ITHACA, N.Y. — It’ll be something of an unsettled week ahead, though not all that unpleasant. A cool start gives way to temperatures near 80°F by midweek. Thunderstorms are likely Wednesday as more unstable air comes in ahead of a slow-moving storm system, followed by quieter, more seasonable conditions for the weekend.
Your Weekly Weather
It’s a grey if mild Sunday across the Southern Tier as two complementary areas of low pressure are passing near the region. The first is a stronger coastal storm system working its way up the Atlantic Coast northeastward from the Jersey Shore past Cape Cod and towards Atlantic Canada. The second is a weaker storm system passing to the north over Ontario and Quebec. The combined result of this is a rather broad area of unsettled weather, with most of the precipitation closer to the cores of those respective systems, resulting in very limited rain across Tompkins County overnight into this morning.
However, as that counterclockwise-spinning northern low passes Ithaca’s longitude, that cold frontal boundary will swing through, and there is some enhancement of cold air advection thanks to the second low to its southeast. The snow will stay well to the north, though that colder air would be cold enough for snow, if there was actually enough moisture and instability to locally tap into.
For the rest of your Sunday. winds will be breezy out of the northwest behind that cold front, which is crossing through this afternoon. The few scattered showers still present will wither away by sunset and the skies will clear up somewhat as temperatures slide down through the 50s. Overnight tonight, it will be dry with partly to mostly cloudy skies, and temperatures will continue to drop with that cold air blowing in, settling for a low in the lower 30s by sunrise Monday morning.
High pressure will work its way in from the Western Great Lakes for Monday, and this will clear out most of the remaining cloud cover during the morning, with generous amounts of sunshine for the afternoon and evening. However, we’ll be on the cold sector of its clockwise flow, and temperatures will be below normal for late April, topping out in the mid 50s. Monday night will start off mostly clear, but turn mostly cloudy after midnight as the tip of a Upper Great Plains low’s warm front brushes Tompkins County as it moves northeastward, while the Great Lakes high shifts eastward and merges into the larger circulation of a high over the Southeastern United States. A few showers are possible, but most areas will remain dry with lows in the mid 30s.
Tuesday will be significantly warmer with the combined clockwise flow of the Carolinas high and counterclockwise flow of the Great Plains low resulting in a strong southwesterly flow pumping lots of warmer air northeastward into the Southern Tier. The air will be fairly stable, and it should be by most accounts a beautiful day, with partly cloudy skies and highs in the mid 70s. Tuesday night will see a shortwave ride around the edge of the high pressure system’s ridge, and that might trigger a few rain showers after midnight, but they’ll be sparse. Most places can expect a mostly cloudy night with lows in the mid 50s.
Wednesday will be an unsettled if warm day as that low over the Great Plains begins to track across the Great Lakes. Tompkins County will remain in its warm sector as the storm system passes to the west, and the day will start off mostly cloudy and largely dry. However, this storm system will inject a lot of instability into the atmosphere, and with temperatures near 80°F, that will be ample heat energy for some afternoon and evening thunderstorms, so be mindful if you’ll be taking advantage of those warm temperatures, you’ll want to have a convenient place to ride out the rain and lightning if need be. Wednesday night will continue to be unsettled as models show the low pressure area stalling out over or northeast of Tompkins County. The risk of thunderstorms will subside with the loss of daytime heating, but showers will continue through the night with near-overcast skies and lows in the upper 50s.
Thursday will be cooler, though still mild. With that stalled out low and a reinforcing flow of moisture from the lower Mississippi River Valley, it’ll be an overcast day with scattered showers, especially as the wave of southwesterly moisture hits from about 2 PM through 2 AM Friday morning. Highs will be in the mid to upper 60s. Thursday night will see clearing out as we head towards daybreak Friday, with cooler air coming in behind the low as it finally dislodges and slowly pushes northeastward. Lows will be in the upper 40s.
Friday will be cooler still as cooler air wraps around the low, now over Maine and Canada. A few lingering showers during the morning will peter out as the low drags eastward and drier air works in during the afternoon. Highs will be near 60°F. Friday night will be dry and partly cloudy as high pressure works its way in from the Upper Midwest, with lows in the lower 40s.
At this time, the weekend is looking dry and seasonable. Saturday will be partly cloudy with highs near 60°F, Saturday night will be in the low to mid 40s with partly cloudy skies, and as the high pushes eastward and milder air wraps around its core, Sunday will be dry and a little warmer with highs in the mid 60s.
Taking a look into the first week of May, the large-scale pattern favors a persistent ridge of high pressure over the Southeastern United States, with an upstream jet stream trough over the Pacific Northwest. This likely translates to above-normal temperatures for the period, as well as drier-than0normal conditions. Since the Southern Tier will be on the edge of the ridge at times, this will allow for incursions of cooler (more seasonable) air and potential rain at times, though instances will be few and far between during the start of May. The warmer temperatures will be pleasant for early May, though continued long-term dryness and mild drought conditions remain a concern as we head into the warmer side of spring and towards the summer months.