On Saturday it became toasty here in Northwest, with many locations gets into the 70s and lower 80s. Yet a number of locations exprienced daily minimum temperature records in the morning--here is the proof from the National Climatic Data Center records website. The blue dot indicate a tie for the record and stations with an x set a record.
To see what was going on, take a look at the vertical sounding at Spokane, WA for 5 AM on Saturday morning. With high pressure we had clear skies (good infrared cooling) and light winds (less turbulent mixing of warm air from above). Thus, air near the surface cools efficiently at night. The air temperatures aloft have warmed considerably the past few days, much of it due to compressional heating from sinking air in the high. Thus, we have had surface-based temperature inversions (temps INCREASING with height). During the day, the surface is heating from the sun and the warm air is getting mixed down to the surface, thus temperatures soar.
The combination of cold air at the surface in the morning, and warm air aloft that mixed down during the day, was a huge diurnal range between the high and low temperatures---concrete-cracking range. Consider a few examples. Pasco went from 32 to 79: 47 F change!
And happy mothers day....Moms may need a sweater in the morning, but a short-sleeve shirt will be mandatory this afternoon, as many enjoy highs reaching into the upper 70s and 80s.