blizzardof96

Interesting. I think you're right. Looking at the YYZ daily data they have 13.4cm recorded on Feb 17th. Good chance that YYZ recorded more than 1.6cm past midnight.

Looks like ~3" here in kingston with a glaze of ice underneath. YYZ reporting a 6" storm total although I suspect many parts of the city are above that. Considerable blowing and drifting as well.

It was bang on this afternoon with the timing of the GTA changeover. Very helpful for these events.

Pouring rain here in Kingston with snow being reported in Ottawa. Mixing line located from north of Belleville - Perth - Kemptville, expected to push southeast over the next few hours. Expecting a fairly decent amount of PL before changeover to snow.

Something that popped into my head that is kind of interesting. My first memory of posting on this forum was with the Feb 7/8 storm in 2013. Crazy to think that it's been over 9 since since then and that we still interact from time to time on this forum. Time flies.

18z 3kNAM big hit for GTA with amounts near 10". Low tracks ~990mb through Erie, PA always seem to get it done around here.

Agreed. I think they'll either issue WSWs or snowfall warnings for areas further east into GTA. Probably coming out this afternoon or into tonight. They are always hard to predict though, lol.

EC has hoisted winter storm warnings for SW ON, extending from Windsor-Sarnia-London-St Thomas

Fairly good model consensus on 6-10" for the GTA with 401 bullseye

Measured 18" at my place. Downsview recorded the same amount. Everybody in the neighbourhood agreed that was the most snow they have ever experienced by far. Never seen anything like it before in Toronto.

Can see the differences in the energy over the plains. 0z NAM (left) vs 18z NAM (right).

For Toronto, since 1855: Number of 24"+ events 0 Number of 20"+ events 4 Number of 18"+ events 7 Number of 15"+ events 21 Number of 12"+ events 46 % chance of seeing a 12"+ snowstorm in a snowfall season 28% 15"+ 13% 18"+ 4% 20"+ 2.5% 24"+ RARE

Tough to say at this point. Small changes in the strength/positioning of the plains vort is resulting in practical changes to the low track. This alters the position of the deformation zone. Recent runs have been trending a bit further south/stronger with the plains vort... leading to more phasing with our cutoff low. Under this scenario (eg 18z ECMWF), the heaviest snow band tracks a bit further NW through GTA etc. Another plausible scenario is something like the 18z NAM which is a bit less phased with the low track further east. Future runs (starting with 0z tonight) should help clarify things and build consensus... hopefully.

Fingers crossed that we get into that deformation zone in Toronto

~1.7" recorded at YYZ. About 3" at my place in north Toronto. Most of the city seems to have received between 2-3".

Synoptically speaking, what we have is a weakening vort max ejecting into the plains. As the vort max moves northeast, it is getting elongated/weakened by the confluence zone/upper jet across the Great Lakes region. With the confluence zone in place, the plains energy is quite limited in how far north it can track and how strong it gets. These weak systems can be subtle which the models will rarely handle well. With a better defined low, the models have better legs to stand on from a physics perspective. Very similar setups with a plains wave ejecting towards Great Lakes confluence zone occurred last winter on a few occasions, and the models similarly performed poorly up to the final moments. Surface low peaks in intensity near the western Ohio river before deformation snow band weakens gradually as it moves east through MI and ON. In addition to these factors, slight changes in the upstream trough across the four corners region can make a difference in how the vort max ejects/tracks. These differences can also alter the orientation of the leading wave from neutral/positive/negatively tilted.

Any thoughts on the 12z HRRR track?

Here's the spread in model snowfall output for YYZ. The variation is pretty ridiculous given the fact that snow is expected to start falling in just over 30hrs from now. I agree, I think 5-10cm is reasonable for the GTA. Some communities across S ON may see 10-15cm but too early to know where/if that might set up. I'm not convinced that we see a whiff south like the ECM/RDPS are showing -- they may be overcorrecting.

Ya, I agree with the bolded. We may start off as a bit of light rain. What will probably happen is that as the main deformation band moves through on Saturday evening, precip rates should be heavy enough to cause low level temps to fall below freezing rather quickly. Once that happens, temps won't recover as winds are locked in a NE direction.

Yep, the rain/snow transition time will be key. That will be dictated by the track of the surface low. A spatial mean of the 12z GFS/GDPS/RDPS/UKMET/6z ECMWF supports a general 5-10cm south of the 401 and 10-15cm north of the 401. Will see if that holds and whether model consensus starts to build over the next 24-36hrs. I think your forecast is a pretty good starting point with some room to increase if consensus builds.

Through hour 90

Here's a look at 18z GFS and GEFS snowfall

12z EPS

Agreed. If the 12z GFS/ECMWF surface low tracks are close to being correct, we see the front move through on Saturday which ushers in NNE winds at the surface --- continuing through Sunday. That is a recipe for quite a bit of frozen precip across the GTA (snow-freezing rain-ice pellet mix).