I was going to suggest a low hoop tunnel and heavy plastic film, so you could re-use it in spring and fall for other temperature protection tasks. But a circular hoop might not have a steep enough pitch to throw snow off the top ... it might build up too much weight and collapse.
You COULD build a pup-tent-shaped "hoop" tunnel if you used 1/2" EMT metal conduit and bent them into steep Vee s instead of half-circle "hoops".
e.g.:
http://www.homedepot.com/p/All...
$2.39 for 10' lengths
They also make 3/4" EMT conduit, $3.54 for 10 feet.
