10/21/04 FCST: Upper Midwest

[Robert Dewey]

Latest NWS discussions across the MS Valley and Ohio Valley concerning the even (THU through FRI timeframe) are less than impressive this go around. Not even a mention of severe from MKX, GRR, DTX, IWX, etc... DTX does say that it is possible the low could just sit and spin in the southwest (since the jet on the backside of the system is stronger than what models are indicating, that means it could dig even deeper than expected), and not even eject for quite some time (i.e. a cutoff low that will just sit there and weaken)... Only time will tell...

 

[Jeff Snyder]

FWIW, there is a general bias for models to move troughs out of the western/southwestern US too quickly. And indeed, we've seen this again with the GFS as the last-week Wednesday target has now moved to MAYBE Thursday and more likely at least Friday. I'd be weary about examining model specifics this far out, and this general west-coast trough (and associated southwest flow aloft in the central US) climatologically favors severe weather events. Of course, the low-level fields are still to-be determined, and it are these low-level fields (moisture, shear, etc) that I think will make or break the possible event when the main system does eventually come out. IF we can get >mid-60 Tds westward to atleast the central OK/KS/NE area, I think there will be SOME significant severe weather associated with this system, but whether it's in the plains or east of there is still up in the air.

 

[Robert Dewey]

FWIW, there is a general bias for models to move troughs out of the western/southwestern US too quickly. And indeed, we've seen this again with the GFS as the last-week Wednesday target has now moved to MAYBE Thursday and more likely at least Friday. I'd be weary about examining model specifics this far out, and this general west-coast trough (and associated southwest flow aloft in the central US) climatologically favors severe weather events. Of course, the low-level fields are still to-be determined, and it are these low-level fields (moisture, shear, etc) that I think will make or break the possible event when the main system does eventually come out. IF we can get >mid-60 Tds westward to atleast the central OK/KS/NE area, I think there will be SOME significant severe weather associated with this system, but whether it's in the plains or east of there is still up in the air.

It's hard to do, but I am not gonna look at a single model until WED or early THU, and see what has become of the situation. I believe there is a "law" out there, something about a watched pot never boils... Well, I'm gonna close my eyes to the models, and things better start boiling, LOL...