North American Weather (U.S.A & Canada)

[Coopsy]

Coops - you have just basically summarised, weather wise, the main reason why i hope to reside in that part of the world one day

Like many, im a fan of weather extremes - that is just fantastic

Real winters, proper summers - like they should be

Thats one aspect I really like aswell, you know each year you are going to get the extremes, unless you live in the far west of canada

[Ross B]

Heavy rain, tornado warning sirens sounding in downtown Chicago

I saw that storm on the news when i got up this morning. The lightning was flashing every second!

I'm doing well with storms over here in Florida, i'm currently on the 3rd storm of the day! I think that brings the total to somewhere near 15 for a 9day period which is extremly lucky!

[Coopsy]

Or unlucky if you are a sun worshipper and went there on holiday for a tan lol. I guess the storms come and go and inbetween its nice and hot and sunny though?

[stewfox]

Similarly, Denver has just broken a record; they recorded 19 days of 90oF or over which beat the previous streak of 18 set in about 1903. In fact, Denver is also up to 100oF at the moment.

I’m always amaze how warm Denver can get in the summer and the number of days in winter when it can get 50F + even in January

Its 5,280 feet above sea level !

Can anyone explain why /how a place a mile above sea level can get over 100f ?

[Coopsy]

This summer has been a tale of two halves. The morning/early afternoon starts off beautiful blue skies and lovely weather, by the afternoon there are thundserstorms and rain. Its getting a bit tedious now. I think we are upto about 25 thunderstorms for the season. Last week we had 3 separate storms in one day

[WhiteFox]

Severe thunderstorm warning issued just to my north:

* SEVERE THUNDERSTORM WARNING FOR... SOUTHERN WESTCHESTER COUNTY IN SOUTHEAST NEW YORK... NEW YORK (MANHATTAN) COUNTY IN SOUTHEAST NEW YORK... BRONX COUNTY IN SOUTHEAST NEW YORK... CENTRAL BERGEN COUNTY IN NORTHEAST NEW JERSEY...

In fact, a tornado warning has just expired for Westchester County and Bronx. A train of storms has now developed, and as I speak it is like night-time outside (it's not quite 6pm here). The storms have developed very quickly this afternoon:

[Coopsy]

4th day straight of 30oC temps here in southern Alberta. Night time is unbearable with temps in the 20oC's. Not used to it but not complaining.

[Roger J Smith]

Cold front is slowly building up here, Rich, we have had it hot also for several days, but the front is about ten miles to my west now, hasn't moved much since 5 pm but should be into central BC by mid-afternoon Monday, some risk of storms for you tomorrow evening and overnight, then a better chance on Tuesday when the fronts move through (by then, probably two of them). I think it will be about 32 C again for you on Monday, 24 C on Tuesday but cooling off after a second front passes in the afternoon.

As to why it gets so warm in Denver at that altitude, actually it is rare for temperatures to get much over 35 C there but it can reach 40 C, it's basically just the fact that Denver is in the same climate region as the lower and much hotter parts of west Texas, eastern NM and western KS into s.e. CO where max temps of 40-45 C are not that uncommon from May to July at least.

If you were following the storm chases, you'll recall that quite often, a warm front stalls out across Colorado near Denver and pinches off around Denver airport, so there are actually quite a few days when Denver reaches 27 to 32 C while an hour away it is 35 to 38 C. However, if that front pushes north to the Wyoming border or even central Wyoming as it sometimes does, then this superheated air mass can move as far north up the foothills as it can go before being cut off by that warm front. Usually in these patterns, there is low pressure near Salt Lake City and a drier and slightly cooler brand of air squeezed into the mountain regions.

There are also patterns that appear some years with heat over the interior west and a slight downslope effect into eastern Colorado, and that's when Denver can actually hit their highest temperatures of all.

That's a weak analogue of the winter chinook. The chinook blows compressed warm air down the Front Ranges and further north, the Rockies, into Alberta, Montana, Wyoming, South Dakota, Nebraska and Colorado, depending on the gradient and the position of any low pressure. The chinook is more common further north, but when it comes to Colorado it often comes with a violent W to NW wind that causes damage around Boulder and north of Denver. And it can raise the temperatures to 60 or even 70 F in winter. Colorado is far enough south that it can also just be on the mild side of the jet stream in winter and receive some reasonably mild air from the southeast, but this tends to get foggy on the upslope sometimes and then it often turns to a steady rain in advance of a heavy snow that will follow when low pressure gets away from the foothills and out into the high plains. This is why Denver has such violent changes in weather, the source regions for vastly different air masses are all around, and the local downslope effects can delay cooling until a critical change in wind direction ends the compression and so the temperature can drop 30 or 40 degrees in an hour or two. This is also true up into Canada on the east side of the Rockies.

