A simplified and condensed view for a model that can be helpful for many pilots.
Standing at a mountain start site early, you will notice every now and then that the wind picks up a little and slows down again. Congratulations, this is a thermal bubble! With more time and sun the breaks between these bubbles usually get smaller until a constant flow of thermal air is in place. Good pilots will monitor this carefully to decide when it is safe for them to start.
This pattern can also be seen at winch tow places or in the flatlands. Now and then the wind picks up. A thermal starting will mean air being sucked towards the thermal. So in case the wind sock starts to indicate a zero wind or even a little wind from behind, the thermal most likely is in front of you.
Thermal Bubbles can be thought of as kick off thermal due to not enough hot air mass being available to continuously feed this initial thermal rising.
A stationary or continuous thermal starts to exist if the air mass rising will continuously drag further hot air which then is also rising and continuously feeding this kick off thermal. For constant thermals basically the ground or mountain slopes need to heat up enough with respect to the overall air mass to provide enough air mass with a temperature difference big enough. Stationary or continuous thermal and will be the latest around noon and ending in the evening. Of course noon and evening are relative with regard to time zones, seasons and where to look for thermals.
A cloud is the result of air masses that have been rising up to the point where the formerly less dense air mass has the same density as the surrounding air. At this point the main vertical movement will come to an end. Given that the air is not as dry as to take in the thermals' moisture a(nother) cloud begins to form.
Clouds build up and fall apart, the moisture aka water vapor in the air mass will condensate and a cloud begins to form. Condensation means the moisture changes its physical state into a more favorable meaning less energy intense (due to physics) state. The gaseous water vapor will become liquid water. Along with this process further heat (since energy is being freed) and will be released by this condensation. This will work like an afterburner for the cloud boosting cloud growth.
Thermals Are With The Sun
Remember that for an air mass to rise, this mass needs to be warmer than the surrounding air. For air to rise it needs to heat up. To heat up the sun needs to warm the surface. This means, best chances for thermals are in places where the sun hits the ground as vertical as possible at that time of day, simple as that.
Where To Look For Thermals
During the day the sun will roughly “rise in the east” and “down in the west” (not taking into account differences between northern and southern hemisphere and time within the year).
Taking this into account thermals will start on east southeast slopes in the morning, move to southern oriented slopes around noon, switch to more southwest slopes in the afternoon and finally end in the evening on west oriented mountain slopes. Remembering that the ideal angle of the sun should be vertical for optimum energy intake, flying steeper slopes in the morning, less steep slopes around noon, steeper slopes again in the afternoon and really steep slopes in the evening. Why really steep slopes in the evening as opposed to (regular) steep slopes in the morning - the surrounding air is warmer in the evening