ITHACA, N.Y. — Remember last year, how much of December was pleasantly warm, and it was nearly 70 degrees on Christmas Eve? Yeah, so do we. Which is gonna make the polar sting of the next couple of days hurt that much more.
Two rounds of Arctic air are expected to swing through the region over the coming days, with the first icy blast coming in on the heels of a cold front later this evening. As a result, it’s going to be cold. Really cold. High temperatures Thursday and Friday will struggle to make it out of the teens, and most places in Tompkins County can expect low temperatures early Friday morning to be hovering just above or right around zero degrees.
While those numbers aren’t especially impressive, the bigger concern will be the strong northwest winds that will kick up with the entry of the Arctic air mass. With winds gusts of up to 30 MPH, wind chills into the -10 to -20 degree range are possible. Over this time period, Ithaca and its environs can also expect snows of 2-4 inches, mostly a result of lake effect snow bands passing over the region.
In some news outlets, they’ll talk up the polar vortex as the scary science of the day. Truth is, the polar vortex isn’t all that unusual or scary. Typically, it sits over the North Pole, but in cases where the vortex weakens (which can be due to a number of factors, like stratospheric warming events and atmospheric teleconnections with El Nino phases), parts of its frigid air mass can spin off and press southward against the jet stream, where it interacts with mid-latitude systems to create ridges of high pressure and troughs of low pressure (the troughs being the spun-off parts of the vortex). If one is under the ridge, conditions are warmer than normal, and if one is under the vortex, it can be a real bone-chiller. Your cold snaps and your January thaws.
Adjacent air masses help determine the depth and size of the vortex, and eventually the cold air moderates and the vortex weakens enough that the cold air mass recedes back to the polar latitudes, or breaks off from its polar source, becoming a cut-off low and melting away like a chunk of ice in a warm drink.
After that glacial chill on Thursday and Friday, local conditions will change rather dramatically as warm air gets pumped up by a low pressure area passing over the western Great Lakes and eastern Canada – Ithaca will be under a warm jet stream ridge ahead of this lobe of the polar vortex. As a result, temperatures will rapidly rise above freezing on Saturday, and it comes with the risk of some mixed precipitation – snow, to wintry mix, to cold rain Saturday evening and night, and then back to snow showers on Sunday as the low passes and cold air flows back into the area as part of Arctic air trough number two.
However, luck is on Ithaca’s side, as much of the Arctic air in the second wave is expected to moderate after sitting over the Midwest and Upper Great Plains for a couple of days. As a result, Monday and Tuesday are looking to be sunny, with temperatures just a little below normal, in the mid to upper 20s F for highs and lows in the teens.
Here’s the TL;DR for you cool kids – if you’re going to Minneapolis, Chicago or Standing Rock in the next seven days, it’s going to be frigid and unpleasant. Here, it will be cold, but not abnormally so – some areas could flirt with setting record lows, but there will only a few at most.
Looking longer term, the Climate Prediction Center is hinting at a deep jet stream trough in the western U.S., and a ridge in the east. That means warmer than normal temperatures are a good possibility as we near the Christmas holiday. Don’t expect anything like last year though – the temperature anomalies are expected to be modest, so upper 30s or 40s perhaps.