ITHACA, N.Y. — Don’t put away the summer gear just yet. An early fall heat wave will bring near-record heat, and the high pressure system supporting that heat wave will result in dry conditions for much of the week ahead. A cold front moves through Saturday morning and temperatures will drop down to much cooler readings for next weekend.
Temperatures will trend warmer through the middle part of this week. High temperatures on Tuesday and Wednesday will be near current records, with the possibility of new records being set. #nywx #pawx pic.twitter.com/xMSbdsZGaV— NWS Binghamton (@NWSBinghamton) October 1, 2023
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An expansive area of high pressure is moving eastward from the Great Lakes and into Upstate New York, directly overhead Monday, and shifting southward Wednesday. This will shunt storm systems well to the north and south of Tompkins County, and mild temperatures today and tomorrow will climb to near-record values for mid-week as southerly flow kicks in on the rear flank of the high and ushers unseasonably warm air northeastward into the Finger Lakes and Southern Tier.
Now, being early October, record heat means values in the mid 80s midweek. Overnight lows will be in the mid 50s to around 60, and the humidity will be noticeable but not particularly muggy, with dewpoints generally in the low 60s. All in all, its shaping up to be a warm quiet week until a cold front sweeps in with a strong Canadian low during the day Friday.
For the rest of your Sunday, expect clear skies and a light north wind, pleasant for your outdoor activities as the leaves begin to turn. Highs will be warmer than yesterday, in the upper 70s. Tonight will host a few passing clouds and calm winds, with lows in the mid 50s. Thick fog will be possible in the valley areas towards sunrise Monday.
Monday sees the high move overhead, with slightly warmer and more humid conditions, but otherwise much the same. Skies will be mostly sunny with highs near 80. Monday night will see mostly clear skies with lows in the upper 50s, with widespread morning fog possible.
Quick digression, but you might be wondering why fog is more common in the fall – that’s because you still have warm, moist ground from the summer, but you also have longer nights with the loss of daylight. Radiational cooling of the air overhead and elevated dewpoints created by surface soils allow temperatures to slide down and reach the dewpoint value, triggering water vapor to condense out and forming fog.
Tuesday will be near-record highs. Skies will be near-clear and temperatures will be in the lower 80s (just to note, the current deterministic model blend calls for 83 degrees, the record is 84). Tuesday night will see passing clouds, some morning fog again possible, and lows in the upper 50s.
Wednesday will be another warm day with highs in the mid 80s, though with the record high of 88, the chance of breaking the record is lower. It will be mostly sunny with a south wind and rather humid. Wednesday night will see mostly clear skies with lows around 60 – the warmer daytime high means it will take longer to fall near dewpoint values, so morning fog will be less prevalent.
As the storm system approaches from the west Thursday, enhanced southern winds will mix a deeper (wider) layer of lower atmosphere, and with partly to mostly cloudy skies, temperatures won’t be as warm. Highs will be around 80. Thursday night will see mostly cloudy skies with lows around 60.
Right now, the expectation is that the rain will be scattered showers Friday, on-and-off during the morning and afternoon, continuing into Friday night. Not a total washout, but you’ll need an umbrella as that cold front approaches from the west. It will be mostly cloudy and breezy with highs in the mid 70s. Friday night will see occasional showers, mostly cloudy skies, and lows in the mid 50s.
The cool down next weekend will be stark, with showers and mid 60s for Saturday, and perhaps barely breaking 60 with partly to mostly cloudy skies Sunday. Temps likely stay in the 50s for highs outside of Ithaca.
The medium-range calls for a jet stream ridge in the Western United States, and a downstream trough over the East. This should result in cooler-than-normal temperatures for Tompkins County, though it will also tend to be on the dry side. Some of the highest elevations like Connecticut Hill may see their first decent frosts with this cold spell, though temperatures look like they’ll still be too warm for significant frost in Ithaca and along the lakeshore. Highs in the 50s will moderate back to more seasonable values in the 60s as the week progresses.