Good entry! I would only mention this:

С пacxoй! А какой прогноз погоды на выходные? -> Какой у вас прогноз погоды на выходные?

I think it's a little unnatural to use "A" here, though most of the speakers wouldn't notice it. We use "A" in the beginning of the sentence:

1) to introduce a new topic.

2) to show the difference between two things.

3) to ask a question back, to ask a question about a thing that you've just mentioned about yourself, F.E.:

С пасхой! У нас отличный прогноз погоды на выходные! А у вас? 

С пасхой! Какой прогноз погоды на завтра в вашем городе? А на выходные?

or

A - С пасхой! Какой у вас прогноз погоды на выходные?

B - Хороший. А у вас?

In your example there's nothing to compare, and to start a question with "A" sounds like you say "By the way" - a little strange, because there was no previous topic. We can use it like that in spoken language to draw attention, like this:

 - А ты не знаешь, где все ложки? Hey, do you know where all the spoons are?

But in your entry that's not the case too. :) Hope that's not too confusing.

Even more weather...

Well, I didn't manage to study any Russian yesterday but here's my efforts for today.

С пacxoй! А какой прогноз погоды на выходные у Вас? Нам oбещают солнечную погоду. К сожалению, У меня нет свободного времени. Я еду в Лондон. 

All corrections and comments gratefully received!

Even more weather...

Well, I didn't manage to study any Russian yesterday but here's my efforts for today.

С Пacxoй! А какой прогноз погоды на выходные? Я думаю, oбещают солнечную погоду. К сожалению, у меня нет свободного времени. Я еду в Лондон.

All corrections and comments gratefully received!