I had an azalea right next to a sloping roof and, I would even throw the shoveled snow on it, it handled it pretty well. I was a mature shrub, about 4ft tall and 3ft wide. Mine had pink flowers, but I also have a azalea with white blooms.

I can't think of many evergreen shrubs that are both as small as you'd like and will survive the snow sliding off the roof. Most coniferous evergreens, including junipers, don't regrow from dormant buds on older wood. If a branch gets damaged/broken by heavy snow or ice slamming down onto it, you will have a hole in the shrub. With broad-leafed evergreens like Rhododendrons, broken branches will regrow from dormant buds, but will leave the plant uneven - sort of a Charlie Brown Christmas tree look - unless you trim it right after blooming to even it out, and it still may get more damage the next winter. IME, snow off my one story ell roof hits plants a lot harder that what comes off my snow shovel. IIRC you have a two story roof over this area(?), so I expect that at least some winters you will have significant damage to plants that are above ground based on my experience with a roof that drops snow in one part of my garden.

If the soil isn't limey, you could look at Vaccinium vitis-idaea/ligonberry or mountain cranberry. It's evergreen. Partridge berry/Michella repens is an evergreen perennial that hugs the ground and might have little damage, though I don't know. Low bush blueberry might do OK since they survive in the zone along the road where the town plows pile snow. I haven't grown cotoneaster, so I don't know how it would survive the snow drop.

There are some dwarf spirea that are in the 18-24" range (so a little too tall) that have white flowers like S. betulifolia 'Tor' and S. japonica First Additions 'Super Star'. They both have spring/summer white flowers and colorful autumn foliage. If the branches are damaged by the falling ice, cut them to a few inches in spring just before the leaves start emerging and they will regrow quickly. I don't know if any are shorter than these.

Similarly to 'Silver Mound' artemisia, Calamintha nepeta ssp. glandulosa 'White Cloud' might well work. The catmints I grow in my garden (though I don't grow this one) all look good until covered with snow, sort of a frosty gray mound, though they emerge from the snow needing to be clipped back since they look quite messy.

I grow 'Annabelle' hydrangea, spirea, and a quite vigorous Rhodie under my one-story snow drop zone, but I control where and when the snow drops since we rake the roof. I rake away from the Rhodie unless the snow is fluffy. I know I can trim to a few inches both 'Annabelle' and the spireas, so I don't bother to avoid them. I looked around to see if there were shorter smooth hydrangeas (H. arborescens), but the few selections I found all seem to be closer to the height of 'Annabelle' (which is 4') than to what you want.

Holly and Yew regrow from old wood, so they would tolerate aggressive pruning to keep them the right size, and could (eventually) recover from heavy snow damage. In your zone your best bets would be Blue Princess and Blue Prince (meserve) hybrid holly or maybe American holly. A nice blue spreading Yew might work. Bigger Yew hedges survive getting buried, but look misshapen, in my experience.

Just went to Russell's Garden Center. The gentleman in the nursery recommended dwarf spirea, a holly (can't remember the variety) or blue star juniper. Upon further conversation, he told me that the dwarf spireas only come with pink flowers and the holly will not tolerate the full sun. He also mentioned that all the shrubs for Fall planting should arrive in about 2 weeks. So I will go back in 2 weeks.

Russels may only carry dwarf spirea with pink flowers, but you can probably find white-flowered dwarf spireas either at other local nurseries or on-line.

My in-laws have a holly hedge (variety unknown since it came from the grocery store) in full sun that's probably 15 or 20 years old. It gets a bit of winter burn above the snow line in bad years, but recovers relatively quickly in spring. It's big and tall, though, far too large for your space. I don't know if there are dwarf hollies that like full sun.

I thought of one other suggestion, a white flowering or silver foliaged heather. Evergreen and flowers.

Thanks for the Heather suggestion. Yes - I plan to visit some other local nurseries to see if I can find the spirea. Or see what others say about the holly. Though it was good to find out that the fall planting shrubs aren't sure for a couple weeks - I'd rather not get something that has been sitting in a pot all summer long.

In the meantime, I purchased a couple white chrysanthemums at the grocery store this morning. So I can at least get something into that bare dirt! A temporary solution!

