ITHACA, N.Y. — As we’re now entering the throes of meteorological winter, where Mother Nature loses its patience with us and throws us at its mercy, we’re in for at least a quiet week ahead, with generally dry conditions and increasingly warm temperatures as we head through the week.
Your Weekly Weather
It’s been a mostly cloudy day with some scattered light snow bands coming southward from Lake Ontario. As the coastal low that strengthened Friday into Saturday deepened and moved northeastward, its wind field expanded to tap into ever greater amounts of polar air in Northern Canada. That frosty air is now wrapped into the northerlies on the backside of its counterclockwise circulation, passing over the relatively warmer waters of the lake. The resulting heat energy transfer basically feeds the development of clouds, convection and the lake effect snow bands we’ve seen this weekend. The snow accumulation has been light and patchy, enough to make the roads slick but otherwise nothing more than a nuisance – in contrast, being stuck in the storm’s cold backside as well as its precipitation shield resulted in snowfall totals of over one foot in central Massachusetts.
Let’s start off this week’s forecast by noting there is nothing like that in this week’s forecast. If you love the snow, enjoy the meager amount there is. If you don’t love the snow, you can feel better knowing dry conditions and a warming trend will melt that snow away as we head through the week.
Things will be fairly quiet in the short term, as high pressure over Canada provides a cold if stable air mass aloft. The winds will shift to a more west-northwesterly angle heading into the overnight hours Sunday night, and this will steer any further lake activity back to the northeast towards Syracuse. However, the cloud cover will be persistent, which will limit the drop in temperatures. Plans for a few scattered flurries but no accumulations, and mostly cloudy skies with lows in the mid 20s in Ithaca’s urban core and along Cayuga Lake, and low 20s in the outlying towns.
Monday will be a cold but generally quiet day as the northwesterly flow keeps temperatures in the low 30s for highs with mostly cloudy skies as some low-level moisture persists, and a weak short wave (pulse of instability) passes in the periphery of the coastal low, which will be making a mess of Atlantic Canada. This short wave may produce some more persistent snow showers in tandem with the instability of the lake (enhanced lake effect, basically), but there’s enough dry air mixed in the mid-levels of the atmosphere to keep accumulations very light if any, less than half of an inch, and that would mostly fall in the 3-6 PM timeframe. After that shortwave passes Monday evening, though, things should turn quieter once again, with cloudy skies Monday night and lows in the low to mid 20s.
Tuesday will be another chilly day, as northerly winds pick up with another developing coastal low, but this system will be too far south and east to provide anything in the way of precipitation. It will be partly cloudy with highs in the mid 30s. Tuesday night will be mostly cloudy with lows in the mid 20s.
A trough will dig into upstate New York from Canada Wednesday, but the southeastward movement of the trough really puts the potential precipitation threat to the north and east of Ithaca, and with a building ridge over the Midwest, westerly winds behind the trough will channel somewhat milder air into the Southern Tier. It will be mostly cloudy with a few rain showers in the afternoon and evening hours, with highs in the low 40s. Wednesday night will be dry, with mostly cloudy skies and lows in the low 30s.
Thursday will be warmer and sunnier as a ridge of high pressure builds in from the southwest. Plan for partly cloudy conditions and highs in the mid 40s. Thursday night will be continued calm conditions, with partly cloudy skies and lows in the low 30s.
Friday will likely pretty prove even warmer as the flow of warm air increases ahead of a storm system over the Great Plains. It will be mostly cloudy with highs in the upper 40s. Friday night will host mostly cloudy skies with lows in the low to mid 30s.
The weekend will be on the warm side for mid-December as southerly flow continues ahead of the Great Plains low, but it will be unsettled as that storm passes to our northwest. This direction of motion will keep us in the warm sector of the low (reminder, air flows counterclockwise around northern hemisphere low pressure systems) until it passes our longitude Sunday night, when colder air begins to come down on it backside. But in the meanwhile, expect scattered rain showers Saturday with highs in the upper 40s, a mix of rain and snow showers Saturday night with lows in the mid 30s, and rain showers Sunday with highs in the mid 40s.
Extended Outlook
Looking ahead into the second half of the month, the pattern generally favors a broad jet stream ridge centered over the upper Great Plains, with some variability in its maximum amplitude to allow for enhanced precipitation potential over the Pacific Northwest and the Northeast. At a glance, this is not a favorable pattern for a White Christmas, but as always with temperatures sliding above and below freezing on a near-daily basis, timing of precipitation will be everything.