ITHACA, N.Y. — Hope you all enjoyed that taste of September-like weather we had, because it’s August, the middle of meteorological summer, and climatology is the greatest single predictor in a long-term forecast. This week, we’ll see temperatures running on the high side of normal, with ample humidity to really make it feel oppressive – not only will there be frequent pop-up thunderstorms, but heat advisories are likely to be issued as we sweat our way towards a late week cold front and a more temperate weekend.

Your Weekly Weather

The primary weather feature in the atmosphere this week is a large and strong area of high pressure parked over the western Atlantic Ocean, really a dual-maxima high extending from Bermuda northward into Atlantic Canada. As air circulates clockwise around highs in the Northern Hemisphere, and being a very large ridge of high pressure, lots of hot, moist air is being churned up from the Deep South and Gulf of Mexico, and into the Northeast. The high pressure system’s large size also makes it difficult to dislodge and push westward along the mid-latitudes, meaning these conditions will last for several days until it weakens and a westward-moving low pressure storm system can jostle it out of place and move it away from the Northeast.

In that sense, with only modest changes from day to day, the forecast that follows will have a “wash-rinse-repeat” feel to it, similar highs and conditions from one day to the next, until the cold front comes through late week. Please note that early indications show the heat index in the upper 90s and low 100s during the afternoon and evening hours Monday, Tuesday, Wednesday and Thursday, and maybe Friday. There will likely be multiple days of heat advisories, so take precaution if you’ll be outdoors for extended periods and stay cool and hydrated.

For the rest of your Sunday, expect some scattered showers and thunderstorms, none of which will be particularly strong or long-lasting. Highs will top out in the mid 80s with muggy a dewpoint in the upper 60s, and partly cloudy skies alongside those pop-up showers and storms. These will die down after sunset with the loss of daytime leaving, leaving partly cloudy to mostly clear skies overnight with humid conditions and a low in the upper 60s.

Monday will be as the southerly flow of heat and moisture grows with slightly stronger winds out of the south. It’ll feel sticky outside, with highs in the upper 80s and a dewpoint in the low 70s, leading to a heat index in the upper 90s. A few scattered showers and thunderstorms are possible in the 2-8 PM time frame, but these are not looking to be all that widespread due to unfavorable atmospheric dynamics. Monday night will be humid but dry and mostly clear with a low in the upper 60s.

Tuesday will see stronger southerly flow as a storm system presses against the high from the northwest and rides over the ridge up north. Lows rotate counterclockwise, so its flow will enhance the clockwise southerly flow to its east. Temperatures will be in the low 90s with a tropical dewpoint in the low to mid 70s, with the heat index into the 100s. The low to the northwest will make the atmosphere more unstable and favorable to thunderstorm development through the afternoon and evening, though severe thunderstorms are unlikely, with heavy rain being the biggest threat. The instability and remnant heat will continue the thunderstorm risk overnight Tuesday, with scattered storms and partly cloudy skies with a muggy low around 70°F.

Wednesday will see showers and storms continue as the storm system continues to induce unstable conditions even as it passes to the north, with no relief from the heat. Temperatures will be in the low 90s with dewpoints in the mid 70s, likely one of the muggiest days of the year, and heat advisories are likely. Rounds of showers and thunderstorms will pass throughout the day, but become more prevalent in the afternoon and evening, with partly cloudy skies otherwise. The storms will taper off as the atmosphere stabilizes with the low moving further away after sunset, and it will be dry after midnight Wednesday into Thursday morning, with partly cloudy skies and lows in the upper 60s.

Thursday will see a weak short wave pass along the edges of the ridge, so a few scattered showers ans thunderstorms are likely in the afternoon and evening, but otherwise it’ll be dry, hot and humid with partly cloudy skies and a high in the low 90s. Showers and storms should wind down after midnight, with partly cloudy skies and overnight lows in the upper 60s.

Friday stands to offer some relief late in the day as a stronger area of low pressure presses southward from Hudson’s Bay Canada into the Northeast. This will usher in cooler and less humid air from the northwest, but it won’t arrive until about sunset. This leaves one last muggy and stormy day, with mostly cloudy skies and rounds of showers and thunderstorms throughout the day, but primarily from 2-8 PM. Highs will be in the upper 80s. Friday night will see showers and storms diminish after sunset with dry, partly cloudy conditions after midnight. Cooler and drier air will work into Tompkins County, with overnight lows in the low 60s.

Saturday and Sunday are looking rather pleasant as that cooler air settles into the region with Canadian high pressure to the northwest. Expect a few passing clouds Saturday and a high near 80°F, and upper 70s and sunny on Sunday. Overnight lows will be seasonably mild, in the upper 50s with mostly clear skies.

Graphics courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Looking into mid August and the usual arrival of thousands of college kids into Ithaca, the large-scale pattern favors a strong ridge of hot air over the Pacific Northwest, a weak trough over the Western Great Lakes and Midwest, and a more modest ridge of hot air over the Eastern Seaboard. The only relatively cool area will be the Desert Southwest due to the hot desert air being carried northward and monsoon flow from the Pacific driving the development of some clouds and thunderstorms that will help keep the temperature down in places like Phoenix and El Paso. Closer to home, precipitation is expected to be near 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.