ITHACA, N.Y. — To quote the website Urban Dictionary, Ithacating is “A type of precipitation that is unidentifiable – it is usually a mixture of snow/hail/rain/slush coming from the dark grey sky, while it is absurdly cold outside.” Absurdly cold is subjective, sure, but the start of the week is one of those close classic Ithacating cases. It’ll be precipitating, you just don’t know what wet or solid form it’s going to take. It’ll turn drier albeit still mostly cloudy later in the week, with seasonable cold.
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Steady light snow has started to move in across Tompkins County, part of a rather complicated meteorological environment that involves a deep but weakening low pressure area with somewhat limited moisture passing over Ohio and into the Northeast, and a second system developing off the Virginia Coast and tracking northeastward, which isn’t as well organized yet, but will strengthen and has oceanic moisture at its disposal. The current batch of snow is the work of the weakening Ohio system. The batch that will swing through tonight is likely more the result of the coastal system, with a deformation zone (band of heavy precipitation) most likely to occur to the southeast of Tompkins County.
There is limited potential of the Ohio system, temperatures are hovering around freezing, and it’s an unfavorable geographic setup for the coastal system. As a result, precipitation will be limited today and tonight, mostly in the form of snow but with brief periods of sleet, graupel (snow pellets) and rain possible. Temperatures will stay in the low 30s overnight. By Monday morning, the warmer spots by the lake may see a new inch of snow, and up on the hills perhaps a little more, 2-3″. Not a big deal as winter weather goes, but give yourself time to brush off the car and do be careful if you’ll be out driving this evening, as untreated roads may be slick with that icy mix.
While too far south and east to pose much direct risk, the counterclockwise flow of the coastal storm will provided for an unsettled Monday as northerly winds blow across Lake Ontario and allow for some lake-enhanced rain and snow showers. With highs in the upper 30s under overcast skies, generally these will be a cold rain, and should any snow fall, no accumulations are expected locally. As the coastal storm lifts away to the east, there will be a lull between it and a high pressure system centered over the Lower Mississippi, which will allow for calm air Monday night with a few lingering lake effect snow showers as they dissipate with the loss of wind fetch across the lake. Expect cloudy skies, perhaps a coating of new snow at most, and lows around 30°F.
A weak shortwave (pulse of instability) will pass through Tuesday, a sort of “spoke” the “hub” that is the coastal storm, so this will keep conditions cloudy with a few light snow showers present, but nothing particularly threatening. Highs will be in the mid to upper 30s. Tuesday night will host cloudy skies and a few lingering snow showers as the short wave heads east, with a low in the upper 20s.
Wednesday will generally be dry, but cloudy with an isolated snow shower or two possible as broad counterclockwise flow builds with the strengthening of the low to the east, meaning northerly winds and some lake-enhanced instability. Highs will be in the mid 30s. Wednesday night will be mostly cloudy and dry as the Atlantic low’s eastward motion counteracts its broadening circulation, and lows will be in the mid to upper 20s.
From Thursday on, the Southern Tier will be under the influence of a Canadian high, but far enough southeast of its core that frigid polar air is not expected. It will be mostly cloudy Thursday with highs in the mid 30s. Thursday night will be mostly cloudy and dry with lows in the mid 20s.
Expect more of the system fro Friday as the high stays largely in place. It will be mostly cloudy with highs in the mid 30s. Friday night will see partly to mostly cloudy skies and lows in the low 20s.
Saturday and Sunday are a bit of a tougher call at the moment as a storm system builds in the Lower Mississippi River Valley and moves around the broad flow of the high. At this point, it looks too far southeast to penetrate the high’s influence, but things can change in 5-7 days, so if you have outdoor weekend plans, keep an eye on the forecast. For now though, on the gambit that the models remain consistent in their interpretation and the low stays to the southeast, expect mostly cloudy skies Saturday and Sunday with highs in the low to mid 30s and overnight lows in the lower 20s.
Looking ahead into mid-January, the large-scale dynamic models favor a broad jet stream ridge that allows warmer air to move poleward, but unstable weather around the Gulf of Mexico is likely to contribute to cloudiness and slightly cooler than normal conditions in the Deep South. Bear in mind, when talking above normal in these circumstances, we’re approaching the annual climatological bottom for average highs (which is what the dashed lines are in the plots above, the daily average is about 25°F in Ithaca in early January), so we’re still talking chilly, with perhaps a few degrees more than typical highs in the low/mid 30s and lows in the teens that are usual for this month.