ITHACA, N.Y. — Think of it as the water station during a hot summer foot race. A Canadian low will provide modestly cooler and drier air for the start of the week, but the heat dome builds back for another long spell of hot and humid conditions for Thursday onward.

Your Weekly Weather

At the moment, it’s a warm summer afternoon across Upstate New York as a weak trough extending from a Canadian low swings across the region. This trough is ushering in some mildly cooler and drier air, to the extent that the more appropriate phrasing might be “less hot” and “less humid”. High temperatures are still topping out slightly above normal, in the mid 80s in most areas with a dewpoint in the low to mid 60s – humid, a touch muggy, but not disgustingly so as the case has been for much of the past week when was had dewpoints pushing into the low 70s.

The trough has injected some instability into the atmosphere overhead, and that with the usual diurnal heating is feeding the formation of widespread if otherwise low-impact cumulus clouds across the Southern Tier, with a few thicker bands embedded where topographically-induced channels of instability have developed. A few showers and thunderstorms are bubbling up in Pennsylvania and the Allegheny Plateau, and it’s possible a few may fire off in the vicinity of Tompkins County in the wake of the trough. But generally, these not be all that strong and widespread, and most areas are expected to stay dry for the remainder of the day. Sunday night will see the clouds wither away with the loss of that daytime heating, and we can expect dry conditions with partly cloudy skies overnight and a low in the low 60s.

Monday will see a renewed risk for some late-day showers and thunderstorms as the Canadian low pulls away early, and a second weak shortwave (pulse of instability) quickly pushes through during the afternoon and evening, firing off a few showers and thunderstorms in its wake. These storms will need a diurnal heat injection to develop, and so it’s really more of an afternoon/evening risk, 2 PM to 8 PM. As before, these will not be widespread. Most areas can expect to remain partly to mostly cloudy, with highs in the low 80s. Monday night will see slightly cooler and drier air filter in behind that shortwave, leaving us with partly cloudy skies overnight, and a low around 60°F. This will be one of the first nights in a little while you can sleep with the windows open and not feel sticky or sweaty from the mugginess. Enjoy it while you can, because it won’t last long.

Tuesday is arguably our most comfortable day of the week. With that shortwave still clearing out to our east, we can’t totally discount the possibility of a shower or two mainly to the east of Ithaca, but they’ll be widely isolated.  Behind it and ahead of the “heat dome” to the southwest will be a bubble of drier, more stable air. This will make for a fairly pleasant day Tuesday, with comfortable humidity (still a touch humid in the low 60s for dewpoint) and partly cloudy skies with highs in the low 80s. Tuesday night will host a few passing clouds with a low around 60°F.

Wednesday will be a touch warmer and more humid as the high shifts eastward and, being on the  back half of its clockwise flow, the winds turn light out of the south. That said, the air should remain relatively stable, with partly cloudy skies and highs in the mid 80s. Wednesday night will be humid and mild, with partly cloudy skies and a low in the mid to upper 60s.

Thursday sees the ridge, the edge of the “heat dome”, approach the Southern Tier once again, with the jet stream straddling its crest to our northwest. This will introduce repeated injections of unstable air, with the energy to feed pop-up showers and thunderstorms as that hot, humid air makes it way in from the southwest. The models do not have great agreement on how much the actual heat dome itself builds over the eastern Great Lakes – the more it does, the hotter and drier it will be (the ridge will quelch storm development because the ridge is a “cap” on convection, squashing it before it can really build up).

For now, expect an unsettled, hot and muggy day Thursday, with scattered showers and thunderstorms during the PM hours as a wave rides along the jet stream/ridge edge. Highs will be around 90°F. These storms could be strong, with gusty winds and torrential downpours, so be mindful of severe thunderstorm warnings during the later afternoon and evening hours. Thursday night will see showers ans storm early, decreasing as the night progresses, with mostly cloudy skies otherwise and a low in the upper 60s.

Friday should be somewhat more settled as the heat dome encroaches and pushes the jet further northeastward, but a few showers and thunderstorms are still possible along the fringes, which includes Tompkins County. Otherwise expect partly cloudy skies with highs in the upper upper 80s to around 90°F. Friday night will be partly cloudy with an isolated shower or two, and a low in the mid 60s.

The weekend will be hazy, hot and humid. For now, we’re presuming we stay at the heat dome’s edge. Expect highs in the low 90s both Saturday and Sunday, very muggy conditions, and convective showers and thunderstorms, some of which could be strong, during the late afternoon and evening hours. It will be humid and drier overnight, with partly cloudy skies and lows in the upper 60s.

Graphic from the NOAA Climate Prediction Center.

Extended Outlook

So is there a sustained break from this heat and humidity in the works? Short answer: no. Slightly longer answer: not in the next couple weeks. As the expansive ridge of intense heat builds to the northeast, sustained above normal temperatures, with above normal humidity, are likely to continue.

Graphic from the NOAA Climate Prediction Center.

In fact, it’s looking like we’ll need to be very careful in the week after this one, with excessive heat and humidity posing significant risks over a multi-day period. This hot weather won’t be calling it quits anytime soon.

Brian Crandall

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