CNN reports that Mnunchin has called the nation's largest investment banks over the weekend to reassure them that Trump will not fire Powell. There is a copy of his letter on Twitter. Treasury is one of the departments shut down. CNBC has a story on his letter noting that Treasury has essential employees on the job and that the system has normal liquidity.
Here's a typical article on Yahoo! on the markets, with a comparison to 1987. I remember Oct. 19 that year well. A friend met me at SFO airport and told me that the market had crashed.
The media, especially CNN, makes a lot of the partial shutdown.
Update Dec 25
Catherine Rampbell on how Trump would handle a financial crisis.