The GDPNow model incorporates the balance of trade (imports vs exports) in its model. Some companies front-loaded imports recently to try to combat immediate effects of potential tariffs (a hedge of sorts), which drastically changed the recent balance of trade, and likely impacted the GDPNow model predictions.

That said, predicting the economy in the short term is a loser’s game in general. Most (all?) economic models break completely when something changes direction.

“More heat than light” by Philip Mirowski is a great primer on the fallacies of neoclassical economics, and how they try to emulate the sciences and create physics-like models and equations which fail to actually model or forecast the ‘real’ economic world. Modern economics is not a science, but is envious of science.