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> Southern Ontario LES Potential, Nov 12-13
blizzardOf96
post Nov 11 2012, 01:14 PM
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A temperature gradient of 20C between the lake temperatures and the 850mb temperatures will be setting up with the passage of the strong cold front. A strong WNW flow behind the front with a very low amount of directional shear will make for ideal LES parameters. This may be the first major event of the season.
Lake huron and georgian bay temps are about 10C:
Attached File  glsea.gif ( 25.64K ) Number of downloads: 0


A 13C temperature difference needs to be present between the lake temperatures and the 850mb temps in order to see heavy bands of LES. By the text output from the NAM coming out of borden airport we can see 850mb temps below -10C for quite an extended period of time. It is the same case for toronto and surrounding areas. This would mean about a 20C temperature difference setting up:

Attached File  Screen_Shot_2012_11_11_at_1.09.49_PM.png ( 33.36K ) Number of downloads: 0


Looking at the skew-t plot from toronto after the passage of the cold front we can see a W wind with little directional shear. This will allow these bands to form off of the great lakes.
Attached File  nam_hgtprs__conus_48_A_us4300_7900skewt1.png ( 22.34K ) Number of downloads: 0


We can see early LES bands already forming on the NAM 4km WRF off of lake michigan, superior, huron and georgian bay with the passage of the cold front. I am curious to see what the RAP will show when it gets into range.
Attached File  wrf_ref_nmm_ne_46.png ( 224.73K ) Number of downloads: 4


This post has been edited by blizzardOf96: Nov 11 2012, 02:36 PM


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travis3000
post Nov 11 2012, 01:24 PM
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What date is this for?


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blizzardOf96
post Nov 11 2012, 02:33 PM
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QUOTE(travis3000 @ Nov 11 2012, 01:24 PM) *
What date is this for?


Tuesday of this week.


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blizzardOf96
post Nov 11 2012, 02:46 PM
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12z NAM we can see a strong SW then W and eventually a NW flow coming of of lake huron and georgian bay. The strongest bands will be setting up from W to E from 0z to 12z tuesday. Areas in and around the GTA will probably pick up some light snow or a coating but nothing major probably. A similar situation to last weekend will set up except more widespread and intense bands off of the lakes.
SW:
Attached File  nam_mslp_uv10m_east_15.png ( 718.21K ) Number of downloads: 2

W:
Attached File  nam_mslp_uv10m_east_18.png ( 715.03K ) Number of downloads: 1

NW:
Attached File  nam_mslp_uv10m_east_20.png ( 700K ) Number of downloads: 1



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blizzardOf96
post Nov 12 2012, 03:45 PM
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12z NAM 4km WRF showing some bands setting up in a WSW to ENE fashion:

Attached File  wrf_ref_nmm_ne_22_1.png ( 232.89K ) Number of downloads: 2


HRRR is showing a similar setup as well:

Attached File  rap_ref_neus_19.png ( 170.84K ) Number of downloads: 0


850mb Temps below -9C:
Attached File  rap_pr1_slp_t850_neus_19.png ( 230.73K ) Number of downloads: 0


NAM wind direction and speed:

Attached File  nam_mslp_uv10m_ne_8.png ( 480.83K ) Number of downloads: 0


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Ryan45
post Nov 12 2012, 04:14 PM
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hearing about wet snow tonight...


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blizzardOf96
post Nov 12 2012, 05:56 PM
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hrrr at hour 14:

Attached File  ptyp_t3sfc_f13.png ( 145.17K ) Number of downloads: 0


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dsichewski
post Nov 12 2012, 09:37 PM
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any update on this by chance?
thanks
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Torontoweather
post Nov 12 2012, 09:52 PM
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there is an interesting feature over Michigan right now producing light snow across a large area. I think this is in association with the winds/LES, but it doesn't really look like LES bands. Anyways, will be interesting to watch the movement of this as well as potential LES bands of Huron and Georgian bay... Looks like they may just be starting...
http://www.weatheroffice.gc.ca/radar/index_e.html?id=WSO


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blizzardOf96
post Nov 12 2012, 10:28 PM
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QUOTE(Torontoweather @ Nov 12 2012, 09:52 PM) *
there is an interesting feature over Michigan right now producing light snow across a large area. I think this is in association with the winds/LES, but it doesn't really look like LES bands. Anyways, will be interesting to watch the movement of this as well as potential LES bands of Huron and Georgian bay... Looks like they may just be starting...
http://www.weatheroffice.gc.ca/radar/index_e.html?id=WSO


I noticed that too, if you check out the water vapor loop it looks like it is courtesy of an ULL moving eastwards across lake superior.
Attached File  iswvcne_0045.gif ( 95.64K ) Number of downloads: 0


Light snows are breaking out on the south side across michigan and heading eastward but seem to be weakening:

Attached File  Screen_Shot_2012_11_12_at_10.34.27_PM.png ( 159.21K ) Number of downloads: 0


This post has been edited by blizzardOf96: Nov 12 2012, 10:33 PM


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