blizzardof96

Keeping a close eye on the easterly flow LE setup. Lake effect snow band forms tomorrow afternoon and continues through Friday AM. Impacts expected across Toronto to Hamilton corridor with highest amounts near Oakville, ON or Mississauga lakeshore.

I'm thinking that the impacted areas will likely see 5-15cm of snow. Narrow bullseye may exceed 20cm.

2 minutes ago, Ottawa Blizzard said:

Hoping for 8" at least out of this one. 

RADAR looks good... I think we can probably pull off 8"+ assuming the dry slot remains south of us. Time will tell.

Snow has started in Toronto as winds are picking up. Let the fun begin!

29 minutes ago, snowstormcanuck said:

Going to be interesting tonight. 700mb low will take a track well to the west yet models painting in heaviest snow closest to Lk Erie.  Think they may be underestimating the mid level dryslot per usual.  Wouldn't be surprised to see the heaviest snow actually set up just NW of Toronto rather than Niagara region.

Agreed completely. Several indicators pointing towards more of a 401/407 jackpot zone, in my opinion.

My current thinking is a widespread 6-10” across most of S ON, including the Windsor-London-KW-GTA corridor. Local amounts up to 12”. Hamilton-Niagara area is 8-12” with local amounts up to 15” given lake enhancement and upslope flow. Wind gusts ~40-60km/hr will create blizzard like conditions tomorrow night. Peak snowfall rates >1”/hr likely for several hours tomorrow night.

3 minutes ago, blizzardof96 said:

Negative tilt is becoming more pronounced across the Southern Plains before ejection:

Resulting in significant changes at the surface

Negative tilt is becoming more pronounced across the Southern Plains before ejection:

What's interesting about this inverted trough setup for S ON is the mid-level convergence axis and moisture transport advecting in from both the GOMEX and ATL sectors

16 minutes ago, snowstormcanuck said:

Goofus kuchera clown map with 9" at yyz.  Inverted surface trough from EC low on steroids.

Check out that gradient! Burlington pier at 11.1" with Buttonville at 3.6".

18 hours ago, snowstormcanuck said:

Ah you ninja'ed me.  Are the 1991-2020 numbers out?

18 hours ago, Snowstorms said:

Nah, I created a spreadsheet of every winter since records began at YYZ LOL. 

Re your last post. That November storm was pre sweet. Widespread 8-10". I'll be happy if we can have a 4th consecutive winter >100cm. That last time we had 4 consecutive 100cm winters was back in the 70s. 

I also did some recent analysis  -- with emphasis on the Oceanic Nino Index (ONI) relationship. Here's what I found out:

1) Toronto YYZ had an average annual snowfall (1979-2020 climatology) of ~108cm with a standard deviation of ~33cm.

2) When DJF ONI > 0.5 (El Nino), 5 years had above normal snowfall and 10 were below normal (1979 - 2020)

3) When DJF ONI < -0.5 (La Nina), 10 years were above normal and 5 years below normal (1979 - 2020)

Average seasonal snowfall by decade:

1970s: 139.2cm

1980s: 101.3cm

1990s: 103.0cm

2000s: 121.1cm

2010s: ~115.2cm 

50 year average (1970 - 2020): ~116cm

3 minutes ago, snowstormcanuck said:

2.4" at YYZ as of 18z. Even with only scraps the rest of the way should eke out low end of my forecasted 3-4. 

I'll take the 3" and run. Happy with it. Throw in some blowing/drifting with those strong easterly gusts off the Lake.

31 minutes ago, snowstormcanuck said:

+SN at 11am.  Grass completely covered. That death band looks like it dropped 1-1.5" in 30 minutes.  Too bad it's so narrow. 

Yes, we're going to have slot issues making the pcpn more showery.

Looks like main snowfall axis is going to push well north of modelled position, which is a pretty remarkable north trend of the 700mb RH zone. Will see how much activity can build into GTA off the lake with the low level easterlies.

