Yeah, 4/5/1972 was a true unicorn in that it operated as the perfect hybrid between our cold-core and warm-core setups.
There was indeed a deep longwave Pacific trough anchored offshore, with cool westerly flow aloft. Then the initial cold front moved inland that morning.
But on the 5th there was also a very warm season-esque shortwave driving northward off the OR/CA border that advected in southerly flow behind the Pacific front and effectively created an open warm sector across the inland PNW despite the cooling upper level airmass.
Strong, cool westerly flow aloft+ strong moisture rich southerly flow at the lower levels= Significant wind shear for your spinners. And the steep lapse rates and forcing necessary to fire up organized convection and vertical growth.
It was a pretty juicy mini warm sector too. On the eastside Pasco hit 76 that day and even behind the cold front, PDX was a mild and moist 62/51 spread as the squall line moved in that afternoon.
It's often overlooked that day also had an F3 tornado near Creston and another F2 in Stevens County as the shortwave swung north and cut into the warm sector in Eastern WA. It was far more organized and regional event than any of our garden variety cold core funnel setups.
It was a weird event. Storms fired along a Pacific cold front with T/dT spreads around 62/55. Simply put it was an atmospheric river which attacked the coast at the right angle, after a few days of persistent warm SSW flow and with a whole winter's worth of ground moisture.
We've had a few garden variety postfrontal thunderstorms in Seattle this spring. Around average. Could get some more cold core stuff if the long range is to be trusted.
Yeah, responded to this yesterday I believe, but from what I read it was cold core...as almost all west side PNW tornadoes are. Temps were in the 50s when it occurred.