286 FXUS64 KOUN 210358 AFDOUN Area Forecast Discussion National Weather Service Norman OK 1058 PM CDT Fri Aug 20 2021 ...New AVIATION... .SHORT TERM... (This evening and Overnight) Issued at 139 PM CDT Fri Aug 20 2021 We have gone ahead and issued a short fused heat advisory for this afternoon for portions of north-central into central Oklahoma where dewpoints and temperatures are running a few degrees above previous forecast. Winds are elevated across much of the area which will help alleviate heat stress some (based on wet bulb globe temperature risk), but we still want to advertise caution for those planning to spend extended periods of time outdoors this afternoon as heat index values reach 105 to 110. Further to the west, veering low-level winds and deep mixing have allowed for dewpoints to mix out a bit more early this afternoon. A frontal boundary has been slowly working southward into southern Kansas and will serve as a focus for convective development later this afternoon. Retained a low chance for storms across northern Oklahoma through this evening as storms try to work their way slowly southward out of Kansas. A few storms are also possible further south across far western OK ahead of a dryline across the TX panhandle, but chances here are lower than further north. The hot and deeply mixed boundary layer will lead to a favorable environment for strong downburst winds with any storms that do develop. Later this evening expect the front (or convectively enhanced outflow) will work further southward into Oklahoma, potentially as far south as the I-40 corridor by sunrise Saturday. A few showers and storms will be possible along the boundary overnight but coverage is not expected to be very high given veering low to mid- level flow and a lack of convergence along the boundary. Ware && .LONG TERM... (Saturday through next Thursday) Issued at 151 PM CDT Fri Aug 20 2021 Saturday will bring one more chance for showers and storms before the upper level ridge pushes everything out. Between the front in northwest Oklahoma and any leftover outflow boundaries from Friday's convection, we should see some areas of convergence to aid in storm development. Environment will be unstable and moist (as on previous days), but shear will be weak. Heavy rain will again be the primary hazard, though a few briefly strong to severe storms will also be possible (again, much like previous days). Area is hard to pin down as convection will be scattered and dependent on the location of remnant boundaries, but timing is expected to be late afternoon into evening (fueled by daytime heating). Speaking of daytime heating, heat indices will again reach into the 100s tomorrow afternoon. Another heat advisory may have to be considered, but there's too much uncertainty in the area (will be affected by convection and outflow) right now. Sunday the upper ridge builds in. Temperatures will be at or just above normal (potentially near heat advisory criteria some days) and precipitation chances will be minimal. Cluster analysis still suggest some possibility of a system impinging on our forecast area late in the week, but the majority of solutions keep us dry. Day && .AVIATION... (00Z TAFS) Issued at 624 PM CDT Fri Aug 20 2021 Thunderstorms may enter north central Oklahoma early Saturday from southern Kansas. The resulting outflow boundary will turn winds northeast over this area with south winds over the southern two- thirds of Oklahoma. Scattered thunderstorms are possible Saturday afternoon along the outflow boundary, but coverage is expected to be too low for inclusion in most TAFs. && .UPPER AIR... Issued at 139 PM CDT Fri Aug 20 2021 No upper air flights are planned at this time. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 74 92 74 94 / 20 20 20 0 Hobart OK 74 96 74 96 / 20 20 10 0 Wichita Falls TX 77 96 75 96 / 20 10 0 0 Gage OK 69 92 70 95 / 20 30 20 0 Ponca City OK 71 91 72 96 / 30 30 20 10 Durant OK 76 95 74 95 / 10 10 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...Heat Advisory until 9 PM CDT this evening for OKZ007-008-012-013- 018>020-024>032-039>042-045-046. TX...None. && $$ SHORT TERM...08 LONG TERM....14 AVIATION...09