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Weather summary for all of Southern Ontario and
The national Capital region
Issued by Environment Canada Toronto at 2:04 AM EST Thursday 3
February 2011.

Updated storm reports.
==weather event discussion==

The low pressure centre which tracked across the lower Great Lakes
Is over the Atlantic early this morning. Much of southern and
Eastern Ontario received a wide swath of snow Tuesday night and 
Wednesday February second. Brisk to strong northeast winds 
accompanied the snow reducing visibilities significantly. Blizzard 
conditions affected some areas including Hamilton with 8 hours of 
blizzard conditions, with near blizzard conditions in nearby regions.

Even Wiarton willie was snow-bound, and didn't see his shadow, but 
graciously provided a snow observation.

The table below shows the total snowfall amounts and wind gusts 
received by Environment Canada as of 10 PM Wednesday. Snowfall 
amounts are difficult to measure where heavy winds accompanied the 
snow. Those observations are indicated as estimated amounts.

Location                   snowfall amounts (cm)

Windsor airport                     22
London airport                      19
Sarnia                              15-20 (estimate)
Kingsville                          20
Thornbury                           30
Hamilton (west mountain)            28 (estimate)
Niagara Escarpment (Thorold)        29
Dundas                              25
Burlington/Ancaster/waterdown       23 (estimate)
Fergus                              15
Kitchener                           15
Balaclava (ne of Owen Sound)        33
Wiarton                             23
Kincardine                          32
Orillia                             19
Coldwater (nw of Orillia)           20
Shanty Bay (near Barrie)            22
Muskoka                             17
Ashburn (N of Whitby)               20
N Richmond Hill                     17
Toronto                             13-19
Brampton                            19
Trenton                             17
Brighton                            15
Peterborough                        12-15 (estimate)
Cornwall                            25-30
Casselman (E of Ottawa)             20
Ottawa airport                      15
Gatineau                            12

                           Wind gusts (km/h)

Long Point                         118
Erieau (se of Chatham)              83
Port Weller (near St. Catharines)   84
Burlington                          84
Windsor                             78
London                              68
Toronto Island                      67

Please note that this summary contains the observations at the time 
of broadcast and does not constitute an official and final report of 
the weather events or the high impact events attributed to the 
weather events.




Update 2010-02-02: As this major storm continues to track northeast, snow accumulations in southern Ontario will generally be less than anticipated in some areas due to the high ice, rain and sleet content of the precipitation from the warm sector of this massive extra-tropical cyclone. The cold front associated with the low will continue to produce cold snow over the Great Lakes region for the next 12-24 hours as the storm continues to feed moisture from the south into the circulation. Strong winds across the frontal boundaries will contribute to significant blowing snow and and lake effect snow in the lee areas of the Great Lakes for most of Wednesday, and as the snow pack chills, ground level whiteouts may be frequent in open areas.

A major storm system is expected to develop out of the central US and extend across southern Ontario and the US Northeast through Wednesday, February 3, 2011, bringing possible snowfall amounts to the lower Great Lakes basin in excess of 20 in. (50cm), with possible amounts to 18 in. (45cm). Forecast models are in good agreement as to the severity of the storm. This storm will be the first major storm for the GH-GTA; southwestern Ontario has already had record multi-day lake effect storms this winter.

This should be considered a dangerous winter storm. Heavy and blowing snow combined with a temperature of approximately -10C create a dangerous and life-threatening exposure risk.

The first panel below is the GFS model snow accumulation forecast through February 3, 2011,

and the following panel is the NAM 84hr forecast snow accumulation model. Both project anywhere from 30-45cm of snow for southwestern Ontario and the GH-GTA, and some lake effect enhancement is expected.

Environment Canada update, Saturday, Dec, 12, 2010 3:59PM

Special weather statement
Issued by Environment Canada Ontario region. 3:59 PM EST Saturday
11 December 2010.

Special weather statement issued for..
City of Toronto
Windsor – Essex – Chatham-Kent
Sarnia – Lambton
London – Middlesex
Simcoe – Delhi – Norfolk
Dunnville – Caledonia – Haldimand
Oxford – Brant
City of Hamilton
Halton – Peel
York – Durham
Huron – Perth
Waterloo – Wellington
Dufferin – Innisfil
Grey – Bruce
Barrie – Orillia – Midland
Belleville – Quinte – Northumberland
Kingston – Prince Edward
Peterborough – Kawartha Lakes
Stirling – Tweed – South Frontenac
Bancroft – Bon Echo Park
Brockville – Leeds and Grenville
City of Ottawa
Prescott and Russell
Cornwall – Morrisburg
Smiths Falls – Lanark – Sharbot Lake
Parry Sound – Muskoka
Renfrew – Pembroke – Barry’s Bay
Burk’s Falls – Bayfield Inlet.

Winter storm threatening Sunday into Monday..

A low pressure system over Iowa will track east towards the lower Great Lakes and will intensify into a winter storm by the time it reaches Western New York state by Sunday evening.

