000 FXUS64 KOUN 230337 AAB AFDOUN Area Forecast Discussion...UPDATED National Weather Service Norman OK 1037 PM CDT Sun Apr 22 2018 .AVIATION... 23/06Z TAFs. Will keep MVFR forecast going first several hours of forecast with moisture wrapping around on the back side of the departing storm system. Otherwise, VFR conditions with occasional VFR ceilings possible much of forecast period. Winds will veer around to northeast and even southeast latter part of forecast as surface ridge builds over region. && .PREV DISCUSSION... /issued 628 PM CDT Sun Apr 22 2018/ AVIATION... 23/00Z TAFs. MVFR conditions are expected to spread over KPNC down through KOKC/KOUN this evening into the overnight hours as moisture wraps around departing storm system. VFR conditions expected at this terminals toward and after 12Z. VFR expected elsewhere through forecast period. Northerly winds will continue and light through this forecast period. PREV DISCUSSION... /issued 229 PM CDT Sun Apr 22 2018/ DISCUSSION... A distinct upstream circulation from the primary closed low circulation was seen clearly in moisture channel imagery around midday over our east-central counties. Aside from some morning light rain or drizzle across this area, primary impacts have been to enhance cloud cover. Stratus is likely to persist across the eastern portion of the area into the evening, gradually clearing tonight. As the closed low departs, a Pacific shortwave trough will amplify tonight/early Monday over the northern Rockies. This feature will then traverse much of the Plains states through Wednesday as it moves southeastward. Forcing/mid-level frontogenesis will interact with increasingly moist environment (PWAT ~75th percentile for late April) to bring some needed precipitation. This should be primarily anafrontal behind southward surging cold front, with limited instability precluding a severe thunderstorm threat. Using ensemble approach and adjusting slightly for trends (slower system with less influence/phasing with northern stream wave), we made minor changes to QPF initialization. This keeps 0.25"-0.50" on average across drought-stricken western Oklahoma, with slightly higher amounts Wednesday. On Wednesday, due to the slowing trend, we have higher probabilities and greater QPF slightly further north compared to previous forecasts. We also lowered temperatures slightly in anticipating of greater precipitation and cloud coverage. Differences in medium range guidance emerge as this shortwave departs. GFS is more confined with Great Lakes shortwave suggesting little influence in our area, while ECMWF is more amplified and brings a period of ascent to the area late Thursday and Thursday night. Since ECMWF has support from at least one GEFS member, we will maintain slight/low-chance probabilities of showers, mainly focused across northern and eastern sections of the forecast area. Meager moisture should limit coverage and also limit instability, so thunderstorm chances appear to be low at best. Confidence continues to decrease into the weekend. An amplified upper flow pattern will continue with mean ridging building across the area. As western troughing increases, southerly low- level flow will bring moisture back. The deterministic GFS is furthest east with the upper level ridge axis by Saturday and shows a lead shortwave and precipitation across western sections of the area. This is in contrast to the ECMWF/EPS and to some degree GEFS mean. Given this, confidence is low that any precipitation will occur over the weekend. As mid-level heights build and we eventually end up on the windward side of the upper level ridge axis, temperatures will warm significantly. We have increased Sat-Sun temperatures above previous forecast given this pattern. BRB FIRE WEATHER... Soaking rains yesterday should hopefully accelerate greenup across the entire area, thus we seem to have peaked with regards to the fire season. Nevertheless, a warm/breezy pattern will develop this weekend and elevated to near-critical fire weather conditions could develop. High-end fire threats aren't expected, but depending on the state of the fuels, an increase in initial attack activity could occur Saturday and Sunday. BRB && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 47 72 49 75 / 10 0 0 10 Hobart OK 43 74 49 75 / 0 0 0 20 Wichita Falls TX 46 75 51 80 / 0 0 0 10 Gage OK 42 73 48 66 / 0 0 10 30 Ponca City OK 47 72 47 72 / 10 0 0 10 Durant OK 50 73 51 76 / 0 0 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ 23/11