Considering visiting the Berner Oberland in a few weeks, June 11-15 but am concerned about the weather forecast with rain forecast very day. As an alternate we can by pass Wengen and head to Italy. Thoughts

>> . . . June 11-15 but am concerned about the weather forecast with rain forecast very day<<

That is two weeks from now -- I'd check the forecasts about June 9 or 10

Wengen IS amnong the wetter places of Switzerland whereas the Valais is the driest area.
According to the actual Swiss weather forecast, the weather will remain fine until Wednesday/Thursday, then it will get more and more rainy with a peak around Sunday, followed by rather sunny weather in the dry areas and more clouds and thunderstorms along the Northern slopes of the Alps (Bernese Oberland - Lucerne - Appenzell).
The probability of the previsions for after June 10th is very low (around 40 per cent).
Actual webcam from Wengen (Maennlichen): https://panocam.skiline.cc/maennlichen1

I Hope Swiss weather forecasts are as unreliable as Belgian forecasts.
We'll be in the Luzern area Wed-Sun, then in Graubünden for a few days, further to Ticino, Valais and Vaud at the end of the month.
Oh well, we'll have to take it as it comes.

Sounds as if the weather next tuesday to friday will not be very good for traveling into the alps in the Bernese Oberland. Need to make hotel commitment by tomorrow which is why we can't wait until June 9 to make a decision

We are coming from Frankfurt and our default plan if Wengen weather is not good for visiting the alps on the 12/13/14th of June is to train to Chur and take the Bernina into Italy

So you want to travel during 5 hrs through the alpine area in the case the weather should be really bad ini the alps.

Bernina runs in any weather - and weather could be different down there but could also be funky - the prospect for Wengen seems rather nice as Alps go.

Have a look at the live webcams
of Wengen https://panocam.skiline.cc/maennlichen1
of the Bernina line https://berguen-filisur.graubuenden....cam/piz-darlux
and of the Alps of Valais https://lhm.roundshot.com/

and you will see the difference.
If you want to go to rainy areas, you will have to accept rain.
If you don't like rain, you might go to dryer areas.

I spent a week in Wengen, in about the same time frame, in 2016. We had about 3 days out of 7 that were suitable for the high mountain activities. The rest of the time, we did other things. We had a rail pass, so we made daytrips to Bern, and the open air museum at Ballenberg. That's my standard advice to someone going to the Berner Oberland: alot as much time as you can to this portion of the trip, but be ready to do other things when the weather interferes.

As to the forecast, it is often the case that you get late afternoon showers in the mountains, and some days where rain is in the forecast will still be suitable for high mountain excursions in the morning.

And boattrips on lakes bookending Interlaken can be OK too - getting off and on at neat places.

" We have 4 nights and three days and wish to visit the alps. Understand that this is not advisable if it’s raining or cloudy. So rain and clouds part of the day should be ok. Just don’t want to visit the BO for this short visit if the probability of losing 2-3 days because of all day clouds and rain is high"

Do you want to visit the Alps or the Bernese Oberland and nothing else? In the latter case " the probability of losing 2-3 days because of all day clouds and rain" is really high. In other areas of the Alps not.

Frankfurt to Chur will be a six hour train ride - changing in Zurich - Zurich nice town to look around just near the train station - if looking for a break. Bahnhofstrasse near the station is called one of the most elegant streets in Europe due to HQs of many banks. You can build in your transfer times so if looking for a walk to salve your legs there's one possibility. Chur is nice but has little of significance - at least for me the day I stayed there.

In the case of bad weather in the Alps, I would take the direct Frankfurt - Milan train

The only weather forecast I trust when travelling to or in Switzerland is the official website of the Federal Met Office:
https://www.meteoswiss.admin.ch/home.html?tab=overview
Any other apps or global weater websites are complete bogus, especially with any forecasts of 48 hours and more, when going to the mountains. They lack the local expertise of real human beings who are very knowledgeable about the typically volatile weather in the Alps and factor that in when making the predictions.
Unfortunatelly, the more comprehensive weather bulletins are not available in English - but you can try to run the German or French version through Google Translate, if you need to.

What would one look for on Meteo centrale to evaluate whether or not taking the Bernina express is a good idea or not? Look at the Chur weather forecast during the time the train would be running? Is five days out accurate enough or must one wait til 48 hours before?

For Bernina Express area, open the link sent by Cowboy and enter the village names Filisur, Samedan, Brusio
For Loetschberger area, open the link sent by Cowboy and enter the village names Thun, Frutigen, Ausserberg, Gondo, Camedo
For Gotthard Panorama Express area, open the link sent by Cowboy and enter the village names Brunnen, Wassen, Faido, Lugano
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