ITHACA, N.Y. — There is a sense of meteorological delirium that goes with the first 70°F day of the season. Some treat it like it’s Heaven on Earth, and they break out the shorts and the grills like it’s mid-June. Everyone deserves to enjoy it at least a little bit – winters are long and cold, and it’s a welcome reprieve.

That said, anyone who’s spent a few trips around the sun in or around Ithaca knows that the first warm days are usually timed with mud season. All the existing snow and ice melts off rapidly, and aside from ice jam issues (which we’ve already had), it means inches of water-laden snow rapidly percolates into the ground – good for groundwater replenishment, but the clay soils and rapid runoff that early spring tends to bring gives the Ukrainian “Rasputitsa” a run for its money.

Anyway, turning towards this week’s weather, we’ll be seeing a cold front come through after sunset tonight, which will bring the temperatures down from today’s lofty highs, and Monday will be a rainy washout. But temperatures will be above average for most of the week ahead, and there’s a few nice days in store later in the week.

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As of this writing, it’s 71°F at the Ithaca-Tompkins Airport, and some of the models have high temperatures making a run to 75°F before the low late-day sun angle and increasing clouds tamper down the maximum heating potential of those strong southwesterly winds. One factor that helps is that the air blowing in right now is quite dry, with a dewpoint in the lower 40s. Air with a lower moisture content warms up and cools off more quickly.

This is really a matter of being in the right place at the right time of day. The front is currently a little east of Detroit and Toledo, and ahead of it you have the maximum flow into the warm sector – the low is centered over Ontario, and as air circulates counterclockwise with low pressure systems in the Northern Hemisphere, the warm sector is southwest of the low – where Tompkins County is. A tight pressure gradient amplifies those southwesterly winds, and the mid-to-late afternoon is typically when maximum heating takes place, it’s a little after maximum solar radiation and when the transmission of surface heat from that maximum solar radiation takes place. This means Tompkins County is currently among the warmest spots in the state, let alone the Northeastern United States.

However, all good things must come to an end. The low over Ontario will continue to move eastward, and its associated cold front will begin to push around sunset, though remember, low sun angle and clouds will mean the temperature will have already started dropping. Therefore, it’ll likely be in the low 60s in Ithaca by sunset. The wind gusts will max out in the next hour or so (some isolated 40+ MPH gusts are possible), and then those two will fall back a bit as the core of the low passes closer and the overall winds start to shift. Don’t expect much in the way of rain with this initial passage; some linear but scattered showers and even a few thunderstorms will pass through in the 5-7 pm range, earlier side of that range if you’re west of Ithaca, later if east. But not everyone will see rain, and it won’t last long. The system is quick moving, so once the winds turn to the northwest, they’ll calm down fairly quickly, so overnight temperatures will drop but it won’t be too breezy. It’ll be partly cloudy overnight with lows in the upper 30s by sunrise Monday.

So, the reason why Monday’s the washout is because of a second system that will be following along the channel of instability left behind by the cold front of today’s storm system to the north. That front will help draw a large, moisture-laden system from the Lower Mississippi River Valley, through the Ohio River Valley, and directly over upstate New York as it continues northeastward. It’ll start raining around sunrise and continue through the whole day. Expect cloudy skies and a half-inch to an inch of rain, with some embedded weak thunderstorms. Winds will once again turn to the southwest ahead of the low, but only for a few hours. That’ll still be enough to bring temperatures into the upper 50s. But the cold front with this low should pass through around sunset Monday with gusty winds that will turn from southwest to the northwest, and rain will change over to snow showers as it tapers off overnight, with lows around 30°F.

A broad area of high pressure will build in for Tuesday, and it’ll be a much quieter and cooler day. With light northwest winds and that stable high pressure air, it’ll be mostly sunny with a high in the upper 30s. The high passes overhead overnight Tuesday, with partly cloudy skies and lows in the mid 20s.

Wednesday sees milder air return as a storm system passes well to the north and helps create some southerly flow over the Finger Lakes, while a storm system off the coast should remain far enough away so as to not be a major factor in our local weather conditions. Plan for highs in the upper 40s with partly to mostly cloudy skies. Wednesday night will be partly cloudy with lows in the upper 20s.

High pressure over the Western Great Lakes will continue the quiet conditions and southwesterly flow for Thursday. Highs will once again be in the upper 40s with partly cloudy skies. Thursday night will see partly to mostly cloudy skies and light southerly winds, with a relatively mild low in the mid 30s.

Friday is the start of a rather complicated setup. A portion of a low will break off over the Southern Great Plains and spin up into its own discrete storm system as it moves northeastward into the Ohio River Valley. However, as it starts to press into the northeast, a developing coastal low will grow large enough and strong enough to absorb the smaller low and create a very broad storm system that expands to cover an area from Miami to Quebec City. Tompkins County will be in the warm sector of this broad storm system Friday, and the weaker low will result in less rain than the coast, with some light to moderate rain showers and highs in the low 50s. Friday night sees the rain build in more persistently with oceanic moisture, and it should stay warm enough, upper 30s to low 40s, to remain rain through the night.

However, by Saturday, Tompkins County will be in the cold sector. An early high in the low 40s will drop through the day, though current forecast models show the bulk of moisture east of Tompkins County by the time the temperatures drop below freezing. Rain will change over to snow showers as northwest winds increase, and temperatures drop through the 30s during the day Saturday, to a blustery and cold Saturday night with lows in the upper teens. Sunday will only be in the low 30s for highs, with milder conditions returning for the start of the following week.

Graphics courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Looking into mid-March, an initial pattern for a broad and deep jet stream trough over everywhere but the West Coast will transitions to a weaker and shallower trough still centered over the Upper Midwest with a more zonal pattern further upstream from the Pacific. Downstream over the East Coast, the shallower trough will allow a jet stream ridge to retrograde and build towards the east, but in the Southern Tier and Finger Lakes, that’ll just translate to below-normal temperatures becoming near-normal. the back edge of that ridge/leading edge of the trough will allow for moisture to move northeastward from the lower Mississippi River Valley, so more precipitation than normal is expected during the ides of March and St. Patrick’s Day.

Brian Crandall

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