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Area Forecast Discussion
Issued by NWS Topeka, KS
Issued by NWS Topeka, KS
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691 FXUS63 KTOP 141102 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 602 AM CDT Wed Aug 14 2024 .KEY MESSAGES... - A Heat Advisory remains in effect for much of the area this afternoon as heat index values climb to 100-107 degrees. - Thunderstorms, some severe, impact the area this evening with large hail, damaging winds, and locally heavy rainfall being the main hazards. && .DISCUSSION... Issued at 351 AM CDT Wed Aug 14 2024 An upper ridge resides across the Southern Plains with a decaying MCS pushing east across Nebraska. Precipitation on the southern extent of this complex has built into far northern Kansas, but intensity is lacking with all lightning behind confined north of the stateline. Isentropic ascent on the nose of the low-level jet has led to a band of storms from eastern Nebraska into northeast Arkansas, but this will continue to be pushed east by the low-level jet. Lingering precipitation ends this morning as increasing southerly flow shunts a warm front north into southern Nebraska by this afternoon. Morning cloud cover gives way to mostly sunny skies and allows temperatures to reach into the 90s. Short-term guidance has shifted the surface low slightly further north which brings an attendant dryline into portions of central Kansas. As a result, dewpoints may be lower than currently forecast which could limit how high heat index values reach this afternoon. There still looks to be at least a couple hour window for 100-105 degree heat indices in this area as warmer temperatures behind the dryline could offset the fall in dewpoint. Best chances for heat indices of 105-107 degrees reside across east central Kansas where dewpoints will remain in the low to mid 70s through the afternoon. The Heat Advisory remains in effect through 7PM this evening. A shortwave ejects across the Plains this afternoon and evening, pushing a surface trough into the area. Ascent from the passing wave and convergence along the surface trough will be sufficient for convective initiation to occur between 5-7PM across central Kansas. MUCAPE of 2000-3000 J/kg will support robust updrafts, but effective shear of 25-30kts and a weakness in the 4-6km wind field could cause updrafts to struggle to maintain intensity. Nonetheless, these storms could be severe and produce large hail and damaging winds, especially considering inverted-V profiles and DCAPE of 1000+. Storm motions largely parallel to the surface trough could lead to training of storms unless the advancing shortwave keeps the overall complex of storms moving east. If storms train over the same areas, the flooding potential increases with PWATs of 1.75-2.25", supporting 1-3 inch per hour rainfall rates. The tornado threat is low, but locally backed winds near the warm front could provide enough vorticity for a spin up. The surface trough stalls across the area on Thursday with several perturbations in the flow passing through. The first wave could keep some showers and storms around through the morning hours ahead of the next wave that moves through during the afternoon and evening. Key mesoscale details such as how much heating will take place after any morning convection are uncertain, but the passing wave could generate additional storms during the afternoon and evening. Shear is better, but instability is weaker compared to the environment that is expected this afternoon. If sufficient destabilization can occur, strong to severe storms are possible with large hail, damaging wind gusts, and locally heavy rainfall being the main hazards. The pattern turns drier overall Friday into the weekend. However, passing waves of energy between the eastern trough and southwestern US ridge bring periodic chances for showers and storms. Temperatures remain right around climatological normals for this time of year in the upper 80s to low 90s. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 602 AM CDT Wed Aug 14 2024 Scattered to broken cigs between 700-1000ft persist for the next couple of hours before VFR conditions return. Winds increase from the south through the day with occasional gusts of 20-25kts before subsiding this evening. Storm chances increase this evening and overnight, but coverage of storms remains uncertain. Refinement in timing and impacts to terminals from storms will be needed with future TAF issuances. && .TOP WATCHES/WARNINGS/ADVISORIES... Heat Advisory from 1 PM this afternoon to 7 PM CDT this evening for KSZ021-KSZ022-KSZ023-KSZ024-KSZ026-KSZ034-KSZ035- KSZ036-KSZ037-KSZ038-KSZ039-KSZ040-KSZ054-KSZ055-KSZ056-KSZ058- KSZ059. && $$ DISCUSSION...Flanagan AVIATION...Flanagan