From an [article](http://www3.nhk.or.jp/news/easy/k10011086301000/k10011086301000.html) written on the 7th of the month:

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> 東京から日本のほかの場所に向かう「下り」の飛行機は、１１日が特に混み**そう**です。東京に向かう「上り」の飛行機は、１５日〜１６日と１９日〜２０日が混み**そう**です。  
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>  For planes heading from Tokyo to other places in Japan, the 11th will seem particularly crowded. For planes heading towards Tokyo, the 15th to 16th and 19th to 20th will seem crowded.
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I'm confused by the nuance that そう is adding to these sentences. I'm assuming these are guesses based on previous years' flight statistics, so I would have expected something like はず or よう to be used instead.

Could you please provide some explanation as to why そう is the best choice, and whether はず or よう would also be appropriate here?

My understanding is that 混みそうです means that when I look around I will have a feeling that it is crowded ("It will seem crowded"). Whereas 混むようです means that based on evidence I predict it will be crowded ("It seems that it will be crowded"). Could you please confirm or correct my error in understanding?