FXUS64 KOUN 210447 AFDOUN Area Forecast Discussion National Weather Service Norman OK 1047 PM CST Wed Jan 20 2021 ...New AVIATION... .SHORT TERM... (This evening through Thursday) Issued at 245 PM CST Wed Jan 20 2021 Isentropic ascent is resulting in scattered to numerous showers this afternoon, with the most prominent band along and north of I- 40. Rainfall amounts have generally been light (trace to a few hundredths). Ascent is progged to weaken as flow generally veers along with the advection of drier air. A weak boundary will move into the northern half of Oklahoma late tonight and slowly progress southward tomorrow. Winds will become light and variable in the vicinity of boundary before gradually shifting to the north-north east/east. Some patchy fog may develop along and just southeast of the boundary late tonight into tomorrow morning. Tomorrow afternoon should be warmer than today for most locations with higher ceilings/more insolation. The wind shift will be just south of I-40 tomorrow afternoon. The warmest temperatures will be across the southern half of Oklahoma and north Texas--in close proximity and just south of the aforementioned boundary. Mahale && .LONG TERM... (Thursday night through next Tuesday) Issued at 444 PM CST Wed Jan 20 2021 An active weather pattern is expected in the long term period with a series of troughs dropping over the W/SW CONUS. Precipitation chances are frequent through the end of next week. The nearly-closed upper low pressure system, currently situated off the coast of Baja, moves ashore early Thursday morning. There is above-average model agreement that this low will weaken and become an open wave while crossing the southern portions of AZ/NM. The vorticity maxima approaches western north Texas, and given the associated dynamic lift and deep moisture available, we have added a chance for light rain showers (or sprinkles) from Friday 00Z through Saturday 00Z (mainly south of I-40, including western north Texas). Opted to nudge towards superblend/CONSSHORT for 00Z Friday and the superblend/GFS for 06Z Fri through 00Z Saturday. Also added a slight chance for isolated thunder over western north Texas early Friday morning as the surface low passes just south of the area; operational models were indicating weak elevated instability of about 200 Joules/kg and bulk shear near 55 knots. No severe weather is expected. High pressure exits Canada and the NE winds will continue to advect cooler air over our area. Clouds should diminish over the northern half of Oklahoma and high temperatures will be about 10 to 15 degrees cooler than Thursday. By Saturday morning, low level flow shifts S/SE and moisture advection will increase cloud cover once again. Isentropic upglide may produce light showers or sprinkles on Saturday. With increasing WAA over W Oklahoma and western north TX, highs on Saturday look to be about 10 degrees warmer than central Oklahoma. By Sunday, the low-level thermal ridge (~850mb) moves over our area providing us with the warmest temperatures of the week - near 70 degrees F over western north TX. A cold front enters northern OK on Sunday, though deterministic models differ on timing. Greatest rain chances are on Sunday and Sunday night, especially across S/SE Oklahoma. Some weak, elevated instability will be present ahead of the front, and therefore, isolated thunderstorms are possible on Sunday afternoon into Sunday night. From this point, models diverge and details are less clear. Wintry precipitation is possible across northern Oklahoma late Monday into Tuesday morning as a shortwave approaches and colder air filters in behind Sunday's front. Then, another upper trough approaches, potentially deeper than its predecessor. Wintry precipitation associated with this system will be possible across northern Oklahoma middle of next week. Thompson && .AVIATION... (06Z TAFS) Issued at 1045 PM CST Wed Jan 20 2021 A area of very low clouds covers much of central and south-central Oklahoma at 0445Z. This area of clouds will clear gradually from west to east, but at the same time expand to the north. Clearing times at KOKC and KOUN are not exactly certain, but should be around 06Z and 07Z, respectively. The clouds should reach KSWO around 08Z, KPNC about 10Z. In north-central Oklahoma, it is possible that FG will form if/when the low clouds drift to the east, because of weak convergence along a surface trough, and ample low- level humidity. In any case, it is likely that low clouds and/or low visibility will persist in north-central Oklahoma almost until midday. Other than minor wind changes, no further significant weather is expected after 18Z Thursday. CmS && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 39 57 38 51 / 10 0 20 10 Hobart OK 38 60 38 52 / 10 0 30 20 Wichita Falls TX 42 63 44 54 / 10 10 40 30 Gage OK 31 60 29 49 / 10 0 10 10 Ponca City OK 32 58 33 49 / 20 0 10 0 Durant OK 43 61 45 57 / 30 10 40 40 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ SHORT TERM...10 LONG TERM....01 AVIATION...23