12Z GFS shows dynamic upper level disturbance sweeping into the northern plains and upper midwest on Thursday. Strong wind fields and potent instabilities suggest convection is likely if this run verifies.
THE FRIDAY INTO SATURDAY TIME FRAME COULD BE A SIGNIFICANT SEVERE
WEATHER DAY FOR SOUTHWEST MICHIGAN...THINK OF OCTOBER 24 2001.
Originally posted by Dan Cook
DVN's mentioning an \"active day\" for Thurs.
Originally posted by Glen Romine
Maybe noone has looked at last night's GFS, but indications are that the main upper wave will not eject until Friday, not Thursday, so there may not be much forcing around for convection on Thursday to get excited about. Strong jet dynamics are forecast to promote some convection in the northern plains, where moisture will be limited. That said, always a chance of a smaller scale feature that won't be resolvable until the lead time shortens substantially that might make things happen elsewhere as ample moisture and instability should be surging up the Miss. River valley - but probably will remain capped to surface convection (though elevated warm air advection precip might lead the warm front across the upper Great Lakes). If this trend continues, I'll start a new thread for Friday if one doesn't already exist after a few more run cycles.
ETA does look positively titled at first, but I believe if there was an extension to the 84hrs (lets say out to 108hrs or so or TRUE ETA (no GFS extension)), it would soon go negative...
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.