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February 25-27 Winter Storm Part 3


Brewers

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Pretty bad model failure with the Feb 25 0z and 12z runs...looking at what's going on in central Iowa. 

 

Des Moines...rip city.

 

METAR KDSM 261454Z 01016KT 1/4SM R31/2200V4000FT +SN FZFG VV004 M01/M03 A2977 RMK AO2 TWR VIS 1/2 SLP090 SNINCR 2/5 P0017 60030 T10111028 55005 $

That really is a nice band moving westward through Polk county.

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Yup. Gained another degree the last hour. Writing's on the wall here. Still should be a decent moderate snowfall but nothing out of this world.

You know, it wouldn't surprise me if only 4-6" actually accumulated in the city.

 

Temperatures continuing to rise here, and that's with a snowpack and an east wind, the coldest wind you can get in these parts. If this were December 26, it would be a totally different story, i.e. lower sun angle.

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We'll obviously get some dynamic cooling, but the warmer the boundary layer the more difficult it is to overcome. I think the first 3-5 hours now of pcpn is shot south of the 401. Probably RA mixed with SN with no accums. You're still probably ok. We'll change to accumulating snow overnight, but the loss of that prime snow accumulation time will hurt us in the city in the end.

 

I think near the Lake shore, amounts will be limited but still a good 8-15cm is quite possible but away from the Lake, 401 and north including YYZ i believe amounts of 13-20+cm are possible and more the further north you head. Again lets see the temperature anomalies over the next few hours. We still have a snow pack on the ground and that may help keep temperatures at the surface colder. 

 

Is everything running good up until this point, comparing the surface to the models? 

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We'll obviously get some dynamic cooling, but the warmer the boundary layer the more difficult it is to overcome. I think the first 3-5 hours now of pcpn is shot south of the 401. Probably RA mixed with SN with no accums. You're still probably ok. We'll change to accumulating snow overnight, but the loss of that prime snow accumulation time will hurt us in the city in the end.

I'm not so sure about that. Rates are going to be pretty strong and with cool winds off the lake, this thing hitting after sunset, and decent snow cover, temps will firmly stay around zero. Especially at onset of precip the temps are going to drop. With the high precip rates the sfc temps will cool as the p type will be snow. Or I could totally bust. But after quite a few snowstorms on Vancouver with sfc temps at 2 degrees I'm not overly concerned

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NAM remains a worthless POS.

 

12z NAM text data for the "backside" stuff for LAF...6.5" of snow. That is flat out stupid and wrong.

 

 

15 02/27 03Z   32     32     318       3    0.21  0.00    538    535   -1.5 -23.2  997 100 SN    006OVC246    1.0    0.818 02/27 06Z   32     31     274       6    0.12  0.00    536    534   -2.3 -24.2  997 100 -SN   005OVC236    1.2    1.021 02/27 09Z   31     31     257       8    0.03  0.00    537    535   -2.9 -24.1  998 100 -SN   006OVC094    0.3    2.224 02/27 12Z   31     30     249       9    0.03  0.00    536    535   -3.9 -24.6  999 100 -SN   006OVC206    0.3    2.627 02/27 15Z   31     30     244       9    0.06  0.00    535    535   -5.2 -24.4 1000 100 -SN   006OVC248    0.6    0.630 02/27 18Z   32     31     253       9    0.13  0.00    534    535   -5.9 -24.3 1001 100 -SN   006OVC249    1.3    0.533 02/27 21Z   32     32     271      10    0.11  0.00    534    535   -6.5 -24.7 1002 100 -SN   007OVC251    1.1    1.636 02/28 00Z   32     31     285      11    0.04  0.00    533    537   -6.7 -24.7 1004 100 -SN   007OVC144    0.5    1.839 02/28 03Z   31     30     299      12    0.02  0.00    533    538   -6.6 -24.7 1006 100 -SN   007OVC112    0.2    2.9
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This storm has huge positive bust potential for someone in lower Michigan. Accumulation maps from DTX are very conservative.

