Area Forecast Discussion
Issued by NWS Topeka, KS
Issued by NWS Topeka, KS
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798 FXUS63 KTOP 061045 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 545 AM CDT Mon May 6 2024 .KEY MESSAGES... - Dense fog early this morning, generally south of I-70. - Severe storms are likely this afternoon/evening. Hail up to three inches in diameter, winds to 80 mph, a few strong tornadoes and isolated flash flooding are all possible. - Mild and mainly dry the rest of the week. && .DISCUSSION... Issued at 335 AM CDT Mon May 6 2024 The ingredients are coming together for a higher-end severe weather event this afternoon and evening. There are two main scenarios that could play out, one that is more likely and one that is more impactful: Scenario One: A line of storms quickly develops across central Kansas and marches eastward through late afternoon and evening. This is the most-likely scenario. All model guidance depicts a robust line of storms developing and moving into Republic, Cloud and Ottawa Counties in the 4-6 pm timeframe. This is plausible as shear vectors are generally more parallel off the front which favors upscale growth and congealing of cold pools quickly after convective development. Despite cloud cover for most of the day, ample instability is expected given strong warm/moist advection ahead of the front and an EML bringing steep mid-level lapse rates over the area. With effective shear of 50-60 knots, ML CAPE of 1500-2500 J/Kg, lapse rates of 7-8 C/Km and a strongly veered wind profile with effective SRH of 200+ M^2/S^2, all severe hazards are possible, including hail up to three inches in diameter, wind gusts to 80 mph and tornadoes. As the line of storms pushes eastward into the evening the hail threat should subside slightly, but the low-level jet will likely increase in strength and shear vectors could become more favorably oriented for QLCS tornado development. The line of storms is expected to be out of the area by midnight. Scenario Two: A line of storms quickly develops across central Kansas, but isolated supercells also develop ahead of the line. This is the less likely, but more impactful scenario. Everything that was described in the first scenario would remain true in this scenario, but isolated supercells would develop out ahead of the front. As they would not be driven by frontal forcing or likely have to compete in an environment with other storm interactions, they would be more free to develop deviant motion. This would greatly enhance their ability to utilize environmental vorticity, leading to a higher-end strong tornado threat and giant hail possibility. Several CAMs depict such a scenario playing out, but there are a few limiting factors that make this scenario less likely. First, we may remain capped all day under a layer of stratus. Second, ascent is mostly co- located with the front, so without a lifting mechanism, even without the presence of a cap, initiation would be challenging at best. Regardless of what scenario plays out, this has the potential to be a very impactful severe weather day. Another potential impact from today`s storms is that of flash flooding. While very high rain rates are expected given the impressive thermodynamics and kinematics likely today, storm motions of 40-50 mph should keep the flash flood threat minimal. The exception would be if training storms develop or isolated cells develop ahead of the main front. After the front moves through today, quiet and mild weather is favored for the rest of the week. A few low chances for some showers appear here and there, but no major storm systems look likely in the near future. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 543 AM CDT Mon May 6 2024 LIFR/IFR becoming MVFR later this morning. Low stratus and some fog continues to impact the terminals this morning. Stratus should lift and fog dissipate around 15z. A line of thunderstorms (some likely severe) will move through later this evening (generally 23z-04z). && .TOP WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 9 AM CDT this morning for KSZ040- KSZ054-KSZ055-KSZ056-KSZ058-KSZ059. && $$ DISCUSSION...Jones AVIATION...Jones