The polar vortex has broken loose from its northern confines, bringing brutally cold air, the likes of which has not been seen for nearly twenty years, into the central part of the continent today. That frigid air will arrive in the city this evening, making for a bitterly cold day tomorrow.

What is a polar vortex anyway? In this case vortex is just a scary-sounding word for the two semi-permanent low pressure systems that normally spend the winter north of Baffin Bay or over Siberia. What's happened this week is that a big trough in the jet stream has managed to dislodge the vortex and send it southward so that it will pass just north of the Great Lakes before heading toward Greenland. Perhaps the most unusual thing about this polar vortex is how long it has been since the last outbreak of this magnitude. Twenty years! These things used to happen much more frequently.

The cold front that is the leading edge of the frigid air mass passed through the city this morning and we'll see our temperatures plunge to near freezing by evening and into the single digits by tomorrow morning, close to January 6th's record of 6 degrees. On top of that the winds are expected to pick up to around 20-25 mph, with gusts greater than 40 mph, pushing wind chill values to -15 degrees or worse. That's cold enough to cause frostbite to exposed skin in less than 30 minutes so be careful out there! Also keep in mind that all the water from today's rain and melting snow is going to freeze solid overnight.

The NYC Office of Emergency Management has issued a number of tips for making sure you make it through this vortex with all your fingers and toes. In addition to slitting open a Ton-Ton and taking refuge inside, the OEM suggests:

  • Wear a hat, hood, or scarf, as most heat is lost through the head.
  • Wear layers, as they provide better insulation and warmth.
  • Keep fingertips, earlobes, and noses covered if you go outside.
  • Keep clothing dry; if a layer becomes wet, remove it.

Read the full breakdown of advice here.

Tomorrow is only going to warm to 10-12 degrees or so and the wind chill will stay in the negative teens all day. However, the temperature will begin to rebound on Wednesday as the polar low heads toward Greenland. Wednesday's high looks like it will reach the mid 20s. We could be above freezing by Thursday and easily into the mid 40s on Saturday.