Weather Discussion - Friday February 25th 2011

Today's post will be short and sweet as I have alot going on today.
First off.... the storm system that moved into Southern Ontario today was not much of a snow maker for many areas. Snowfall was pretty much confined to areas along the north shores of Lake Erie with 5-10cm reported there. Upwards of 15 or so has been reported around Niagara Falls. Futher north of that line totals dropped off very quickly.
We were always on the nortern fringes of this storm, but as it approached it was a bit further south than orginally expected, thus the lower snowfall amounts.

There is another weak system that will cross the regions later in the day Saturday that will give a coating to a few cm for the region.

Temperatures will be below seasonal values for Friday night and Saturdy, but that will be short lived as milder air begins to creep in Sunday.

Normal Highs currently range from +2 in the SW to -1 north of the GTA

The big story will be the milder air and heavy rain moving in for Sunday and Monday. Rain,may start as wet snow, but quickly change over to straight rain as the milder temperatures move in. 20-30mm can be expected from this system and temperatures may reach double digits across the region along with gusty southerly winds. It will turn colder behind the storm with a brief changeover to snow, but the majority of the precipitation is on the warmer side of the storm.

GFS Model Forecast for Monday.

Long Range Models continue to see wild temperature swings into the first part of March. Still along  way off,but there is a very large storm system for March 5th that will be snow according to the current model guidance. That will likely change, but it's worth keeping an eye on.

The warmest temperature across Southern Ontario yesterday was:

Toronto City Centre Airport  +3°C @4pm

Special Weather Statement Issued - Re Wintery Weather

Special weather statement
Updated by Environment Canada
At 10:01 PM EST Thursday 24 February 2011.

Special weather statement issued for..
City of Toronto
Windsor - Essex - Chatham-Kent
Sarnia - Lambton
Elgin
London - Middlesex
Simcoe - Delhi - Norfolk
Oxford - Brant
City of Hamilton
Halton - Peel
York - Durham
Huron - Perth
Waterloo - Wellington
Belleville - Quinte - Northumberland
Peterborough - Kawartha Lakes
Stirling - Tweed - South Frontenac
City of Ottawa
Gatineau
Prescott and Russell
Smiths Falls - Lanark - Sharbot Lake.

..Significant snow likely overnight and Friday..

---------------------------------------------------------------------
==discussion==
An intensifying low pressure system currently located over
Southwestern Kentucky will track south of the lower Great Lakes on
Friday reaching New England by Friday evening.  Snow in advance of
this system is expected to reach the Windsor area after midnight and
continue to spread east reaching the western end of Lake Ontario
towards dawn and the Ottawa area by midday.

Current projections suggest that areas just north of Lake Erie will
receive in the order of 10 to 15 centimetres increasing to 15 or
possibly 20 for Niagara and Dunnville regions where a winter storm
warning is in effect. The greater Toronto area is more likely to
receive closer to 10 centimetres beginning near or shortly before
dawn. Regions along the north shore of Lake Ontario near and east
Of Belleville may also receive in excess of 10 centimetres
potentially reaching 15 from Prince Edward county through Kingston
and along the St Lawrence river. A winter storm watch is in effect
for these areas northeast of Lake Ontario and may be upgraded to
warning as the axis of heavier snow becomes more certain. Winds of
30 gusting to 50 or 60 km/h and local blowing snow will also affect
some parts of Southern Ontario.

The snow will taper off from west to east beginning early Friday
afternoon in Windsor as the low moves further east.  Snow will end in
Toronto by late afternoon and in Ottawa by early evening.

Weather Discussion - Thurs Feb 24th 2011

A weak system with a trailing cold front will cross Southern Ontario today and with it some light snow and the chance of some freezing rain, especially in southern sections and just to the north of the Lake Erie shoreline. Nothing in the way of much accumulation is expected from any snow that does  fall.
Temperatures today will begin to nudge above the freezing mark with +2 or +3 degrees widely felt across the region from Windsor to the Golden Horseshoe and north of the GTA.

The major weather story today however, will be an approaching Colorado Low which is expected to give upto 20cm of snow for areeas from Windsor through to Hamilton . North of that line, snowfall totals whould drop off significantly. Computer models have been moving the track of the low north and south over the past few runs, so the exact track is still a bit uncertain. What does seem certain however is that areas just on the north shores of Lake Erie to Niagara will see the  most snow from this system. 

The Weather Network has produced this snowfall map... There is a wide margin (10-20cm) for some areas, but as I mentioned above, models are not to sure on the exact track with this. Any shiift further north or south could sifnificantly change the outcome of the snowfall totals. Winds will be strong as there is a strong pressure gradient and this will cause extensive blowing and drifting snow.

