While heavy rain is expected to dampen Canada’s 150th birthday celebrations Saturday on Parliament Hill, high-level security experts in both police and intelligence agencies are hoping the only explosions heard will be emanating from the thunder clouds overhead.

A national security memo, obtained by CTV News, has the ISIS terror group again “explicitly” naming Canada as a target, with its text warning Muslims to avoid markets and large gatherings as it threatens to use “explosives, vehicles and beheadings to kill crusaders.”

This threat is a recent one. It was intercepted after the Manchester bombing in England on May 22 when a homegrown Muslim extremist in a shrapnel-laden suicide vest killed himself and 22 young people attending an Ariana Grande concert.

Despite this latest warning, however, Canada is maintaining its terror threat level at medium, where it has remained since October 2014 following the attack on Parliament Hill by a supposedly “lone wolf” follower of ISIS who first killed Cpl. Nathan Cirillo as he stood guard at the Tomb of the Unknown Soldier before storming the Centre Block where he was eventually shot dead.

It was an attack that traumatized the vast parliamentary precinct, and had then Prime Minister Stephen Harper and MPs from all parties in lockdown for most of the day.

While intelligence sources have reportedly picked up no cyber-traffic about a plot to specifically disrupt Canada Day, the intercepted memo has security personnel actively concerned.

“Given the current threat environment, it is increasingly necessary for law enforcement officers to be aware of possibly suspicious incidents that may be indicative of pre-attack planning,” the memo reads.

“The planning cycle of self-directed extremists is becoming increasingly shorter, and subsequently more difficult to attack.”

"According to the memo, ISIS has warned Muslims to avoid markets and public gatherings in Canada, and threatened to use...." https://t.co/AHxDHuhxdT — Bob Zimmer MP (@bobzimmermp) June 28, 2017

2/ "& threatened to use explosives, vehicles and beheadings to kill crusaders.” Be aware & if you see something suspicious let police know! https://t.co/OKfZ8ACDRz — Bob Zimmer MP (@bobzimmermp) June 28, 2017

In the lead-up to Canada Day celebrations, Ottawa is already a drivers’ hell, with major access routes around Parliament Hill preemptively blocked off, and all transit buses widely re-routed, as large concrete blockades and dump trucks prepare to be hauled in as additional barriers to potential bomb-laden vehicles or vans looking to mow down revelers.

The level of security, in fact, is being called “unprecedented.”

Police with long-gun carbines, a rarity in Ottawa, will be in full force around Parliament Hill when Canada Day dawns, with upwards of 500,000 party-goers expected to cram its surrounding expanses to celebrate the country’s historic birthday.

And there is cause for some anxiety. Syed Soharwardy, a Calgary imam and founder of the Islamic Supreme Council of Canada, has been very vocal lately in expressing his concern about the growing number of young Muslims or Muslim converts in Canada who are buying into the ISIS dementia.

“There is a lot of recruitment going on,” he said. “And security can do very little to stop it.”

And it is not as if there will be no high-profile targets. During the day-time celebrations, for example, Prime Minister Justin Trudeau and Governor General David Johnson will be joined on stage by Prince Charles and his wife, Camilla.

There will also be the anchors of every major news network in Canada.

In the meantime, all Parliament Hill attendees Saturday had best be prepared for searches. No booze, no drugs, no hard-cased coolers and no aerosol cans.

“We are very aware of what is going on around the world,” said Ottawa Police Insp. Murray Knowles.

So forearmed is forewarned.

Fingers crossed.

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