Precipitation associated with this system is expected to begin in Southwestern Ontario after midnight tonight.. Reaching the greater Toronto area and Eastern Ontario including the national Capital region by Sunday morning.

There is still some uncertainty with regard to its exact track and the type of precipitation associated over southern and Eastern Ontario as this messy low pressure system gets closer. If the low Pressure centre tracks further north than expected..The rain-snow
boundary will also shift north resulting in very little snow near the lower Great Lakes. However if the storm centre tracks further south Than expected..Heavier snow may become an issue for areas near lakes Erie and Ontario.

Latest indications suggest that in regions south of a line from about Sarnia through Vaughan to Cobourg..Precipitation will likely start Out as wet snow or a wet snow and rain mix..Possibly changing at times to rain Sunday. A changeover to all snow is expected Sunday evening as colder air starts to pump in from the north in the wake of the low. Snowfall accumulations are difficult to forecast at thisTime due to the rain versus snow problem..So a range of a couple cm near the Lake Erie and Lake Ontario shorelines to 10 to 15 cm of the white stuff in areas near the line is possible.

In regions southeast of a line from about Peterborough to Ottawa.. Precipitation will likely begin as snow..Then change to freezing rain Sunday morning or early Sunday afternoon. The precipitation will likely change over to rain Sunday evening in Eastern Ontario before
changing back to snow late in the evening or overnight again due to colder air starting to pump in from the north in the wake of the low. With freezing rain expected to be the main precipitation type, a freezing rain warning has been issued for Eastern Ontario and
snowfall accumulation are expected to be 5 cm or less.

North of a line from about Sarnia through Cobourg then northwest of a Line from Cobourg to Ottawa..Precipitation is expected to be mostly or all in the form of snow with significant amounts of 15 to 25 cm quite likely by Monday morning. A winter storm warning has been
issued for regions near and east of Georgian Bay as a result. As the winter storm moves northeast across Extreme Eastern Ontario into Québec Sunday night into Monday morning,. Strong north to northwest winds will develop in its wake. These winds will usher in much colder air and result in blowing snow in some areas by Monday.


Big Upcoming Snowstorm for the East?


By Meghan Evans, Meteorologist
Dec 5, 2010; 11:35 PM ET

Story has been updated 12/6/2010 2:00 pm….

Monster Storm Closes in on 50 Percent Snow Cover by Christmas

A storm that will take shape by the middle of December will cross the country and could end up developing into a major snowstorm for portions of the mid-Atlantic and New England.

There are different storm track scenarios at this point that mean the difference between mostly rain or a potential blizzard along the Interstate 95 corridor from Washington, D.C., to Boston.

So far, Chief Long Range Forecaster Joe Bastardi has been correct with the Winter Forecast for the Northeast with his prediction that late November to December would be cold and stormy for many.

According to Bastardi, “Repetitive cold waves and the threats of storms will keep hitting parts of the East in the weeks leading up to Christmas.”

“One or two of these storms has the potential to become a major snowstorm for portions of the mid-Atlantic and New England, including the storm that may hit the East from December 12-14.”

Expert Senior Meteorologist Henry Margusity has also been warning about how the cold pattern in the East could soon yield the season’s first major snowstorm.

Scenario One: Major Snowstorm for Interior Northeast

In the first scenario, the storm could cause significant snowfall and wind across portions of the Midwest and the Ohio Valley states, impacting places like St. Louis, Chicago, and Indianapolis.

The storm would then cut across the interior Northeast in the first scenario. Mild air would be drawn into the I-95 corridor, making it a rainstorm for the big Northeast cities.

Meanwhile, the interior Northeast, perhaps from Pittsburgh to Buffalo would get a dumping of heavy, disruptive snow, because this region would lie on the cold, northwestern edge of the storm.

Scenario Two: Major Snowstorm for Interstate 95 Corridor

“If the storm brushes up the Eastern Seaboard, several inches of snow could lead to major travel disruptions in the big cities from Washington, D.C. to Philadelphia and New York City to Boston,” according to Expert Senior Meteorologist Carl Erickson.

On top of heavy snowfall, blustery winds would add to this winter storm scenario by causing blowing snow and potential whiteout conditions at times.

Lake-effect snow to the lee of the Great Lakes would be likely to accompany this scenario as well with an arctic blast of air blowing across the relatively mild water of the Great Lakes.

Another Possibility

Erickson points out that there is one other possibility with this storm, stating “One other scenario is that the storm takes shape too far off the coast, which would promote a frigid, dry northwesterly flow of air into the Interstate 95 corridor. If this were to occur, there would be potential for even more heavy lake-effect snow downwind of the Great Lakes.”

A stalled low pressure system off the east coast of the Canadian Maritimes is being blamed for redirecting the jet stream, producing a steady cold polar flow of air out of the northwest across the Great Lakes region, resulting in steady accumulations of snow in the SE lee of the lakes. The wintry blast, which started at the tail end of last week, is not expected to abate before late Wednesday or early Thursday. Its not yet been determined whether records have been set yet, but portions of southwestern Ontario have received as much as 114cm of snow since the squall period began.

