ITHACA, N.Y. — The hottest July in 65 years has yet to let up, but there’s hope later this week. After another day of record heat, it’s looking like a cold front passing through Monday night into Tuesday will bring something close to seasonable temperatures to the Southern Tier, if still a little warmer and more humid than usual.

Your Weekly Weather

We’re finishing out this weekend on another hot and humid note, with temperatures across Tompkins County in the mid to upper 80s for highs, and a dewpoint right around 70°F, which is pretty darn uncomfortable and makes it feel like temperatures are several degrees warmer than they actually are. This is thanks to the heat dome that has continued to dominate weather across the lower 48 the past few weeks – the dome has been weakening, but the area of highest pressure has shifted eastward to the Southeastern United States, and with the clockwise flow around areas of high pressure in the Northern Hemisphere, that means that the hot, humid air of the Lower Mississippi River Valley is being advected northeastward into our region.

There is some light at the end of this hot, humid tunnel, at least, as a Canadian low pushes southwestward across Ontario and Quebec Monday night into Tuesday. The attached cold front will usher in more temperate air from continental Canada, which will bring temperatures down to near or a little above normal for most of the week, as well as more comfortable humidity. With the heat dome weakened, the front will shunt much of its hot, humid airmass southeastward, and it’s looking like it’s been vanquished, as the long term models predict a jet stream over the middle of the continental United States, and two smaller, less oppressive ridges of warm air over the inner mountain west and eastern seaboard.

For the rest of your Sunday, it will be quiet, with rather muggy conditions and mostly sunny skies. Expect if quiet if humid overnight with a few passing clouds and lows in the upper 60s.

Use caution if you’ll be outdoors for an extended period on Monday. It will be very hot and humid, with air temperatures in the low to mid 90s and dewpoints in the low to mid 70s, which is extremely uncomfortable and will result in a heat index in the low 100s. The worst of this heat and humidity will be from about 12 PM to 5 PM, and a Heat Advisory is in effect from 11 AM to 8 PM Monday. (Need tips for dealing with the heat and recognizing heat illness. We got you covered – click here.) Winds will pick up out of the southwest as the cold front begins to approach in the PM hours, and skies will go from mostly clear to partly or mostly cloudy by later afternoon and early evening. That approaching front will also stir up the atmosphere and make it more unstable, and with all the heat energy available, some scattered showers and thunderstorms are likely in the late afternoon and evening hours. Some of these storms could be strong, with gusty winds and heavy downpours that could set off flash flooding, so be on the lookout for possible flood or severe thunderstorm warnings later in the day.

The frontal boundary will begin moving through the Southern Tier after midnight Monday night into Tuesday morning, so if you’ll be out, you’ll want an umbrella handy, as scattered showers and thunderstorms early in the night become more numerous heading through the AM hours before sunrise. It will be a damp, mild night, with mostly cloudy skies between rounds of showers and storms, and lows in the low 70s.

The front itself should pass through Ithaca right around sunrise Tuesday. Plan for scattered showers and thunderstorms with mostly cloudy skies in the morning, though being so early in the day, there won’t be enough heat energy available to result in severe storms. Rain and storms will wind down and skies will steadily clear up through the day, with the vast majority of the rain out of Ithaca by about noon, and an hour or two later for towns east of the city of gorges. It will be a rather humid day with highs in the upper 80s, but that humidity is more due to the evaporation of puddles from the rain than from the air mass moving in, which will be drier and more stable. Tuesday night will be drier, with a few passing clouds and lows in the low 60s.

Wednesday will be a more comfortable summer day, if still a little warmer than normal and a tad on the humid side. Highs will be in the mid 80s with dewpoints in the low to mid 60s. Most areas can expect mostly sunny skies, but rather curiously some of the forecast models show at least a few rain showers developing downstream of the lakes early Wednesday – yes, it is not the typical time of the year for lake effect, and in fact during the heat of the day, the lake cools the air above it and stabilizes it, creating an “oasis effect” in towns near Lake Ontario and Lake Erie. However, the heat of the past few weeks has baked the surface layer of the lakes, making them warmer than usual, with record warm surface water values, into the upper 70s in some spots. Being warmer than our overnight lows, and with westerly winds running down the length of the lakes, this could create a destabilization needed for lake effect showers, which would then drift east-southeastward across the northern half of the Finger Lakes. So if you’re anywhere from Ithaca northward and see a few drops Wednesday, write it off to a quirk of latent heat and atmospheric physics. Wednesday night will be quiet, as the winds shift to the SW and away from capturing a significant influx of heat energy from the lakes. Expect a few passing clouds and lows in the low 60s.

Thursday should be a quiet day dominated by an area of high pressure over the Western Great Lakes. Expect partly cloudy skies, a touch humid and highs in the low to mid 80s. The winds will shift to the northwest early in the day, capturing the short axis of the Great Lakes and thus unfavorable to those unusual summer lake effect showers. Thursday night will be partly cloudy with a low around 60°F.

The high over the Western Great Lakes will move only very slowly eastward, meaning a fairly quiet warm weather pattern will be in store for the next several days. Friday should be another rather humid and slightly warmer than usual July day, with mostly sunny skies and highs in the low to mid 80s. Friday night will be mostly clear with lows around 60°F.

For your weekend, generally speaking it’ll be pleasant for your outdoor activities. Saturday will be partly cloudy with a high in the mid 80s. Saturday night will be partly cloudy with a low in the mid 60s. A weak shortwave (pulse of instability) may attempt to pass along the edge of the high Sunday, setting off a few showers and thunderstorms, but otherwise partly cloudy conditions are expected, with highs in the mid 80s.

Graphics courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Looking ahead into the first week of August, the warmer-than-usual weather pattern is expected to continue, as a potential cutoff low settles over the Lower Mississippi River Valley, enhancing a jet stream ridge over the eastern seaboard. Precipitation is expected to run fairly close to normal for the period.

Brian Crandall

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