Markham and surrounding areas didn't get a drop of precipitation, in any form, until 10am. There's been light snow fall since but nothing that would suggest reducing train service. I recognize many Stouffville, LSE and RH trains have path dependencies on weather on the other end of the GTA but many people won't appreciate that nuance.
Similar to Jan 26, Toronto got buried in 60cm of snow while we got 10cm, maybe 15cm, of snow that stopped at 6am. All roads, sidewalks and school parking lots and pathways had been plowed around here by 7:30am which made for an awkward YRDSB panic closure more than 12 hours prior to any snowfall after TDSB made their decision. I took the ST line to Union before taking the UP north to YYZ and flew out perfectly on time that day even though Toronto was buried in snow.
It adds to the "maybe follow standard operating procedures" to react to weather in real time rather than 12 hours in advance of an unreliable forecast.