Not a heather, but a Heath. Erica carnea 'Springwood White'.

Low to the ground, evergreen and covered with White flowers very early in Spring. 10 inches high and about a 2 foot spread.

My suggestions are perhaps a combo including low growing junipers and cotoneaster (nice glossy deep green hearty foliage , w/ red berries.) I actually have 2 or 3 mature junipers that i am considering replacing (though i do love them, it's because of space constraints). They are blue star and a variegated gold and blue one. Each one is about 40" W x 30" D. (contact me via my member profile if you're interested)

Cotoneaster is very attractively used all over the Mt Auburn cemetery.
http://www.finegardening.com/rockspray-cotoneaster-horizontalis

http://www.finegardening.com/evergreen-hollies

http://www.finegardening.com/fragrant-sumac-rhus-aromatica-%E2%80%98gro-low%E2%80%99

One thing to consider: you might enjoy planting some bulbs that will come up through the branches of your groundcover. I was thinking of the alliums that, once bloomed, can still look cool when their heads are left on, like christophii and schubertii and other globe-headed ones...

p.s. no offense intended towards russell's (they sell alot of great things) but i really think Mahoney's Winchester and Stonegate in Lincoln- are much better for your search on this one. They both just have a LOT more plants along these lines. (Maybe i've gone at the wrong time over the years, but i've always found them weak in the woody plant sector, though strong in perennials and particularly indoor plants/annuals.)

Thanks for the additional input Mindy. And a huge thanks for pointing out mature dimensions. 40" is quite large and could really end up dominating the space. It's not like you can dig up and divide shrubs!

I do plan on going over to Stonegate. My little one starts school on Tuesday, so I'll have the opportunity to shop in peace! I bought a bunch of plants at Mahoneys - the Wayland one - and they all died on me. So I don't shop mahoneys any more.

I do plan on picking up bulbs. I've always had white daffodils, tulips, alliums, muscati, crocus and hyacinth in that garden. When I dug up the garden, I didn't take the time to go searching for unmarked bulbs. And I noticed quite a few scattered bulbs while the workers were working. So I may end up with some bulb surprises next spring!

I am now the proud owner of 2 blue star junipers and a cranberry. We will see how they handle the snow this winter.

I was also thinking of something to hang over the retaining wall. I had been thinking of cotoneaster. But the tag at Russell's said it gets 3' tall. The guy recommended Deut-something. But it won't handle the snow. So I will watch the roof avalanches this winter and mark where I could possible plant the deuts next spring.

Hopefully I can get this stuff planted this weekend and then can post some photos. It's been a fun, yet stressful, project.

Probably Deutzias. There are short ones, like 'Chardonnay Pearls' or 'Nikko', both of which have white flowers. If the branches break and you have to prune it, you'd lose the spring bloom.

There are a whole range of sizes that Cotoneaster are available in. You might be able to find a shorter one, like 'Tom Thumb' AKA 'Little Gem' which gets in the 1 1/2 foot tall range.

I think you'll like the cranberry, which is more of a groundcover than a shrub, but is a really nice tidy evergreen. Blue star juniper is handsome, but I've never grown it.

I was told the cranberry turns a deep red burgundy in the fall. I thought it would look nice with the bluish tinge to the junipers. My only concern with the cranberry is if the soil will be wet enough.

I was told the deutzias would get destroyed by the roof snow. So if I can pick the spots in front of and in back of the snow fall. But then - I'm still debating if I want plants hanging over the retaining wall. It's New England field stone. And it was expensive. So not sure I want to cover it up.

Still thinking of adding a Heather and/or spirea.

Cranberry does fine with average moisture garden soil, but looks fairly bad in dry soil. Give it some mulch and water if the soil gets dry.

Rather than think of plants that will take the punishment of giant clods of snow falling on them from house-height and limiting your selection to those few that fit the criteria, why not just mitigate the effect of the falling snow by building A-frames that can be places over the shrubs for those months when snow is a problem? Think: the plywood frames that people put over their mailboxes to protect from the snowplow's wrath, You could even wrap them with Xmas lights. ;-)