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Feb 3rd - 5th Potential strong stm threat


Brian D
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23 minutes ago, Chicago Storm said:


The GEM makes sense when you look under the hood.

SLP doesn’t really deepen until it’s passing NE of the area. WAA doesn’t take off until east as well, and 850’s are actually out of the west of a period of time.

On the flip side, the GFS has good snows further south for a different reason. It has the SLP strengthening sooner, with more WAA sooner and further west. However, the further south track helps bring the good snows further south.


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Ok, fair points.  That being said, I think it would be foolish at this point to expect several inches out this setup where I am.  Maybe there's a better shot of that in far northern IL.  

At least it looks like we'll break even or possibly gain some snowcover here before we move on to the weekend.

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12 minutes ago, Hoosier said:

Ok, fair points.  That being said, I think it would be foolish at this point to expect several inches out this setup where I am.  Maybe there's a better shot of that in far northern IL.  

At least it looks like we'll break even or possibly gain some snowcover here before we move on to the weekend.

Valid. I'm not even fully sold for here as of yet, even though trends have been more favorable overall.

I'd probably go 1-3" along/north of I-88 for now.

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KLOT not impressed with snow chances and agrees with Hoosier

The jet core will continue to strengthen as the system treks
eastward which should be able to drum up a decent surface low via
cyclogenesis along the developing baroclinic zone as lead dome of
colder air funnels into the trough axis. As the system nears the
Great Lakes, the increased strengthening evidenced via the negative
tilting of the trough and increased frontal strengthening should
lead to a significant deepening of the associated surface low.

We will be maintaining a southeast surface wind over the snowpack as
warm south/southwest flow off the surface pumps in some warmer air
aloft. This suggest there could be small window for brief freezing
rain at onset Thursday morning, though it does not look to be long
lived. Precip type appears to be snow north initially and rain
south, with a generally changeover to a mix or rain for most areas
except for northwest of Chicago which could remain as a wet snow.
The period of highest confidence for precipitation is Thursday
afternoon with the left exit of the upper jet in place, maximized
isentropic lift, and strong q-vector convergence fields with the
increased height falls. This would be the wild card period if snow
remains dominant near and northwest of Chicago, but with system
strengthening/deepening the pattern of maintaining warmer air aloft
suggests the layer would warm enough unless precip rates were to
remain sufficiently strong.

There are some model differences in the strength of the low, but all
generally show a stronger system with a deepening low with a fairly
significant pressure rise on the back side as colder air funnels on
in. This is the period of continued upper low strengthening combined
with the strong surface cold front.  Bitterly cold air accompanied
by a "wall of wind" behind the front should result in a rapid
changeover to snow if it had not occurred already. QPF should be
starting to taper, but there appears a window time where forcing,
decent lapse rates aloft, cold air, and strong pressure rises could
result in a brief period of moderate snow and wind gusts in excess
of 40 mph Thursday later in the evening and dangerous travel
conditions. This does appear to be well after the evening commute.
At this time model guidance has not changed much with the overall
snow forecast, maybe slightly higher for snow near Rockford and less
farther south and east, with the highest probabilities of a few
inches of snow (maybe several north central IL) northwest of
Chicago. The combination of snow and wind could certainly warrant
some kind of winter weather alert.
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Re; LOT AFD:

^ not RC. Disregard.:lol: That said, the last line is more telling. And 2-4" North and West burbs and 1"-2" along the I-88 corridor with wind and temps crashing should be fun. Potential for more is still on the table.. Reread that write up again, and  think it's pretty good and actually think they are fairly impressed.

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20 minutes ago, Baum said:

Re; LOT AFD:

^ not RC. Disregard.:lol: That said, the last line is more telling. And 2-4" North and West burbs and 1"-2" along the I-88 corridor with wind and temps crashing should be fun. Potential for more is still on the table.. Reread that write up again, and  think it's pretty good and actually think they are fairly impressed.

Interesting that 18z NAM  has more snow via both Kuchera and 10:1 closer to metro Chicago and less and NW and west which is against the KLOT forecast. Just happy that the system went  away from a rainer and snow eater. 

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21 minutes ago, McHenrySnow said:

No major changes on the 18z NAM it appears.

Pretty big changes upstairs (see below), but it didn't really translate to much difference at the surface. The splotchiness of snow accumulations in these parts is indicative of dynamic cooling. Probably going to have to rely on that south of ~88/290 as others have mentioned. Don't think we should disregard that scenario given the ingredients showing up on a lot of guidance: steep lapse rates, 500-250mb left exit region dynamics, highly focused WAA, but air temps will almost certainly be above freezing for at least a few hours S/SE of wherever the surface low ends up tracking. Whatever snow ended up falling in those areas may not accumulate on roads (unless it's heavy) but could add to the snow depth a bit. 

trend-nam-2021020218-f060.500hv.us_mw.gif.0727e5471d85d29b9139796813e3341e.gif

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Well, I hope you guys enjoy. My model did ok showing this system. Thought it had a better chance coming my way. Oh well, 3-6" of powder before the Arctic relocates is ok too. Snow pack good enough to handle the cold, which is a good thing. 

Go for it Cheese Heads and Polar Bears lol !

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2 minutes ago, purduewx80 said:

Pretty big changes upstairs (see below), but it didn't really translate to much difference at the surface. The splotchiness of snow accumulations in these parts is indicative of dynamic cooling. Probably going to have to rely on that south of ~88/290 as others have mentioned. Don't think we should disregard that scenario given the ingredients showing up on a lot of guidance: steep lapse rates, 500-250mb left exit region dynamics, highly focused WAA, but air temps will almost certainly be above freezing for at least a few hours S/SE of wherever the surface low ends up tracking. Whatever snow ended up falling in those areas may not accumulate on roads (unless it's heavy) but could add to the snow depth a bit. 

 

Yeah, the nice thing is snow will stick to snow, so even if we wouldn't see much on paved surfaces, it might be enough to counteract melting and/or increase total depth. 

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I keep thinking back to January 2019, the week of the extreme cold from the displaced polar vortex and remember a system that had what would normally be a garbage track for Chicago surprise us with an all snow front end thump. I believe we got 3 or 4" in the city. It warmed up above freezing and we had drizzle the rest of the day and then the arctic front eventually made it through the area the next day or so? 

 

Anyhow, this reminds me of that somewhat. Not necessary the atmospheric setup, but the heavy wet snow preceding the arctic blast. 

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31 minutes ago, Brian D said:

Well, I hope you guys enjoy. My model did ok showing this system. Thought it had a better chance coming my way. Oh well, 3-6" of powder before the Arctic relocates is ok too. Snow pack good enough to handle the cold, which is a good thing. 

Go for it Cheese Heads and Polar Bears lol !

What is "your model"? Keep seeing you reference it but only image you have posted is a paint rendered image. Are you referring to something like LRC/BSR/Heady Pattern?

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1 minute ago, WeatherMonger said:

What is "your model"? Keep seeing you reference it but only image you have posted is a paint rendered image. Are you referring to something like LRC/BSR/Heady Pattern?

No, it's my own creation. Sorry for the simple maps, tho. Not a graphics person. Just a simple paint program.

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