Thanks for the heads-up, U.S. Stratcom!
A nuclear exchange would be survivable for most. I-131 decays out very quickly (a few days), and slower decaying elements (e.g., cesium) aren’t dangerous unless ingested and soon wash away with rain and sink into soil. There are quite a few sites and books with instructions for surviving fallout. Most long range nuclear weapons are very low yield now due to improved accuracy (better for the environment).
The only weapons now that would generate much fallout would be cratering devices (ground bursts), which would be aimed at remote military facilities and very long airstrips suitable for bombers. Air bursts would generate much less fallout.
I bet their declaration of an unpredictable environment won’t change the amount of money they have budgeted or staff billeted for predicting things.
“The spectrum of conflict today is neither linear nor predictable.”
Since militaries suck at responding to nonlinear and unpredictable things this is very bad news. The most nonlinear and unpredictable thing in the US military is the chain of command.