221 FXUS63 KTOP 081956 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 256 PM CDT Sat Aug 8 2020 .SHORT TERM...(This evening through Sunday) Issued at 246 PM CDT Sat Aug 8 2020 Early this afternoon a broad upper level ridge was centered across the southern Plains with the upper ridge axis extending northward across KS into NE. The mid level perturbation that rounded the upper ridge axis this morning, was tracking southeast across MO into northern AR. Low-level WAA/isentropic lift was causing scattered to broken CU across the eastern counties of the CWA. Where skies have cleared across the central and western counties of the CWA, temperatures have warmed into the lower 90s with heat indices around 100 degrees. The cloud cover across the eastern counties should begin to scatter out through the late afternoon hours. Heat indices across much of north central and central KS should reach around 105 degrees through the late afternoon hours. The heat indices may be a bit lower across northeast KS but they should reach between 100-104 by 5 PM. Therefore, I plan to keep the heat advisory going through 8 PM this evening. The east central KS counties will probably see a rapid rise in heat indices betweeen 4 and 5 PM as dewpoints were in the mid to upper 70s, thus heat indices should rise to 104-108 degrees by 5 PM. Tonight, during the late afternoon and evening hours scattered to numerous thunderstorms will develop across the high Plains of northeast CO and western NE. All the CAMs show any complex of storms that may develop will weaken as they move east across west central KS and central NE. Therefore I kept PoPs below 15 percent. If a more organized MCV can develop from the high Plains convection, and shift east across the northern portions of the state, then there may be a better chance for a few elevated thunderstorms across the northern counties of the CWA from 12Z SUN through the mid morning hours of Sunday. Weak isentropic lift combined with a 35 to 45 KT LLJ may also provide enough ascent for a few isolated elevated thunderstorms. At this time my confidence remains low enough to keep PoPs below 15 percent but I will keep 10 to 14 POPs in the grids after 9Z SUN through the morning hours on Sunday. Lows will drop into the lower to mid 70s. Sunday, expect another hot and humid day as the upper ridge shifts only slightly eastward and may amplify a bit across eastern TX/eastern OK. After some morning clouds skies should become mostly sunny by afternoon. High temperatures will reach the mid 90s across much of the CWA with some upper 90 degree readings across the southwest counties. Dewpoints during the afternoon will remain in the lower to mid 70s, thus heat indices will be in the 102 to 108 degree range across the CWA. Another heat advisory will probably be needed for Sunday afternoon for portions of central, east central and northeast KS. Minimum temperatures Saturday night did not look warm enough to extend the heat advisory through the night. Therefore the next forecast shift early Sunday morning can issue the heat advisory for Sunday afternoon .LONG TERM...(Sunday night through Saturday) Issued at 246 PM CDT Sat Aug 8 2020 Sunday night through Tuesday, an upper level trough will shift east across the northern and central Plains into the southern Great Lake States. This will cause a surface cold front to slowly push southward into the CWA late Sunday night then remain stationary across the CWA through Tuesday. The front will provide enough sfc convergence along and south of the front for scattered showers and thunderstorms, also isentropic lift north of the boundary will provide ascent for scattered showers and thunderstorms. NAM/ECMWF show the southern portions of the central Plains H5 trough amplifying across eastern KS Monday afternoon through Tuesday morning, which will provide ascent from increased DCVA for potentially more widespread showers and thunderstorms. The overall effective shear looks weak but if the instability increases enough then there could be some pulse type storms that may provide strong gusty winds in the vicinity of the more intense pulse updrafts. Also, there could be a potential heavy rain threat Monday evening into Tuesday morning, due to the high PWs and slow storm movement. Highs will be a bit cooler, with mid 80s to around 90 degrees expected. Tuesday night through Saturday, an upper level ridge will amplify across the southwest US and central Rockies. This will keep eastern KS in northwest flow aloft. Any embedded mid level perturbations may provide enough lift for a chance of showers and thunderstorms through the period. The ECMWF shows a more amplified mid-level perturbation digging Southeast across the state Wednesday night into Thursday morning, which may provide us with our best chance for showers and thunderstorms. A surface ridge of high pressure will build southwest across northeast KS during the end of the work week into Saturday, which will keep the CWA drier and cooler. Highs will be in the 80s through the periods but humidities will decrease through the end of the week with the northeast surface parcel trajectories. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1226 PM CDT Sat Aug 8 2020 The MFVR broken ceilings over the KTOP and KFOE terminals should scatter out by 19Z SAT. Low-level wind shear within the lowest 1200 feet will increase to 30 to 35 KTS at the terminals after 2Z SUN and last through the night before deeper mixing increases surface winds after 13Z SUN. Otherwise, expect VFR conditions after 19Z SAT. && .TOP WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM CDT this evening for KSZ008>012-020>024- 026-034>040-054>056-058-059. && $$ SHORT TERM...Gargan LONG TERM...Gargan AVIATION...Gargan