Cutoff upper level lows (ULLs) are notoriously tough to model. After a couple days of uncertainty, a consensus appears to be emerging among global NWP models, though the GFS is still too quick to progress the SW US ULL, which is a systematic bias in the GFS.

The last 10 runs of the GFS saw a trend from a weak cutoff low & no central US cyclone, to a recent amplification trend. This is also in part due to a trend towards increased ridging over AK, amplifying the upstream trough over the NW US that it interacts with.

The ECMWF on occasion tends to exhibit a slow bias with progressing cutoff ULLs, but in this case appears to have had a progressive bias as well. Last few runs have trended noticeably slower.

And for the sake of some humor in these times, this is what GIMP did to @TropicalTidbits’s maps when I tried making this GIF...