Lake effect snows occur when cold winds blow across the warm fall and early winter waters of the Great Lakes, picking up moisture. Once these winds come onshore, the air mass rises and cools, depositing the moisture as snow in the lee of the lakes. This is a surface effect. Most of these LES squalls are less than 12,000 feet in depth, and as a result, disappear from radar about 100/160km miles out from the radar site as the beam overshoots the snow deck. The Great Lakes region is prone to these squalls up until about February, when the lakes begin to freeze over much of their surface, depriving the wind of moisture. This transition can be seen as January skies change from cloudy and flurry, to clear and cold in early February.

The following two animations show the composite reflectivity pattern from KBUF in Buffalo, NY, showing the band alignment with the NW–>SE wind direction for december 5, 2010 and December 6, 2010, respectively. The darker the blue, the more intense the snow. Moist winds off Lake Huron and Georgian Bay in the upper left materialize as snow bands further enhanced by lakes Erie and Ontario as they cross into Ohio and New York State. The snow bands are largely continuous back to the upper lakes, but, are not seen because the radar beam has passed over top of the snow bands at the Lake Huron and Georgian Bay shorelines. (Click on animation image if animation doesn’t self start.)

The second animation for December 6, 2010 (cities layer is suppressed) shows the orographic (cooling as the moist air rises over landform) condensation into snow, in the second half of the animation as a crescent shaped band forming southeast of Georgian Bay, near the centre of the animation. The wind rises up the gentle slope of the Oak Ridges moraine, just above the north shore of Lake Ontario.

Environment Canada discussion:

Weather summary for all of Southern Ontario and the National Capital
Region issued by Environment Canada Toronto at 6:15 AM EST Tuesday
7 December 2010.

Significant lake effect snowfall reports.
==weather event discussion==

The traditional snow belts of Southern Ontario are in the midst of a
major multi-day snow squall event. Brisk northwest winds from Lake
Huron and Georgian Bay have produced impressive snowfall
accumulations over the past couple of days. Heavy snow squalls will
continue today and Wednesday likely giving remarkable snow totals
well over one metre in and around the London area as well as some
locales to the southeast of Georgian Bay.

Snowfall reports as of 6 PM Monday and fallen since Saturday night,
except for lucan which has received a staggering 114 cm as of
6 AM.
Location snowfall amounts (cm snow)

London 45-55
London aiport 53
Southeast of London 65-70
Lucan (northwest of London) 114
Dorchester (east of London) 42
Goderich 15-20
Mount Forest 10
Lakelet (near Clifford) 18
Paisley (ne of Kincardine) 5-10
Niagara 14
Toronto downtown 2-4
Toronto north 12
Newmarket 30
Maple 15-20
King City 20
Schomberg 33 as of 8 AM Monday
Beeton (south of Alliston) 81
Thornbury 40
Barrie 10-15

Please note that this summary contains the observations at the time
of broadcast and does not constitute an official and final report of
the weather events or the high impact events attributed to the
weather events.

Looking at radar patterns for winter weather around the great lakes makes a couple of observations pretty evident. Much, if not most of the winter weather involves cloud decks of 10,000 feet or less. This especially true for “lake effect” snow storms which are directly a result of the moisture contribution of the relatively warm lake water. The first image below shows streamers (darker blue) developing on the lee shore of Lake Erie as the moisture laden air cools coming onshore, and sets up a dump of light snow in Niagara and east of Buffalo.

The red arrow shows the air mass direction, which just happens to be right down Lake Erie. The western end of Lake Ontario shows the development of new streamers from the short fetch of open water at the western end of the lake. (The areas of high intensity just southeast of KBUF are “windfarm anomalies” – the large spinning blades of windfarms are creating havoc with doppler radar. There is serious concern for interpretation of severe weather due to these anomalies.)

Lake effect snows tend to cease if the winter is cold enough to freeze Lake Erie and the western end of Lake Ontario. Subsequent snow after that comes from larger continental low pressure systems moving across the region. It is easy to see however, that until the lakes freeze, lake effect snow can impact any part of the shorelines depending on wind direction.

The second image shows the Echo Tops pattern for the same period. The grey areas indicate tops of 5-10,000 feet or less. This is the radar interpretation of the vertical density pattern of moisture over the region. Its apparent straight out that these lake effect squalls are thin and have little vertical development.

From a radar interpretation perspective this lack of vertical development is important. Since the radar beam sweeps upward at fixed angles relative to the horizon, it is easily seen that because of the shallow altitude of the cloud deck, the beam will overshoot the deck in a fairly short distance. This creates the idea that the event is very local to the radar site, when it fact it may encompass a very much larger region. The national maps at the top of the EWR pages will confirm how broad the weather pattern is, and illustrate why its important to understand the visual limit of the radar in low decks. The chart below will show the relationship between beam height and distance from the radar site.


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