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Feb 17-19th Potential Of Potential


Chicago Storm
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STL had a pretty intense band set up about an hr ago - ~25-30dbz. We're back down to light snow. 

Picture2.jpg

Our AFD mentions up to an inch in our metro associated with the area of lift. [on an unrelated note: I'm really trying to expand my knowledge of some of these terms they use in the AFD - frontogenesis, isentropic lift. I'm not in any math heavy fields, and I looked through the weather 101 forum without much avail to find a conceptually-focused guides that could help me interpret better. If anyone has any good, beginner-friendly sources I'm all ears and open hands]

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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.

hrdps-toronto-precip_3hr_inch-1613563200-1613656800-1613732400-40.thumb.gif.81fd8f27b18af50e298fc2e1b2abbf05.gif

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1 hour ago, blizzardof96 said:

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.

hrdps-toronto-precip_3hr_inch-1613563200-1613656800-1613732400-40.thumb.gif.81fd8f27b18af50e298fc2e1b2abbf05.gif

whats your thoughts for the rest of the GTHA? 

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1 hour ago, blizzardof96 said:

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.

hrdps-toronto-precip_3hr_inch-1613563200-1613656800-1613732400-40.thumb.gif.81fd8f27b18af50e298fc2e1b2abbf05.gif

Interesting to see the trend of having the band impact the City.   Sfc low well to the south so normally this would back the winds enough to keep everywhere east of Oakville out of the game.  This band might be rooted further up in the atmosphere were winds are more ELY?

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23 minutes ago, snowstormcanuck said:

Interesting to see the trend of having the band impact the City.   Sfc low well to the south so normally this would back the winds enough to keep everywhere east of Oakville out of the game.  This band might be rooted further up in the atmosphere were winds are more ELY?

Wonder if this ends up producing more than the Tuesday storm? Do soundings support lake effect?

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30 minutes ago, snowstormcanuck said:

Interesting to see the trend of having the band impact the City.   Sfc low well to the south so normally this would back the winds enough to keep everywhere east of Oakville out of the game.  This band might be rooted further up in the atmosphere were winds are more ELY?

Exactly. The band steering flow is likely coming from the ~925-850mb layer where winds are stronger and have an ESE component to them.

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1 hour ago, snowcaine said:

One of those situations where it could be 0 to 9 inches anywhere along a 60 mile distance.

My forecast would probably be 3" for Toronto, but 0" is entirely possible, as is 7"

Well the synoptic will probably drop a couple of inches at the very least but I get the point: we could whiff entirely on the LES.

Going 3.5" at YYZ with high uncertainty.

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2 hours ago, mississaugasnow said:

whats your thoughts for the rest of the GTHA? 

This is a tough forecast due to the localized nature of the LE banding.

I think many communities within the GTHA (besides northern areas near the 407) will see 5-10cm. The >10cm amounts will directly align with the narrow streamer expected to come in off Lake Ontario. Location of this band varies depending on which model you trust. NAM/3kNAM have the bullseye near Oakville/Burlington while RGEM/HRDPS have a downtown TO -- Mississauga bullseye. The GFS & ECMWF look similar in positioning to the RGEM suite...so something to keep in mind. I definitely think Downtown TO -- Southern Mississauga -- Oakville have the potential to exceed 10cm but small differences in wind direction will make all the difference. Hardest hit areas (localized) will probably approach 20cm.

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2 hours ago, 500 mbvort said:

Wonder if this ends up producing more than the Tuesday storm? Do soundings support lake effect?

Here's an RGEM sounding valid 6z Friday. It's using the 850mb flow as the steering flow... note the easterly wind at that level. Surface flow northeasterly.

The banding is shallow... below ~850mb, which is typical of these easterly flow events. 850s are about -10C which gives about ~16C deltaT with the Lake temp. This is supportive of something popping up.

 

rdps_2021021718_036_43.76--79_42.thumb.png.140a786744db338ca6f1e9dba264ab02.png

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31 minutes ago, blizzardof96 said:

This is a tough forecast due to the localized nature of the LE banding.

I think many communities within the GTHA (besides northern areas near the 407) will see 5-10cm. The >10cm amounts will directly align with the narrow streamer expected to come in off Lake Ontario. Location of this band varies depending on which model you trust. NAM/3kNAM have the bullseye near Oakville/Burlington while RGEM/HRDPS have a downtown TO -- Mississauga bullseye. The GFS & ECMWF look similar in positioning to the RGEM suite...so something to keep in mind. I definitely think Downtown TO -- Southern Mississauga -- Oakville have the potential to exceed 10cm but small differences in wind direction will make all the difference. Hardest hit areas (localized) will probably approach 20cm.

