Rex block causing record-breaking heat in NWT
Digital Reporter
Wednesday, May 20, 2015, 4:31 PM - Warm air continues to surge into northwestern Canada, causing heat records to be broken in northern Canada Thursday.
As of 4:26 p.m. ET, twelve records had been broken in the north, six in the Northwest Territories and six in the Yukon.
Records were broken in the Prairies as well.
The unusual weather is due to a meteorological term called rex block, which occurs when an upper-level high sets up to the north while an upper-level low is found below.
This cuts off the normal west-to-east flow of the jet stream, resulting in an abnormally warm air surge in the northern provinces as the jet stream is forced to align in a more defined north-to-south position.
"While a deep trough brings cooler temperatures that will last through the remainder of the week to eastern Canada, communities in northwestern Canada will be hogging all the warmth," says Weather Network meteorologist Erin Wenckstern.
"For over a week, a persistent pattern over western North America has produced record-breaking temperatures for northern B.C., Alberta, Saskatchewan and into the Yukon and Northwest Territories."
A rex block can remain stationary for several days.
We typically see this type of blocking pattern during the spring months, but it's not uncommon in the fall as well.
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On Monday, Inuvik hit a high of 28C, replacing a May record of 25C set back in 1998. As of 4:26 p.m. ET Thursday, Inuvik climbed to 24 degrees Celsius.
While warm weather isn't the norm for the Northwest Territories this time of year it's not out of the ordinary to see summer-like surges in the spring, Wenckstern says.
The rex block is impacting parts of the Prairies as well, with portions of central and northern Saskatchewan expecting temperatures in the low thirties Thursday.
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How long will it last?
"Looking at the long-range models, it appears another surge of warm air will reinforce this pattern through the weekend," Wenckstern says.
"So, it looks like northerners can expect the trend to continue a little while longer."
