ITHACA, N.Y. — Today is the first day of astronomical summer as of 11:32 PM, and it’ll start off with a swelter as high dewpoints and above normal temperatures create a steamy setting to begin the week. A cold front passing through Monday night will rapidly usher in cooler and drier air to make for a mostly pleasant week to follow.

Your Weekly Weather

It’s a warm and rather humid Father’s Day around the Southern Tier and Finger Lakes as a high pressure system east of Florida and over the Atlantic Ocean churns hot, moist air northward in its clockwise circulation. Temperatures are well into the 80s across Tompkins County, with temperatures likely to top out in the upper 80s in the valleys and urban core, and mid 80s on the hilltops and closer to Cayuga Lake and the moderating effect of its waters.

The combination of heat energy and a more unstable atmosphere thanks to the more buoyant moist air in place will allow for some pop-up showers and thunderstorms to fire up this afternoon and evening, especially in the time period of 4 PM-8 PM. Stronger thunderstorms are somewhat more likely south and west of Ithaca, where there’s more heat energy to tap into and develop those storms. Generally speaking, though, most places will stay dry through the evening. What storms do develop will dissipate with the loss of daytime heating, and it’ll be a dry if muggy night tonight. Skies will be partly cloudy and lows will be in the upper 60s.

If you can stay near a fan or air-conditioned place on Monday, it is recommended you do so. A strong southerly breeze will really crank up the heat and humidity, with highs in the low 90s and dewpoints in the low 70s, which will make it feel like it’s near 100°F. Keep yourself cool and hydrated, and remind yourself of the warning signs of heat exhaustion, especially if you’ll be working outdoors. The only saving grace to this sweltering air mass is the impending approach of a cold front with an area of low pressure passing over Canada. Skies will be increasing cloudy after late morning, with the first showers and thunderstorms building up west of Ithaca during the early afternoon, with waves of showers and thunderstorms passing through ahead of the front between 2 PM and 10 PM.

Along with the heat index, we’re expecting some severe thunderstorms scattered across the region during the afternoon and evening on Monday, due to the very unstable and high heat energy environment. Where they develop, these storms will be capable of damaging winds, large hail, & torrential downpours with flash flooding; an isolated tornado or two will be possible. Please pay attention to your phone or radio in the event an emergency weather advisory is issued for your community, and have a plan to get indoors and to safety in the event of a severe thunderstorm warning.

The front will pass through not long after sunset Monday, and this will cut off much of the energy for severe weather, but rain and weaker thunderstorms will continue through the night before cooler and drier air works in for Tuesday. It will be rainy with a few rumbles of thunder Monday night, with most cloudy to overcast skies and lows near 60°F.

Tuesday will be a much cooler day, though some rain showers will persist during the morning and afternoon, especially to the east of Ithaca. Highs will only be in the upper 60s with mostly cloudy skies turning partly cloudy in the evening. Tuesday night will be cool and quiet, with decreasing clouds, from partly cloudy around sunset to nearly clear skies by morning, and lows in the upper 40s.

Wednesday should be a pleasant and comfortable day as high pressure builds in from the Ohio River Valley. Expect a few fair weather clouds, comfortable humidity, and highs in the mid 70s. Wednesday night will see the high pressure area pass overhead, and the stable atmosphere will mean a mostly clear night with lows in the low 50s.

Thursday will be somewhat warmer as the high continues to move east and we end up on the backside of its clockwise circulation in southerly flow, but in this case the air being advected into the area originates from the Jersey Shore and Atlantic Ocean rather than the Deep South – i.e. not too hot or humid. Highs will be near 80°F with a comfortable dewpoint in the mid 50s, with mostly clear skies. Thursday night will see a few increasing clouds but remaining dry, with lows around 60°F.

Friday will be warmer and more humid, with highs in the mid 80s and dewpoints around 60°F (noticeable but not awful), as a cold front to the northwest over Canada amplifies the southerly flow of the rear flank of the high. This front is a slow mover though, so Friday should be dry during the daylight hours, though with increasing clouds throughout the day. Some showers may move into the region, especially north and west of Ithaca, after midnight and heading into Saturday morning, but most towns will remain dry with partly cloudy skies and lows in the mid 60s.

Saturday will be unsettled as the front approaches, with partly cloudy skies giving way to scattered showers and thunderstorms in the afternoon, and highs in the mid 80s. Saturday night will see continued scattered showers and storms with lows in the mid 60s, and Sunday will see scattered rain showers with partly cloudy skies and highs in the low 80s.

Graphics courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Looking into the end of June and start of July, the long-term trends look to be fairly similar to what they have been – a pronounced ridge of hot and dry air over the Western United States, with downstream moisture and coolness. In this case, a jet stream trough suggests enhanced thunderstorm development around the Gulf of Mexico (no organized tropical storms are being sniffed out from the models, as the jet stream shreds tropical systems apart) and will lead to cooler-than-normal conditions over the Deep South, and wetter than normal conditions across much of the Eastern United States.

The crest of the next downstream eastward jet stream ridge, however, will be far enough west to allow for potentially warmer-than-normal conditions over New England, for those of you who might be thinking of a trip out that way for the Independence Day weekend.

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