The Met Office now have a much improved Mountain specific forecast. Detailed forecasts include a break down of elevation to show temperature, wind, gusts and wind chill.
This is the traditional mountain weather forecasting site. You'll often find this forecast printed in cafe's, hostels, tourist information so it's worth becoming familiar with the format.
The SAIS publish daily reports of observed and forecast, avalanche, snow, and mountain conditions for the 5 most popular mountain areas of Scotland. They provide a daily avalanche hazard report which will be displayed in cafe's, hostels, tourist information, etc. So it's worth becoming familiar with the format and how to understand the content.
The latest tool for winter adventurers is a handy app with a host of features to help you stay safe in the mountains. Slope aspect and angle tools, avalanche hazard reports, snow stability observations.
Each winter, usually from December to March, Fell top assessors walk up Helvellyn. They check conditions, take photos and supply a report to add to the Met Office weather forecast that appears 365 days a year .
FATMAP is an outdoor adventure platform for web and mobile. We use both platforms to help with route planning and decision making. The 'avalanche' map layer provides an excellent visual representation of the avalanche prone ground (30 degrees and above).
Bing provide an Ordnace Survey mapping layer for all of Great Britain free of charge! The mapping layer is based on the Ordnance Survey Landranger series (scale 1:50,000).
Google Earth Pro is now free. It gives you a high resolution 3D view of the route you're planning. It allows you to get a good picture of what the terrain will look and feel like along your planed route. You can download the full version or just install the app.