(WAND) - Named after Daniel Rex, a meteorologist who first described the pattern in the 1950s, the Rex block is a specific type of atmospheric blocking pattern that disrupts the normal west-to-east flow of the jet stream. It can lead to persistent and often extreme weather conditions. Â
A Rex block occurs when:
A high-pressure system (ridge) is located directly north of a low-pressure system (trough).
The configuration is vertically stacked (one above the other) and becomes stationary or slow-moving.
This setup effectively blocks or diverts the usual movement of weather systems, sometimes for days or even weeks. Â
In central Illinois' case, this blocking pattern will last for days, keeping occasional showers in the forecast through this weekend and into early next week. As the depth of cold air aloft increases, cold air funnel clouds may also be seen this weekend.  They rarely reach the ground, and typically dissipate once precipitation begins. Â
