ITHACA, N.Y. — At this midpoint of the month, we’re running at double our typical rainfall for April, and it doesn’t appear that we’ll be drying out much anytime soon. A storm system galloping across the area today will trigger more showers and potentially some severe thunderstorms. After a brief dry respite for the beginning of the week, showers and seasonably cool temperatures will be on deck for the next several days.

Your Weekly Weather

It’s a cloudy Sunday as a compact, but fast-moving area of low pressure rushes southeastward across Upstate New York, trapped in the larger flow of a storm system to the north, and moving like the spoke on a wheel. The real threat with this system is that if any sustained period of sunlight occurs, that’ll inject heat energy into an unstable environment where low-level winds will be blowing at a different direction than winds at higher altitudes (wind shear) as a cold front moves south and east across the region. Shear can cause a storm’s updraft of energy and moisture to tilt with height, which allows the updraft to sustain itself for longer and create stronger thunderstorms.

Generally speaking, the risk is highest south of Ithaca, where a little more heat energy and sunlight will be available. Damaging winds and golf-ball sized hail will be the primary threats, though an isolated tornado or two can not be ruled out, especially further south into Pennsylvania.

High-resolution models show a potent squall line moving southeastward in the 3-10 PM timeframe, but the line won’t really organize here because of the morning rain tapping out some of the atmospheric energy available, and the clouds preventing much in the way of new heat energy from bubbling up. The highest risk is from Binghamton south and east, but do pay attention to the weather if you’ll be out and about later this afternoon and evening for any severe thunderstorm warnings.

For the rest of your Sunday, expect showers and some thunderstorms, some of which could be severe, from mid afternoon until a little after sunset. Skies will be near-overcast with highs in the mid 60s. New rainfall amounts will be in the 0.25-0.50″ range. Sunday night will see showers ending, with mostly cloudy skies overnight and lows in the md 40s.

That larger area of low pressure digs in northeast of Ithaca, while high pressure asserts itself from the northwest. The high should win out over Tompkins County, with dry weather, partly to mostly skies and highs around 60. Monday night will see skies become mostly clear with lows around 40, though if the winds settle a little more, I would not surprised if there’s some frost on the hilltops come sunrise Tuesday.

High pressure should retain control for one more day as a storm system organized over the Great Plains and begins to move ENE Tuesday night. It will be mostly sunny with highs in the mid 60s. Tuesday night will see increasing clouds with lows in the low 40s.

Rain showers begin to arrive from the west with the low’s warm front Wednesday morning, and become more widespread during the afternoon. Overall precip amounts through sunset are expected to be low to moderate, and highs will be in the mid 60s with near-overcast skies. Wednesday night will see periods of rain and even a few thunderstorms, with lows in the upper 40s.

The low will pass to the northwest of Tompkins County, which keeps the area in the warm sector Thursday. Expect scattered showers between the warm and cold fronts, with mostly cloudy skies and highs around 60. Thursday night will see a few rain showers, mostly cloudy skies and lows in the mid 40s.

The cold front of the low should swing through the area later Friday. Expect rain showers and mostly cloudy skies with highs around 60, as the front shouldn’t arrive until evening. Friday night will see a few isolated showers, partly cloudy skies and lows around 40 as cold air begins to filter in.

Looking ahead into next weekend, a few lingering showers will be possible earlier Saturday on the back end of the cold front, but it should dry out later, with partly cloudy skies and highs in the mid 50s. Saturday night will be dry and around 40s, and highs in the mid 50s with partly sunny skies appear likely for Sunday as well.

Graphics courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Looking into the end of April, the large scale pattern favors a jet stream ridge in the west, and a trough in the east. Temperatures are expected to be below normal in Upstate New York, if also a little drier than normal as the jet brings in drier Canadian continental air. There is some concern, especially southwest of Ithaca where its has been warmer, of frost/freeze damage to outdoor plants and crops, and locally temperatures will come close to freezing Sunday and Monday night before moderating as we head into the following week.

Brian Crandall reports on housing and development for the Ithaca Voice. He can be reached at bcrandall@ithacavoice.org.