There is a table in JAR OPS 1.297 titled application of aerodrome forecasts to pre-flight planning. It includes details for destination, take-off alternate, etc. At a glance an example of something to disregard comes under the tempo and prob column. You may disregard forecast improvements in this category. It makes sense and errs on the side of caution not to anticipate an improvement in conditions if they only have a prob30 chance of occurring.