ITHACA, N.Y. — Think of it as the last gasps of summer. As we enter the middle of October, temperatures will be unseasonably mild and sunny skies will bless our realms, but as Game of Thrones fans would opine, the White Walkers draw near, as temperatures drop sharply for the weekend.
Taking a look at the final September numbers, with an average temperature of 64.1 °F, September finished 4.1 °F above normal. It was also substantially wetter than usual, with a total of 5.36″ recorded at the Northeast Regional Climate Center/Cornell Game Farm Road weather station, well above the long-term average of 3.69″. The daytime highs were 2.4 °F above normal, and the nighttime lows 5.7 °F above normal, which is not unusual for a wet month – cloud cover from overnight rain events would help keep heat in, and a higher dewpoint from rainfall moistening the air slows and may even halt the fall in overnight temperatures.
As far as where the numbers fall into climatological rankings, September 2018 ranks 17th out of 126 years of records, and continues a noticeable unusual data trend where after decades of more moderate values, average temperatures have been ticking upward, only just starting to catch up with values from the first half of the 20th century. Rainfall was also well above average, ranking 14th in the 126 years of records.
For the record, there have been no measurable September snows in the precipitation totals. Winter is coming, but there’s no need to rush the White Walkers.
This week should be a pleasant one to be out and about for work, but you’ll definitely want an umbrella for Thursday, and a jacket for the cool days afterward.
— NWS Binghamton (@NWSBinghamton) October 8, 2018
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The presence of shallow, cool air over the Northeast, and much warmer air eroding it from the south and west made for some very large temperature gradients over upstate on Monday, with temperatures around Albany in the upper 50s, and high temperatures near Buffalo reaching the mid 80s. As the Canadian high shifts east and the flow of cool air is steadily reduced, the warm air has steadily eroded the cloud cover and the temperature climbed into the 70s. Areas east of Ithaca have stayed cloudy and drizzle-filled heading into Monday night, with fog in many spots, while Ithaca proper and points west experience mostly cloudy skies with warm and muggy conditions, as temperatures remain in the upper 60s for overnight lows.
Tuesday will be a summer-like day for Tompkins County, as the clockwise flow of an offshore high pressure area brings substantial warm and fairly humid air into the region. With a steady south breeze, most places can expects to climb into the mid or upper 70s under partly cloudy skies. Tuesday night will continue that summery feel with temperatures only falling into the mid 60s with some passing clouds.
Wednesday will be another warm one, with the likely addition of tropical moisture as Hurricane Michael passes to the south and east (it will be a very bad week for the Florida Panhandle). Once again we can expect partly cloudy skies and somewhat humid conditions with highs in the mid 70s.
Wednesday night will be when the next system starts to approach from our west, a rather strong cold front. Ahead of the front, increasingly unstable conditions will lead to rain. With the tropical moisture feed, there will be enough water vapor in the atmosphere to encourage downpours Thursday morning and afternoon, which given saturated soils, could lead to potential flash flooding. A mitigation factor will be that the system should move fairly quickly, limiting the time period in which heavy rain could occur.
So for Wednesday night, it will be mild and humid in the mid 60s, with cloud cover building in and showers likely by midnight, and rain in most areas by daybreak. Thursday will be a rainy if mild day, with potential downpours so keep an eye out for flooding advisories. Temperatures won’t climb much, holding around 70 °F.
The front will move in by around sunset Thursday, and the rain will rapidly taper off to dry if mostly cloudy conditions. With cooler air coming in on northwest winds behind the front, temperatures will get down to the upper 40s by Friday morning. During the day Friday, it will really start feeling like fall, as temperatures will struggle to get out of the low 50s with partly to mostly cloudy skies.
You’ll want the thicker jacket if out Friday night – temperatures could get down to the upper 30s by early Saturday morning, and frost is not out of the question for some of the more rural and hilly areas. Saturday will likely only top out in the low 50s under partly cloudy skies, maybe not even breaking 50 °F in the outlying towns, and Saturday night will be upper 30s and partly cloudy. Sunday will be a bit warmer ahead of the next frontal boundary in the mid 50s, but the increased cloud cover will mitigate what satisfaction those extra degrees might give.
For those hoping for another warm spell, you might be out of luck for now. The NOAA Climate Prediction Center is forecasting a deep and potent trough in the jet stream that will bring unusually cool conditions to most of the continental United States apart from the West Coast and the tip of Florida. On the bright side, no major storms are expected in our area, though it will definitely feel like winter is coming as we head into the second half of the month.