TULSA, Oklahoma - A storm system threatening Oklahoma this weekend will bring a chance for severe storms Sunday night and through the day on Monday. 

Tonight, we should see some showers move through Green Country with a few rumbles of thunder possible but the threat for severe storms will hold off until late Sunday. 

An upper level system sliding by will combine with a cold front to produce storms as early as 6 pm on Sunday. Showers and storms will continue overnight into Monday morning. The main threats will be hail and damaging winds. Large hail near golf ball size as well as winds near 60 miles per hour will be possible. 

There is small window for tornadoes that spin up quickly. That window will be open for a few hours after initial storm development. Exact timing and location of storm initiation is still being determined. 

Rain and storms will most likely be occurring all day Monday. Activity should expand across much of Green Country and into southeastern Oklahoma by late morning. The cold front will stall for a little while during the morning hours, causing storms to stick around longer. Eventually the cold front will slide southward along with a surface low over south central Oklahoma.

Leftover showers will be possible for much of Monday but the threat for severe storms will increase over southeastern Oklahoma out ahead of the cool front. All modes of severe weather will be possible: hail, damaging winds and an isolated tornado. The tornado threat is slightly higher on Monday.