After the 61 mm of rainfall recorded 8 km from me at the downtown Montreal reporting station, Quebecers and southern Ontarians will get a reprieve from the dreary maritime weather on Wednesday and Thursday complete with temperatures in the mid to upper 20s.
However, a cold front approaches the region on Friday, which clashes into pockets of over 1200 j/kg of modelled SBCAPE.
But, bulk shear is very abysmal, mostly under 25 kt, which means that organized convection and severe weather is not expected.
Luckily, I dug deeper into the stack of model supercomputer-fed printer output and found what I was looking for under 11 feet of repetitive sunshine and warmth solutions that belong in the cylindrical file.
Through the glass, I see S QC and E ON rounding a large H5 ridge, putting us in a northwesterly flow situation, starting on Sunday and continuing through at least Tuesday if the 18Z GFS and 12Z ECMWF are to be believed. 850 mb temperatures exceed 15 C and approach 20 C, complete with substantial moisture return, resulting in dewpoints in the low to mid 20s (enhanced by residual soil moisture like a picnic enhances an ant infestation) in addition to temperatures near 30 C.
A northwesterly H5 flow combined with a westerly to southwesterly surface flow produces lots of bulk shear. When you have lots of bulk shear, lots of things can happen, including this scenario:
CAPE is not very high, but H85 temps indicate the potential for considerably greater surface heating; regardless, STP and SCP values are indicating decent supercell/tornado potential. PWATs near 50 mm combined with freezing level heights over 600 mb on this model run (18Z GFS) near Montreal, setting the stage for very-high precipitation efficiency, which favours lots of something that we definitely, positively, surely need: heavy rain.
Interests in E ON and S QC should be closely watching this potential event, preferably through The Convective Magnifying Glass™.