Area Forecast Discussion
Issued by NWS Topeka, KS
Issued by NWS Topeka, KS
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815 FXUS63 KTOP 192349 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 649 PM CDT Thu Sep 19 2024 .KEY MESSAGES... - Warm afternoon followed by scattered thunderstorms this evening across far eastern KS, a few severe possible. - Widespread rainfall over the weekend. Potential for 1-3 inch totals in spots, especially along/north of I-70. - Cooler conditions arrive behind Sunday cold front passage. && .DISCUSSION... Issued at 227 PM CDT Thu Sep 19 2024 The main near-term concern is thunderstorm potential along and ahead of a cold front that is just beginning to move into north-central Kansas. The main upper low driving this cold front is all the way up in southern Canada, so our area is far removed from the best upper support and height falls. Our 18z sounding supports this, with a strong subsidence inversion around 550 mb and plenty of dry air aloft. These will act together to limit convective development this evening. On the other hand, the low-levels are more favorable for storms to form. Southerly winds have kept dewpoints near 70 degrees across far eastern Kansas, and deep mixing in the boundary layer is helping to erode the low-level cap that exists. As the front moves east this evening, still think low-level convergence and lack of CIN will be enough to develop a few thunderstorms across far eastern Kansas 5-8 PM, despite the unfavorable mid-level ingredients. Assuming a few storms do form, 35 kts of shear and 2000-3000 J/kg of MLCAPE will be enough for damaging winds and large hail. Can`t completely rule out a brief tornado if winds stay more southeasterly in the wake of early-day convection, but the overall threat is very low. The bulk of the threat will end by 10-11 PM as the front continues pushing east and the boundary layer cools. Friday will be a quieter day as the front stalls to our south and heights rise across the region. Still looks to be a warm day with highs in the 90s assuming clouds become mostly clear north of the warm front. Friday night and into Sunday, attention turns to an upper low over the Southwest that will lift northeast towards the Plains. As this occurs, isentropic ascent over top the old frontal boundary (which will slowly lift north as a warm front) will lead to repeated rounds of showers and storms. The main question is how far north the warm front lifts as the system approaches and surface low pressure deepens over the High Plains. Heavier rain, potentially several inches in spots, will occur to the north of the front`s eventual position, while lighter rainfall totals will occur to the south. Much warmer temperatures are also expected south of the front vs to its north, particularly Sunday as the surface low moves across the area. Currently leaning towards a slightly farther south track of the warm front and surface low, with the heaviest rain along and north of Interstate 70. However there is certainly room for changes either north or south. Beyond Sunday, cooler and drier conditions are expected as the low pulls off to the east and upper troughing amplifies over the Ohio Valley. Lingering cloud cover may keep temperatures in the 60s Monday, while even the 75th percentile of high temperatures stay in the 70s through mid-week. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 647 PM CDT Thu Sep 19 2024 The storm chances this evening will be east of the terminals. Expect scattered high clouds and southwest to west winds will become light and variable through the night, then winds will become easterly at 8 to 10 KTS by early Friday afternoon. && .TOP WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Reese AVIATION...Gargan