EFFECT SNOW: COLD WINDS BLOWING ACROSS WARM WATER BREW
INTENSE FORECASTING AT NOAA’S NATIONAL WEATHER SERVICE
Meteorologists Must Discern Where Narrow Bands Will Leave Residents
2, 2007 — Having to deal with the large scale winter snowstorms
that blanket much of the northern United States every winter is a big
challenge. But those living in the Great Lakes area must also contend
effect snows. These snows often generate enormous amounts of snowfall
over localized, and sometimes heavily populated, regions downwind of the
Great Lakes. (Click NOAA image for a larger view of satellite
image showing lake effect snow. Please credit “NOAA.”)
the NOAA National Weather Service
is just as skilled at forecasting and tracking localized lake effect snow
as it is with larger scale snow storms. The forecasters at the NOAA
National Weather Service Forecast Office in Buffalo, N.Y., pride themselves
on making accurate lake effect snow forecasts. In fact, thanks to the
Buffalo office, residents were warned more than 24 hours in advance of
the tremendous lake effect snows that buried much of the Great Lakes region
earlier this month.
This advance warning is significant considering these snows occur on the
same scale as a summertime thunderstorm. Of course, it also helps that
those living in this area are well prepared for and equipped to handle
Effect Snowfall Extremes
unofficial report of 77 inches of snow in a 24 hour period was
recorded at Montague, N.Y., during Jan. 11 to 12, 1997.
On Dec. 26, 2001 to Jan. 1, 2002, Montague, N.Y., received 127
inches of lake effect snow, making it one of the highest snowfall
totals for any storm on record.
The most snow in a winter season occurred in 1976 to 1977. It
was an extreme winter in the Northeast and a little town known
as Hooker, N.Y., received 467 inches of snow that season.
effect storms that buried many parts of New York state with near-record
breaking snow in February 2007 were unusual in terms of its duration,
but such storms are not uncommon at this time of the year, according to
Niziol, Buffalo native and meteorologist-in-charge of the Buffalo
lake effect snows last a day or two, but this episode lasted more than
a week,” said Niziol. “The only other time this has happened
recently was Christmas 2001 when a similar weather pattern in the Great
lakes region brought a five-day total of 81.6 inches of snow to Buffalo
and a total of 127 inches of snow to the town of Montague, N.Y. —
just east of Lake Ontario. Such storms reinforce this region’s reputation
as one of the snowiest regions east of the Rockies.”
explained that lake effect snow is one of the most difficult challenges
facing weather forecasters in the Great Lakes region. Snowfall amounts
are often referred to in feet rather than inches. Although lake effect
snows generally result in less death and destruction than other types
of severe weather (i.e., tornados and hurricanes), they often produce
significant impacts on travel, commerce and industry.
National Weather Service Forecast Office in Buffalo
NOAA National Weather Service Forecast Office in Buffalo, N.Y., provides
forecasts for the two largest snow belts in the Great Lakes region (i.e.,
Lake Erie and Lake Ontario) and has been involved in lake effect snow
research and forecasting for decades. The office is “located in
one of the best natural laboratories for [winter] weather and the recent
lake effect snowfall confirms this,” said Niziol. El Niño-induced
above normal temperatures hampered lake effect snows earlier this winter.
However, now that El Niño has dissipated
and temperatures have dropped back to normal levels, the Great Lakes region
has seen the return of lake effect snows.
Makes Lake Effect Snows so Unique?
effect snows are extremely localized snow storms that occur downwind of
the Great Lakes in the late fall and winter. Lake effect snows typically
form discrete, narrow bands of snow, which are often characterized by
intense snowfall and limited visibility. The bands occur throughout the
Great Lakes region, both in the United States and Canada.
The main difference between a lake effect snow and a “standard”
snowstorm is the area that is blanketed by such events. In a large scale
snowstorm, such as a Nor’easter, snow may
cover several states at one time. In a lake effect storm, the snowfall
may be confined to only a portion of a county.
effect snow occurs when cold air, often originating from Canada, moves
across the open waters of the Great Lakes. As the cold air passes over
its unfrozen, relatively warm waters of the Great Lakes, its warmth and
moisture are transferred into the lowest portion of the atmosphere. As
this warm air rises and cools, its moisture condenses, leading to cloud
formation and ultimately snow on the downwind (or leeward) sides of the
Great Lakes. The wind direction determines where the snowband will occur.
Because winds accompanying arctic air masses generally originate from
a westerly direction, lake effect snow typically falls on the east or
southeast sides of the Great Lakes. (Click NOAA image above for
a larger view of diagram showing lake effect snow event. Please credit
a typical winter storm lasts a few hours to a few days, lake effect snow
often produces snow continuously for up to 48 hours in a particular area.
Snowfall rates from a single intense band of lake effect snow can approach
six inches per hour at times. As long as the wind remains steady and out
of the same direction, a single band of lake effect snow can remain stationary
for several hours or, in rare instances, several days at a time.
unique aspect of lake effect snows is the extreme variability that can
occur in space and time," said Niziol. "It is not uncommon for
sunny skies at a particular location to be quickly replaced by blinding,
wind-driven snowfall in a matter of minutes." Similarly, snowfall
accumulations can vary from trace amounts to a couple feet over a very
short distance (i.e., several miles). One of the more challenging aspects
of forecasting lake effect snow is pinpointing exactly where the heaviest
snow will occur because even small changes in wind direction can significantly
alter the areas to be impacted.
lake effect snow is expected, a variety of Lake Effect Snow Watches, Warnings
and Advisories can be issued by the NOAA National Weather Service. Exact
snowfall criteria differ across geographic regions in the Great Lakes.
