ITHACA, N.Y. — Many of you are itching for a dose of nice spring weather – the not-damp, not-cold kind, something that lifts spirits and makes the buds on the tree pop open. For that we have some good news, as temperatures climb into the upper 60s and 70s for a portion of the week, though it will be showery. Unseasonable chill and rain look to resume by the end of next weekend, however.
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A large and well-developed low pressure storm system off the coast of Atlantic Canada brought significant rainfall to Upstate New York yesterday, and while the rain has moved out, cold northerly winds on the backside of the counterclockwise-spinning storm system are funneling brisk Canadian air into the region. Along with substantial cloud cover and some light instability showers, both rain and snow, temperatures are stuck in the mid 30s to mid 40s across Upstate.
Don’t expect much in the way of appreciable precipitation today, though a few raindrops or a dusting of snowflakes are certainly possible. These showers will whittle away and the clouds will break up a little bit as we head into the evening, and that will give a little time for the high sun angle and extended amount of daylight we see this time of the year to do some work on the thermometer, raising temperatures to highs in the low 40s in Ithaca and around 40°F in the outlying hilltops. Sunday night will be cold and quiet as high pressure moves in from the south. Expect decreasing clouds overnight and a low in the upper 20s.
Monday will be pleasant and milder as high pressure briefly takes the reins. Cloud cover will increase throughout the day as highs reach the upper 50s. Some showers are likely to work their way into Tompkins County by around sunset as a low pressure storm system moves from the Western Great Lakes into Canada, passing to our north but sweeping across Upstate with its associated cold front and precipitation shield. This is not a strong storm and its distance well to the north will limit overall impacts. The primary impact will be a rainy night Monday, with periods of light rain, overcast skies and lows in the low 50s. New rainfall amounts will be between one-tenth and one-quarter of an inch.
This rain should end by Tuesday morning, and behind the front the wind patterns will be weak. High pressure over the subtropical Atlantic Ocean will build in briefly, filling the gap between lows well to the north and east, and a developing system over the Great Plains. This Atlantic high will bring southerly winds into Tompkins County, and result in a very pleasant day, with partly to mostly sunny skies and highs in the upper 60s. Clouds will increase Tuesday night with a few isolated instability showers possible before sunrise as that Great Plains storm system spins up over the Upper Midwest and its warm front slides through the Southern Tier. Lows will be in the lower 40s.
Wednesday will be a warm but unstable day weather-wise. Firmly in the warm sector of that broad storm system centered over Minnesota and the Dakotas, temperatures will make it into the low 70s, but the air will be much more moist, and a moist atmospheric column is inherently less stable (moist air rises more easily because water vapor weighs less than air). A weak shortwave in the warm sector will easily set off a round of showers, though the energy is lacking for thunderstorms. Rainfall amounts will be less than one-tenth of an inch under mostly cloudy skies. Wednesday night is relatively mild as Tompkins County stays in that warm sector, with mostly cloudy skies, scattered rain showers, and lows in the mid 50s.
Thursday we’ll want to keep an eye on because the storm system’s front take on occluded characteristics – the cold air overruns the warm air. This can be favorable for thunderstorm development, but right now it looks like the afternoon-evening timing for frontal passage will not be enough to counteract the lack of energy overall. We’ll want to make sure that doesn’t change, because this is a setup favorable for organizing thunderstorms. For now, it looks like rain will occur primarily in the morning Thursday with scattered showers in the afternoon and evening, tapering off shortly after sunset. Highs will be in the low 70s with partly to mostly cloudy skies, and breezy south winds turning to the west as the day progresses. Thursday night will be see clearing skies, a few lingering showers, and lows in the low 40s.
Friday will be cooler behind the cold front, as the broad low now spins away over Canada, dragging down lots of cooler Canadian air, but far enough to the northwest to limit its impacts locally. Except a dry and comfortable day with a few passing clouds and highs near 60°F. Friday night will see partly cloudy skies and a low in the upper 30s.
Next weekend is looking a touch cool as that low passes to the north. Saturday will see a chance for a few lake-enhanced showers and highs in the upper 50s, and Saturday night will be cloudy with lows in the low 40s. A storm system moves in for Sunday, bringing another round of rain and highs in the low 50s.
Looking into the second half of April, the large-scale pattern in the jet stream favors a deep trough over much of the United States, with only some modest retreat for a bubble of warmer subtropical continental air over the Desert Southwest later in the period. The downstream ridge in the jet will be over the Western Atlantic and conducive to tapping into oceanic and Gulf of Mexico moisture, meaning both cooler-than-normal conditions and slightly wetter-than-normal conditions for the period.