The Rex Block pattern that has been in place for quite awhile in the Western U.S. is set to break down in a big way in the next week, leading to a much stormier pattern for much of the country. The chances of severe weather in the U.S. may also be on the increase.

The current pattern with the highly amplified Rex Block in the west that has been present for awhile.


The GFS depiction of the upcoming pattern, with a very unsettled and stormy pattern setting in.

Moisture problems…again: Anytime you see west or southwest flow aloft over the Plains, especially this time of year, your mind goes to severe weather.

  • The current pattern will drive a strong cold front south well into the Gulf of Mexico. Getting recovery this time of year is a bit more time-consuming due to the lower sun angles.
  • The first freeze for parts of the Plains will occur this week because of this front.
  • Despite that, temperatures should rebound into next weekend.

Dewpoint map valid Wednesday morning.

Severe Weather Time? SW Flow over the Plains raises alarm bells for storm chasers to be sure, but our old nemesis from the Spring is back in the basic question of will there be enough moisture to make things interesting?

  • We are watching Sunday and Monday for any chances of severe weather initially in this new pattern.
  • There will be a cold front in play during that period as well as a developing dryline.
  • How moisture and thus, instability, turn out will depend on how dramatic the current cold front scours the Gulf. We will know more about that on Thursday morning or so.
  • The one thing we aren’t unsure of: there is going to be more than enough wind shear for severe storms.

We’ll have more on all of this later this week.