Turkey's President Recep Tayyip Erdogan ratcheted up the threats the other day.

Turkey said it will “soon” take further steps in northern Syria, as Kurds in the area reported 159 “attacks” in July near Afrin at the hands of the Turkish and its Free Syrian Army (FSA) militias.
"We are determined to extend the dagger we have put into the heart of the terror entity project through the Euphrates Shield Operation with new moves,” Turkish President Recep Tayyip Erdogan told a crowd in Malatya on Saturday, not specifying what entity he was referring to.

It's perfectly clear that Erdogan means Syrian Kurds.

Turkey’s official Anadolu news agency said Saturday that the military dispatched artillery to the border province of Kilis to reinforce units there.
The six-vehicle convoy included tanks and howitzers to be positioned across from the Kurdish-controlled Syrian region of Afrin, according to the private Dogan news agency.
In late April, Turkey began relocating military units to Sanliurfa province across from another YPG-controlled area.

Why now? The Kurdish-controlled areas, outside of their assault on Raqqa, have been relatively quiet in recent days.
One reason might be because the Pentagon's involvement in Syria's Kurdistan has become much deeper under Trump.

Under President Donald Trump, the US-led coalition has developed closer coordination with a collection of militias and tribes called the Syrian Democratic Forces (SDF), directing air and ground assaults. Senior State Department and USAID officials have visited Raqqa’s outskirts to coordinate efforts to help displaced civilians and secure the city’s future once ISIS is driven out. US officials have also carved out a semipermanent diplomatic presence close to the northern Syrian city of Kobane.
...The US and its Western coalition partners, especially the UK and France, have also become increasingly visible stakeholders in the war effort.

If Syrian Kurdistan declared autonomy, it would put the United States in a very sticky situation.

Unlike in Iraq or Afghanistan, Washington has no official invitation from Syria’s government in Damascus, and stopped disclosing numbers of deployed troops months ago. But there are believed to be around 2,000 US Army Rangers and Marines, along with Special Forces personnel, in Syria, and the Pentagon’s 2018 budget includes $500 million to train and equip Syrian forces fighting ISIS.

Maybe it's because of our increasing presence in Syrian Kurdistan that Turkey's news agency provided a map and details of U.S.-run military outposts in northern Syria.