SOMBA K'E/YELLOWKNIFE
It is not entirely clear whether Yellowknife has ever experienced a mid-April thunderstorm like what was experienced Monday night, according to Environment Canada.

Lighting crashes behind Farncois Thibault's 'United in Celebration' statue on the shores of Frame Lake during last night's massive lightning storm in Yellowknife. April 18, 2016 - Cody Punter photo A rare lightning storm over Yellowknife as seen from Pilot's Monument. April 18, 2016 - Shane Magee/NNSL photo

Residents flocked to social media to post photos of the spectacular light show and comment that they were both thrilled and in some cases a little scared. Residents have been comparing it to July 30, 2014 when the city went dark in the middle of the day after a thunderstorm combined with smoke and ash appeared over the city to create an apocalyptic-like scene.

David Phillips, senior climatologist with Environment Canada, said he has never heard of such a storm at this time of year in Yellowknife.

"No way. You have something in eastern Canada called a thunder snow," said Phillips.

"You don't get thunder snows where you are because it is usually too cold. But what is so shocking about this is that it came with rain. It was 8 C at midnight - normals would have been at minus eight. In an average year (Yellowknife) gets about four thunderstorm days. But they fall in July and August and they usually happen in the late afternoon or early evening. You don't get any in April - the data shows almost zero."

Phillips called it the fluke of all flukes. Despite more than 40 years in the weather business, he said he never ceases to be amazed by what Mother Nature concocts.

Brian Proctor, a meteorologist with Environment Canada based in Edmonton, agreed with Phillips' analysis. Without data to back it up he suggested it has been 10 or 15 years since Yellowknife experienced a thunderstorm in mid-April.

"It was a very, very active low pressure system that developed (Monday) afternoon. It surfaced just east of the Rockies, just south of Fort Liard about 6 p.m. It tracked east-northeastward quite rapidly. That low pressure system and the cold front that was associated with it that provided the impetus of the thunderstorms that developed."

He added the storm was centered just north of Yellowknife and completely lit up the agency's lightning detection system. Proctor noted very little precipitation fell during the storm in what he called a unique weather event.

"These events are not very common in the Yellowknife area," said Proctor. "We've had very warm air flooding into northern Alberta, Saskatchewan and B.C. over the past 24 to 36 hours and that just brought up all that available energy for the potential for thunderstorms to develop. The key thing that set this off was the cold front. It was the trigger to the instability. The low went just directly north of Yellowknife."

Proctor said the mild temperatures that Yellowknife experienced last weekend were part of the same flow that brought the city the storm. That warm air had come from the U.S. plains and traveled across the western Canadian provinces and into the southern portion of the NWT.

"It was 27 C in the Edmonton area on Monday," Proctor pointed out.

Judy McLinton, spokesperson for the Department of Environment and Natural Resources (ENR) stated in an e-mail that about 4,000 lightning strikes were recorded as the storm passed over northern B.C. Yukon and the NWT. There were no reported fire starts in the NWT, she added.

The NWT Power Corporation did not report any storm-related outages and no flight disruptions were reported at the Yellowknife Airport.

The weather did a 180 degree turn in Yellowknife. It went from a relatively balmy 13 degrees with partly sunny skies and light winds on Monday afternoon to -1 C with winds gusting to 55 km/h and cloudy skies by late morning yesterday. The forecast for the rest of the work week is for temperatures highs of around -6 C or slightly colder than normal, then warming up to about the freezing mark for the weekend.

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