ITHACA, N.Y. — It’s been a dry month and a dry summer so far, with drought advisories beginning to arise across the Northeast. With any luck, an incoming storm system will make a dent in that precipitation deficit, with a hotter and more humid weather pattern to follow during the rest of the week.

Your Weekly Weather

Cloud cover has been building this afternoon as the next low pressure storm system begins to move towards Upstate New York. Current trajectories show the core of the low moving from the Midwest, over Lake Erie and Lake Ontario on Monday, and continuing northeastward into Maine and Canada.

The low’s warm front will swing into the area tonight, with the first showers and thunderstorms arriving around sunset, a little later to the north and east of Ithaca and a little earlier to the south and west. Unlike other recent storm systems, this one has a lot of moisture to tap into, both in the air here already and in the even moister air mass it’s drawing into its clockwise flow. This is going to allow for some moderate to at times heavy rain overnight, with overcast skies and lows in the upper 60s.

Monday is pretty much a washout. While there will be a brief period of more sporadic scattered showers in the late morning and early afternoon, a very unstable atmosphere will allow shower and thunderstorm cells to fire up for the afternoon, and the cold front will press towards Tompkins County later in the day, ushering in another round of widespread rain, moderate to heavy at times. There is a marginal severe thunderstorm risk (gusty winds, maybe small hail), but the primary risk will come from flash flooding. Through Monday evening, it looks like 0.50-1.50″ of rain across Tompkins County, though locally higher amounts will be possible in areas hit by stronger thunderstorms.

Monday might see a few breaks in the clouds during the relative mid-day dry spell, but generally it will be a cloudy and oppressively muggy day, with highs in the low 80s and dewpoints in the low 70s. The cold front will move through a little after sunset, slowly but steadily bringing the rain and thunder to an end over the following few hours and allowing skies to partially clear out overnight. Lows will be in the mid 60s.

The back side of the low wraps into its northwesterly flow hot and humid air driven into the Upper Midwest by an expansive high pressure system over the Southeast. As a result, while a cold front will have passed through and there will be a northwesterly breeze, the incoming air mass will be anything but cold. Tuesday will be a hot and muggy day, with highs in the low 90s and dewpoints in the upper 60s. This moist, buoyant atmosphere will allow for some pop-up showers and thunderstorms during the late afternoon and early evening. Tuesday night will see those cells peter out with the loss of daytime heating, leaving partly cloudy skies overnight with a mild and rather humid overnight low in the mid to upper 60s.

The flow changes from NW to SW overnight Tuesday into Wednesday as the southeast high asserts itself, and establishing a more direct flow of hot and humid air will create a slightly hotter and more humid environment. With temperatures in the low to mid 90s and dewpoints around 70, it will feel more like 100 degrees during through the afternoon and early evening, and heat advisories may need to be issued. Do exercise caution if you’ll be out and about – stay hydrated, wear light, breathable clothes, take frequent breaks if you’ll be exerting yourself, and check on friends and neighbors who lack A/C. The airmass will also be a little more stable with the strong influence of the high, so pop-up storms are unlikely during the day, just partly cloudy skies. A storm system passing to the north will trigger some scattered showers and storms overnight Wednesday, though these will be light to moderate. Lows will be around 70 with mostly cloudy skies.

That storm system over Quebec will be a destabilizing influence Thursday as the frontal trough lags to the southwest, so expect another hazy, hot and humid day with convective showers and storms popping up throughout the day. With those cells and a few more clouds, highs will be in the upper 80s, though it will feel like the 90s with dewpoints around 70, with a strong southwest breeze. Thursday night will see the showers end as the frontal boundary heads east, leaving partly cloudy skies and lows in the mid 60s.

Friday will see a modestly cooler and drier air mass enter as the winds behind the Canadian low turn more to the WNW and bring in air from the Upper Midwest. It will be a dry day with partly cloudy skies, highs in the mid to upper 80s, and somewhat more comfortable dewpoints in the low 60s. Friday night will host a few passing clouds and a low in the lower 60s.

Looking ahead into next weekend, expect muggier air to return, with hazy/hot/humid conditions in store for Tompkins County. Both Saturday and Sunday look to be around 90 with afternoon and evening pop-up showers and storms, and partly cloudy otherwise. Overnight lows will be in the mid to upper 60s.

Graphics courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Looking ahead into the end of July, the large-scale pattern favors a ridge of unseasonable heat across the entire lower 48 of the United States. The ridge will be most pronounced in the Pacific Northwest and the Great Plains, and the relative weakness over the Northeast and Mid-Atlantic will allow some continental storm systems to slide into the region, with elevated chances for above-normal precipitation. In other words, the heat and humidity are likely to continue for some time yet.

Brian Crandall

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