Does anyone know of a website or general guidelines or other wilderness wisdom about how to guess what the snow depth will be after a period of warm temperatures and rain?

In my specific case, there is 20 inches of snow, and there will be a day of rain with temperatures 40-50F for a day. I need to guess on the likelihood of needing snowshoes.

Andy, if you do not take the snowshoes, the chance that they will be needed will approach 100%.

There are too many variables. Some of it depends on the ground temperature with the snow on top of it. Some of it depends on the temperature and texture of the snow.

--B.G.--

This isn't what you meant, but

Go to the NOAA snow website:

http://www.nohrsc.noaa.gov/interactive/html/map.html?mode=pan&zoom=&center_x=++-122.317&center_y=++45.317&ql=station&var=ssm_depth&snap=1&o9=1&o12=1&o13=1&lbl=m&min_x=-124.19166666667&min_y=43.908333333334&max_x=-120.44166666667&max_y=46.725&coord_x=-122.31666666667&coord_y=45.316666666667&zbox_n=&zbox_s=&zbox_e=&zbox_w=&metric=0&bgvar=dem&width=600&height=450&nw=600&nh=450&font=0&js=1&uc=0&zoom8.x=8&zoom8.y=9

Generally speaking, rain doesn't melt much snow, but it does consolidate it. It is rather surprising. In the Northwest, we have lost of days where it rains on top of the snow (it seem like most of this winter has been like that) but not much melting. The thing is, the snow gets really hard. With that much snow, I wouldn't bring snowshoes, as you'll probably have dry spots. Even if you get snow, you won't sink in much. I would bring something like Yaktraks, which are much lighter and much easier to put on than snowshoes.

You don't say where you live, but here in Washington there are a bunch of back country weather stations called snotel sites that collect info on the snowpack and transmit it back to somewhere. I think pretty much anywhere with mountains will have a system like this. Try google-ing the word snotel and your state name. The website for Washington is.

http://www.or.nrcs.usda.gov/snow/maps/washington_sitemap.html

I've found NOAAs modeling program to be pretty darn accurate. Here's the short link: http://www.nohrsc.noaa.gov/interactive/html/map.html

Works even if you don't have Snotels in the relevant areas. Make sure to pay attention to all the data field options.

"I've found NOAAs modeling program to be pretty darn accurate."

It's not perfect

It gives snow for areas about 1/2 mile square. If I'm hiking on a ridge much smaller than this, it can correctly say there's an average of almost no snow over the 1/2 mile, but on the ridge there can be impassablay deep snow.

Or it will say the snow has melted off somewhere, but actually it takes a couple more or less weeks before it actually melts off.

But you can work with these limitations.

Andy, definitely take snowshows for the reason that rained-on snow freezes overnight to form a HARD crust. That crust will likely support you but be slippery as he!!. (Don't ask how I know.)

Modern snowshoes usually have aggressive toothed cleats and these will halp to keep you from sliding. In my experience MSR Lightning 'shoes give you the most "gription".

Also take ski/walking poles W/ snow baskets. And son't forget well-ventilated raingear like a Packa.