The following criteria apply to areas of the eastern Great Lakes:
- Lake Effect
Snow Watches mean that conditions in the atmosphere are primed to produce
lake effect snow. Watches are issued from 24 to 36 hours in advance
of an anticipated event.
Effect Snow Warnings mean that more than seven inches of snow are expected
in a 12 hour period or more than nine inches of snow in a 24 hour period.
Effect Snow Advisories mean that four to seven inches of snow are expected
in a 12-hour period.
does the NOAA National Weather Service Forecast Lake Effect Snow?
lake effect snows impact such a small geographic region, it was only recently
that they could be predicted by NOAA’s regional and national scale
computer models. Forecasters also rely on locally developed methods to
predict such events. Forecasters at the Buffalo office for example, used
lessons learned from years of operational experience and rules of thumb
to develop their own forecast tool called BUFKIT.
BUFKIT is a computer application that uses high-resolution numerical weather
prediction data to enhance forecasts for local scale snowstorms near the
Great Lakes. The local scale data sets are interpolated from hourly forecast
data from one of NOAA’s National Centers for Environmental Prediction
models. The data is collaborated by voluntary local snow spotters. BUFKIT
quickly and easily streamlines the process of assimilating these data
sets for operational use in the real-time forecast environment. The data
sets are extremely well-tailored for the prediction of lake-effect snow
because they provide the high degree of temporal and vertical resolution
necessary to evaluate these local scale events.
designed in the early 1990s to help predict lake effect snow, BUFKIT is
so successful and user friendly that its use has been expanded to include
other local scale weather predictions, including floods, thunderstorms
and high winds. Today, BUFKIT is being used at more than one hundred locations
throughout the United States and Canada.
Lake Effect Snow Occur in Areas other than the Great Lakes?
the term lake effect snow refers to storms occurring on the Great
Lakes region, in theory, anywhere cold air move across a warm body
of water (lakes, bays, oceans and even reservoirs), the same mechanisms
will produce similar local scale snows. For example, similar snow
storms are known to occur off the Great Salt Lake in Utah, Finger
Lakes region in New York state and Lake Champlain bordering Vermont
and New York.
effect snows” have been observed in Delaware Bay, Chesapeake
Bay, and Massachusetts Bay/Cape Cod and even continental land masses
passing over open ocean waters have produced “ocean effect
snows” near Long Island Sound, the Gulf of St. Lawrence and
the Canadian Maritimes.
similar to the lake effect snow may also occur in other parts of
the world, near large lakes and other regions such as the Sea of
Japan, Bay of Finland and in Scandinavia near the Baltic Sea.
To more accurately
measure the snow that fell from such localized storms, the office trained
hundreds of volunteers from across the region to call in snowfall measurements.
The network provides forecasters with real-time updates on conditions
and snowfall accumulations.
is NOAA doing to improve Lake Effect Snow forecasts in the future?
NOAA continues working to improve lake effect snow forecasts using satellite
data, advanced high resolution computer models and collaborative partnerships:
is using satellites to help track and forecast lake effect snow. NOAA
geostationary operational environmental
satellites (GOES) are being used to monitor the location and movement
of lake effect snow bands both during the day and night using infrared
satellite technologies. NOAA also uses its polar-orbiting
environmental satellites (POES) to obtain accurate lake surface
temperatures — an important factor in determining the potential
for lake effect snow — using Advanced Very High Resolution Radiometer
(or AVHRR) remote sensing technology. The NOAA
Great Lakes Environmental Research Laboratory then uses this data
in combination with ice cover data from the NOAA
National Ice Center to compile digital maps known as the daily
Great Lakes Surface Environmental Analysis (or GLSEA). This information
is then fed into computer models to predict snowfall in the Great Lakes
Over the past 10 years, new and improved numerical models and forecast
techniques have greatly improved lake effect snow forecasts. For example,
because of increased spatial and temporal resolution in NOAA’s
regional and national scale models, many meteorological parameters associated
with the Great Lakes can now be incorporated into these models, including
Great Lakes surface temperatures. NOAA’s research efforts are
also concentrating on real-time mesoscale numerical models that will
predict not only the location and movement of lake effect snow, but
accurate snowfall amounts as well.
NOAA’s National Weather Service Forecast Office in Buffalo, N.Y.,
is involved in a NOAA-funded
Cooperative Program for Operational Meteorology, Education and Training
(COMET) project wiith the State University of New York at Oswego
to evaluate computer models designed to help further improve Lake Effect
Snow forecasts. The Buffalo Weather Forecast Office, located near the
Canadian border, also coordinates the Great Lakes Workshop on Operational
Meteorology, an annual conference dedicated to share new forecast techniques
and technology to improve the prediction of all types of weather associated
with the Great Lakes region.
Effect Snow Monitoring
One of the best ways to monitor and track lake effect snow during
the winter season is to go to the Buffalo
Weather Forecast Office Web page (or other NOAA National Weather Service
forecast offices across the Great Lakes region) and use the Buffalo local
weather radars to track the movement of the lake effect snow bands in
near real time. If you want to learn more about the topic or look back
at lake effect snow storms on the eastern Great Lakes, go to the NWS
Buffalo Lake Effect Snow Page.
TO DELIVER COLD-HEARTED VALENTINE: Persistent February Chill Supporting
Array of Winter Weather Woes
NOAA National Weather Service Eastern
Region—Latest Winter Weather Watches and Warnings Issued
NOAA Weather Safety
Storms: The Deceptive Killers (PDF)
Lake-Effect Snow Summary
NOAA Storm Watch
NOAAWatch—Storms and Hazards
National Weather Service, (301) 713-0622