[quote="bmwhype2"]So long as you use an umbrella when it rains, you (will/would) be dry.
I beleive you have to have 'that' and the verb in infinitive form without 'to' Or use of 'if' for a desire statement to be in subjunctive.
I got interested in finding out the difference between 'so long as' and 'as long as'. So here is what my google revealed:
Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
as long as, so long as (subord. conjs.)
These two are interchangeable and Standard; they mean “since,” “during the time that,” “if,” and the like: As [So] long as you’re satisfied, I am too.
https://www.bartleby.com/68/53/553.html