Reading up for IFR before doing the actual course, and comparing it to real-world scenarios, I have a question.

Southern Ontario is being hit with snow all over and many YYZ flights got cancelled.

Through the day I was staring at YYZ GFA, METARS/TAF, RVR, prog charts etc.

I'm not sure specifically why the flights were getting cancelled. Icing chances seemed much lower than some of my VFR flights, winds were gusting to 16 and ceilings in the morning were around 4000 AGL.

Visibility did drop (reading SPECIs in METARS) to 1/4sm and the RVR bottomed out at 2600 before going back up. Minima however is around 600 for departures.

I was looking at flights to KBOS for friends all of which got cancelled, but the weather only got better eastward, to VFR in BOS.

The real bad weather, higher chances of TCU, severe turb were west of us moving in slowly.

So why were all these flights cancelled? Is the minima higher as per company policy? ( cant see how the airport can raise minima for special weather).

If icing isn't an issue, can the volume of snow alone ground aircraft? (never heard of this one before).

You will find out in your career that delays in the airline world is generally not because of us pilots... were very efficient.

If you think about an airport environment you have to plow runways. Taxiways. Aprons. Ramps. If a plane is on a planned 45min turn, everything has to be perfectly planned to have to "turn" the plane in the allotted time. Then we taxi to deice. There could be a lineup.
Between airports there can be airspace restrictions, or ground delay programs, where due to gate delays because of longer than usual turns, flights are limited to those particular airports = more delays.
I'd be curious from any regular YYZers how long it takes for the airport and their particular airline to recover.
I know next door it can take upwards of 36hrs to fully recover

Teeg wrote: ↑Tue Jan 29, 2019 5:05 am You will find out in your career that delays in the airline world is generally not because of us pilots... were very efficient.

If you think about an airport environment you have to plow runways. Taxiways. Aprons. Ramps.

Ditto what Teeg wrote. Detroit cancelled some flights too. Nothing to do with the aircraft or pilots, it was entirely runway conditions and preparation for the coming weather.

I'm waiting for that winning comment, "this is everyday weather for Saskatoon, and they don't any delays or cancellations, while YYZ has to call out the army".

Yeah.

A major cause is low arrival rates when using the 15L and R runways. They just can't handle many arrivals. With no arrivals there can be no departures. Other factors are delays of ground staff to bring the aircraft into the gate, deicing delays, snow removal etc.

It's fairly rare that an airline flight is cancelled because the flight itself would be unsafe or impossible. It's more to do with the airlines cancelling half the sked hours in advance in order to keep the remaining half running sort of on time, instead of the every flight running 5 hours late.

Thanks guys, these comments validate my thoughts on the technical reasons why the flights were cancelled. I thought I was missing something in the WX forecasts. It's all just capacity planning.