NWS Storm Prediction Center is forecasting a Derecho centered on parts of Oklahoma this evening into tonight, with widespread damaging winds and embedded swaths of significant hurricane-force wind gusts from 80-110 mph. Isolated large hail up to baseball size are possible.
Embedded tornadoes are anticipated as well, with the greatest potential for strong (EF2-EF3) tornadoes across southwest Oklahoma this evening.
Sunday's moderate risk area has been expanded to a wider region covering most of Oklahoma.
Timing
Late this evening. See graphic below.
Severe thunderstorm and tornado watches are already being issued.
A simulation of what the radar will look like this evening. The system will move in the northeast direction.
These storms will be triggered by the same upper-air disturbance that brought severe weather to California, including up to 81 inches of snow in the Los Angeles County mountains.
The differential temperature over the region today -
Plus the low pressure area caused by the storm system in CA, strong winds just above the surface and lighter winds at the ground create conditions favorable for supercell and derecho development.
Derecho
From en.wikipedia.org/… — A derecho is a widespread, long-lived, straight-line wind storm that is associated with a fast-moving group of severe thunderstorms known as a mesoscale convective system.
Derechos can cause hurricane-force winds, tornadoes, heavy rains, and flash floods. In many cases, convection-induced winds take on a bow echo (backward "C") form of squall line, often forming beneath an area of diverging upper tropospheric winds, and in a region of both rich low-level moisture and warm-air advection.
According to www.weather.gov/…
By definition, if the wind damage swath extends more than 240 miles (about 400 kilometers) and includes wind gusts of at least 58 mph (93 km/h) or greater along most of its length, then the event may be classified as a derecho.
The graphic below shows how derechos form. Warm moist air from the right travels up the column at the front end, rain cooled air descends rapidly to ground level creating high forward winds, which in turn feeds more moist warm air to the upper layers.
Precautions and Preparedness
Avoid travel. Stay home. Stay informed. Secure loose items. Expect power outages. Keep all batteries charged.
Shelter in an interior part of the home at the lowest floor.