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10/28/2011
Larry Costanzo
| Category:
Industry News
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A potent October snowstorm will target the Northeast Saturday. Below we have the forecast and we will also dig into why it's so difficult to forecast major snowstorms this early in the season.
Northeast
Snow Forecast
Low pressure will track up the East Coast on Saturday producing
significant snow across the Northeast.
Below is our forecast accumulation map showing the
heaviest amounts west and northwest of the I-95 corridor.
In the pink shadings we could see 6 to 12 inches of heavy, wet snow.
This includes cities such as Allentown,
Pa., Poughkeepsie,
N.Y. and Worcester,
Mass. Early season snows are notorious for causing tree
damage and power outages and this storm will be no exception.
While the heaviest amounts are most likely to fall northwest of I-95,
some accumulations are also possible closer to the coast along the
Philadelphia to New York City to Boston corridor.
Precipitation will start as rain in these locations, but may change
over to snow. How quickly this occurs and how much snow falls is
dependent on the availability of enough cold air, which is difficult to
forecast early in the season. Below we will explore "Is it cold enough
for snow?"
Local forecasts: Washington
| Philly
| NYC
| Boston
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Northeast
snow forecast next 48 hours..
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Is
it Cold Enough for Snow?
Early season snows present some difficulties for forecasters.
What may look like a straight forward forecast of snow in December is
trickier in late October. The simple reason:
temperatures at and near the surface typically just aren't quite cold
enough yet. This is the "climatology you have to fight" to get a decent
snow event this early in the season, even with a fresh, cool area of
high pressure in place ahead of the storm as depicted in the image
below.
Article: How
rare is October snow?
This is not to say it isn't
cold enough for any snow to fall. As long
as the cold (i.e. sub-freezing) air aloft is
deep enough for snow crystals to survive the journey down to the
surface without melting, you can get snow falling with surface
temperatures somewhat above freezing. A stronger storm system, as
computer models suggest this weekend, can also help increase the chance
of wet snow by cooling the air through a process called "dynamic
cooling."
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What
we expect Saturday.
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Saturday morning, as the system is getting organized over the
Mid-Atlantic States, surface
temperatures will be "marginal"...from the upper 30s to the
40s in much of the Northeast. Temperatures could hold at these levels
through much of the day.
Could some wet snowflakes mix in with rain, at times, with
those temperatures along the I-95 corridor? Sure.
In fact, if enough cooling does occur, we could
be talking about more than just snowflakes mixed with rain.
Accumulations would be possible in grassy areas and on other surfaces.
However, another factor to consider is the temperature of the
ground itself.
It's been a warm October so far in much of the Northeast, New
England in particular. So, any falling wet snow that hits the pavement,
in particular, could melt soon after contact. If snow rates are heavy
enough, the warm ground obstacle to accumulations could be overcome.
That effect would be most pronounced on major roadways. On the other
hand, trees would cool quickly enough for snow to stick.
The image below shows the track of the low and
what we are watching for in the Northeast on Saturday. There are still critical
uncertainties with the exact track of the low and how much cold air and
moisture will combine.
If you live near and particularly west of the
I-95 corridor of the Northeast, stay tuned to The
Weather Channel and check back with weather.com as we close out the
week.
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What
we expect.
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See original article at: http://www.weather.com/outlook/weather-news/news/articles/weekend-storm-wet-snow_2011-10-26
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