ITHACA, N.Y. — After what had been a fairly warm and quiet week for February, winter has reloaded and has Tompkins County in its crosshairs. A Winter Storm Watch has been issued for what is likely be a substantial snowmaker, ice glazer, and commute-wrecker Tuesday.
After subzero temperatures, a change of pace was welcome. And what a change of pace it was. At the airport, temperatures swung from a low of -11 °F on the morning of February 1st to a high of 62 °F on last Monday the 4th. At the Cornell Game Farm Road weather station in Dryden, the temperature swing was even greater, from -14 °F to 61 °F. It’s not something that’s easily tracked in the climatological record, but there are likely few swings more extreme than that in Ithaca’s recorded meteorological history.
With the passage of a cold front on Friday, the winds kicked into high gear, with a 43 MPH gust recorded at the airport late Friday night. This weekend was cold, but fairly quiet. However, as winter weather often does, that relative calm is about to change, and you’re going to want to have a shovel and your de-icer of choice handy.
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If there’s any silver lining to the forecast coming up, it’s that there’s no extreme temperatures in the forecast. That said, it will be an active weather pattern, with multiple chances for sleet, freezing rain and ice accretion during the week.
At present, a large and strong area of high pressure is moving eastward out into the Atlantic; Sunday’s highs were a few degrees warmer than Saturday because the clockwise flow around the high tapped into warmer air to the southeast and advected some of that milder air into the Southern Tier. Going into tonight, there is a mid-level atmospheric disturbance passing through the region, but the air overhead is very dry. While some cloudiness and a few light snow showers are likely, it won’t be anything substantial due to the lack of moisture. Lows tonight will be in the mid 20s in urban Ithaca, low 20s in the outlying areas.
Monday is a rather complex setup. A warm front to the south will serve as a conduit for areas of low pressure to traverse northward and eastward, but will battle it out with a cold, dry Canadian high pressure system to the north. For Monday, Tompkins County will be under the influence of that high, and it will be mostly cloudy with highs in the low 30s. As we head into Monday night, those lows and associated moisture and precipitation will eat away at the high’s southern edge, so they’ll slowly advance into the region going through the overnight hours. It’ll be cloudy, the snow is not likely to show up until after midnight, and it won’t be persistent until around daybreak Tuesday morning. Lows will be in the low 20s.
Tuesday’s where things get complicated, and problematic. The weather models are, to varying degrees, forecasting a warm layer in the middle of the atmosphere. Warm air is lighter than cold air, so it tends to ride up and over cold air masses. Now keep in mind, this is coming in while precipitation is already occurring. If you have snow forming up aloft, melting partially into sleet or completely into rain as it passes through that warm middle, and then it hits the ground where temperatures are a couple degrees below freezing, allowing it to fully freeze up again – this could very quickly turn into a major ice event.
Here’s what it’s looking like for time frames. Tuesday morning, the commute will be snowy, and a few inches of snow are likely to fall up through about noon. At that time, sleet is expected to mix into the snow, and that will probably be another inch of a snow/sleet combination. By 3-4 PM, the warm air layer will have thickened enough to turn the precipitation into rain, which with the snow on the ground and temperatures around 30 °F at the surface, meaning it will freeze to untreated roads and other untreated surfaces. Temperatures will slowly climb as we find ourselves wedged between two low pressure systems along the front, but sleet and freezing rain will persist through the evening commute and into Tuesday night, with temperatures warming to above freezing after midnight. It would not be a surprise to have just a cold rain for at least a few others Wednesday morning before sunrise.
Wednesday morning will see a shift to snow, as temperatures hover around 32 °F. There will not be a warm layer to melt the inch or so of snow that falls, but the winds will pick up Wednesday afternoon as the second low passes to the northeast and its rear flank cold front passes through, with gusts up to 35 MPH. Wednesday will be cloudy, around freezing, with scattered snow showers and gusty winds. Wednesday night will see the winds calm as the cold front moves away, and temperatures will drop to the lower 20s.
Keep in mind, this is a really complicated setup with two moisture-heavy lows and temperatures hovering around freezing for most of the event. It will not take much to make it a more snow-heavy event, or a more ice-heavy event. Keep an eye on the forecast and for any updates as the system evolves.
Thursday will be warmer and drier, as a high pressure system over the Southeast draws up milder air. Apart from a few lingering rain or snow showers, it will be mostly cloudy and dry, with highs in the low 40s. Thursday night will be cloudy with lows in the low 30s.
Friday is round two for storm systems, as a second low develops in the southern Great Plains and moves northeastward through the Ohio River Valley. Ahead of the low, its counterclockwise circulation with work with the high to funnel warmer air into the region, so highs are likely to make it into the mid 40s Friday with rain building into the region during the morning hours. Some cooler spots may start off with a freezing rains, but all areas should transition to a cold non-freezing rain by afternoon.
It will rain into Friday night with lows in the mid 30s, and with a second low developing off the coast and rapidly intensifying, a rain to snow transition is expected Saturday, with early highs around 40 dropping to the teens by Saturday night as precipitation tapers off. Sunday will be quieter, mostly cloudy with highs in the upper 20s.
It would be nice if the weather turned mild and fairly quiet after a rough week. It would also be wrong. The atmospheric has been locked in what’s known as a negative phase PNA (Pacific North American) pattern. This is an atmospheric teleconnection to ocean temperatures, and a negative pattern tends to be more common with La Niña events, though the current conditions are neutral. This, combined with an abundance of cold cir and lower-latitude jet stream, will allow a colder-than-normal pattern to dominate over much of the continental United States. There’s some wiggle room here in the Northeast for a more modest cold pattern depending on how the jet stream is oriented and the amplitude of ridges of warm air, but overall, the unusually cold air is expected to shift eastward into the eastern third of the country by the second half of the month.