An unforecasted dilemma

Thank you, John. That's absolutely and refreshingly true. Now here's the real question. If such words are valid but not explicitly listed in the dictionary, do they count as valid words in the game "Scrabble"?

Just to let you know, Microsoft's built-in dictionary is lame and I would never use it as a standard. I have to use the "add word" function often.

I don't know how the OP was wanting to use 'unforecasted' in a sentence, but I would say it's probably not the word to use unless it's being used to describe something that is normally forecasted (such as the weather or stock market trends).

A 'forecast' conjures up (in my mind, anyhow) purposely collecting data and performing research in order to reach a supportable theory of what is likely occur in the future.
ex: "After analyzing recent trends in the marketplace, we forecast that this company will see healthy profits well into next year".

Its synonym 'prediction' (in my mind) differs in that it is does not necessarily involve any purposeful research - it may even be nothing more than a random, spur of the moment guess.
ex: I predict that the Colts will win the Superbowl, with a score of 32-17.

When the Colts lose 50-3, *I* will say, "Well, I didn't quite predict that, did I?". Meanwhile, the master statisticians who picked the Colts as favourite after identifying and comparing hundreds of factors specific to this matchup - well, I would expect them to shake their heads and say, "A Bears blowout - that was certainly unforecasted!" :o)

So as for using the word in regards to a dilemna or problem - chances are the current unfortunate situation was just unforeseen or unpredicted, and not due to an incorrect forecast. Use the word 'unforecasted' according to the situation.

Nope, doesn't count for Scrabble, despite the validity, it has to actually be listed in the dictionary, and the official Scrabble dictionary, sadly, is the wholly lacking Merriam-Webster's.

Doesn't the word "forecast" come from 'fore' (as in beFORE) and 'cast' (as in, to cast dice or knucklebones)? The Romans (among countless other more recent peoples, I am sure) used to cast the knucklebones of sheep as a way to predict the future. So forecasting is literally casting some kind of set of aleatory objects to see how they land or arrange themselves, and specifically, doing so beFORE the event that is being predicted. I mean, clearly, we don't do that today when we forecast the weather, I just think that when you look closely at a word you can find that nuance is quite a personal thing and that while meaning per se might be agreed upon, we each have our own possible and perfectly valid ideas of nuance.

I experience the same issue with this word. My use is specific to an event that was "forecast" and a variance was not properly included in the data collection.

For example: "The original forecast called for a demand of one million units at account X for product Y. Unfortunately, the unforecasted drop in demand due to condition Z will likely net only half"

My dilemna is whether the use should be "unforecast" or "unforecasted"

The past participle of 'cast' is 'cast' for instance 'After they had cast their bets.....'
So it should be 'unforecast' without the 'ed' for instance 'the forecast thunderstorm did not come about.'