This is the GFS surface map for 7am tomorrow morning, you can see the Low moving just to the south of the Great Lakes. Keep an eye on the dashed blue line. That's the freezing line in the upper atmosphere and generally determins whether rain or snow will fall. Notice how close it is to Souuthern Ontario.  

Environment Canada has issued Winter Storm Watches for these regions as significant amounts  of snow and blowing snow can be expected. Upwards of 25cm. These are the areas under the Winter Storm Watch as of Noon today.

There is another storm on the horizon.... first a small area of snow for Sunday, then the main system coming in behind it. The difference with this one, will be a change over to rain as a strong push of milder air moves in to the region. Current models are indicating 25-30mm of rain from this system Monday. That could spell trouble in some areas with the melting snowpack causing some localized flooding.

Long  Range trends are showing a real roller-coaster ride in terms of temperatures over the next 15 days with plenty of precipitation events during that period as well.

Where was the warmest city in Southern Ontario yesterday.....

Hamilton, Kitchener,   +1°C @2pm
Several other cities reached that temperature across Southern Ontario

Special Weather Statement Issued by Environment Canada

Special weather statement
Issued by Environment Canada at 2:27 PM EST Wednesday
23 February 2011.

Special weather statement issued for..
City of Toronto
Windsor - Essex - Chatham-Kent
Sarnia - Lambton
Elgin
London - Middlesex
Simcoe - Delhi - Norfolk
Dunnville - Caledonia - Haldimand
Oxford - Brant
Niagara
City of Hamilton
Halton - Peel
York - Durham
Huron - Perth
Waterloo - Wellington
Belleville - Quinte - Northumberland
Kingston - Prince Edward
Stirling - Tweed - South Frontenac
Brockville - Leeds and Grenville
Cornwall - Morrisburg.

..Potential for patchy freezing rain tonight and possible significant
Snow late Thursday night into Friday..

---------------------------------------------------------------------
==discussion==
An upper disturbance tracking south of the lower lakes tonight will
bring some patchy precipitation to Southwestern Ontario after
midnight reaching the west end of Lake Ontario and the Niagara region
early Thursday morning.  The precipitation will likely fall mainly in
the form of snow but there is a risk of freezing rain south of a line
from Goderich to Toronto.  Any freezing rain is expected to be brief
and transitory in nature.

The next feature to affect Southern Ontario is a low pressure system
originating from the Southwestern United States.  This storm is
expected to track south of the lower Great Lakes on Friday to reach
New England by Friday evening.  However the exact track remains
uncertain at this time.  Current projections suggest that areas near
the lower Great Lakes and the St Lawrence river could see significant
snowfall amounts, strong winds, and blowing snow beginning late
Thursday night and continuing during the day on Friday.

Environment Canada will continue to monitor this developing storm
system and will issue updated statements as more information becomes
known.  Please consult the latest public forecast for more details.

Wednesday February 23rd Discussion

High pressure is certainly in control over Southern Ontario with sunshine across the board today. Temperatures will begin to creep up towards the freezing mark for many areas as the strong late February sun warms things up.
UV index values will also be around the 4 or Moderate mark for the region.

Now a few things to take a look at....
There is an approaching cold front that will likely bring a few scattered showers to the region Thursday afternoon or evening. Now, I say showers because temps will be to mild to support snow, however there could be some wet snow involved in the overnight period. Temperatures on Thursday will be into the low single digits across Southern Ontario. The cold front will not do much to lower the temperatures as there is another system right on it's heals.

Snow from this system will likely move in Friday during the day or later afternoon. We will be on the northern fringe of the precipitation shield so any slight movement to the south would mean the difference between getting a couple cm of snow or nothing. The temperature profile of the atmosphere is marginal over Southern Ontario for Friday, however i do think it will be cold enough to support snow. Nothing major at this point.. just a coating is likely to maybe 2cm max.

Another thing Im watching is a storm system moving in for Monday. At this point in the game, it appears to be a rain storm as there will be a good push of mild air coming up form the south. The storm is fairly deep on the computer models which will allow a strong inflow ahead of it. Precip may start as snow or freezing rain, but quickly change to rain as the warmer air moves over Southern Ontario. I will certainly keep you updated on the progression of this storm.

The next couple of weeks will be a stormy period as the storm track moves across Southern Ontario. It's going to be a tough time forecasting as temperatures will be close to the freezing point which could mean the difference between getting dumped on with snow or plain old rain.

Visible Sat Image of Southern Ontario today. Notice the ice breaking up on Lake Erie.

The warmest temperature recorded yesterday across Southern Ontario according to METAR reports.

Parry Sound  -2°C at 5pm
Several centres recorded high temps of -3°C