:: Maybe, maybe not?
Models and statistics are aiming once again for an unseasonably stormy Monday. Today, the first official day of Autumn, witnessed high temps better suited for mid July. Central Dakotas saw record breaking temps in the upper 90's ahead of the main culprit for the storms predicted to move into our forecast tomorrow -- a deep long wave trough digging from Alberta well south across the Intermountain West. This feature will translate slowly west through tonight and tomorrow and bringing with it monsoonal moisture tapped from the SW CONUS. Already, precipitable water levels are high, but as the low level flow from the system gets a boost from a small tropical low parked over LA tomorrow, Gulf of Mex moisture will begin to transport on the flow as well.
Dynamics for the system are a hard read thus far on the models. Notably, NWS-MPX has not had a HWO out for a good part of this evening, and I imagine they are wrestling with the same questions I have. Frontal system associated with the upper trough is driving some decent convection across the Dakotas today, and SPC put out WWa's for the activity, but without any deep shear the cells are remaining elevated across the high plains, and not acting up on the severe side of things. 00z models keep the mediocre dynamics trending through the 24-hr period, which could spell lots of soaking rain for us, but not much in the way of severe weather.
Notwithstanding the synoptic analysis thus given, the rain chance is there along with thunder (and thus, lightning). So, we could see some dangerous storms anyway. SPC also noted lack of shear dynamics in their issuance of a slight risk inclusion for the TC Metro tomorrow, but also noting that the tropical lapse rates bring pumped northward from the LA low will aid destabilization of the atmosphere tomorrow. NAM seems to manage this well, showing a late morning temps of 10°F at H70 quickly cooling through 20z-00z. Approach of LLJ ahead of the front will increase moisture and aid destab as well.
For now, it looks like common forecast grids (both commercial and NWS) are pointing to a mid-afternoon init period, probably across central MN. Relative storm motion and growth per modeling would bring rain to TC Metro near supper time, if not a touch sooner (another rush-hour storm, anyone?) Will have to do another look in the morning, particularly at RUC modeling of CAPE and shear values as the day progresses.