ITHACA, N.Y. — If you thought you could finally put away the snow brush and shovel, dig them back out. A late-season winter storm is likely to drop a modest but plowable snow across parts of Tompkins County during the early hours of Monday morning. The weather turns warmer and decidedly less wintry for the rest of the week ahead.
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It seems a bit strange to speak of snow when the weekend has been filled with ample amounts of sunshine, courtesy of a strong area of high pressure currently centered over Quebec. While the strong high has kept the air very stable and limited the development of cloud cover, it has also kept things on the cool side for late March, with highs in most of the area in the upper 30s this Sunday.
The storm coming in late tonight into Monday morning really consists of two components, a pulse of instability (short wave) passing over the Great Lakes and a developing storm system moving from the Carolinas northeastward into the Atlantic. The northern and southern disturbances are expected to phase together, merging into one system and strengthening in the process.
The models are not in excellent agreement on this event, with variations on when they phase, and the exact track of the merging system. Generally speaking, the sooner they phase, the more westward the area of heaviest precipitation will be; the quicker the merged storm strengthens, the more cold air it can pull in from Canada, and the snow it can produce. The GFS (American) forecast model projects later phasing (moving the maximum precipitation eastward), and the ECMWF (European) and CMC (Canadian) favor a little sooner, setting up the heaviest precipitation a little more to the west, and with colder air wrapping around the low more quickly.
In either case, it looks like Tompkins County will be spared the heaviest snow. Ithaca and the communities adjacent can expect about an inch of snow, perhaps 2″ in the hills, mostly falling in the 3-8 AM time frame tomorrow morning. Temperatures will be right around 32°F, so this will be a heavy, wet snow, the kind that makes those big, clumpy snowflake masses as they fall. Further out towards eastern Dryden, Caroline and Danby, closer to the primary storm track and further up in elevation, 3-4″ of snow is more likely during the morning hours on Monday. With temperatures hovering around freezing, the rain-snow line will be very elevation-dependent; this is one of those instances where it may be snowing hard in Danby or Ellis Hollow, and raining in Ithaca at the same time.
By 8-10 AM (sooner in the valleys, later on the hills), everyone should transition over to a moderate if cold rain, lasting through the afternoon hours as highs top out in the upper 30s. The rain will begin to wind down around sunset Monday evening as the storm system pulls away to the east, and Monday night will be overcast with lows in the mid 30s. Total rainfall Monday will be between one-tenth and one-quarter of an inch.
Tuesday will be quieter as an area of high pressure builds in behind Monday’s storm. This is a fast-moving high, and by Tuesday afternoon we’ll already be on its backside (western flank). With its clockwise flow, that will allow temperature to warm appreciably, with highs around 50°F and partly to mostly cloudy skies.
The drawback to this quick-moving high, however, is that another storm system will be coming in behind it. This low will move from the Ohio River Valley, transfer energy to a developing system over the Mid-Atlantic states, and then the coastal storm will move out over the ocean. Temperatures will be warm enough that this will be an all-rain event. Overcast skies will return by midnight Tuesday, with the first few rain showers by Wednesday morning, and overnight lows in the mid to upper 30s. Wednesday will be a grey, rainy day, with consistent light to moderate rain from mid morning through early evening, and tapering off into the night. Highs Wednesday will be in the upper 40s, with total rainfall between one-half and three-quarters of one inch. Wednesday night should see the showers full shut down by midnight, with overcast skies afterward and lows in the upper 30s.
Thursday isn’t looking too bad, but you’ll want to keep the umbrella handy. A high over the Southern Appalachians will channel milder air into the region, but a weak wave of instability reaching out of Canada might set off a few showers during the afternoon hours. It will be mostly cloudy otherwise, with high temperatures in the upper 50s. Thursday night will also be unsettled as multiple, weak waves continue to sweep through, so plan for a few light rain showers, mostly cloudy skies and lows in the upper 30s.
Friday will be drier as a Canadian high tries to keep the next wave suppressed to our south; that high will also allow some cooler air to seep in. It will be partly cloudy with highs in the low 50s. Friday night will see a chance for rain or snow showers as the wave to the south tries to build in, and it will be cloudy with lows in the mid 30s.
The weekend starts off unsettled, but seasonably mild. Saturday will see a chance for snow showers early, followed by rain showers after sunrise, and highs in the low to mid 50s. Saturday night will be mostly cloudy with a few rain showers and lows in the upper 30s. High pressure takes the reins for Sunday, with mostly sunny skies and highs in the low to mid 50s.
Looking ahead to the end of March and start of April, a ridge in the jet stream is expected over the upper Great Plains, with a concentration of unseasonably warm air over the Dakotas and near to slightly-above normal temperatures for the Northeast. However, it also comes with what’s expected to be a dry pattern over much of the northern half of the country, so the usual April showers might be a little late in coming this year.