Here's another angle.

I have been waiting for ages to see one with this pattern. (See gaster pattern in the revised edition of Akre et al (1996)) on my webpage on acedemia.edu great find!!!! See if you can photograph more next year! This is one of North Americas least studied wasps. There are a few more specimens of D. alpicola mixed in the norvegicoides section (from Alaska) as well as one worker in the Vespinae section).

Happy to make your day! Here's a Flickr album with all 18 pictures I took. What is the best time of year to look for this species?: https://flic.kr/s/aHsk5E9Qci

I would add those photos to bugguide as there are only a few photos of this species on bugguide. Although there are a few more misidentified under norvegicoides such as this male from Sitka Count, Alaska:
(1.) http://bugguide.net/node/view/157956/bgimage
(2.) http://bugguide.net/node/view/157955/bgimage
and this queen from Ketchikan, Alaska:
(3.) http://bugguide.net/node/view/19457/bgimage
Last but not least is these additional workers from Whitehorse, Yukon Territory, Canada which can be found in the Hornets & Yelowjackets section:
(4.) http://bugguide.net/node/view/954818/bgimage
(5.) http://bugguide.net/node/view/954819/bgimage

As far as time of year for looking for them goes, I would have to say queens will most likely be found from May to early June with nests being found in trees, bushes, wall voids, in structures such as a woodshed or under the eaves of a house. Some nests can be found low to the ground or even half buried in soil with the top half of the nest being attached to a low hanging branch of a tree or vine nests will last until late August-early September I would imagine.

Workers will most likely start being found in June - August.

Males can most likely seen pollinating flowers in meadows from late July through late August. I would love to see more photos of this rare wasp and also of some nests if you can find them. This is one of the least studied wasps in North America. In fact only a few nests have been recorded. 2 were recorded in Alaska under the name Dolichovespula saxonica which was a misidentification.

(See Wagner (1978):The Genus Dolichovespula and an addition to its known species in North America:
http://www.academia.edu/1463501/Wagner_1978_The_genus_Dolichovespula_and_an_addition_to_its_known_species_of_North_America_Hymenoptera_Vespidae_

and also Eck (1983,1984,1987)). Four additional colonies were recorded by Robert Jacobson under the eaves of an open "A" Frame woodshed:

(See paper here on the nesting biology of D. alpicola): http://www.academia.edu/5526305/Jacobson_and_Akre_1996_Errata_on_the_revised_edition_of_The_Yellowjackets_of_America_North_of_Mexico_with_additional_distributional_records_and_nesting_biologies_of_North_American_Vespine_Wasps_Hymeoptera_Vespidae_Vespinae_

I really hope you get to find and photograph these rare wasps. It would be a contribution to science! Good luck.