Step 1: Make a pile of trash cans
Step 2: Create a plug for building the inside of the igloo part 1
Step 3: Build the plug part 2
Cover the cans with one or more tarps, I used a big tarp folded in 4. You can pack down the snow a bit around your pile, but
Step 4: Blow snow onto the plug, then start digging out the cans
Then, dig out the trash can at the bottom.
Step 5: Finish the igloo
Smooth out the walls and ceiling so that any meltwater runs down the walls instead of dripping on you. Put a small chimney hole straight up through the top of the ceiling, this allows CO2 and candle smoke to exit safely.
To gauge wall thickness, put some 18" long sticks thru the walls from the outside, and then dig out the interior till you get to the sticks.
It won't collapse suddenly, but over a matter of days it may slump and eventually cave in. You can use the snowblower to add more snow on top and then dig out the interior more.
Make the center floor area higher - with gutters around the edges to cach meltwater and to get you up into the warmer air.