ITHACA, N.Y. — If there’s any solace in this year’s socially-distanced pandemic-stricken Thanksgiving, it’s that the weather will be rather pleasant for late November. You can catch up with your loved ones under partly cloudy skies and needing only a light jacket. Once we get past the current storm system affecting our area, a late November ridge will provide milder temperatures and dry conditions for the holiday and next weekend.
We’ll see some light rain off-and-on thru Mon. morning as a storm system moves across the area before ending. A wintry mix of lake-effect precipitation should develop S/E of Lake Ontario Mon. afternoon. The wintry mix should change to all snow after dark. pic.twitter.com/Aiysb6fHlm
— NWS Binghamton (@NWSBinghamton) November 22, 2020
Your Weekly Weather
It’s been a rather dreary Sunday, with overcast skies and occasional light snow showers across Tompkins County. The culprit for today’s gloomy weather is an area of low pressure in the Ohio River Valley lifting northwestward, a track that will bring the core of the low across upstate New York overnight. Today’s snow showers are the first batches of precipitation ahead of the system. The proverbial silver lining to this track is that it should pass to the west of Tompkins County, which means the colder air and the snow within its precipitation shield will generally stay to the west as well – given that lows spin counterclockwise in the Northern Hemisphere, the southwest quadrant is the warm sector, where milder air is advected into the system’s circulation on southerly winds.
This will create the rather unusual effect of temperatures continuing to rise after sunset, as the low approaches and the pressure gradient tightens with the strengthening storm system, increasing the southerly flow. While in the upper 30s now, by midnight temperatures will likely be in the mid to upper 40s across most of Tompkins County. The bulk of the precipitation will be between 10 PM and 4 AM (some areas might see a few more scattered light snow showers or rain showers after sunset), and that will be in the form of rain, one-tenth to one-quarter of an inch across the area. The cold front associated with the low will swing through in the 4-6 AM time frame as the system passes Ithaca’s longitude, but by then most of the precipitation will be well to the northwest. A few rain showers will persist to about 7 or 8 AM, and that could be snow at higher elevations, but but no measurable snowfall is anticipated.
Monday will be a drier day, with a northwest breeze, mostly cloudy skies, and highs in the low 40s. Some lake effect rain showers will be possible north and northwest of Ithaca, though the angle of the winds will be too westerly to bring potential rain bands down to Tompkins County. Monday night is a little more favorable as the wind takes on a slightly more northerly angle over Lake Ontario, but marginal instability and weak flow means that only a few rain and snow showers are likely, mostly north of Ithaca – most areas will only see a few sprinkles followed by a dusting of snow at most. Otherwise, plan for mostly cloudy skies with lows Monday night around 30°F.
Tuesday will be cold but dry as high pressure passes to the north, channeling air from northern Canada down into the Southern Tier. Skies will be mostly cloudy, with highs in the upper 30s. Tuesday night will be quiet as the high continues to move east and winds slacken, with mostly cloudy skies with lows in the upper 20s.
On the backside of that high, with is the warm sector for highs given their clockwise circulation in the Northern Hemisphere, temperatures will rebound considerably on Wednesday as a southerly breeze develops. It will be mostly cloudy early on with highs around 50°F, but by late afternoon, skies will turn overcast and rain will begin to build in ahead of an approaching low, part of a fairly expansive frontal boundary from the Gulf of Mexico all the way up into Quebec. Models show this embedded low weakening and a new core redeveloping well to the northwest in Canada, a setup which brings the benefit of warm sector flow, with not much of a cold front to follow because the low falls apart as it approaches. So from Wednesday evening through the overnight into Thursday, expect periods of rain from 4 PM to 4 AM with the most widespread rain from 7 PM to 1 AM, but with lows in the mid 40s it should stay rain throughout. New rainfall amounts will be between one-tenth and one-quarter of an inch.
The rain should taper off by sunrise Thanksgiving Day as the decaying system moves eastward, and high pressure over the central Appalachians will provide for southwesterly flow during the day. It will be pleasant for late fall, with partly cloudy skies and highs in the mid 50s. Thursday night will be mostly cloudy with lows in the low 40s in Ithaca and along the lakeshore, and upper 30s in the higher elevations.
Friday will be another nice day as that high persists for another day. Expect mostly cloudy skies and highs in the mid 50s. Friday night will be mostly cloudy, with lows around 40°F.
A shortwave is likely to arrive on the backside of the high Saturday into Sunday, but as model soundings show a lack of moisture in the atmosphere, it will be more clouds than rain. Saturday will be mostly cloudy with highs around 50°F, mostly cloudy with lows in the mid 30s Saturday night, and mostly cloudy with a chance for rain showers Sunday with highs around 50°F.
Looking into the start of December, the large-scale pattern presents a broad ridge in the jet stream with modestly warmer than normal conditions here and a persistent unsettled area over the Southeastern U.S. We will likely start the month on the wet side and trend drier as the ridge shifts eastward to encompass more of the eastern United States. Longer range outlooks suggests a substantially warmer than normal December (if with near-normal precipitation), a long-range setup that decreases the prospect of a White Christmas, but meteorologically speaking a lot can change in a month.