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February 25-26 Winter Storm

wisconsinwx

By wisconsinwx,
in Lakes/Ohio Valley

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snowstormcanuck

snowstormcanuck

Posted
Posted

Canuck, what are you thinking for northeast Toronto? Think I could see 10"?

 

You're in a very good spot. I thought the NAM had a monopoly on weenie snowfall output. How wrong I was. 18z GFS has 1.65" of QPF, all snow, before we turn over to some drizzle later on Wednesday. I think this is overdone, but about 1.00" of QPF looks possible. With 8:1 ratios, I'm liking about 8" in the far north of the city, 4-7" along the 401, and maybe only 3 or 4" downtown and near the Lake. Prelim numbers so I'm being conservative. Best chance for 10" or more I think is probably going to be just to your north, but it's close.

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Snowstorms

Snowstorms

Posted
Posted

You're in a very good spot. I thought the NAM had a monopoly on weenie snowfall output. How wrong I was. 18z GFS has 1.65" of QPF, all snow, before we turn over to some drizzle later on Wednesday. I think this is overdone, but about 1.00" of QPF looks possible. With 8:1 ratios, I'm liking about 8" in the far north of the city, 4-7" along the 401, and maybe only 3 or 4" downtown and near the Lake. Prelim numbers so I'm being conservative. Best chance for 10" or more I think is probably going to be just to your north, but it's close.

 

My early preliminary thoughts so far are like this; I believe closer to the shore line, amounts will be lesser and I don't want to get into detail but long story short, i think 3-4" at this point is a safe bet along the shore line, then around 401, 4-6, possibly 7" and then about Steeles and North, i believe amounts of 5-8" or so. 

 

I'm being conservative, as temperature profiles are critical but we still have 48-54 hours till this storm arrives. 

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snowstormcanuck

snowstormcanuck

Posted
Posted

My early preliminary thoughts so far are like this; I believe closer to the shore line, amounts will be lesser and I don't want to get into detail but long story short, i think 3-4" at this point is a safe bet along the shore line, then around 401, 4-6, possibly 7" and then about Steeles and North, i believe amounts of 5-8" or so. 

 

I'm being conservative, as temperature profiles are critical but we still have 48-54 hours till this storm arrives. 

 

Seems reasonable. It's too bad that high pressure cell over QC became so stale. It's in a good spot but there's just no arctic air left. Otherwise this'd be an open and shut case.

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Gino

Gino

Posted
Posted

Since the decision I made not to go with a watch has become a heated topic of discussion, I figured I'll chime in and elaborate a bit more here than what was in the AFD.

 

First, the notion that there has to be a watch out before every decent snow event I think is absurd. The public is aware a storm is coming and I'm not sure there is anything different 99% of the general public would do at 5 pm Sunday if there was a watch that they can't still accomplish if a watch goes out at 4 am. Those with weather sensitive plans for Tuesday will see our website which is highlighting a winter storm potential as is our official forecast. Winter storm watches are not designed to be issued prior to winter weather advisories, a watch means there is a high likelihood of meeting warning criteria (6" in 12hours or  8" in 24 hours). We do have some flexibility to take into account mitigating factors (extreme blowing/drifting, hitting at rush hour, first storm of season, etc) and that is one reason I considered issuing a watch today.

 

Regarding the whole in the W/W/A map, there was collaboration between me, IWX, DTX, GRR, DVN, MKX, and ILX today. ILX/DVN were both not planning to change there watch and ILX even thought of trimming the eastern extent of their watch. IWX/GRR/DTX were not going to issue a watch, then literally as my AFD was going out at 255 pm, IWX sent a message saying they changed their mind and were going to do one. Had I known that GRR/DTX/IWX were going to issue a watch, that is something that I would have considered and weighed into my decision.

 

Meteorologically speaking, Tuesday's event is far from a slam dunk heavy snow event. Thermally there are HUGE question marks, particularly at the surface. While I would agree and did mention in the AFD that there is a chance for a significant, high impact event, I think there is a slight higher chance that most areas end up with less than 3" of snow from Chicago south and east. Models struggle horribly with 2m temps when there is WAA over a snowpack and exhibit a cold bias. While yes, the SREF does have temps at 30F and Tds in the mid 20s when the snow starts, what does the SREF have for temps this afternoon? It and all the other models were too cold with temps today, even 6 hours after initialization the NAM and GFS temps over the snow pack were 4F+ too cold. If can't get BL temps right 6 hours after initialization, how can anyone have high confidence that they are right 48 hours out? Not to mention we saw a lot of snow melt today (looking like areas of our SE CWA have bare ground already) and will see more snow melt tomorrow, which the models will no doubt be oblivious to still treat it 2m temps like there is a glacier on the ground!

