ITHACA, N.Y. — Don’t think about putting away the umbrella just yet. The pattern of stormy if mild weather will persist through the week.
River Flooding and yet more Flash Flooding is possible overnight as heavy rain continues to soak NY and PA. Additional rainfall of 1.5-3.0″+ is possible by daybreak. If venturing out tonight, remember to Turn Around, Don’t Drown! pic.twitter.com/7nqzW9pX3T
— NWS MARFC (@NWSMARFC) August 14, 2018
AT THE REQUEST OF SENECA COUNTY, TRAVEL ON RTS 96 AND 89 N OF TOMPKINS COUNTY SHOULD BE AVOIDED DUE TO NUMEROUS ROAD WASHOUTS & CLOSURES.
— Tompkins DoER (@TompkinsDoER) August 14, 2018
If we’re looking for silver livings to the present meteorological situation, one could suppose that NOAA’s downgrade of the prospects of an active or even a normal hurricane season could be a plus. Conditions settling in over the Atlantic basin are increasingly El Niño-like, which increases wind shear over the Atlantic Ocean and helps prevent tropical storm development. Unusually cool tropical ocean surface temperatures are also doing their part to tamper down this year’s hurricane season.
What does El Niño mean for our weather? Typically, not a whole lot. El Niño, or more scientifically the warm phase of the El Niño Southern Oscillation (ENSO), is a smaller driver in the large scale atmospheric oscillations than can affect our weather patterns in the Northeast – typically, the Arctic Oscillation and its close relative, the North Atlantic Oscillation play a much bigger role for us, and neither of those is especially predictable because they’re driven by atmospheric pressure patterns, and lack atmospheric teleconnections to oceanic pools of heat. A typical El Niño will adjust the polar jet northward, so we tend to be drier and a few degrees warmer during El Niño autumns and winters, but very strong El Niños such as 1997-98 and 2015-16 can produce extreme warm conditions.
We could certainly use some dryness at this point, but a truly rain-free period in our weather is a long way out.
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The big driver of our recent wet weather woes has been a large and potent cutoff low, which separated from the Jet Stream and lingered over the Ohio River Valley before pushing northeastward, with its core currently passing overhead as it continues to slowly move on out. Think of it as an eddy of a stream – cutoff from the main flow, it just kinda wanders in place until it can be jostled and pushed out by stronger, higher-amplitude ridges or troughs further upstream. The location of the low to our west allowed it to tap into moist, unstable air from the south, and draw it poleward over Pennsylvania and New York, leading to the numerous heavy rains and flood advisories posted throughout the region.
For today, with the low overhead, expect rounds of heavy rain and thunderstorms interspersed with dry, cloudy periods – generally, it’s looking like this morning is round one, the afternoon will be relatively dry, and then round two will be during the late afternoon and evening. A Flash Flood Watch is in effect for all of Tompkins County until midnight. Parts of Schuyler County near Watkins Glen are under a Flash Flood Warning, meaning flash floods are imminent or occurring. Highs today will be in the mid to upper 70s with 0.5-1″ of rainfall, though locally higher amounts will be possible.
For tonight, things should quiet down as the low pressure area moves east. Rain should end by midnight as a weak high pressure area works its way in, and it should be partly cloudy by morning. Lows will be in the low 60s.
Wednesday is looking drier, if still fairly hot and humid. Temperatures will climb into the mid 80s under partly cloudy skies, but the weak high and a stalled frontal boundary to the north will allow enough instability to produce some isolated showers and thunderstorms during the afternoon. The air is dry enough that no heavy or long-lasting rain events are expected. Things should calm quickly after sunset and the ebbing heat of the day, so Wednesday night will be partly cloudy, a touch muggy, and lows in the mid 60s.
For Thursday, the weather will once again be unsettled as a trough of low pressure and multiple fronts press into the Southern Tier. Timing for all these events is still a bit uncertain, but will play a role in how strong the thunderstorms become (it depends on the amount of heat energy they’ll be able to tap into). At this point, it’s looking like an afternoon warm front and an evening cold front. With moist southwest flow, rains could be intense and more flash flooding is possible. Expect mostly cloudy skies with periods of rain, heavy at times, and highs in the low to mid 80s. Thursday night will be muggy with scattered showers and lows around 70 °F.
Things improve somewhat for Friday after the frontal passage, but the front will stall along the East Coast, and it and a high pressure area to the west will battle for dominance over our weather. This means there will be a persistent chance of rain through the end of the weekend. Friday will be mostly cloudy with scattered showers and thunderstorms and a high in the mid 80s. Saturday will be partly cloudy with a chance of showers and a high in the upper 70s, and Sunday with be partly cloudy with a smaller chance of showers and highs around 80 °F.
Conditions over the next couple of weeks are expected to remain abnormally warm and wet, according to the NOAA Climate Prediction Center. A persistent jet stream trough over the central third of the country will result in repeated surges of warm, moist air from the Southeast and into the Mid-Atlantic and New England. This moist air will allow for heavy rainfalls when unstable weather conditions are present.
On the West Coast, they’ll be getting surges of hot air from the desert Southwest, meaning excessively hot and dry conditions and a recipe for intensifying wildfires.