FOUS30 KWBC 130047 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 847 PM EDT Sun Apr 12 2026 Day 1 Valid 01Z Mon Apr 13 2026 - 12Z Mon Apr 13 2026 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF CENTRAL AND SOUTHEAST TEXAS... ...Texas... 01Z Update: Current CAMs are struggling with the handling of this evening's QPF distribution with the best handle being maintained by the RRFS, but even that is struggling a bit in the grand scheme. Shortwave analyzed in Coahuila is still set to eject into TX overnight with modest return flow off the Gulf anticipated for areas of Hill Country to points east. Previous convection likely maintained cold pool structure from earlier this afternoon, but weakening convection overall should allow for boundary remnants to slowly shift north which is being seen via the convective motions the past hour. A separate shortwave over north-central TX will advance to the northeast during the evening with its own round of convective enhancement leading to cells propagating into the I-35 corridor mainly south of the DFW metro before moving into east TX overnight. The question becomes the potential convective initiation from the LLJ coupled with the ejecting shortwave out of MX. Hedged towards the maintenance of the SLGT risk from previous forecast as the environment is ripe for heavy rates >2"/hr along with a remnant boundary capable of a focal point for back-building. This SLGT is relatively conditional for this evening, but what could form certainly has the potential to be something more significant, similar to what transpired earlier today with perhaps a little less vigor due to a lower level of instability and relevant theta_E. A MRGL extends around the periphery of the SLGT with a northern extension close to the I-20 corridor near Dallas-Fort Worth. ...Great Lakes... 01Z Update: Scattered flooding due to a mess of hydrologic factors across the Great Lakes will continue overnight with the best opportunity lying east of Lake Michigan where a shortwave from the southwest will migrate into the region with another round of rainfall. Grounds across northern MI are becoming very saturated with the snow/ice melt and the rainfall the past 24 hrs. Expect this to continue through the evening with the next wave likely to impact the eastern Lake Michigan shores from I-196 up to Traverse City. The focal point will lie within that area over into the northern mitt north of I-96. Additional totals of up to 1-1.5" are possible this evening which could lead to isolated instances of flash flooding and even more river flood concerns. The MRGL remains in place for northern MI. Kleebauer Day 2 Valid 12Z Mon Apr 13 2026 - 12Z Tue Apr 14 2026 ...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE UPPER MISSISSIPPI VALLEY AND UPPER GREAT LAKES REGION... 20Z Update: Little change was necessary to the inherited MRGL risk across the Upper Midwest and Great Lakes. High neighborhood probs (60-90%) for >1" totals across the region coupled with rapid snow melt over the U.P. and northern WI should enhance hydrologic concerns for the period. Minor flooding occurring in D1 will generally continue through D2 as another round of convection will impact the area from eastern MN through the northern half of MI. There's some elevated probabilities for rates exceeding 1"/hr across portions of WI tomorrow evening as a formidable LLJ and increasing convergence within a progressing warm front could very well maximize the potential for heavier precip. This would be the most notable location for the setup, but the setup is relatively short- lived, so did not feel an upgrade was necessary. Kleebauer ..Previous Discussion.. Another round of showers and thunderstorms will move through the Upper Mississippi Valley and Great Lakes during the afternoon and evening hours, prolonging the threat for excessive rainfall, increased snow melt and flash flooding. A Marginal Risk remains in effect from eastern Minnesota to northern Michigan. Campbell Day 3 Valid 12Z Tue Apr 14 2026 - 12Z Wed Apr 15 2026 ...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE TEXAS HILL COUNTRY TO THE UPPER MIDWEST/GREAT LAKES REGION... 20Z Update: The broad MRGL risk for D3 was generally maintained with multiple areas likely to see convective activity during the period. The main area of focus will likely occur over the Midwest as increasing diffluent axis downstream of a deep western trough will enter the area with convective development likely to occur over IA and motion to the east-northeast. A developing upper jet coupling will likely aid in regional ascent with fairly generous instability axis situated from the Corn Belt to the southern Great Lakes and points south. Models are in agreement on there being a solid precip footprint, but they are all over the place in regards to the placement. In any case, there was still some time to review with the CAMs guidance coming into the picture by tomorrow, so will wait to see if there will be another upgrade potential with this setup, which is leaning more towards a necessity considering the above synoptic and thermodynamic variables. Kleebauer ..Previous Discussion.. Multiple rounds of strong to severe thunderstorms expected from Texas to the Midwest states, given favorable wind shear and instability in place as multiple impulses eject across the Plains. Gulf moisture will be funneling northward between the trough over the Rockies and the ridge over the eastern states. The environment will be favorable for a few mesoscale convective systems to develop and the limited eastward progression will likely result in areas that have excessive rainfall leading to some instances of flash flooding. A Marginal Risk area span from the Texas Hill Country northeastward to the Midwest and western Great Lakes. 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