FOUS30 KWBC 162020 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 420 PM EDT Thu Apr 16 2026 Day 1 Valid 2016Z Thu Apr 16 2026 - 12Z Fri Apr 17 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF CENTRAL MISSOURI THIS AFTERNOON... Introduced a Marginal Risk area where clusters of slow moving thunderstorms developed...mainly in central Missouri where strong daytime heating was occurring under very cold mid-level temperatures which resulted in steep lapse rates and allowed for CAPE values to build to around 2000 J per kg. Flow aloft is weak...resulting in 1 inch per hour rates due to slow cell motion. Given the potential for additional convection...opted to introduce a Marginal risk area at this point. Refer to WPC MPD 0114 for additional details. Bann Day 2 Valid 12Z Fri Apr 17 2026 - 12Z Sat Apr 18 2026 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE MIDWEST, MID-MISSISSIPPI VALLEY INTO THE SOUTHERN PLAINS... 20Z Update: The synoptic evolution described in the previous forecast has not changed in the latest model depictions as a broad axis of heavy rainfall stemming from widespread convection is anticipated from the Central Midwest down through portions of the Southern Plains. The main change(s) from the previous forecast were an expansion of the SLGT risk to the southwest, including more of central and eastern OK, as well as an extension north to include some of the more sensitive areas of southern WI and adjacent northern IL/IN. The latest 12z HREF continues its trend on a slow shift to the south with the areal QPF footprint signaling more excessive rainfall prospects of 2+ inches now south of I-70 in MO into more of northeast OK. This matches the ML suite from both the EC AIFS and AIGFS outputs, both of which have been consistent in their interpretations of heavier rain south of the global deterministic suite the past few days. Probabilistically, the trends have favored a particular zone spanning the area between Kansas City to Tulsa along the KS/MO border down through northeastern OK as the primary area of focus as this zone nestles perfectly within the evolving upper jet coupling that will materialize during the synoptic evolution occurring over the Central and Southern U.S. Neighborhood probabilities of 50-80% of at least 2 inches are located across portions of eastern KS into west-central MO, overlapping an area of more sensitive grounds after a heavy rain episode occurred over the area just north of Springfield, MO this past evening. The overlap coinciding with higher probs for at least 2 inches pin-points an area of interest and is well-within the favorable environmental conditions that will be in-place downstream of the approaching trough ejecting out of the Rockies. Combination of deep moisture advection and suitable instability noted by a strong theta_E ridge developing across the Southern Plains to Midwest should promote relatively good rate potential as probs for hourly rates remain very high for >1"/hr (60-90%), and modest for even upwards of 2"/hr (15-25%) that would easily exceed the hourly FFG threshold in place over the aforementioned area. In this case, the SLGT risk would be deemed a higher-end risk with a potential for even an upgrade if the trends continue to favor that area of the CONUS seeing appreciable rainfall tomorrow afternoon and evening. Further north, the area encompassing the Central Midwest around southern WI and northern IL remain in a more sensitive hydrologic state due to the multi-wave convective episodes and upstream snow melt aiding in swollen creeks and rivers throughout the region. The impending setup would likely embrace a northern edge of heavier precipitation based in the broad convective pattern materializing over the course of Friday afternoon and evening. A strong mid-level shortwave ejecting through the north-central Plains should allow for a zone of rapidly developing convection across northern MO through northern IL and southern WI after 19z as the frontal approach likely enhances a convergence pattern over the area. This should be enough to generate scattered thunderstorms across the region leading to locally heavy rainfall over the saturated areas referenced above. The combination of primed antecedent conditions at the ground level and favored kinematic pattern have allowed for an expansion of the SLGT risk further north to account for the heightened threat given the recent trends in CAMs and associated HREF QPF outputs. Kleebauer ..Previous Discussion.. A deep, positively-tilted longwave trough advancing into the Plains will promote broad areas of ascent from the Southern Plains to the Midwest. A well-defined axis of diffluence ahead of the mean trough with several shortwaves rippling through the flow will enhance an area of convective development within a strengthening warm-sector environment positioned between a strong cold front over the High Plains and a quickly advancing warm front migrating poleward through the adjacent Mississippi and Ohio Valleys. This environment will be rather favorable for a broad footprint for heavy rainfall. There has been a persistent south/southwest trend with the axis of highest QPF for several model cycles which now focuses over northeast Oklahoma to north-central Missouri with areal averages of 1-2 inches with isolated maximums nearing 3+ inches. Campbell/Kleebauer Day 3 Valid 12Z Sat Apr 18 2026 - 12Z Sun Apr 19 2026 ...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTH, LOWER MISSISSIPPI VALLEY AND TEXAS... 20Z Update: MRGL risk inherited was relatively unchanged across MS/LA/Eastern TX as model guidance maintained general continuity in the evolution of heavy precip likely developing along a convergence axis situated along an approaching cold front from the north and northwest. Totals seem consistent between 1-3" for the main axis of development between the eastern edge of Hill Country in south- central TX up into the Piney Woods area of southeast TX through the Lower Sabine into southwest LA. This area has some of the higher FFG's nationally, so the prospects for flash flooding will likely be most coincident with more urbanized zones where run off capabilities are highest. This would likely occur in the suburbs of Houston and Lake Charles, along with a place like Beaumont where urbanization is most prevalent. The main change was a removal of the MRGL risk across south-central TX to the Rio Grande where guidance, both deterministic and ML, have reflected a relative min in QPF compared to areas downstream along with high FFG's likely to thwart flash flood potential. In coordination with the local WFO's accounting for the change, the risk area was removed for the period. Kleebauer ..Previous Discussion.. The frontal system described above will continue to advance eastward with the trailing tail of the cold front dropping south/southeast through Texas and the Lower Mississippi Valley. Gulf moisture will be advecting northward into the Southern Plains and pooling across Texas. PW values of 1.4-1.7 inches will be present over much of eastern Texas and Louisiana during this period. Strong convergence will lead to showers and thunderstorms focusing along and ahead of the frontal boundary, especially for the later half of the period. Areal average of 1 to 2 inches expected with hourly rainfall rates greater than 1 inch/hr as well may lead to isolated areas with flash flooding concerns. A Marginal Risk area is in effect from South Texas to northern Mississippi. 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