ITHACA, N.Y. — It’s been a long, cold spell. From Christmas day until about noon yesterday, temperatures in Ithaca never saw the warm side of 32°F. Two weeks of frigid air. But to be fair, it’s also not all that uncommon. According to data from the Northeast Regional Climate Center, Ithaca never once climbed above freezing from February 10th – March 4th 2015, and a second extended cold snap plagued the areas from January 15th-31st 2005.

The Analysis

Jan. 1, 2018 through Jan. 7, 2018 temperature rankings, relative to other such periods. Cities in purple boxes denote those that had at least a top five coldest Jan. 1 through Jan. 7 period on record in 2017-2018. Map tools created and hosted by the Southeast Regional Climate Center (SERCC).

The unseasonable cold was felt up and down the East Coast, with many locations from Maine to Florida and out as far as Texas and the upper Midwest experiencing record cold in the past two weeks. On the flip side of that side of that coin, Alaska reported its warmest December on record, with temperatures 15.7°F above normal. Given that Alaska is twelve times bigger than New York State, that is pretty intense.

The explanation for these unusual conditions is that there was a deep, powerful jet stream ridge in the western United States thanks to a number of reasons (anomalous warm Pacific waters, weather events over Asia affecting the mid-latitude downstream), and like a wave made by shaking a jump rope up and down, a wave in the jet stream that creates a big ridge usually creates a big trough as well. Events at the poles allowed for a weakening and displacement of the “polar vortex”, and parts of the vortex broke off and slid down into the trough with Arctic air in tow. The cold reinforced the trough as the warm Pacific Ocean reinforced the ridge, and once a pattern is in place, it can take weeks to trigger a weather “regime change”.

That’s what is happening now, at least briefly. The ridge is breaking down out West as a powerful oceanic storm invades the coast, creating impressive rainfall amounts and the risk of mudslides in wildfire-ravaged California. In the east, a ridge is building, meaning warmer temperatures are on the way for at least a couple of days.

The Forecast

GFS forecast model precipitation, sea level pressure and 1000-500mb thickness (temperature proxy) for 8 PM Wednesday. Warm air will be moving in from the southeast as rain builds in from the west. Model image courtesy tropicaltidbits.com.

Weather-wise, today shouldn’t be too shabby. With high pressure overhead, it will be mostly cloudy with a few dying flurries, but otherwise dry and topping out in the mid 30s, or right around freezing in rural areas or higher elevations. Tonight will be seasonably cold and quiet, with passing clouds, the bright winter moon, and temperatures in the mid teens with a light northwest wind.

Wednesday looks to be more active. As the high pressure area moves east, a strong area of low pressure will bring moisture and deep warm air towards our region. Mostly cloudy skies will give way to overcast conditions and mixed precipitation ahead of a substantial warm front. If you’re out Wednesday evening, be wary of potential sleet and freezing rain. Whatever does accumulate should be light and brief, as the changeover to rain will be quick. Expect highs in the mid to upper 30s, with temperatures not really falling back during the night as the bouts of rain continue, so Wednesday night will likely stay above freezing as warm air continues to flow (advect, to be technical) into the region.

Thursday and Friday will be warm, quite warm. Problem is, you won’t really get to enjoy it. Right now, forecast models are pretty confident in highs around 50°F both days, and lows in the mid 40s Thursday night. But it will be cloudy, with rain becoming more frequent as Thursday goes on, and Friday is looking like a moderate but steady rain. With moisture tapped from the Gulf of Mexico, the rain will likely sum up to 0.5-1″ over the course of Wednesday night – Friday.

There is some concern from NWS Binghamton that, given the rapid ice build-up in the past two weeks, the big warm-up and the heavy rains expected, ice jams may occur. The snowpack is pretty dry and the river levels are low, but the possibility can’t be totally written off, so keep an eye out if you live in a vulnerable area (near a creek or stream, especially Fall Creek).

Friday night and Saturday are looking a bit complicated. A cold front will slowly push through, and on its backside cold air will rush in, though not as harsh as the extreme cold we’ve seen lately. Models are hinting at possible mixed precipitation and ice accumulation Friday night, so use caution. Temperatures will fall back into the upper 20s Friday night, and stay there during the day Saturday. Martin Luther King Day weekend is likely to finish with temperatures below normal, with highs around 20 Sunday and Monday. If it makes you feel better, a second, more substantial warm spell seems plausible as we go through next week.

Brian Crandall

Brian Crandall reports on housing and development for the Ithaca Voice. He can be reached at bcrandall@ithacavoice.com.