Textbook leading 700mb FGEN band. Note the strong intersection between DGZ relative humidity, omega and mid-level frontogenesis.

Just now, Snowstorms said:

I've noticed these type of deformation bands always set-up away from the Lake especially north of 401. Thermals look good for some decent dendrites too.

What's your take on any potential lake enhancement? 

With regards to lake enhancement, I don't see that being a major component of this system for GTA. Sounding data indicates surface winds are ENE with winds veering with height (i.e 850mb winds ESE and 700mb SW). This amount of directional shear doesn't support organized enhancement. Sfc-700mb temps are in the range of -9C to 0C which is also a bit warm for organized enhancement. We would typically want inversion heights to be more elevated & mid-level temps a bit cooler given lake temps about 5-6C.

4 minutes ago, Snowstorms said:

HRDPS is bullish for the GTA tomorrow. If that FGEN band materializes as shown on the models, there could be an intense burst of +SN for 2 hours tomorrow morning. 

Wouldn't be surprised to see 4-6"+ tomorrow. 

The FGEN banding does look like it will thump for a little while tomorrow morning into early afternoon. I'm expecting 2-4" across most of S ON, with local amounts of 4-6" across parts of GTHA that cash in on banding features. Easterly wind gusts 40-60km/hr.

1 minute ago, snowstormcanuck said:

Looking forward to the TSSN from SE NE and S IA videos on youtube following this.

Nice to hear from you!

Our Texas low begins to develop tonight. Moisture trajectories look good out of the Gulf of Mexico.

6z NAM with a significant jump north relative to 0z

3 minutes ago, RCNYILWX said:

Very valid points you make aside, I'm struggling to come around to the idea that the precip shield of a well developed mid latitude cyclone is going to be that bullied by confluence from the north when the system had already established an expansive moderate to heavy precip shield. I think that it would be a more gradual process.

An event that comes to my mind from growing up in NY is the Feb 5-6 2010 mid atlantic "snowmageddon" blizzard. That was probably the strongest west based -NAO on record amidst a record prolonged -AO. The confluence over the NYC metro was true buzzsaw stuff on the north edge. But yet the system itself didn't get shredded apart, it just led to one of the most extreme north side gradients you'll ever see (~30" in PHL and T at KNYC). As a snowlover, it was a nightmare scenario.

But I think I go back to it because I want to believe a model like the GEM is depicting too rapid of destructive interference on the system. Itll happen eventually but I'd think longitude of my area has more wiggle room than points east. It's like a hurricane making landfall, it loses its heat source and eventually the whole system winds down but the precip doesn't fall apart immediately.

If we're talking unimpeded Gulf trajectories, a well developed trowal and intense low and mid level f-gen into Iowa at our latitude, is the precip shield all of a sudden gonna dance southeast because of confluence? I'll end my rambling but that's my thought process on this. I buy the weakening eastward of the synoptic system because it makes sense but not such a rapid modulation of the precip swath.

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Good points being made. I agree.

Two main reasons why the sfc low begins to weaken as it moves east, in my opinion:

1) H5 vort max peaks in strength over the S Plains states

2) Vort max begins to elongate/stretch/weaken as it becomes under the influence of the Quebec confluence zone

Could be some convective feedback on this run pulling the low a little bit too far NW into the heavy banding on the NW quadrant. Also might just be representative of the low becoming vertically stacked as the cyclone approaches the occlusion phase.

The NAM low track remains south of the Ohio River whereas the majority of 18z EPS & GEFS tracks are north of the ohio river

18z EPS

6 minutes ago, michsnowfreak said:

What does this mean in translation lol? (I cant believe I'm asking someone to extrapolate the nam )

It would probably have a low track fairly similar to the 12z GFS. My opinion is that the GFS/NAM shift towards a ECM/GEM/UKMET/EPS look as we move forward.

Final frame of the 18z NAM. Taken with a grain of salt but it seems to be further south with the northern stream vortex.