 

While winds will be easterly, due to the screwy pattern, we will be experiencing strong low level WAA on Tuesday. Model 2m temps generally climb above freezing over about the SE 1/2 of my CWA and MOS temps are in the mid to upper 30s. Models are definitely hinting at dynamic and evaporative cooling taking place and cooling the column enough for snow, but with a known cold bias at 2m they still keep temps at or just above freezing. That will make it hard for snow to accumulate quickly unless it's snowing like a SOB and even then it might be hard for it to stick on roadways for an extended period of time. Also, the sun angle is higher and even though we will be cloudy, the sun this time of year will have an impact on accumulation potential when temps are marginal like they are progged to be on Tues. Even if temps get below freezing, much of the lift is progged to be focused above the prime dendritic growth zone during the most intense snowfall, which is also not conducive for high SLRs. 

 

Is there potential for dynamic cooling to be really strong and it snow hard enough to cool temps below freezing and allow for significant accums over 6"? Yes. Do I think that is likely? No. I think the more likely scenario is it snowing hard for a few hours and picking up accums similar to what we saw with the last storm. For what it's worth, our forecast pretty much all along was 3-5" or 3-6" and that verified well with 2.5-5" across the CWA, yet how many people griped and moaned about us being wrong again. There is already a perception out there in the public that forecasters are always overhyping storms and to some extent I think there is some validity to that point. There were schools that no doubt saw some TV mets showing their in house models spitting out 8"+ the day before that last storm and actually closed schools for a 3" snow in Chicago!! The difference between a big problem and a total bust with late and early season storms is very small and it makes them notoriously difficult to forecast. I think the chances of getting 6" of snow by 00z Wed are low and I think the chances of getting less than 3" of accumulation are higher with a decent shot we end up somewhere in the middle. That to me does not scream that a watch is necessary or needed at this point. I'm sure everyone will be well informed about the snow potential even though there's no watch out and if the midnight shift decides a watch is justifiable, they can have it out before most people wake up tomorrow and everyone will still have more than 24 hours to prepare for the storm.

 

Today's forecast and headline decision was not an easy one and a case could have certainly been made to go with a watch, so I can totally understand the discussion here, but I just wanted to explain some of my reasoning a bit further. For what it's worth, I drove into work today fully anticipating putting out a watch, it wasn't until I started really digging into the analysis and models did I change my mind!

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weatherbo

weatherbo

Posted
Posted

So you think it is down sloping? That stinks, as down sloping is pretty much a slam dunk then with the winds.

it's the only thing I can think of that would give the models such consistency in a precip gap in this area.  That, and down sloping was mentioned in APX's afd, saying parts of nwl L mich coast area might reach 40 Tuesday.  Always the Grand Traverse area that feels it most pronounced.  Down your way, I'd think less of a factor, but IDK for sure.

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weatherbo

weatherbo

Posted
Posted

Thanks Gino. Really no need to defend yourself, but great to read your explanation. You're an exceptional met. At times, especially this year I put you ahead of skilling.

after reading his discussion, I realize why he is paid to do what he does and I am not.  Also I like the subtle shade at skilling.... deserved as well.  skilling is irresponsible with that rpm crap.

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IWXwx

IWXwx

Posted
Posted

Gino, thanks for taking the time to explain your thoughts in your detailed post.

 

One point that you made that really bugs me is the TV met issue of broadcasting unrealistic outputs from in- house models. I won't point any fingers, but with the last system I saw some maps broadcast by a highly respected TV weatherman that had no hope of verifying. The public pays much more attention to those maps on TV than any NWS product. However, when the TV met forecast busts, the NWS receives the brunt of the criticism.

 

EDIT: I see that others shared my thoughts at the same time I was typing them.

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Gino

Gino

Posted
Posted

Thanks Gino. Really no need to defend yourself, but great to read your explanation. You're an exceptional met. At times, especially this year I put you ahead of skilling.

 Thanks, really wasn't defending the decision so much as explaining it further. No one has the definite right answer this far out and this is a great discussion debate to have!

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