ITHACA, N.Y. — After last week’s wild weather, a less perilous if still active weather pattern is in store to close out 2020. A storm system entering into the Southern Tier promises a wet if mild New Year’s Eve. Weaker storms during the day Monday and during Wednesday night portend a fairly grey week ahead, though most of the precipitation will be rain instead of snow.
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Overcast skies have steadily broken apart to allow in a generous amount of sunshine this afternoon as high pressure system briefly builds in from the south-southeast. The southerly flow on the backside of the clockwise-circulating high has also allowed temperatures to warm up a few more degrees over Saturday, with highs in the mid and upper 30s throughout Tompkins County and most of the Southern Tier.
Unfortunately, this brief period of blue skies will be coming to an end as an area of low pressure passes to the northwest. On the bright side, that track to our northwest places us in the warm sector of the storm system’s counterclockwise circulation, and so most of the precipitation will come in the form of rain rather than snow.
Temperatures won’t be dropping much overnight tonight as cloud cover builds back in and the southerly flow is enhanced by the incoming storm. The low around of around 30°F will occur some time during the evening, before ticking up a few degrees overnight to something closer to the mid 30s with gusty southerly winds and overcast skies Monday morning.
Monday will be a grey day with some scattered rain showers, though a few higher elevations may start the day with a few snow showers before switching over to rain. Highs will top out around 40°F with new rainfall amounts less than one-tenth of an inch. The storm system will pass Ithaca’s longitude by about sunset, which will allow cold air to work its way in on the storm’s backside Monday night. Rain showers will change back over to snow, but new accumulations will generally be an inch or less, with cloudy skies beginning to break up by morning, and lows in the low 20s.
Tuesday will be chilly but generally quiet as high pressure briefly builds in once again. On the smaller (meso) scale, some lake effect snow is possible north and east of Ithaca, but locally any snow showers will be brief and light, with little new accumulation expected. With the northwest wind, highs will only top out in the upper 20s under mostly cloudy skies. Tuesday night will see the fetch shift and any snow showers in the vicinity will reorient northward and away from Tompkins County, and some of the cloudcover will dissipate as well. These clearer skies will allow for a cold night with lows in the mid to upper teens.
Wednesday will be somewhat milder as the high progresses eastward, and it will be a calm, seasonably cold winter day with partly cloudy skies and highs in the mid 30s. However, cloud cover will build steadily through the day to near-overcast by sunset as the next storm system begins to work its way in. This will be a broad, multi-pronged system (really, a pair of storms) extending from Texas to Canada and bears similarities to last week’s Christmas Eve storm. However, the storm will not have the same deep tap of moisture into the Gulf of Mexico, which would keep new precipitation amounts lower, though the size of the storm system will once again bring temperatures well above normal Wednesday night and Thursday. Wednesday night will have an evening low of around 30°F before southerly winds build and bring the air temperature into the upper 30s by sunrise, and apart from a few rain or snow showers building in by sunrise, it should be dry otherwise.
Looking at Thursday, it will be a cloudy, rainy end to 2020, though temperatures will warm to near 50°F by early afternoon. The first storm moves eastward over Quebec, while the stronger low over the Mississippi River Valley begins to ride along the frontal boundary through the Great Lakes and into Canada. It stays to the west, so we stay in the warm sector, but it brings in a reinforcing shot of precipitation. By late afternoon, the rain will be a steady light to moderate event, so if you have outdoor celebration plans for New Year’s Eve, you’ll want an umbrella, though the extra layer of warm clothes can stay home. Expect cloudy skies and periods of light to moderate rain as we ring in 2021, with lows overnight in the low 40s. Early Quantified Precipitation Forecast (QPF) estimates suggest a half-inch to one inch of rain Thursday and Friday.
The rain will begin to wind down late in the morning on New Year’s Day Friday as the low moves away to the northeast, with scattered light rain showers persisting through the afternoon. The system won’t clear Ithaca’s longitude until about sunset, and that will allow for another mild winter day with temperatures in the mid to upper 40s. Winds will shift to the northwest during the evening Thursday, but only a few lingering showers will be left to change over to snow as we head through the overnight, with mostly cloudy skies by morning and lows in the upper 20s.
A look at the first weekend of 2021 suggests a fairly pleasant Saturday and Sunday by January standards. Dry conditions will prevail as high pressure builds in from the southwest. Plan for mostly cloudy skies with highs in the mid to upper 30s both days, and mostly cloudy, dry conditions overnight with lows in the mid 20s.
For those who prefer warmer winter days, the long-term outlook is in your favor. Forecast models show a persistent ridge over the Eastern United States for the first half of January, which would allow for warmer air into the region. However, its orientation would also allow system to work their way up the Mississippi River Valley into the Great Lakes and Canada, much like our Christmas Eve and New Year’s Eve storms. This continues to provide milder air, at the expense of more frequent and/or higher-amount rain events, so we’ll likely be on the wet side over the same period.