RCNYILWX

Potentially below zero and bare ground. Pass on this winter. It’s been pretty terrible.

I'm sorry to keep harping on it, but the map posted on the main Feb thread shows your standards are pretty high. 125-150% of normal snowfall since January 1st is objectively not terrible. December 1st to early January objectively was terrible. Of course it's been better north and west of us this month and we've missed some fun. But it's been very active since mid January and we had a very good stretch of snow from the January 12th system through Feb 1 and close to normal snow this month. Plus one of the most significant ice storms downtown in years (decades?) on Feb 12th.

 

 

 

When was the last time a storm didn't track over us? Hoping this is the last(if it in fact does), and we get some that are a bit more suppressed to give us a few late season snow events before spring is sprung.

I have my eye on Tuesday-Tuesday night for fronto snow. GFS has been consistently more north, favoring WI, but 12z GEM was nice for northern IL.

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18z NAMs came in way south/east, with surface low tracking over Chicago area. 3km is even farther south than 12km. Both show a rain/thunder to heavy snow and wind scenario for northern Illinois. Only run that's shown this so we'll see if it's a one off. Would certainly fit the idea of the low coming in farther south.

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They’ve had a couple good ones in a row now. I’d argue the northern Indiana/central Illinois/Chicago crews have gotten the shaft the past several winters in a row. What’s even more frustrating is when your snow total is overstated time and time again by a certain airport 17 miles to my northwest...

Pretty sure you're overstating futility there. Midway 3SW had 39.1" last year (more than ORD's 36.1) and will finish above normal for this season too with 38.3" so far, vs. 41.2" at ORD. Even if you're lower than MDW 3SW, I'd bet you're over 30" for this season, which is still near normal to date.

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Even if it shifts further SE the WAA seems to just bring the possibility of ice into the LOT area moreso than snow.

Comment I made wasn't about expecting more of a snow threat anywhere in CWA on the front end of the system, need very significant changes for that to happen. Wouldn't be surprised if it verifies weaker on approach and thus tracks more overhead before strengthening vs. cutting to our west. A majority of 00z European ensemble members had the low tracking over northern Illinois.

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Nice bump southeast on the Euro.  Heavy snows threaten the northwest portion of the DVN cwa on that run.  Just need another bump or two southeast please.  

Wouldn't be too surprised if it bumped more southeast, seems like a majority of the decent surface lows this winter have ended up southeast of the medium range operational model consensus.

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A little more now.

PRELIMINARY LOCAL STORM REPORTNATIONAL WEATHER SERVICE CHICAGO IL122 PM CST MON FEB 18 2019..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON.....DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....           ..REMARKS..1200 PM     SNOW             OHARE AIRPORT           41.98N 87.90W02/18/2019  M4.9 INCH        COOK               IL   OFFICIAL NWS OBS            STORM TOTAL SNOWFALL. 0.6 INCHES SINCE 6AM. 

Up to 41" on the season. With the pattern looking cold and active to close out the month and into March, a good chance to get to 50+ at ORD.

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advisory map looks a little strange with LOT bypassing a good portion of its CWA. Though I agree 2-4" over 12-18 hr period on a Sunday in late winter it probably is nor necessary.

ILX advisory for their northeastern counties is for inclusion of freezing drizzle on top of snow accums up to 2". Without that, they probably wouldn't have issued. If freezing drizzle looks more likely to occur down in southern LOT CWA, we may need to expand the advisory and perhaps include the Chicago metro counties not in headline for map purposes. Agree that a long duration 2-3/2-4" snowfall on a Sunday otherwise probably doesn't need one.

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Too bad this wave is dampening as it goes east. Good part of Iowa up to the Mississippi River get a solid advisory to possibly warning criteria snow. Though it falls over a long duration. Nam snowfall output looks very odd. It is very blotchy and sporadic. Doesn't make sense with the simulated reflectivity it is showing. RAP and HRRR to me have a more realistic snow swath 

I believe the NAM12 is suffering from unrealistic dry air issues that cause that splotchiness to the output. Have seen this issue several times the past few winters. Best way to compare is how you did with the simulated reflectivity vs the QPF/snow output. Other models look much more realistic as you said, including RAP/HRRR.

 

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3k NAM is trending this towards a DAB event for chunks of LOT. 

Looks like it's playing catchup. 12z run bumped up from 06z run pretty significantly.

