REX BLOCK

The yellow fuzzy line with the arrows is loosely aligned with the Jet stream. Take note of the general arced shape of the jet as it moves in from the pacific and enters North America. This is a ridge of high pressure. With the pattern that we’re in now, air moving across the pacific is splitting as it nears the west coast; some is moving north and some is heading south. With this “split-flow”, a blocking form usually develops and we’re seeing that now with a closed isobar below the high, under the ridge. This upper air pattern of a High over a Low is a called a rex block and can stay fixed in position for days.

As the ridge out west begins to further build we’ll get into a northwesterly flow regime here. Look at how wavy the flow is just below the ridge, heading into the central part of the country. Each wave, coupled with daytime heating could kick off heavy bouts of rain in the form of showers and t-storms.

By the time we reach the middle to end part of the week we’ll be watching closely for the possibility of a nocturnal complex of showers and storms developing. Right now early Friday morning is looking interesting. We’ll be monitoring developments closely.

Posted by Ted Zarras at 9:30 AM