ITHACA, N.Y. — It’s been on the warm and dry side for the past several days, but we’ll see some moderation in temperatures and the chance for some rain in the coming days. Wednesday and Friday night are looking like the best opportunities for some welcome precipitation in Ithaca and Tompkins County.

Your Weekly Weather

It’s a warm if mostly cloudy Sunday across Upstate New York as a cold front descends from Canada southeastward across the region. There are some lower-level cumulus percolating with the heat of the day and some atmospheric instability, thinner if more expansive cirrus aloft, and some areas of more spotty cloudcover over the Hudson River Valley, as cooler air flows down the Adirondacks and provides for some regional stabilization of the atmosphere (subsidence).

The cold front doesn’t have a lot of moisture available to it, and the atmospheric energy is limited to daytime heating, so we’re seeing a few showers and thunderstorms pop up around Ithaca’s latitude and northward, but not much to worry about – yet. As more heat is injected into the atmosphere, and the encroaching cold front provides for a kick of instability, there is a risk, primarily south of Ithaca later this afternoon and evening, for some energetic, stronger thunderstorms. As it is rather breezy, air mixing down from further aloft could produce some gusty, damaging winds with a few of these cells, so if you’re south of Ithaca, Binghamton or the Northern Tier, you’ll want to keep an eye out for any severe thunderstorm warnings that may crop up. For Ithaca northward, the timing of energy and instability isn’t in sync and so the pop-up showers and storms will stay on the weaker side.

Quick aside as I hit the ‘publish’ button – there is some ‘oomph’ to this air mass, with temperatures ranging from 80°F Danby to 70°F in North Lansing, which is a fairly steep gradient for a warm-season frontal boundary.

Once the front clears in the next two to three hours, skies will clear up and the temperature will slide back though the evening, with partly cloudy skies and mid 60s by sunset. The northwest breeze will also slacken as we head into the overnight hours. For those who like to sleep with the windows open, it’ll be a comfortable night, perhaps even a tad on the cool side, with partly cloudy skies, calm air, and lows in the upper 40s to around 50°F.

Monday will be a fairly quiet day as Canadian high pressure rapidly shifts southeastward across the region and towards the Atlantic Ocean. Expect pleasant conditions with a few passing clouds and highs in the low 70s. Tompkins County will be on the rear flank of that high by Monday evening, which will churn milder air from the Southern U.S. into its clockwise flow, and a milder overnight low along with some partial cloud cover, with temperatures bottoming out in the upper 50s.

Tuesday will be warmer and somewhat unsettled as high continues to draw in warmer, humid air, while the edge of the jet stream ridge that’s dominated the weather for much of the past week shifts eastward. That’s going to allow for less stable air to eat away at the edges and, in combination with the heat and humidity, some pop-up thunderstorms will be possible Tuesday late afternoon and evening, say 3-7 PM. It will be mostly cloudy and muggy with highs in the mid 80s. Tuesday night won’t cool off much with all that moisture in the air, and it’ll be a humid night with partly cloudy skies and lows in the mid 60s.

Wednesday will be more unsettled as a low pressure storm system passing well to the north presses against the jet stream ridge with its cold frontal boundary. This will do a couple of things – one, the southerly flow ahead of the low will be strengthened due to the low’s counterclockwise flow working in tandem with the high’s clockwise flow. Temperatures will jump accordingly, and are likely make it into the upper 80s. This will also create a strong west-southwesterly breeze, and fire off a line of showers and thunderstorms ahead of the front. The worst of it is likely to be between 2-8 PM, but there will be rain showers budding in the heat and humidity from shortly after sunrise to well after sunset Wednesday night, with mostly cloudy skies in-between. The front should pass around sunset Wednesday, which will introduce drier, cooler air into the Southern Tier, with temperatures falling back into the upper 50s with partly cloudy skies and decreasing humidity to more comfortable levels overnight.

Thursday should by most accounts be a gorgeous day thanks to another high pressure system briefly working in from Canada. It will be mostly sunny with highs in the low 70s. A storm system will be passing to the south of Tompkins County Thursday night and Friday, and there is some chance on its northern fringe (i.e. Ithaca/Tompkins) for some showers Thursday night, though nothing drenching. There will be increasing clouds overnight, becoming mostly cloudy by sunrise Friday, with lows in the lower 50s.

Friday will be on the cooler side as that storm system to the south results in mostly cloudy skies (limiting incoming solar radiation and its heating) while northwesterly flow continues from the Canadian high. High temperatures should only make it into the mid 60s, and a few rain showers are possible, primarily south of Ithaca. Friday night will see a shortwave (pulse of instability) associated with the low pass through the Southern Tier, so some rain rain showers are likely overnight with mostly cloudy skies and lows around 50°F.

For Cornell’s graduation weekend, it’ll get off to a cooler start as that northwesterly flow continues. It’ll be partly cloudy with a few isolated showers as the shortwave moves out, with highs in the mid 60s. Saturday will see mostly cloudy skies with lows around 50°F, and Sunday is looking picture-perfect, with a few passing clouds and highs in the mid 70s.

Graphics courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Taking a look at Memorial Day and the start of June, models suggest the Northeast will be cooking under a ridge in the jet stream with near normal precipitation in the Southern Tier. A cutoff low will result in some cooler-than-normal conditions in and around Texas, while an upstream jet stream ridge will make the West Coast feel very summer-like – and for parched and fire-prone areas, that’s not a good thing.

On a side note, the hurricane season started early this year with the formation of Tropical Storm Ana in the Atlantic, which was weak and not a threat to land areas. NOAA is expecting an above-average hurricane season this year, with 13-20 named storms, 6-10 hurricanes, and 3-5 major hurricanes over the next six months.

Brian Crandall

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