RAPGL_prec_kuchsnow_051.png

21z RAP actually looks a bit north of the RGEM, focusing 401 corridor and upslope areas along the escarpment.

A few degrees in wind direction, sfc, 925 and 850 are going to make a huge difference.

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4 minutes ago, snowstormcanuck said:

RAPGL_prec_kuchsnow_051.png

21z RAP actually looks a bit north of the RGEM, focusing 401 corridor and upslope areas along the escarpment.

A few degrees in wind direction, sfc, 925 and 850 are going to make a huge difference.

Agreed wholeheartedly.

That looks similar to what the 12z Euro was showing and is a plausible scenario. Climo argues for the band hugging the lakeshore a bit more but it'll likely come down to nowcasting as the models simply aren't good enough to resolve this event with perfect accuracy.

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13 minutes ago, blizzardof96 said:

Agreed wholeheartedly.

That looks similar to what the 12z Euro was showing and is a plausible scenario. Climo argues for the band hugging the lakeshore a bit more but it'll likely come down to nowcasting as the models simply aren't good enough to resolve this event with perfect accuracy.

Thinking back to that "event" in mid-December when all the models were gung-ho on a major east wind LES event and nothing materialized.  If you do this for a living, I don't envy you. :D 

At least this is more of a seeder-feeder/LEnhS event so I think it's more a question of where and not if. 

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7 minutes ago, snowstormcanuck said:

Thinking back to that "event" in mid-December when all the models were gung-ho on a major east wind LES event and nothing materialized.  If you do this for a living, I don't envy you. :D 

At least this is more of a seeder-feeder/LEnhS event so I think it's more a question of where and not if. 

IIRC that event had lots of dry air to contend with?

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1 hour ago, blizzardof96 said:

This is a tough forecast due to the localized nature of the LE banding.

I think many communities within the GTHA (besides northern areas near the 407) will see 5-10cm. The >10cm amounts will directly align with the narrow streamer expected to come in off Lake Ontario. Location of this band varies depending on which model you trust. NAM/3kNAM have the bullseye near Oakville/Burlington while RGEM/HRDPS have a downtown TO -- Mississauga bullseye. The GFS & ECMWF look similar in positioning to the RGEM suite...so something to keep in mind. I definitely think Downtown TO -- Southern Mississauga -- Oakville have the potential to exceed 10cm but small differences in wind direction will make all the difference. Hardest hit areas (localized) will probably approach 20cm.

I live right on the border between Toronto and York region - around McCowan and Steeles. I'm hoping I can at least squeeze 5 cm/2" out of this, but am not holding my breath.

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4 minutes ago, Ottawa Blizzard said:

I live right on the border between Toronto and York region - around McCowan and Steeles. I'm hoping I can at least squeeze 5 cm/2" out of this, but am not holding my breath.

I think the synoptic will be able to deliver that.  You're not out of the conversation with the LES either but it's not likely to get that far north.

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36 minutes ago, 500 mbvort said:

IIRC that event had lots of dry air to contend with?

 

44 minutes ago, snowstormcanuck said:

Thinking back to that "event" in mid-December when all the models were gung-ho on a major east wind LES event and nothing materialized.  If you do this for a living, I don't envy you. :D 

At least this is more of a seeder-feeder/LEnhS event so I think it's more a question of where and not if. 

Some of the issues with that mid-December event:

1) Dry profiles

2) Lower delta-Ts (850s were closer to -8C) and shallower arctic air

3) Significant veering between sfc-850mb

4) Weaker model support in terms of intensity/duration

 

I think we have a more favourable setup this time, but we'll see what happens tomorrow. RADAR won't be too helpful given the shallow nature of the banding. With lower beam heights, KBUF will likely pick up on it better than WKR.

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20 minutes ago, blizzardof96 said:

 

Some of the issues with that mid-December event:

1) Dry profiles

2) Lower delta-Ts (850s were closer to -8C) and shallower arctic air

3) Significant veering between sfc-850mb

4) Weaker model support in terms of intensity/duration

 

I think we have a more favourable setup this time, but we'll see what happens tomorrow. RADAR won't be too helpful given the shallow nature of the banding. With lower beam heights, KBUF will likely pick up on it better than WKR.

Should be interesting to watch this unfold tomorrow. Here’s hoping for some decent totals.

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