:: Somethings Gotta Give
At time of this writing, many changes are possible to SPC and local WFO grids and forecasts, so I will keep this brief on the synoptical side. Heat Idx is currently over the century mark at Lakeville, as temps over 88 and dewpoints over 70 have built quickly since sunup. The rHum outside is 62%, and it is being felt in earnest, as air conditioning is the rule everywhere across town. Skies are sunny to boot, and warm instability will continue to build in advance of a cold front now lined up from KBDE to just west of KGPZ and then arching back to KAXN and KATY. Associated 1010mb low is now up over Lake of the Woods, and not progged to deepen much more. Nonetheless, height falls should increase during the day for our area as front approaches and diurnal heat aids the differential. CAPE values are in the 2000-3000J/kg range and possibly some 4000J/kg pockets mixed in, and lifting indicies are between -6 and -10! The amount of convection will be regulated, however, by the weakening of the CAP, which has been in place now for the better of 72 hours. H70 temps on recent balloon launches remain at 15°C over our area. However, some models have suggested a rapid cooling of the mid-layers of the atmosphere. Should this be the case, our area could see +TSRA with an intense large hail threat, not unlike last week.
Right now, best guesses are the 1pm-3pm time frame for initiation. Morning progress of the front suggests that this is a on-time guess. Still waiting for new RAOB data to confirm the erosion of the CAP. Best clue so far will be satellite imagry which is beginning to show some instability CU's building just ahead and in vcty of the front.
SPC has us under slight risk for severe weather on the Day 1 Outlook for this system, and new Day 1 is due in 1/2 an hour. Will update as day progresses.