FXUS64 KOUN 251050 AFDOUN Area Forecast Discussion National Weather Service Norman OK 550 AM CDT Sat Sep 25 2021 ...New AVIATION... .SHORT TERM... (Today and tonight) Issued at 337 AM CDT Sat Sep 25 2021 A cold front/wind shift will continue to move southward today before dissipating late this afternoon. The 850 mb temperatures are slightly lower in the frontal boundary's wake, especially across northern Oklahoma. Therefore, the most significant cool- down is expected across northern Oklahoma, where highs will be ~5 deg F lower than yesterday. Elsewhere, since less cloud cover is expected today than yesterday (i.e., more insolation), any change from yesterday's highs should be negligible. As frontolysis occurs this afternoon, surface winds will veer to the east/southeast and then to the south. Winds should be rather light given the relaxed surface pressure gradient. Mahale && .LONG TERM... (Sunday through Friday) Issued at 337 AM CDT Sat Sep 25 2021 Sunday will be a much breezier day as the surface pressure gradient tightens across the Southern Plains. In addition, the low-level thermal ridge to the west will expand to the east. Low- level temperatures will increase markedly (850 mb temperatures are progged to range from ~18 to 24 dec C), which will result in hot temperatures on Sunday with highs in the 90s deg F. These forecast highs are at least 10 deg F above average for late September. Deep, vertical mixing to at least 750 mb across northwest Oklahoma may result in dew points falling into the upper 30s deg F by afternoon. Lower dew points are possible elsewhere as well. Therefore, opted to lower the dew points across the area toward the lower end of the NBM PDF and closer to CONSShort. The vertical mixing will also increase the magnitude of the wind gusts as well. One caveat, which could temper vertical mixing, is that some forecast soundings indicate the presence of cirrus. As a result of the hot temperatures, dry air mass, and breezy conditions, near critical fire weather conditions are possible Sunday afternoon. See the Fire Weather Discussion below for more details. Hot, above-average conditions will continue on Monday with no appreciable change in the air mass. By Tuesday into Wednesday, a closed-low across the southwest United States is progged to open and lift into the Plains. There remains deterministic and ensemble spread on when the open wave will begin to affect the Southern Plains, which is not surprising given that cutoff lows often have low predictability. The earliest widespread rainfall could begin is on Tuesday; however, the probability is higher on Wednesday. Additional shortwave troughs and/or cutoff lows may eject into the Southern Plains through the end of the week, which will result in continued probabilities for showers and thunderstorms. Weak vertical wind shear should temper the risk for organized severe weather. The primary hazard appears to be heavy rainfall with the potential for localized flooding. Mahale && .AVIATION... (12Z TAFS) Issued at 550 AM CDT Sat Sep 25 2021 Unrestricted ceilings and visibilities will continue through the TAF period. Light northeast winds will gradually veer to the east and then southeast this afternoon as a weak cold front dissipates across the area. Winds will veer to the south across the western terminals toward the end of TAF period. Mahale && .FIRE WEATHER... Issued at 337 AM CDT Sat Sep 25 2021 Near critical fire weather conditions may develop on Sunday afternoon across northwest into parts of north central Oklahoma. 850 mb temperatures are progged to increase to ~22 to 24 deg C as the low-level thermal ridge expands to the east. Deep, vertical mixing to at least 750 mb will result in gusty south to southwest winds and dew points falling into the upper 30s deg F. Temperatures will be ~10 to 15 deg F above climatology with minimum relative humidity values near 15% and sustained south/southwest winds at 20 to 25 mph. Wind gusts of 30 to 35 are possible given the vertical mixing. The aforementioned conditions result in forecast RFTI values of 3 to 4. Given that ERC-G values are at ~80 to 90th percentiles, this combination of weather and fuels may result in Red Flag Warning conditions. One potential caveat is that some forecast soundings indicate the presence of cirrus, which would temper vertical mixing and the heating of fuels. If a Red Flag Warning is not issued, a high-end Fire Danger Statement (RFD) should be expected on Sunday. Mahale && .UPPER AIR... Issued at 1200 PM CDT Fri Sep 24 2021 No upper air flights are planned at this time. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 86 61 91 64 / 0 0 0 0 Hobart OK 90 60 92 61 / 0 0 0 0 Wichita Falls TX 91 60 92 61 / 0 0 0 0 Gage OK 86 62 92 64 / 0 0 0 0 Ponca City OK 84 60 94 65 / 0 0 0 0 Durant OK 90 60 92 61 / 0 0 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ SHORT TERM...10 LONG TERM....10 AVIATION...10