ITHACA, N.Y. — Ithaca got its first taste of snow last week, now comes the second helping; a storm system likely to drop 2-5″ in Ithaca and potentially up to 8″ north of the city Monday night into Tuesday morning.

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The broader weather setup is something like this – an area of low pressure will develop in the lower Great Plains and lift to the northeast during the day Monday, and track along a stationary frontal boundary. Two features will determine the amount and timing of snowfall – moisture and resulting precipitation, and the cold air wrapping itself around the storm’s counterclockwise flow.

Image courtesy of the Univ. of Illinois Urbana-Champaign.

Generally speaking, areas south and east of the low will receive most of their precipitation in the form of rain with a quick hit of snow as the system moves past, but if an area is to the north or west of the storm, it’ll already be in the cold sector due to the frontal boundary, temperatures will be at or below freezing as the precipitation moves in, and the snowfall will be much longer with much higher accumulations. How much snow you get is totally dependent on where you are along the storm center’s path – cold sector, warm sector, and when you transition over from the warm to cold sector.

Graphic courtesy of NWS Binghamton.

That snow gradient shows up quite well in the blend of model outputs analyzed by NWS Binghamton. The low practically tracks very close to Ithaca as it moves from southwest to northeast, strengthening as it goes. Cold air will take longer to work in, so a lot of the precipitation will have already fallen as rain by the time enough cold air has worked it way in to transition the rain over to snow. Areas north and west of Ithaca will have cold air in place sooner.

Trumansburg, Ulysses, Lansing and Groton should plan for 3-8″ (the wider range than normal being because of that tight snow gradient). South and east of Ithaca in the valleys of Danby or Caroline will see 1-4″. Newfield, Enfield, Ithaca, Lansing village, Dryden will see 2-5″ in most places, with amounts a little higher on hilltops, and lower in the valleys where a little remnant warm air will delay the rain-to-snow transition.

For timing, we’re expecting the transition in Ithaca around 4-5 PM Monday, with snow falling at a steady light to moderate pace through about 5 AM Tuesday morning, with showers and a another inch possible during the day Tuesday. Temperatures will not get above freezing for a couple of days, so don’t plan for the snow to melt off quickly.  The transition to snow will be around 3 PM Monday in towns north and west of Ithaca, and as late as 7-8 PM Monday in warmer areas south and east of Ithaca.

There is also the risk of ice accretion on roads and exposed surfaces south of Ithaca – while the transition to snow is delayed, it is possible that rain will freeze at the surface prior to the arrival of snow Monday evening. Travel will be potentially hazardous south of Ithaca.

At the moment this Sunday evening, temperatures are pulling back through the 40s as cloud cover slows the drop in air temperature. Rain showers and a steadier rain will build ahead of the system, so expect a few scattered rain showers early tonight, with more persistent rains by late morning and early afternoon Monday. Overnight lows will be in the mid 30s, and the temperature will only climb a degree or two in Ithaca before the cold air makes its way into the region. Areas closer to Binghamton and the push of warmer air ahead of the low will see temperatures rise to about 40 °F before falling back. Lows will be in the mid 20s Monday night.

Tuesday will start with light snow, winding down as the low pushes through New England and into Canada. Most places can expect another 1-2″ from scattered snow showers, with mostly cloudy skies otherwise. The air will be the coldest so far this season, with highs in the mid to upper 20s in the valleys, and low 20s on the hilltops. Tuesday night will see clearing skies and frigid conditions, with lows in the low teens in Ithaca, and 5-10 °F above zero on the hills.

Winds will be sustained from the northwest and sustained around 15 to 20 MPH with gusts up to 30 MPH possible. Expect wind chills in the single digits and teens above zero during the day, and below zero on the hills at night.

The rest of the week is quiet, as an arctic high will result in quiet but very cold conditions down to the Florida coast (it’s not often the models show snow in Alabama in November). Wednesday will see see a few lake-effect snow showers early, but partly cloudy skies otherwise, and a high in the upper 20s. Wednesday night will be mostly cloudy with a low in the mid teens.

Thursday will be a little milder as the core of the arctic high shifts east, putting us in southerly winds on the backside of its clockwise flow. It will still be quite cold for November, with a high in the mid 30s with partly cloudy skies. Thursday night will be mostly cloudy with a low in the mid 20s.

Friday will be a little warmer still as a weak disturbance ushers some milder air in ahead of it. Highs will be in the low 40s under mostly cloudy skies. Friday night will be mostly cloudy with a low in the lower 20s.

The weekend will be cold but quiet, with sunny conditions. Behind the disturbance, highs will only be in the mid to upper 30s Saturday, but milder flow will return for Sunday with a high in the mid 40s.

Graphic courtesy of the NOAA Climate Prediction Center.

Extended Outlook

It looks like the unseasonable cold will last through this week and into early next week, but after that, temperature should moderate to near or even a little above normal (i.e. mid to upper 40s, maybe 50 °F). A trough in the jet stream will be centered over the lower Mississippi River valley, allowing warmer conditions to prevail on the East Coast and West Coast. However, it will also be stormier than normal, as low pressure systems follow along the jet stream. It’s too early to say what Thanksgiving will be like, but the early indications are that it won’t be nearly as cold as last year.

Brian Crandall

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