ITHACA, N.Y. — For those of you dreaming of a white Christmas, it’s not looking for so good. For those of you who really hate shoveling out the driveway, the news is better. A pronounced ridge in the jet stream will allow for temperature as high as 60°F in the coming days, though there will be some risk of rain in the second half of the week.
Your Weekly Weather
It’s been a fairly quiet and sunny Sunday following a powerful frontal boundary that swept across the Eastern Unites States Friday and Saturday, an event that set off a catastrophic tornado outbreak in several states along the Mississippi River Valley. High pressure has built in from the south, and its clockwise circulation has kept temperatures above-average if still cooler than yesterday’s surge of southerly air. Highs today have mostly been in the low 40s across the region.
Sunday night will be tranquil. A very weak short wave (pulse of instability) will be rising over the top of the jet stream ridge and associated high pressure system, but the air is so dry that no precipitation is expected, just a few more clouds building in overnight. Lows will be in the mid 30s in Ithaca and along the lakeshore, and in the lower 30s in the outlying areas.
Heading into Monday, the flow of air around the high takes on a more southerly component, which will raise temperatures higher, into the lower 50s with partly cloudy skies in the morning giving way to nearly clear or clear skies for the afternoon. Some clouds are possible late Monday night into Tuesday morning as a weak storm system passes to the north, but otherwise expect mostly clear to partly cloudy skies, with lows in the mid 30s.
Tuesday will see the dominant lobe of the high pressure system shift northward, which will shift the winds to a more easterly component. Highs will be somewhat cooler but still above-average, in the mid 40s with partly cloudy skies. Tuesday night will be mostly cloudy with lows in the mid 30s.
Wednesday will see a warm front usher through Ithaca and Tompkins County, part of a strengthening storm system over the Great Plains and Upper Midwest. The day will start off dry and mostly cloudy, but as the front approaches, expect some light to moderate rain showers in the afternoon and evening hours, as highs make it into the mid 40s. Wednesday night will see temperatures continue to climb with strong southerly winds following the passage of the front in the afternoon hours, with temperatures in the upper 40s by midnight and perhaps even low 50s by sunrise. Rain showers will continue through the night as well, with overcast skies through Thursday morning.
The powerful storm system over the Great Plains will lift well into Canada before coming close to Ithaca’s longitude, and that more northerly vs. easterly motion will leave Tompkins County in the warm sector of its counterclockwise flow for an extended period. It will feel more like April than December, with a near-overcast skies, scattered rain showers, and highs around 60°F, over twenty degrees above normal. The cold front should pass through around midnight Thursday night, which will bring the rain showers to an end, and bring strong westerly winds that will bring temperatures down to about 40°F by sunrise Friday,
Friday will be quieter, but breezy northwest winds are expected as that storm system passes to the north. Skies will be partly cloudy with highs in the mid 40s, still above normal for this time of the year. Friday night could see some lake effect rain or snow showers in the usual areas closer to Lake Ontario, but otherwise expect mostly cloudy skies and lows in the lower 30s.
Looking ahead into next weekend, we’ll want to keep an eye on a system that will develop over the Ohio River Valley and cross the Mid-Atlantic. The low may draw in colder air from the north and tap into enough instability and moisture to generate rain Saturday, or possible snow Saturday night. However, it’s too far out to make any firm calls. Highs Saturday will be in the mid 40s, and lows in the mid 20s. Sunday will be drier and colder, with highs in the mid to upper 30s.
Looking into the week of Christmas, the ridge over the eastern U.S. flattens out, so temperature will only be a little above normal if at all. Precipitation will be near normal, so a White Christmas isn’t entirely out of the question, we’ll just have to wait and see what happens. Your chances will be better if you plan to head to the mountains of the Pacific Northwest or perhaps the Sierra Nevada of California.