A pattern you have to see to believe, what happens next?
Meteorologist
Thursday, October 4, 2018, 7:55 PM - A pattern like this doesn't come around very often, and the proof is the extreme temperature anomaly forecast for next week. It's possible a part of Canada deals with a winter storm, while another deals with dangerous humidex values.
Read more below on where this pattern is developing and why it's exceptional.
(IN PHOTOS: Over a FOOT of snow slammed Alberta)
PATTERN HIGHLIGHTS
- Those hoping for a one and done snowfall across the Prairies, think again; low to likely develop but ultimate target remains elusive, and may even be northwestern Ontario
- Warm sector of the massive low will surge into Ontario and Quebec, setting the stage to challenge all-time October humidex records
Prepare to be shocked. Imaged below is the extremely rare outlook issued by the Climate Prediction Center in terms of temperature anomalies, where the reds depict well above average temperatures and blues well below average. Note these extreme temperatures are less than two-thousand kilometres apart:
As a meteorologist, it's somewhat unusual to see a 90% probability of above or below normal on a map. But to see both? That's incredibly rare. In fact, over the past half a decade there's only been another occurrence of this:
Climatologist Brian Brettschneider cited this feat has been pulled off before on February 13th, 2018, but that's the only time over the past five years, until now.
CONSEQUENCES OF THIS PATTERN
When such strong air masses come together, it spells trouble. Storm systems are more inclined to develop along this tight temperature gradient and can become particularly strong, as a result. The battle of the air masses is in full swing, but this goes beyond the typical fluctuations experienced in fall.
EXTREME HEAT
Let's start with Ontario heat because we have to watch for all-time October humidex records to be challenged either Monday or Tuesday (there still exists uncertainty on which day cities warm up from south to north).
ALL-TIME OCTOBER HUMIDEX RECORDS
- Windsor: 39.2
- Toronto (YYZ): 39.1
- Montreal: 33.5
See the temperature in Ottawa above? I know, you're probably skeptical of the warm-up, but Monday will feature the warm front surging north across southern Ontario, so Tuesday will be your warmer day, along with Montreal. However, there is one factor that needs to be considered, which will have large impacts on the temperature forecast.
On Monday, notice how Toronto is still relatively cool – that's because of the positioning of the warm front and the winds off Lake Ontario. We need a truly southwesterly flow to soar to our true potential maximum temperature, which we will achieve by Tuesday for the G.T.A.
UNBELIEVABLE WEATHER STAT
As we head deeper into October next week, our daily maximum temperatures will continue to plunge. By next week, the average high at Pearson International Airport near Toronto will be approximately 15°C.
Our overnight lows during the warmest stretch next week may hover above 20° for urban areas, which will be FIVE degrees warmer than our average high temperature for this time of year.
I'll give you a second to digest that...
MUST SEE: ALBERTA SLAMMED WITH OCTOBER SNOWFALL
As of Thursday evening, computer models are suggesting better odds that northwestern Ontario deal with significant snow next week, but solutions continue to oscillate back and forth, so keep checking back for updates through the weekend.
This is a preliminary look at the possible pattern for early next week and while we have extremely high confidence for humid temperatures, the timing of it may change some. Our lowest confidence is with the system placement next week and who will be hit that hardest. It's entirely possible that as folks in Windsor, Ontario swelter outside on their Thanksgiving Monday, those on the Prairies and NW Ontario will be preparing for winter weather to move in.
Only time will tell, so check back regularly for updates on this developing story.
