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December and a Hint of January Pattern Discussion


Bob Chill

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Not sure how you can be expecting a virga fest on a potential event that is 8 days out. So many details yet to be resolved and there are a variety of outcomes possible. I will say that a freezing drizzle event its probably the least likely.

Considering the source region for the moisture is the gulf then overcoming ll cold dry air is quick and easy.

The caveats I'm seeing are being in the crosshairs #1. Geographically, it a narrow band so 75 miles one way or another is make or break. #2 is being on the winning side of the boundary. Again, 75 miles is make or break.

Climo argues for the losing side of the boundary but it's an anomalous airmass so that helps.

Even if we are on the winning side it could be too much win and we are cold and dry. Should be a fun roller coaster of model runs and emotions this week. All options are on the table for days.

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I agree, at this time range it's hard to be definitive about anything.

True I should have used less definitive language given this is still out there in lala land as far as the models are concerned.  I've just seen these overrunning events before and they are so delicate and timing based, and when that arctic boundary is south of your area, it can be real difficult to get the column saturated enough for much precip at the surface.  Obviously it will become more clear as we get closer, but most are sharing their opinions on how it might shake out so I figured I'd add my ideas to the pile. 

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True I should have used less definitive language given this is still out there in lala land as far as the models are concerned.  I've just seen these overrunning events before and they are so delicate and timing based, and when that arctic boundary is south of your area, it can be real difficult to get the column saturated enough for much precip at the surface.  Obviously it will become more clear as we get closer, but most are sharing their opinions on how it might shake out so I figured I'd add my ideas to the pile. 

 

i think the column can get saturated in a setup like this...the big issue is that the mid levels will go above freezing....it isn't a quick thump....as long as we can accept that it will be a messy event (i can) we probably will have something to track at least...those expecting a snowstorm will probably be disappointed

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Considering the source region for the moisture is the gulf then overcoming ll cold dry air is quick and easy.

The caveats I'm seeing are being in the crosshairs #1. Geographically, it a narrow band so 75 miles one way or another is make or break. #2 is being on the winning side of the boundary. Again, 75 miles is make or break.

Climo argues for the losing side of the boundary but it's an anomalous airmass so that helps.

Even if we are on the winning side it could be too much win and we are cold and dry. Should be a fun roller coaster of model runs and emotions this week. All options are on the table for days.

Yes, it will be fun. We have not had one of these to track in ages. But all of us have seen these overrunning set ups with an arctic boundary over the years, and the caveats you mention always factor in to the ultimate outcome to some degree.

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i think the column can get saturated in a setup like this...the big issue is that the mid levels will go above freezing....it isn't a quick thump....as long as we can accept that it will be a messy event (i can) we probably will have something to track at least...those expecting a snowstorm will probably be disappointed

Matt, I'm pretty sure the operational euro is going to take the next low to the lakes based on the 168hr forecast.  Unfortunately, based on the ridge position being so far west and the ridge being really strong something tracking west of us makes more sense than the GFS though the latter of course still is a possibility. 

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You have it up to 192-216? 

 

yes

 

Matt, I'm pretty sure the operational euro is going to take the next low to the lakes based on the 168hr forecast.  Unfortunately, based on the ridge position being so far west and the ridge being really strong something tracking west of us makes more sense than the GFS though the latter of course still is a possibility. 

 

it ends up being a nice event...changes over as expected, but I dont think most of us care about that since it is pretty standard

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Matt, I'm pretty sure the operational euro is going to take the next low to the lakes based on the 168hr forecast.  Unfortunately, based on the ridge position being so far west and the ridge being really strong something tracking west of us makes more sense than the GFS though the latter of course still is a possibility. 

Although the Euro op had a cutter yesterday and the ensembles did not concur. But your point is well taken, a storm cutting to the lakes does fit the pattern and is well within the realm of possibilities.

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Although the Euro op had a cutter yesterday and the ensembles did not concur. But your point is well taken, a storm cutting to the lakes does fit the pattern and is well within the realm of possibilities.

 

There is a very weak low in the lakes which is probably part of the reason we changeover, but not before we get a nice frontrunning thump

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There's just a wall of 1040+hp all across the eastern half of Canada. Keeps the storm from cutting and we are in the win zone all things considered.

The euro is quite different @ h5 compares to the gfs. In some ways I think the euro will end up trending more towards the gfs in coming days. The gfs is much more N/S oriented with the boundary compared to the euro's more E/W orientation.

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There's just a wall of 1040+hp all across the eastern half of Canada. Keeps the storm from cutting and we are in the win zone all things considered.

The euro is quite different @ h5 compares to the gfs. In some ways I think the euro will end up trending more towards the gfs in coming days. The gfs is much more N/S oriented with the boundary compared to the euro's more E/W orientation.

 

Yeah, there's something weird about the Euro's set up..and it kinda keeps changing how we get to the scenario.   12z yesterday had a different look.

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There is a very weak low in the lakes which is probably part of the reason we changeover, but not before we get a nice frontrunning thump

It does take a low to the lakes but has a great 1040 high in a position to produce really good cold air damming.  The CAD signature is really strong on the hi res euro.  I think it's solution is more likely than the GFS one though so far in advance you'd be foolish to rule out either one or something in between.  Still it's looking better and better for us getting some type of winter event. 

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It does take a low to the lakes but has a great 1040 high in a position to produce really good cold air damming.  The CAD signature is really strong on the hi res euro.  I think it's solution is more likely than the GFS one though so far in advance you'd be foolish to rule out either one or something in between.  Still it's looking better and better for us getting some type of winter event. 

 

yeah...It looks like a solid snow event for the western burbs, but no guarantee all the QPF is snow before they changover...even we get some decent snow on the front end...I would love 1-2" and then a wintry mix...even to rain would be ok...It would be nice for december

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yeah...It looks like a solid snow event for the western burbs, but no guarantee all the QPF is snow before they changover...even we get some decent snow on the front end...I would love 1-2" and then a wintry mix...even to rain would be ok...It would be nice for december

It's a nice look and having the low in the lakes being not that strong makes sense since it will be fighting really cold air, dense air. 

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Ian, ice storm pretty unlikely for us in early december, right?  probably snow/sleet mix and then maybe rain for us

not totally sure but in general i think late dec into jan is prob best most places.  verbatim a lot of liquid overnight though which might help if you wanted zr.. temps are kinda marginal around here (i know, lol).

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Looks like we lose 850's and surface between 192-198. Bulk of precip is done for the most part but definitely a period of rain from FDK/JYO on eastward.

Pretty narrow stripe of snow all things considered. Should be some heartbreak later today and some joy tomorrow followed by suicides and then back to joy.

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