 

I'm looking at 0.75-1.00 qpf and my forecast is 3-6 inches? I'm looking at barely any unfrozen precip... possibly all snow.

 

5:1 ratios and warm surfaces will do that

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NAM remains a worthless POS.

 

12z NAM text data for the "backside" stuff for LAF...6.5" of snow. That is flat out stupid and wrong.

 

 

15 02/27 03Z   32     32     318       3    0.21  0.00    538    535   -1.5 -23.2  997 100 SN    006OVC246    1.0    0.818 02/27 06Z   32     31     274       6    0.12  0.00    536    534   -2.3 -24.2  997 100 -SN   005OVC236    1.2    1.021 02/27 09Z   31     31     257       8    0.03  0.00    537    535   -2.9 -24.1  998 100 -SN   006OVC094    0.3    2.224 02/27 12Z   31     30     249       9    0.03  0.00    536    535   -3.9 -24.6  999 100 -SN   006OVC206    0.3    2.627 02/27 15Z   31     30     244       9    0.06  0.00    535    535   -5.2 -24.4 1000 100 -SN   006OVC248    0.6    0.630 02/27 18Z   32     31     253       9    0.13  0.00    534    535   -5.9 -24.3 1001 100 -SN   006OVC249    1.3    0.533 02/27 21Z   32     32     271      10    0.11  0.00    534    535   -6.5 -24.7 1002 100 -SN   007OVC251    1.1    1.636 02/28 00Z   32     31     285      11    0.04  0.00    533    537   -6.7 -24.7 1004 100 -SN   007OVC144    0.5    1.839 02/28 03Z   31     30     299      12    0.02  0.00    533    538   -6.6 -24.7 1006 100 -SN   007OVC112    0.2    2.9

 

has some weird band stalling out sw of the sfc low over LAF lol

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We'll obviously get some dynamic cooling, but the warmer the boundary layer the more difficult it is to overcome. I think the first 3-5 hours now of pcpn is shot south of the 401. Probably RA mixed with SN with no accums. You're still probably ok. We'll change to accumulating snow overnight, but the loss of that prime snow accumulation time will hurt us in the city in the end.

 

Hmm, 12z GFS looks a bit toasty. haha 

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You know, it wouldn't surprise me if only 4-6" actually accumulated in the city.

 

Temperatures continuing to rise here, and that's with a snowpack and an east wind, the coldest wind you can get in these parts. If this were December 26, it would be a totally different story, i.e. lower sun angle.

 

If the wind was more ENE or NE, we'd be colder. It's 090 blowing in right off L Ontario.

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I'm not so sure about that. Rates are going to be pretty strong and with cool winds off the lake, this thing hitting after sunset, and decent snow cover, temps will firmly stay around zero. Especially at onset of precip the temps are going to drop. With the high precip rates the sfc temps will cool as the p type will be snow. Or I could totally bust. But after quite a few snowstorms on Vancouver with sfc temps at 2 degrees I'm not overly concerned

 

This isn't May unfortunately. That's a warming wind.

 

But I hope  you're right about the rates and the snowcover helping out.

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Not feeling it for this area of SE MI, or at least I should say feeling very nervous...has huge bust potential either way, to be honest. We have lucked out most events this winter by overperforming, so you could argue either "seasonal trend" says heavy snow, or "we are due for a bust" says heavy rain. Even if a track was set in stone (which it really isnt) I could see everything from all rain to 10" of cement. Im off to work all day though, so when I get out (7pm) a storm of some form should be raging one way or the other.

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Not feeling it for this area of SE MI, or at least I should say feeling very nervous...has huge bust potential either way, to be honest. We have lucked out most events this winter by overperforming, so you could argue either "seasonal trend" says heavy snow, or "we are due for a bust" says heavy rain. Even if a track was set in stone (which it really isnt) I could see everything from all rain to 10" of cement. Im off to work all day though, so when I get out (7pm) a storm of some form should be raging one way or the other.

Yeah it appears to be a nowcasting event for everyone at this point. Too marginal to call. Every mile off the low track counts, every daytime heating degree and dynamic cooling counts. Best of luck

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