As usual, nice writeup by NWS Sterling:
Two strong cyclogenesis events will occur in the poleward exit
region of the North Pacific Jet during the Tuesday through Thursday
time period. These cyclogenesis events will lead to strong
ridgebuilding downstream across the western CONUS, while also
encouraging a shortwave to dig southward toward TX/Northern Mexico
by late Thursday into Friday. Multiple additional disturbances will
descend down the front side of the developing ridge and interact
with the aforementioned shortwave. The result of interactions
between these disturbances remains highly uncertain. Possibilities
range from phasing between the disturbances, development of a deep
longwave trough, and the formation of a coastal low, to a cutoff
shortwave suppressed well to our south, with predominantly dry
conditions. With significant spread in both deterministic and
ensemble guidance, confidence in any given solution is very low at
this time, with both timing and amount of precipitation in the late
week/weekend period very much up in the air.