ITHACA, N.Y. — Don’t get your hopes up for a white Christmas. A coastal storm is socking Tompkins County with a dose of heavy rain this evening and into tomorrow. While the storm will allow for some cold air and a few inches of snow on its colder rear flank, dry conditions and temperatures above freezing for much of the week ahead will likely whittle that snow down to meltwater by the time Santa’s trip around the globe commences.
Your Weekly Weather
A pair of low pressure systems are impacting the Southern Tier and Finger Lakes this evening. The first is the primary system, a moisture-laden, strong low working its way up the eastern seaboard. The second is a weaker low passing eastward over Ontario and Quebec. The former is driving ample unstable, moisture-laden air into the Northeast, while the latter extends that channel of atmospheric instability to the north and west, expanding the precipitation shield across much of Upstate New York.
The two systems are likely to merge as the coastal low strengthens and moves NNE, onshore and into the St. Lawrence Valley. Through tonight and tomorrow morning, rain, heavy at times, will be prevalent across the area. A Flood Watch is currently in effect for most of the region, with the primary concern being areas of poor drainage, such as urban areas with a lot of paved (impermeable) surfaces, and properties adjacent to small streams and creeks that would be prone to rapid rises in water level. If you live in an area prone to ponding and flooding, pay close attention to drains and sump pumps tonight to make sure they’re working and not clogged by leaves or other materials. The last thing I want to report on is someone’s inflatable snowman plugging a storm drain in Fall Creek and flooding the whole block.
Through tonight and tomorrow morning, most areas from Ithaca west are expected to receive 1-1.5″ of rain, while communities east of Ithaca, closer to the path of the low and its oceanic moisture tap, can expect 1.5-2″. Temperatures will hold fairly steady through the night as we remain in the warm sector of the low for the time being, with temperatures remaining in the upper 40s until sunrise, when the storm passes northward and cold air begins to flow into the region on north winds. Rain will become showery by Monday afternoon, and winds will be gusty, NW 15-20 MPH with 25-35 MPH gusts. Temperatures will slowly recede during the day, from upper 40s at sunrise to low 40s by sunset.
Turning to Monday night, temperatures will continue their steady decline as winds slacken but cold air continues to pour into the region as the low lifts off into Atlantic Canada and high pressure over the Ohio River Valley enhances northwest winds. With a trough of low pressure still in place over the Northeast, precip will continue, if light, with light rain becoming light snow towards sunrise, and lows in the upper 20s.
Tuesday will be a colder day, if drier as that high pressure moves eastward and shunts off the instability and moisture to the east. Periods of light snow will become more scattered by afternoon, with some breaks in the cloud sheet forming as we head into sunset. Highs will only be in the mid 30s, with new snowfall totals 1-2″, higher to the northeast of Ithaca where Lake Ontario can locally enhance snow bands. Tuesday night will see showers ending and skies becoming mostly clear by sunrise Wednesday. Lows will be in the lower 20s.
Wednesday sees the high move slightly to the south and east, though little movement overall. However, it should be enough to drive some milder air from the southwest into Tompkins County. As a result, temperatures will be warmer, near to perhaps a tad above seasonable, with sunny skies and highs around 40. Wednesday night will see gradually increasing clouds, though still partly cloudy when Thursday morning rolls around, with lows in the upper 20s.
Thursday, the first day of astronomical winter, sees two lobes of high pressure, one over the Mid-Atlantic and one over Quebec. A fairly quiet day is expected, with partly cloudy skies and highs around 40. Thursday night will see partly cloudy skies and lows in the mid 20s as that Quebec lobe of the high becomes the more dominant one in the pair, bringing colder air into the Northeast.
Friday will be much the same, if a little cooler thanks to that Quebec high. Skies will be partly cloudy with highs in the upper 30s. Friday night will see partly to mostly cloudy skies with lows in the upper 20s.
Things looks to be dry and on the mild side of seasonable as we head into Christmas Eve weekend. The high slides southeastward, providing milder air around its clockwise circulation, and a weak shortwave low does appear to take a run at Upstate New York Saturday, but models show up falling apart as it runs into the high pressure system. The result is partly to mostly cloudy skies with highs around 40 Saturday, around 30 Saturday night, and mid 40s for Sunday. Not exactly a recipe for a Christmas Day snowfall.
Extended Outlook
Taking a look into the end of 2023, the large-scale pattern calls for a continued, prominent jet stream ridge over much of the continental United States, with above normal temperatures (likely 40s and a few 50s) as we head towards New Year’s Eve. The pattern also favors drawing in moisture from the Gulf of Mexico, so as well as being warmer than normal to close out the old year, it’s also likely to be wetter than normal for the last week of 2023.