There are 2 solutions for fog.
First, Radar/Radar Dectector. Get these installed as soon as they are available.
Second, if you are early in the war, I would suggest diving and waiting it out.
As you have found Heavy Fog is dangerous. Your crew will likely not even report a contact even at 1xTC in that weather. At least not until it's too late. You, however will be able to see the contact in time to react but waiting out Fog at 1xTC is tiresome.
Take option 2. Dive & TC.
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