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Flood fears as warm-up begins to melt snow today

There will be lots of water and it is bound to get messy.

A snow pack up to 88 inches deep dumped over a swath of Western New York by the double lake-effect storms this week will gradually start melting today when temperatures crest above the freezing point for the first time since Monday.

The existing snow will absorb it at first.

The real melt off picks up speed as the weekend wears on into Thanksgiving week, forecasters said.

“Sunday night and Monday, warm temperatures begin the melt – it will melt quickly,” said Jon Hitchcock, meteorologist with the National Weather Service.

Weather service scientists were busy Friday collecting core samples throughout snow piles around Erie, Genesee and Wyoming counties in an effort to estimate the water equivalent in the snow in order to make better forecasts about where the flooding could hit. What they found was that the snowpack in some of the hardest hit areas contains the equivalent of 4 to 6 inches of water.

The weather service has issued a flood watch running from 1 p.m. Sunday through 7 a.m. Wednesday for all of Erie, Genesee, Wyoming, Chautauqua and Cattaraugus counties. “Significant flooding” is possible, the weather service reported.

Flooding would hit urban and low-lying areas first before creeks and streams like Buffalo, Cattaraugus, Cayuga, Cazenovia, Ellicott and eventually Tonawanda creeks begin swelling and overflowing their banks as they quickly take on snow melt from hard-hit areas upstream.

Although Northtowns communities like Amherst, Clarence and Tonawanda escaped the lake-effect snowstorm, they still could be in the line of fire of rising creek waters resulting from the melting snow.

“We’ve had it made for the past few days,” said Williamsville Mayor Brian Kulpa. But he added that the community has to be on guard because the snow melt from Alden and Lancaster will end up running into Ellicott Creek, which cuts through Williamsville and other points in the Northtowns.

The news for the hard-hit areas, while dire, isn’t all bad.

“The good thing is that the ground isn’t frozen,” said John Loffredo, Erie County’s commissioner of public works. “The bad thing is there’s six feet of snow that has to melt. The good thing is that it will probably melt over a couple of days. What we’re looking at is really an unknown as far as flooding goes. We’ve never experienced this before.”

Also, because there’s no significant ice building on any of the waterways, experts noted there’s little threat for ice jam flooding.

There will be a lot of water saturating the ground, however. The runoff will pour into storm sewers, creeks, streams and low-lying areas at once.

How much? “It will depend on how fast it warms up, how long it warms up and how much rain there is,” said Aaron Reynolds, a meteorologist at the weather service.

What the weather service experts did learn from Friday’s snow-core tests is that there is 6.3 inches of water in a 34-inch snowpack resting over Orchard Park. There is a half-foot of water embedded in 32 inches of snow in West Seneca and in 34 inches of snow in Darien of Genesee County.

All that water has to go somewhere.

“Based on information from the National Weather Service, we can expect localized flooding as a result of rising temperatures and poor drainage conditions,” said Bruce I. Sanders of the U.S. Army Corps of Engineers in Buffalo. “This includes snow-covered storm drains in built-up areas and snow-clogged drainage ditches and culverts in suburban and rural areas.”

The weather service forecast projects the thermometer to increase from 32 to 35 degrees between 10 to 11 a.m. today with a breezy southwest wind up to 20 mph. It is expected to remain above freezing through Tuesday night. Between that time, there is a forecast high of 61 degrees on Monday with rain showers.

The warming air temperatures combined with a southerly breeze and rising dew points “will make for a more efficient melting of the snowpack,” the weather service stated.

Forecasters expect up to a half-inch of rain to fall between today and Monday.

“The rain isn’t a big deal but it will add to whatever is going to melt,” Hitchcock said.

What to do?

“People living in areas prone to flooding – and where significant amounts of snow fell – should take time in advance of the warming to prepare for the potential for significant flooding early next week,” the updated weather service statement said.

“In addition to creeks and small streams flooding their banks, general flooding is possible across towns where several feet of snow fell. Drains may be clogged with snow and leaves, and the massive amounts of snow may prevent water from draining efficiently.”

Here’s what to expect day by day:

Today

Rain will likely start falling after 2 p.m. as the mercury climbs to 40 degrees. It will stay there through the night. Less than a tenth of an inch of rain is possible today and tonight but there will be a breezy southwest wind up to 25 mph.

Hitchcock said today’s weather will serve to “consolidate the snowpack a little bit” but won’t cause water to run off resulting in flooding.

“Whatever melts, the snow tends to reabsorb it like a sponge,” he said.

Sunday

“The snowpack will still be in a consolidating phase,” Hitchcock said.

There is a chance of showers after 10 a.m. with a high near 51 degrees helped by a warm south wind. Less than a tenth of an inch of rain is possible, forecasters said.

At some point during the day, that “sponge” that is the snowpack will be as full of water as it can take and critical mass will be reached.

The meltoff will be underway.

“Flooding might be expected to begin Sunday, carrying into Monday,” said Sanders of the Corps of Engineers.

Monday

The melting process will be speeded up by showers between 1 and 2 a.m. and rain after 2 a.m., combined with an overnight low of only 50 degrees and a breezy southeast gusting as high as 36 mph.

“As the snowpack ripens – and with the addition of a half-inch or so of rainfall Sunday night and Monday – the potential for flooding will rapidly increase,” according to the weather service statement.

New precipitation between one-tenth and one-quarter of an inch is possible both Sunday night and Monday.

The forecast for the day calls for mostly cloudy conditions with rain mainly after 4 p.m. with a high of 61 degrees – 17 degrees above the daily average.

“The first concern is general urban flooding in low-lying areas,” Hitchcock said.

Added Sanders: “Stream flow related flooding would be delayed most likely to Monday or Tuesday and minor to moderate flooding may be expected.”

Showers are likely at night.

Tuesday

There’s a chance of rain or snow showers. Temperatures return closer to normal with an overnight low Monday of 38 degrees with a high of 40.

Other creeks and streams will likely already be engaged by flooding at this time, forecasters said, but the slow-rising Tonawanda Creek might not crest until mid-week.

The thermometer returns back below the freezing point at night with a forecast overnight low of 30 degrees.

News Staff Reporter Jane Kwiatkowski Radlich contributed to this report.

email: tpignataro@buffnews.com