areas within the broader Marginal Risk. The first is across portions of the ArkLaTex southwest through northeast Texas. The latest hi-res guidance supports the maintenance of ongoing convection within the Slight Risk for the day 1 period across Oklahoma continuing southeastward along the front into Saturday morning. A wave of low pressure along the front in northeast Texas will also help to maintain/enhance the development of this convection as well as briefly slow the progression of the front northeast through the ArkLaTex, allowing for heavier rainfall totals as storms persist over the region for a longer amount of time before the front begins to sweep southward faster later into the afternoon. The latest 12Z CAMs show the potential for locally heavy totals of 3-4" with rain rates of 2-2.5" per hour. The second region is across portions of the Lower Mississippi Valley later in the day where moist southerly flow from the Gulf will bring a pool of ~70 degree dewpoints northward. These high dewpoints along with daytime heating will lead to a region of 1000-2000 J/KG CAPE supporting the development of heavy- rainfall producing thunderstorms ahead of the front. The combination of this initial development in addition to a second round of storms expected along the front with similarly high rain rates of ~2" per hour will also lead to the potential of locally heavier totals in the 3-4" range. While dry antecedent conditions/high FFGs may limit the overall threat, the potential for these higher rain rates/totals within the highlighted Slight Risks should be sufficient enough for at least a localized/urban scattered flash flood threat. Farther north, convection is likely to be progressive across much of the Lower Ohio Valley along with potential for inhibited destabilization due to more widespread convection across the Lower Mississippi Valley. Too much uncertainty exists to reduce the Marginal Risk area at this time. Notable exceptions to this general regime exist, however, from northern Ohio into southern New York State and Pennsylvania, where models suggest appreciable daytime heating and moderate instability developing. Storms may not be all that fast moving either in Pennsylvania as that region should reside on the southern extent of stronger mid-level flow into southeastern Canada. Convective coverage is a bit uncertain, but any greater-than-anticipated coverage of convection in this environment could locally raise flash flood concerns - especially with low FFGs noted across that area. Putnam/Cook Day 3 Valid 12Z Mon Apr 06 2026 - 12Z Tue Apr 07 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTH TEXAS ON SUNDAY... ...20Z Update... The latest model guidance supports the prior forecast reasoning with the potential for isolated heavy rainfall-producing storms as moisture pools along the frontal boundary. There is some concern that the front will be progressive enough that moisture/CAPE will be swept out of south Texas before the start of the period limiting any threat, but at least for now guidance retains at least some potential. This is particularly true closer to the Gulf Coast portion of the risk area where a surface wave and slower progression of the front into the Gulf further east may keep the front along the south Texas coast long enough to lead to some storms. Putnam ...Previous Discussion... Maintained the Marginal Risk of Excessive rainfall area that was introduced by the WPC Medium Range desk as a west- to- east oriented front makes its way southward. Deeper moisture should be pooling along and south of the boundary with precipitable water values around 1.75 inches in place at the start of the outlook period. Given uncertainties detailed in the Day 2 period with respect to the timing and placement...combined with the 03/00Z NCEP global models now showing the front to be more progressive than in earlier runs which led to CAPE being swept out of South Texas faster...was not inclined to introduce a Slight Risk area at this point. At the same point...spaghetti plots from the non-CAM ensembles still show enough members with 1 inch QPF and a few contours of 2 inch QPF to support keeping the Marginal area with only minor nudges around the periphery. 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