Models are in fairly good agreement this afternoon regarding the evolution of the Western U.S. system and what impacts it will have on Oklahoma.
A large upper low is currently located over Nevada. This low will dig toward Southwest Arizona by late on Thursday. The system will move slowly eastward through Friday and into Saturday afternoon, reaching a position just south of the Four Corners. Through Sunday afternoon, the low will transition to more of an open wave located across Colorado and New Mexico, with southwest flow spreading over the Central and Southern Plains.
There has been little change in the meager amount of low level moisture across Oklahoma over the past 72 hours. This will change early on Friday as sustained south winds over the Southern Plains bring a fetch of rich gulf air into the state which will remain in place through the weekend.
A weak front is located over the Eastern Panhandle this afternoon, and is expected to lift northward late today. Thursday through Sunday will see a north/south trough located over the High Plains with moderate south winds across the state. The surface pattern is likely to become disorganized at times, the result of convective complexes which will begin to work deeper into the state.
Scattered showers and thunderstorms which occur today over Northwest Oklahoma and the Panhandle will likely continue in a weaker form through Thursday morning. More thunderstorms will form during the afternoon across the Panhandle and northwest part of the state. As the upper level system approaches, showers and thunderstorms will edge slowly eastward. Friday will see precipitation across roughly the northwest 1/3 of the state. Clusters of thunderstorms will continue to affect much of the same areas on Saturday. By Sunday, showers and thunderstorms will be possible across the western 2/3s of the state.
There will be some risk of severe thunderstorms through the weekend. The main threat will be isolated areas of large hail and damaging winds. No widespread significant outbreak of severe thunderstorms is expected.
While beneficial rainfall is expected across much of the area currently listed as either having extreme or exceptional drought, some places may see too much of a good thing. By Sunday, widespread 1 to 2 inch amounts of precipitation will have fallen across the western half of the state. The weather pattern favors areas of training precipitation which could lead to some places seeing 2 to 4 inches, and isolated spots well over 4 inches. While it is hard to believe given the current drought, flash flooding could become a problem before the event is over.
In general, temperatures are expected to be near or slightly above normal. However, day to day temperatures will be difficult to pin down in areas that see a large variation in cloud cover and precipitation.
Thursday morning: 67
Friday morning: 67
Friday: 85 / Showers and thunderstorms possible
Saturday morning: 65 / Showers and thunderstorms possible
Saturday: 85 / Showers and thunderstorms possible
Sunday morning: 65 / Showers and thunderstorms possible
Sunday: 85 / Showers and thunderstorms likely