Update: The National Weather Service just issued flood warnings – the highest alert level – for rivers in the southern layer.
Syracuse, NY – In the last days of the year that we would all like to forget, there is a storm that we will probably not be able to.
If the predictions are successful, upstate New York could be plagued by heavy rains, floods, strong winds, rapid freezing, and lake-effect snow. There is a good chance of river flooding in the southern layer, and possible flash floods from the Hudson and Mohawk valleys to the Adirondacks. A foot of snow with a lake effect could cover Tug Hill and Western New York. Gust winds of 50 mph can cause power outages.
All on Christmas Eve and Christmas Day 2020.
The National Meteorological Service is not measuring words about this, even though it uses bold letters in this morning’s briefing.
“The combination of strong winds, high humidity and temperatures and heavy rains will generate a rapid melt of snow and lead to a potentially significant flood event, ”Said the briefing issued by the weather service’s Binghamton office. “A significant flooding of the river is likely to occur later today during Christmas and possibly Saturday. “
The biggest concerns are the river valleys of the Southern Layer, which were buried by up to 44 inches of snow last week and could see the heaviest rain today. But no part of Upstate is likely to escape some of the impacts of this storm system. The National Meteorological Service’s hazard maps have so many layers that it is difficult to separate who is in the flash flood zone, area of strong wind or lake-effect snow watching – or all three at the same time.
It is a complicated mess and forecasters are still not sure how it will all unfold. If you think it is difficult to predict how much snow will fall, it is even more difficult to predict how quickly it will melt. and run into streams and rivers. This will be a critical ingredient for those who are inundated and those who are not.
Here are the latest weather service ideas and schedules.
Temperatures heat up quickly and reach 50 in the middle of the afternoon. It is likely to stay warm all night – Albany is not expected to drop below 50 degrees between 2 pm today and 2 pm on Christmas Day. This warm air will trigger the rapid melting of snow, especially when the winds rise and carry the warmer air through the air pockets between the snowflakes.
The snow that fell last week has compacted, but still retains enough water. Parts of the southern layer have 4 inches of water trapped in the snow; if everything melts, it will put the equivalent of a month of rain on the streets and rivers.
Here comes the rain, take it this morning and it becomes a flood this afternoon and overnight. Except for western New York, almost the entire interior of the state must have at least an inch of rain, and it will be stronger in the south and east – exactly the same areas where all that water is draining from the snow. Binghamton and Albany can have 5 or more inches of rain.
It could also fall hard, as much as an inch in an interval of 12 hours. The faster it falls, the more likely it is that streams and rivers will jump over its banks.
In Catskills, the tendency of mountain slopes to extract water from clouds – known as “orographic support” – can result in up to 5 centimeters of rain.
Of 121 river meters in the state of New York monitored by the meteorological service, 66 are projected to be in or near the flood stage within the next 24 to 48 hours. Smaller streams would likely peak on Friday morning, while rivers, including Susquehanna, Mohawk and Ausable would rise more slowly, reaching the peak on Christmas Eve or Saturday.
Overnight on Christmas morning
As temperatures remain high and rain continues to fall, floods of streams and streets can happen at the worst possible time: in the dark. Children can be cuddled and cozy, but adults will jump out of their beds to check the basement.
Smaller streams are expected to appear later this evening or early in the morning. Oneida Creek, in Madison County, and Schoharie Creek, in Green County, peak around 10 pm.
If that is not bad enough, the winds also increase during the night, increasing the chances of power outages. Syracuse could see its gust peak at about 30 mph around midnight, while gusts up to 50 mph can hit Albany at around 3 am.
Temperatures will drop dramatically as a cold front rolls over at the end of the day. This will slow the melting of snow and end the rain, but at a cost: flooded streets can suddenly freeze, and freezing rain and a little snow can add more slippery layers.
Binghamton and Syracuse could see sub-zero temperatures at 3 pm, while Albany could stay above freezing until 10 pm on Christmas Eve.
Colder temperatures with stronger westerly winds also contribute to lake-effect snow. Tug Hill and parts of western New York can be hit by snow starting on Friday night and lasting until the weekend. A foot or more can fall in narrow bands.
Syracuse can have a few inches of snow.
“This is going to be a problem,” meteorologist for weather service Dave Nicosia told emergency planners this week. “Whenever you add it all up, it is extremely complex.”
SEE MORE INFORMATION
‘Greater’ flood risk in upstate NY: ‘We’re starting to get worried’
The Christmas Eve storm could cause flooding, power outages and icy roads in Upstate NY
Binghamton buried under more than 3 feet of snow: a new record (see photos)