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Southern Ontario Winter '14-'15 Discussion


harrisale

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Are you still expecting a quicker dry air intrusion then the models are currently advertising? I guess the forecast battle is on...

 

Yeah. After 2 decades of doing this, the last winter or two I've finally caught on that it's a bias of almost all the models to under do the aggressiveness of mid-level dry slots. Low-res model QPF output maps aren't going to usually pick up on it. But even still it's pretty evident on the RGEM for instance....

 

http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

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Yeah. After 2 decades of doing this, the last winter or two I've finally caught on that it's a bias of almost all the models to under do the aggressiveness of mid-level dry slots. Low-res model QPF output maps aren't going to usually pick up on it. But even still it's pretty evident on the RGEM for instance....

 

http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

Still early, but the HRRR looks like its in your camp. That mid level dry tongue is much more aggressive then previous runs from this aft. Waiting on consistency.

post-7879-0-74956100-1418255350_thumb.pn

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HRRR has been rock solid with 1-3" amounts for the GTA. That dry tongue is aggressive.

attachicon.gifhrrr_t_precip_ne_16.png

 

In contrast, latest NAM has shifted the pivot point of the defo band to the east, and now has it stalling right over Toronto. Would be looking at 15cm easy if that verified but I'm not buying it at this point. It's the NAM after all.

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Interesting trend with the 00z NAM (regular and 4km) and the 18z hi-res RGEM (2.5 km HRDPS). They all show a decent deformation band tomorrow afternoon into the evening hours. This is after the initial east to west band moves thru in the morning rush. The NAM now shows 6"+ snow in total for the GTA. Even the 12z Euro shows some QPF lingering into the evening hours tomorrow.

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I think we are in a good position when compared to SSC or others in the west end/downtown areas. Its a tough forecast but will probably end up in the 7-15cm range where we are and then more like 5-10cm downtown IMO. In terms of the GB Lehs, its def there as winds are in a nice direction(~340-350).  Would be nice if winds backed just a little bit more although you can see that either way the bay is helping ramp up QPF into the N GTA on the high res models.

Still nothing in northeast Scarborough. I'm guessing this won't start until after midnight now.

 

My final call is 2-4" for Toronto.

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Still nothing in northeast Scarborough. I'm guessing this won't start until after midnight now.

 

My final call is 2-4" for Toronto.

 

Took the whole day to get from a Belleville-Rochester axis to a Peterborough-St. Catharines axis. I'm thinking 1-2am as a start time for the --SN, though you may see it a wee bit earlier out your way.

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Took the whole day to get from a Belleville-Rochester axis to a Peterborough-St. Catharines axis. I'm thinking 1-2am as a start time for the --SN, though you may see it a wee bit earlier out your way.

Looks like the heaviest snow will be during the morning commute after all.

 

Good luck Toronto and southern ON peeps. :)

 

0z NAM and 4km NAM total QPF. 

 

attachicon.gifnam 36 hr total qpf.png

 

attachicon.gif4km nam toronto.png

Thanks Chicago WX. Hopefully it won't be too long before you guys are tracking a storm in your neck of the woods.

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RAP/GFS now onboard with the return eastward of the defo band but 0z RGEM has since dropped this evolution. Models clearly struggling a lot with this and it does have big implications.

6z RGEM will probably bring it back

 

models tend to struggle when trying to pin point where the defo will set up

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RGEM is usually pretty good at picking up moisture drying up.

 

Wouldn't be surprised to see the dry air from the north eat away at some of that moisture.

The 18z RGEM was indicating what the NAM and GFS say now. We'll see what happens. Should be interesting

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GFS says 4"

RAP says 4"

RGEM says 3"

 

Latest HRRR has 4" and so does the RUC. We'll see how it all plays out in the coming hours. Precipitation should move into the GTA by 3-4am with the heaviest rates during the morning rush hour. 

 

Sadly I have an exam tomorrow too. Last one, yes! 

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Moderate snow and blowing snow. Eyeballing we're nearing 2" (so about 1"/hr rates). This keeps up I'm doing a Jeb walk later this morning.

 

Dryslot evident on King City radar though. Already approaching Oshawa. NAM/GFS basically halt it though just east of the city. We'll see what the hi-res models say.

Enjoy!  :snowing:

 

Here it's just a cold (-9 C) star lite sky here with just a dusting (5 mm) of snow still around from yesterday mornings snow showers.

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Not a problem guys. I'll be living vicariously through you all. Hopefully it overachieves. And take/post photos of course, if things go well. :D

 

I echo Tim's thoughts. I've been watching the models move precip west and slightly increase moisture over the past few days. Hope you all enjoy what you're getting.

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Moderate snow and blowing snow. Eyeballing we're nearing 2" (so about 1"/hr rates). This keeps up I'm doing a Jeb walk later this morning.

 

Dryslot evident on King City radar though. Already approaching Oshawa. NAM/GFS basically halt it though just east of the city. We'll see what the hi-res models say.

After a little break in returns around 13z, the HRRR/RAP are showing on a second surge of SN as the band begins to build back east, especially in the NW end of the city. GB is helping out big time.

post-7879-0-86209800-1418296861_thumb.pn

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