This pick up in near-term strength bodes well for small caps over the coming week, but it should be noted that the broader indices like the S&P 500 and Dow Jones Industrial Average are nearing exhaustion.
The biggest USA lender by assets said the new tax law would help future profits by not only reducing the amount it pays the federal government but also by stimulating more business.
Earnings from big banks were mixed, with JPMorgan Chase rising 1.7 percent after beating expectations, even as profits were hit by one-time effects of the tax law changes.
The Russell 2000 is up 56.46 points, or 3.7 percent.
The S&P 500 is up 43.09 points, or 1.6 percent. The tech-heavy Nasdaq Composite Index is up by more than 5 percent.
Warm weather and heavy rain could cause flooding
The weather service in Huntsville said a light glaze of ice and up to a half inch of snow will be possible through this evening. A band of heavier snow is expected to stretch from near Glacier National Park southeast toward the Lewistown area.
Bank stocks also gained from a rise in Treasury yields after underlying USA consumer prices for December posted their biggest gain in 11 months, signaling a pickup in inflation.
Sales at online retailers soared 1.2 percent. Home Depot rose 1.6 percent and Walmart rose 1 percent.
The Dow is up 507.32 points, or 2 percent.
Friday's gains also followed a strong December US retail sales report, which lifted annual retail sales by 4.2 percent, the biggest increase since 2014. On the Nasdaq, 1,808 issues rose and 1,069 fell.