FOUS30 KWBC 231532 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1132 AM EDT Tue Apr 23 2024 Day 1 Valid 16Z Tue Apr 23 2024 - 12Z Wed Apr 24 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Otto Day 2 Valid 12Z Wed Apr 24 2024 - 12Z Thu Apr 25 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. ...In and near OK... Guidance continues to show an area of convective development across central and eastern OK within a low- level convergence field associated with a stalled boundary over the southern Plains north of the Red River. The atmosphere is expected to be uncapped, based on 700 hPa temperatures forecast. Modest instability located over the region due to active return flow regime will aid in the convective pattern and create an environment capable of low- end flash flooding concerns, especially within any training cells within the confines of the stalled front. All guidance, to some degree has a QPF maximum between north- central OK over into the Lower Mississippi Valley. Spread within the model guidance remains high, both in placement and magnitude; the 00z ECMWF remains the wettest. The overall synoptic pattern of precipitable water values approaching 1.5", CAPE of 1000-2000 J/kg, and enough 850 hPa inflow/effective bulk shear to support organized convection. Hourly rain totals to 2" with local amounts to 4" are possible within this environment. Higher FFG indices/drier soils are in place over many of the areas that could receive heavy rainfall. The general model trend has been slightly northward, away from the more sensitive soils caused by recent heavy rainfall near the Red River of the South. Considering the setup, once the guidance shows better convergence, a Marginal Risk could be in the offing. Roth Day 3 Valid 12Z Thu Apr 25 2024 - 12Z Fri Apr 26 2024 ...A MARGINAL RISK OF EXCESSIVE RAINFALL EXISTS ACROSS PORTIONS OF THE PLAINS AND MIDWEST... Strengthening moisture flux across the Plains and Midwest ahead of a low pressure system is expected to raise the precipitable water values to 1.5"+. Inflow at 850 hPa is forecast towards 60 kts, with effective bulk shear to match. A broad area of 1000-3000 J/kg of CAPE is forecast by SREF guidance. Temperatures at 700 hPa suggest a relatively uncapped atmosphere. The above ingredients support mesocyclone formation, which can be producers of heavy rainfall, moreso where cells align, despite what should be quick cell motion. Cell training is possible as the deep layer flow is out of the south-southwest. The guidance has a stronger signal for heavy rainfall somewhere between the southern Plains, Mississippi Valley, and the Midwest Thursday and Thursday night than advertised the previous day, but agreement is lacking on location which is keeping the WPC QPF magnitude modest. Like the previous day, the 00z ECMWF is the wettest with a signal over 9" near the KS/OK border. As heavy rainfall is expected of some magnitude across portions of OK and AR on Wednesday and Wednesday night, expanded the Marginal Risk southward from continuity to cover those areas. Should the guidance converge on location, a Slight Risk upgrade would be possible as we get closer to the event. Hourly rainfall to 2.5" with local amounts to 5" are expected, which would be most impactful in urban areas and areas with saturating soils between now and Thursday. Roth 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