ITHACA, N.Y. — Unlike is astronomical counterpart, meteorological spring is defined as March 1st through May 31st. The temperatures through much of this upcoming week will feel pleasantly spring-like, though unsettled, rainy conditions will put a damper on most outdoor plans.
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The defining feature of our weather for the first half of the week will be a ridge in the jet stream supported by a high pressure system off the coast of the Carolinas. While the clockwise flow of the high will funnel in milder air from the south, the Southern Tier will be on the edge of the ridge, which means that multiple weak storm systems will develop along its periphery, and make their way into Tompkins County. In other words, mild but wet.
It’s a fairly quiet Sunday evening, as today’s blue skies give way to nocturnal cloud cover. These thicker clouds have also started to move in overhead as part of a low pressure area to the north and its warm frontal boundary ushering milder air into the region. Tonight will see an early low of around 30°F, but after 9 PM, warm air advection becomes stronger, enough to overcome the usual radiative cooling that happens after the sun goes down (or, to be more scientific, diurnal impacts). Communities east of Ithaca, where the clouds have yet to move in, will see temperatures fall back a little further into the 20s before they start to rebound. Rain showers associated with the front will begin to move in my sunrise Monday, with temperatures in the mid 30s in Ithaca and towns to the west – eastern communities, like some of the hamlets towards I-81 and Cortland, may start off with some snow showers if the temperatures have yet to rebound much above 32°F.
Benefiting from both the clockwise flow of the Atlantic high and the warm sector of the low to the north, the combined southerly flow will bring temperatures up into the mid 50s for Monday, though it comes with its share of rain. Expect to carry your umbrella around pretty much all day, with the bulk of the precipitation will be moving through between 1 PM and 7 PM. This isn’t a washout, but an off-and-on light rain that will deposit somewhere between one-tenth of an inch and one-quarter of an inch of rain before the frontal boundary shifts eastward enough to give Tompkins County a break. Unfortunately, it’s slow-moving, so some risk of rain showers will remain through the night, as wins calm and temperatures pulls back to the mid 30s for lows.
Another weak storm system will ride from the Lower Mississippi River Valley northeast into the Southern Tier for Tuesday, and with it comes another batch of rain. The warm air advection will not be as strong with the high further east (less influence, weaker flow), but it will still be fairly mild, with highs in the low 50s, with mostly cloudy skies and light rain totaling between one-tenth of an inch and one-quarter of an inch. Behind this system will be some clearing skies Tuesday night, with temperatures falling back into the mid 30s under partly cloudy skies and an isolated rain shower or two east of Ithaca.
Wednesday will still be somewhat unsettled as the departing low wraps some oceanic moisture around itself, which with the remnant instability will be enough to fire off a few scattered rain showers. Temperatures will top out in the upper 40s Wednesday, with mostly cloudy skies in between the showers. Wednesday night will see the atmosphere stabilize as the low moves further away, and it will be dry, with partly to mostly cloudy skies and a low around 30°F.
High pressure briefly skirts by to our south on Thursday, mitigating some of the impacts of the northerly flow from the previous storm system, now over Atlantic Canada and strengthening rapidly. Highs will make it into the upper 40s with partly to mostly cloudy skies. Thursday night will be dry to start, with lows in the mid 30s, and potential rain or snow showers by sunrise Friday.
The weather situation becomes a little complicated for Friday. There will be two weak lows, one moving out of the Southeastern U.S. into the Mid-Atlantic, one over the Great Lakes moving westward. If they can time their passage right, they can combine their energy and become a much stronger storm offshore, which is what the European (ECMWF) and American (GFS) models suggest. If for some reason they start to phase together sooner, it could end up being a very messy situation, but for now, it’s just something to keep an eye on.
Regardless, the strong coastal storm will reduce the size of the jet stream ridge as it kicks up winds and colder air from the north, so Friday will be considerably cooler, around 40°F for a high, with mostly cloudy skies and scattered rain showers. Friday night will be chilly as the cold air advection is in full effect thanks to that powerful low pressure storm system over the Atlantic, and snow showers are likely as that cold air passes over the warmer waters of Lake Ontario. Expect cloudy skies, some light snow showers, and lows in the low 20s.
Saturday is looking like the cold day of the week as high pressure pushes in from the west, doubling down on the cold northerly flow but stabilizing the air aloft. Plan for mostly sunny skies and a high in the low to mid 30s, and a low Saturday night in the low 20s with a few passing clouds. As the high shifts to our east for Sunday, temperatures will warm up once again and the ridge of warm air will build back into our region, with mostly sunny skies and highs in the mid 40s.
Looking ahead into the second week of March, a broad ridge in the jet stream is expected to allow for another round of unseasonably warm temperatures, though like this week, it will be on the wet side, with indications of frequent storm systems passing from the lower Great Plains into the Ohio River Valley and Northeastern United States. About the only places expected to have anomalously cool conditions are Alaska (where the s=extra-strong polar vortex has kept temperatures colder than usual) and the Pacific Northwest. This ridge is expected to shift slightly further eastward and then hold in place for some time, indicating a mild March may be in store for the Southern Tier and much of the eastern half of the U.S.