Latest models (18z runs of ETA and GFS plus 12z EC) show the
reemergence of the southern jet stream, and a large upper low moving
from western Mexico into the southwestern US, concurrent with a strong
upper low forecast to plow into the Pacific Northwest beginning around
Friday morning.
These systems should make significant impact on the increasingly
narrow western ridge. Ensembles suggest decreasing heights across the
western US in favor of more zonal flow, a solution favored in this
morning's CPC discussion which Mike cited above.
We still have problems to overcome, namely the retrograding eastern
trough which merges with a middle Canadian low to form another monster
cyclone north of the border, creating a confluent zone of northwest
flow aloft over areas north of Interstate 70. However, with the
weakening of the ridge in favor of zonal flow, it's possible we can
finally ship these damn Canadian and east coast lows out to sea.
I have some measure of confidence this is possible. If it happens, I
think the generally progressive pattern we've experienced--despite the
consistent blocking--could continue, paving the way for an active
first half of June as shortwaves ride the zonal flow into the central
US unimpeded and with more impressive boundary layer instability after
a week of ridging.
That's some wishcasting, I know, but I think there's evidence things
may improve on a large scale.
None of this matters much to our friends in the field, who have a red
box and a tornado-warned storm in Yuma County, CO right now. I hope
they find a big, backlit cone and snap 2005 out of her trance.
I intend to leave Bloomington Wednesday for possible chasing in New
Mexico on Thursday and Friday, then the Twister Reunion and Picnic
Saturday in Wakita, followed by whatever Mother Nature has in store
for us during the climatological peak of tornado season this holiday
weekend.