ITHACA, N.Y. — You’ve probably heard the old line, “if you don’t like the weather here, wait five minutes.” It’s going to be one of those weeks where you’ll need the umbrella, the winter coat, the rain coat and the rock salt/de-icer depending on the hour. Buckle up.

Graphic courtesy of the Northeast Regional Climate Center.

Weather Recap

As readers may recall, things were a bit busy last weekend, so the monthly weather recap didn’t take place as scheduled. But, taking a late look at the statistics for November 2019, it was undoubtedly a cold month. According to the Northeast Regional Climate Center (NRCC) and Cornell’s Game Farm Road weather station, the average temperature for November was a brisk 34.1 °F, 5.5 °F below normal. That’s good enough for the fourth-coldest November in Ithaca’s 119 years of valid November records (we toss out the eight years from 1918-1925 because the record-keeping was intermittent). The only years colder were 1901, 1951 and 1976. Across the Northeast and Mid-Atlantic, not a single one of the stations under the NRCC’s purview was above normal. Interestingly enough, the fifth coldest year was just last year, 2018.

Doing a little statistical legwork, 2010-2019 would be expected to have three or four years of November average temperature extremes, either in top 20 coldest Novembers or top 20 warmest. In fact, it had six. 2011 and 2015 are in the top 20 warmest, while 2013, 2014, 2018 and 2019 are in the top 20 coldest Novembers. Normally, when I write about the “missing middle”, it’s in a housing article. Here, we could use it to describe our temperatures; in recent years, we have been more prone to swinging to extremes.

Is that related to climate change? Possibly, but not certainly. In a paper published in the scientific journal Nature back in 2018, a group of atmospheric scientists argued that climate change may be resulting in an increased frequency of early-season and late-season severe cold snaps for the Eastern United States. The argument that they make from analyzing decades of observations is that the mid-latitude jet stream is weakening – the jet stream is maintained by temperature and pressure gradients between warmer mid-latitude and colder polar regions, so as the Arctic warms faster than everywhere else, the temperature gradient and jet stream weaken, causing it to meander and letting cold surges and storms shape more of its path. Even among atmospheric and climate scientists, the study is controversial – not the climate change part, but rather, if jet stream behavior is actually directed by Arctic warming. As statisticians say, correlation doesn’t mean causation.

Graphic courtesy of the Northeast Regional Climate Center.

On the precipitation side, at least, there was nothing especially noteworthy. With 2.53″, the month was on the dry side (3.16″ is the average), but not extremely so. Snowfall was also a hair below normal, 4.0″ vs. 4.5″ expected by the end of November.

Then December 1st came. Hey, we’re not abnormally dry anymore!

Your Weekly Weather

This week is likely to add some more inches or fractions thereof to the total precipitation, though thankfully most of it should come in liquid form. Starting off this Sunday evening, we’re on the backside of a high pressure system over the Atlantic and continuing to move eastward. Sunday warmed up nicely in Saturday in large part because the flow around highs is clockwise in the Northern Hemisphere, so the backside is a milder southerly wind.

Coming into our region for Monday and Tuesday is the warm sector of a large area of low pressure trekking northeastward from the Great Plains, over Illinois and Michigan and into Canada. That path keeps the Southern Tier in the warm sector of its flow – lows have counterclockwise flow in the Northern Hemisphere, so their milder southerly flow happens ahead of them. Tompkins County will still have rain and grey skies, but let’s be honest, no one really feels like shoveling another foot of snow right now.

With the low and high in tandem, the stiff southerly breeze will allow temperatures to actually tick up a little bit tonight, from about the mid 30s now to upper 30s by daybreak Monday morning. It’ll be cloudy, and by the time of your Monday commute, rain will begin to enter the region. Don’t expect heavy rain and don’t expect it to be constant; it’s looking like light to moderate rain showers scattered throughout the day – not a soaker, but a presence all day long and into the evening. With that southerly wind still going strong, temperatures will continue to climb even after sunset, from low 40s in the morning to upper 40s by late Monday evening. Total rainfall amounts will be between one-quarter and one-half of an inch.

Tuesday will have an early high temperature in the upper 40s, maybe before sunrise or shortly after. At around that time, the low crosses Ithaca’s longitude well to the north, but that still places Tompkins County on the backside of the low, so northerly winds will kick in. Expect scattered light rain showers and cloudy skies throughout the day, with temperatures dropping to about 40 °F by sunset. The rain will taper off Tuesday night as the low moves further away, but the clouds will linger, so expect dry if cloudy conditions and a low in the upper 20s.

Wednesday will be cold but mostly dry except for some isolated flurries – the lake effect machine will likely turn on, but the winds will be due westerly, so Tompkins County will be far away from the downwind lake effect snow bands. Expect a flurry or two with mostly cloudy skies and a high in the low 30s. Wednesday night will cold and quiet, with mostly cloudy skies and a low in the upper teens.

Thursday is looking to be the coldest day of the week, as a high moving in from the west reinforces the northwesterly flow of Arctic air into the Southern Tier. Highs will stay in the upper 20s with mostly cloudy skies and an isolated snow shower or two, but as the high quickly shifts to our east during the afternoon hours Thursday, winds will turn light out of the south and slow the drop in temperature. Lows Thursday night will hold around 20 °F in Ithaca and the upper teens in the outlying areas.

Friday will be modestly warm and partly sunny. With the southerly flow from the high, temperatures will make in into the upper 30s for highs. Friday night will only fall back to the mid 30s before stronger southerly flow raises temperatures. It’ll be in the low 40s by Saturday morning and upper 40s for a high as another low tracks up the Mississippi and Ohio River Valleys, once again placing us in the warm sector and bringing rain. Saturday night will only fall back to the upper 30s with scattered rain showers, and Sunday will be periods of rain and cloudy with a high in the low to mid 40s.

Graphic courtesy of the NOAA Climate Prediction Center.

Extended Outlook

For those who want that “White Christmas”, there are mixed signals in the medium range. One thing to keep in mind is that we have snow on the ground now, but the warm spells early this week and next weekend will melt a lot of that with little sign of replenishment. Not all hope is lost, though. The second half of December is looking to be on the wetter side as we find ourselves on the edge of a ridge in the jet stream, so all you need is a storm to come through at the right time (i.e. during a brief colder period) to drop a few more inches to make your holiday merry. However, based on the indicators so far, the chances of a green Christmas appear to be growing.

Brian Crandall

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