FOUS30 KWBC 020043 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 843 PM EDT Wed Apr 1 2026 Day 1 Valid 01Z Thu Apr 02 2026 - 12Z Thu Apr 02 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF TEXAS NORTHEAST INTO THE MID-MISSISSIPPI VALLEY... ...Oklahoma into western Illinois... Recent mesoscale model guidance and radar reflectivity trends show that continuity is generally on track, so changes to the previous risk areas have been minimal. An elongating area of organized convection extends ahead of a convective wave presently in western OK up an existing frontal boundary, with convection showing slight eastward movement. Hourly rain amounts to 2.5" have been seen due to cell training, cell mergers, and embedded mesocyclones. Local totals in the 4" range are possible in this environment where very heavy rain can persist for 1.5 hours or so. The heavy rain potential should continue into the early morning hours of Thursday before fading by 12z. ...Central Texas... A Slight Risk remains across the Concho Valley in west TX as trends for convection running out ahead of a retreating dry line. The atmosphere shows a favorably unstable environment and stout 45-55kt bulk shear axis should allow for the initiation of supercellular convective modes shortly followed by an eventual merger of cells as the LLJ matures further. This is a classic scenario of the southern edge of a larger ascent pattern in spring that tends to be more appreciable for heavy rainfall. Hourly rain amounts to 2.5" with local totals to 4" are possible here as well. Continuity could be well maintained, using the recent mesoscale guidance as a guide. ...Upper Ohio Valley... While convection appears to be on the wane in this area, the mesoscale guidance suggests that some activity could continue to bubble overnight. Local amounts in the 1-3" range occurred here over the past 24 hours. Left the Marginal Risk in this region intact as a course of least regret. Roth Day 2 Valid 12Z Thu Apr 02 2026 - 12Z Fri Apr 03 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF EASTERN IOWA, NORTHERN ILLINOIS, WISCONSIN AND MICHIGAN... 20Z Update: Evolution of the longwave pattern across the Central and Northern CONUS will create a multi-round area of convection over portions of the Midwest and Great Lakes beginning Thursday morning with a second round expected by the evening hours. The first batch of rainfall will be relatively appreciable, but rates will be lacking due to a dearth in the overall instability fields across the Great Lakes. Increasing southerly flow will aid in advection of slightly warmer temperatures and increasing MUCAPE by the afternoon which will act as a key ingredient for convective development later in the day as large scale forcing shifts eastward with a surface cold front approaching from the west adding to the regional ascent pattern. 12z CAMs have shown inferences of heavier rainfall bisecting some of the urban zones located over northern IL into southern WI, extending northeast to western MI just over the lake shore. There are relatively good probabilities >50% within the HREF EAS fields for at least 1" of precipitation, but probabilities for 2" are significantly lower within the same zones meaning there is a general 1-2" mean QPF output from the latest convective allowing models. This is also experienced within the latest bias corrected ensemble forecast, a testament to the general range of outcomes for this setup. The primary area of interest for flash flooding will likely lie over far northern Chicago suburbs up into the Milwaukee metro due to the areal urban footprint and suggestion of heavier rainfall in the area, especially the second round of convection. Fortunately, rates are generally capped at 1-1.25"/hr at peak intensity with much of the CAMs hourly outputs closer to 0.5-1"/hr for the heaviest periods of impact. This lies right on the edge of any FFG exceedance, so the threat will be somewhat capped overall for a multitude of reasons. Decided to maintain general continuity from the previous forecast with only minor adjustments on the northern and southern peripheries of the inherited MRGL risk. Will keep an eye on trends within the CAMs to see if a small upgrade is plausible across the aforementioned area over northern IL and southern WI, but in coordination with the local WFO's and current setup, decided it was not worthy for the upgrade in the risk. Kleebauer Day 3 Valid 12Z Fri Apr 03 2026 - 12Z Sat Apr 04 2026 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHERN/CENTRAL PLAINS... 20Z Update: Only minor changes were made to the inherited SLGT risk across the Southern Plains to Mid-Mississippi Valley as ensemble output remains pretty consistent in the axis of where the heaviest precip is expected for Friday evening into Saturday morning. High 1/3/6 hr FFG thresholds will likely subdue more appreciable risk forecasts as a lot of rainfall will be necessary to approach more substantial flash flood concerns, both magnitude and areal coverage. That said, the longwave pattern and current forecast instability would still be suitable for something bordering into the higher end SLGT risk category, especially for central and eastern OK down into the Red River Basin between the TX/OK border. Will assess trends in the coming forecast periods to see if there is any chance for changes, but right now the overall output from guidance maintains a pretty solid run-to-run continuity with global deterministic indicating perhaps a little more variance in placement of heaviest precipitation corridors. Kleebauer ..Previous Discussion.. Strong to severe thunderstorms along with embedded heavy rainfall will track across the Southern/Central Plains into the Midwest during this period. Moisture (with PWs over the 90th, perhaps 95th percentile) and instability are likely to pool along and ahead of the associated cold front and produce widespread convection. Storms likely beginning in the afternoon are expected to get reinforced through the evening and night hours as a low level jet picks up ahead of the cold front. A Slight Risk was maintained and adjusted to span from northern Texas to southwest Missouri. Campbell 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