[WhiteFox]

As an example of what Roger is describing, in December last year, Denver went from a high of 72oF on Saturday, to heavy snow on Sunday evening followed by a high of 27oF on Monday. Basically anywhere East of the Rockies and North of Northern Texas in the West as far East as Ohio is prone to wild temperature swings which can be at their most intense most during winter time. North of a warm source of moisture in the Gulf, and south of a large cold airmass; perfect ingredients for sharp temperature contrasts and the perfect recipe for tornadoes of course!

[Coopsy]

Thanks Roger, yep it seems this cold front is slower to shift than originally thought. Amazing day again, the 5th day running of plus 30oC. It is currently 31oC at almost 2pm.

Do you think that once this cold front and the low behind it marches through on the jet stream that the high pressure will build back in? I cant seem to tell at the moment

And to add on even further to the above posts, I live in the foothills on the east of the Canadian Rockies and have personally witness it drop from plus 10oC to 0oC in the space of 10 minutes. Its amazing to watch the thermometer drop that rapidly

[Coopsy]

Well that was short lived. After record highs of 34oC on Monday, today's high is 9oC, and there is even snow on the very tips of the mountains. Oh how the weather can change

[Roger J Smith]

Rich, I think the weather should clear up for you tomorrow mid-day, and become quite warm again for the weekend. There could be a bit of cloud around from a warm front on Saturday morning, and even a weak thundershower in the mountains but then it should clear up again and stay warm to Monday, when the next strong front comes through. This one looks simpler and should only last one day before clearing up again, so all in all a pretty pleasant run of weather once this cold wind and showers blow through tonight. Snow level could be well down towards the valley by morning but won't stick around.

Severe storms now developing in western Manitoba and North Dakota.

[Coopsy]

The cold rains stopped here fairly early last night and the snow line has retreated to about 8000ft now. Much clearer though still cool. Hoping it clears up and warms up as Roger said. It certainly looks that way at the moment

[Roger J Smith]

Rich, if you happen to look in on Monday evening, expect a sharp cold front around midnight to 0300 followed by several hours of heavy showers and mountain snow, clearing about 2-4 pm Tuesday. This will slow down when it passes Calgary and bring a heavy rain to eastern Alberta and western SK with some severe storms developing there. It should clear to another nice couple of days, we have sunshine and 20 C here today.

[Coopsy]

Hi Roger. I just checked in to the weather forecast and notice they are going for temps around 3-4oC in the Valley overnight, so the snow will be back on the mountains

After highs yesterday of 29oC, its once again cooling down. I remember you called this exact pattern last week. Good forecast there

[Coopsy]

Extremely wet and windy this morning but at 8am there was no snow on the mountains. It has just stopped (12pm) and after 4 hours the moutanins are covered in thick snow as the cold front passed through, some look like 15 cm's at least. pictures to come

[Roger J Smith]

Clearing turned out to be quite brief between that system and the next one already coming inland here this evening, could be nothing better than a few hours of clear skies or partly cloudy for the mountains tomorrow ... meanwhile that front we were tracking has made it to western Manitoba where it is developing some severe storms this evening.

[Coopsy]

Roger, the weather forecast is going for rain/snow mix here during Sunday with snow in t he evening. Any idea on the accuracy of this report as the way I read the charts dont support this?

[WS Evolution]

Snow on Whistler @ 1850m as seen on their web cam.. looks to be melting though.

[Paul]

It always rains on whistler!

[Coopsy]

Nice day today, max: 17oC. But winds changing round tonight and coming in from the Arctic. Forecast in the early hours of 3-5cm's of snow, upto 10cm's on the hills. And its still August ....could be an interesting winter

[Coopsy]

Well as I sit here eating breakfast, Sunday morning on Aug 31st 2008, thoughts of barbecues and sunshine have given way to bobsleds and skiing as I watch huge flakes of snow falling and accumulations are at 6cm. Temps are 0oC and the fire is on. In summer!!! Pictures to come

EDIT: Here are some pics:

[johnholmes]

lucky man to get almost 3 months without snow - your misery will receive huge support I'm sure on this forum!

[Roger J Smith]

Sorry Rich, I missed your question and the event itself, got bogged down with Gustav-watching.

What's left of Gustav is now in northern Ontario (!) and heading for northern Quebec.

Hanna is moving into North Carolina early Saturday and will bring a heavy rainfall and strong E-NE wind to DC, PHL, NYC and BOS over the weekend before heading for Ireland around Wednesday.

Ike threatens to move past Florida early next week and into the eastern Gulf (oh no not again) towards next weekend.

Lucky all this is going on, because I am in a weather-free zone here with day after day of partly cloudy near normal weather.

[Coopsy]

Very warm weather currently here in souther Alberta, and into southern BC. Temps here in the 20's for the week, all very nice stuff for September