It was a snow squall. A burst of heavy snow that causes whiteout conditions the size of a thunderstorm
A snow squall often is a thunderstorm - just one that happens when it's too cold to rain.
It's pedantic, but a thunderstorm only occurs after a weather observer hears thunder or sees a lightning bolt. It has nothing to do with size or type of precipitation. I'm assuming the NWS called it a squall since it's a common occurrence and the local weather reporters would have used thundersnow if it was a thunderstorm because every meteorologist, weather forecaster, and weather observer I've ever known loves to report thundersnow. (I have no idea why, but it's somewhat rare and fun to say.) I was an AG in the Navy in the early 80's; my first eleven weeks after boot camp were an eleven-week weather school at an air force base.
Strangely, a thunderstorm only requires thunder. It does not require any precipitation.
That may be true of how weather is officially reported at observation stations, but in terms of how a snow squall forms - they are caused by convection (i.e. showers, not just widespread steady precipitation), which is also what you need to generate thunder and lightning. Many snow squalls occur with convection intense enough for some sort of thunder and lightning to occur (it's harder to get lightning in winter because it's often too cold to get enough instability in the atmosphere for it). And yes, thunderstorms can absolutely occur without precipitation at the surface: as you're probably familiar with, the most common way for this to occur is a hot, dry summer day in the west with just enough moisture for a storm, but all the rain evaporates long before it reaches the ground. This is a great way to generate strong to severe wind gusts at the surface, which is a great way to spread fires the storm just started thanks to lightning.
For a snow squall warning to be issued by the National Weather Service, a very precise set of criteria has to be met: visibility must drop below a quarter of a mile and ground temperatures must be below freezing, causing dangerous and life-threatening conditions that will not last more than an hour. (If they last longer, it's not really a snow squall anymore and a winter storm or blizzard warning is more appropriate.)
I should also note that NWS stretches the definition of "thunderstorm" on some occasions - in my experience a severe thunderstorm warning will be issued whenever any convective storm is producing wind gusts over 58mph or 1 inch hail, even if no lightning has necessarily been observed.
I'm a meteorology student now and one of the things you learn is in this field, there's almost always a job out there for you somewhere (you just may not know where to look). Weather is everywhere. Even if you're not at the NWS or a TV station, places like the military or various companies often need meteorological expertise in some capacity to help them make decisions. As for why thundersnow is so common...I'm not sure, other than that it's relatively rare? Jim Cantore certainly made it more popular to talk about it.