845 FXUS64 KOUN 060712 AFDOUN Area Forecast Discussion National Weather Service Norman OK 212 AM CDT Mon Sep 6 2021 ...New SHORT TERM, LONG TERM... .SHORT TERM... (Today and tonight) Issued at 212 AM CDT Mon Sep 6 2021 Heating and deep mixing of modestly moist PBL may be enough for isolated late afternoon convection in southwest Kansas along a subtle differential mixing zone, and will be even more likely again along the Raton Mesa with terrain forcing. If this does happen convection is likely to stay west and north of our area. Veering low level flow should support an increase in temperatures above 3-5 degrees compared to yesterday. Low to mid 90s will be reached areawide. PV anomaly now cresting the ridge and moving toward our region may enhance cirrus some late in the day. There is a signal in the models of enhancement of midlevel moisture ahead of this feature across western Oklahoma late evening/overnight. It probably won't be enough, but an isolated convective shower rooted in this moist layer cannot be completely ruled out. Among the hi-res/CAMs, only NAM Nest shows this at this time. BRB && .LONG TERM... (Tuesday through Sunday) Issued at 212 AM CDT Mon Sep 6 2021 We introduced low precipitation probabilities late Tuesday in northern Oklahoma. Pre-frontal flow in the lowest 3-km quickly veers with height and the west-southwesterly component within that layer has backwards trajectories that show air mass origin in the higher terrain of the Edwards Plateau and Llano Estacado regions. This hot elevated mixed layer will likely cap convection for the most part, but there is a conditional low-probability risk of higher PBL moisture along with frontal convergence being enough for isolated convection very late Tuesday afternoon or early evening. The more moist NAM and NAM Nest do show some convective development along the front. More of the GEFS members show a QPF signal than not, which is in contrast to only a few of the 50 members of the ECMWF/EPS showing a signal. Chances would be higher if more than negligible large scale ascent was present to help more optimally precondition the thermodynamic environment. If this does occur, increasing inhibition mid to late evening would cause convection to diminish. Given the aforementioned warm plume off the higher terrain to the southwest, even warmer surface temperatures are expected Tuesday compared to today. Mid to upper 90s will be widespread. Moisture isn't as anomalous as previous couple of weeks, and with a breeze, heat-related impacts should be minimal. Post-frontal northeasterly flow should hold all but southern portions of the area in the 80s Wednesday. A trend toward hotter temperatures will start Thursday. Friday and Saturday will be the hottest days, though upstream moisture and strengthening lee trough enhancing southerly winds should limit heat-related impacts some, despite dry bulb temperatures reaching 100 at some locations. For reference, here are the average, forecast, and record highs for Saturday at our three climate sites: OKC forecast 98, average 86, record 105 SPS forecast 100, average 90, record 107 LAW forecast 100, average 89, record 107 So, it certainly could be worse. Since RH recovery at night will not be particularly good, we will likely accelerate fine fuel drying through the week. Meanwhile, a more active synoptic pattern across the northern Plains will help force a more pronounced/deeper lee trough and enhance our southerly winds. We could see elevated fire weather conditions develop by Friday into the weekend. Models have been inconsistent about how effective the northern tier shortwave trough will be at sending a cold front into our area next weekend. Most recent runs hold it in Kansas, and thus Sunday looks warmer than earlier forecasts. Medium range ensemble mean dprog/dt are fairly stable into next week showing a flattening/prograding mean ridge and continued hot dry pattern. BRB && .AVIATION... (06Z TAFS) Issued at 1057 PM CDT Sun Sep 5 2021 VFR conditions are still expected with some scattered high clouds spreading over the area. Light east winds overnight will increase from the south after sunrise Sunday morning. && .UPPER AIR... Issued at 658 PM CDT Sat Sep 4 2021 No upper air flights are planned at this time. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 91 69 94 67 / 0 0 10 10 Hobart OK 93 71 97 67 / 0 0 10 10 Wichita Falls TX 93 70 96 69 / 0 0 0 10 Gage OK 93 71 97 61 / 0 0 10 10 Ponca City OK 93 69 97 62 / 0 0 20 20 Durant OK 92 65 94 68 / 0 0 0 10 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ SHORT TERM...12 LONG TERM....12 AVIATION...26