Here are a load of links to various weather forecasts. The links work (at the time of publishing). Get to know 3 or 4 different sites and what reality looks like versus the forecasts. You'll then get a good idea which ones over or under estimate the conditions for your area.
In the Chamonix valley I like the balance between the local Chamonix Meteo and MeteoBlue with comparing to one or two of the other national and international forecasts. I find this gives me a good comparison and a pretty accurate forecast.
METEO.IT ( http://www.meteo.it/meteo/valle-d-aosta/ ). Various options including real-time temp, pressure, wind etc. Also snow reports and some interesting articles. For avalanche forecasts see below.
VDA is Valle D’Aosta: http://cf.regione.vda.it/previsioni.php It has loads of good data and some historic (an hour or two) and actual observed data rather than just a forecast. From the home page the weather, avalanche forecast etc is usually somewhere on the right hands side.
CHAMONIX METEO: http://chamonix-meteo.com/chamonix-mont-blanc/weather/forecast/morning/5_days_weather_forecast.php This is separate from Meteo France and I understand is written by a local weather enthusiast so has human and very local input. It is not updated everyday.
METEOFRANCE: http://www.meteofrance.com/previsions-meteo-france/chamonix-mont-blanc/74400 The national forecast. They have an office in Chamonix so I can only hope there is a good deal of ‘local’ in it. I find it takes a while to load and sort itself out due to numerous, changing ads everywhere.
METEOBLUE: https://www.meteoblue.com/en/weather/forecast/week/chamonix_france_3027301 I like this one for a general forecast. Loads quickly (for me) and I like pictures! Keep scrolling down as there are loads of good things lurking… animated things like the past 2 hr cloud cover, Radar and precipitation ‘nowcast’ for the last hour or so and more.
METEOCIEL: http://www.meteociel.com/previsions-haute-altitude/27625/chamonix_mont_blanc.htm Now you can really start to geek out with this one. It can seem overwhelming with so much data and weird z500, z850 etc but there is a clear explanation at the bottom. There is so much you can delve into here and once you get your head around this you’ll become a weather geek too!
MOUNTAIN-FORECAST: https://www.mountain-forecast.com/peaks/Mont-Blanc/forecasts/3000 This is my go-to site for a quick look because its really easy and clear to use and I can look at a number of elevations really quickly. You can also just move the map around, click on one of the wee triangles and the data automatically updates. I find it suitably accurate for most local activities.
WINDY: ( https://www.windy.com ). This is a really cool site and has an app too. Very easy to use, looks great and more options and overlays you could wish for.
METEOSWISS: http://www.meteosuisse.admin.ch/home.html?tab=alarm As we generally expect from the Swiss, this is pretty clear, easy to use and you can drill-down to local weather stations for real-time data (in some instances). There is so much information on here it takes a while to identify where the useful stuff is.
YR.NO: https://www.yr.no/place/France/Rh%C3%B4ne-Alpes/Chamonix/ I like this. Simple, visual and I find it pretty accurate, particularly for wind.
FNMOC, I always have trouble loading this site due to security threats identified by my browsers. If you can get to load the pages there is some really good, geeky stuff here but also great charts of the weather patterns.