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^
always get a kick how jaded the board gets if we've had a decent run of winter weather by mid February. Only 30 days ago the board would have been lit up stressing over every model run for a potential moderate event like this. Here's hoping we can have an eventful run through mid March and than a quick change to a warm spring.

I'm in same boat as you. Pass on nonsense of last March-April unless we get a big dog locally.

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Models have come into good agreement on a long duration 2-4" event for much of northern IL, with possibility of some minor additional LES accums late Sunday night into Monday morning. Looks good for 3-6" in eastern IA/QCA. Hopefully as cyclone mentioned the long duration can help this to be an overperformer.

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Nice improvement by the NAM tonight, especially in eastern IA/QCA. Would be cool if the blind GFS/FV3 squirrel finally found a nut.

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As far as what occurred with LOT... It was a tough forecast, as those involving different precip types tend to be more challenging.  The way they handled certain things was understandable, but the way they handled other things was more of a head scratcher.  

The initial lack of a warning for ice falls into the understandable category.  There were some indications that there could be maybe close to a quarter inch of ice somewhere (especially given mostly light to moderate precip rates and drops that weren't excessively warm), perhaps around I-88 and/or I-80, but that is borderline for a warning and exact placement was a bit questionable.  

As Monday wore on and it was becoming apparent that temps weren't responding much with the clouds and cool ENE flow, they could have been quicker to issue an advisory farther south in the cwa... Kankakee county, etc, particularly since the threshold for issuing one for ice is very low given the outsized impacts that the most minor glazes can have.  Also as Monday went on, the short range models like the HRRR/RAP were hitting on a corridor of .25"+ ice potential.  But as has been mentioned, those models underestimated the northward extent of the warm nose aloft.  One could argue that perhaps there should have been an afternoon issuance of the ice storm warning for the I-80 corridor, but the majority of the data didn't support one much farther north at that point and I don't view this aspect as being as much of a botch as the lack of an advisory farther south. 

As afternoon turned to evening and it was apparent that the warm nose aloft had gotten farther north, I think it is fair to say that there could have been a quicker reaction to convert to an ice storm warning... at least for I-80 at this point if not farther north.  I'm not really sure what held them back... perhaps they were concerned about temps warming up more quickly toward I-80 and some snow/sleet mixing in at times farther north (per HRRR/RAP) to hold ice accretion under warning criteria.  

Overall, it was not the finest forecasting performance by LOT.  Forecast evaluations happen and they are aware of how they did.  Criticism of NWS and other mets is okay but I think it should always be presented in a tactful way.  I am not singling out anybody in particular because there are other NWS offices and mets who get called out here.  We are fortunate to have professional contributions here, in particular from NWS mets like RC who can offer insight into what we see in those forecasts.  

 

Very good assessment. I think a big challenge in these situations other than making the assumption that the warm nose push will be at least as aggressive as the most aggressive model (NAM) is that we don't have any real time analysis of the warm layer. Aircraft soundings help but they're essentially point based so you can't track the trends and most of the soundings are from the larger airports.  

When the RAP/HRRR is underdoing the northward push and magnitude of the warm layer, it's a big hindrance. That's because the closest we have to real time analysis is the SPC mesoanalysis using the RAP as a background field, so it can definitely throw off even the best forecasters, and played a role in the lack of a lead time to warnings. As to the point about the southern CWA counties, the points you made are very fair. Being off duty for the event and an outside observer but certainly watching things closely, I think the signs were there that temps would mostly be AOB freezing for much longer than expected.

 

Just by tracking the surface wet bulb zero line on mesoanalysis, it wasn't budging and didn't make any northward movement until the late evening. That would also play a role in reaching the warning criteria ice accums farther north. With the surface low well south and east-northeast winds locking in temps mostly 32 or less and pulling from dews in the low-mid 20s over southern lower MI and northeast IN, that argued for multiple hours of flatlining temps. In addition, the sensitivity of even a glaze of ice accums w.r.t. road conditions is something that most of the time we err on the side of caution for and issue an advisory. Certainly a very tough forecast and often times we do perform internal assessments about what went well and what could've been done better in cases like these.

 

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Cutters are certainly gone. Now it appears everthing will run south of OV.

Ensembles still look active with a -EPO/-PNA most of the time and I'll take my chances with that. If it doesn't work out, that's how it goes with weather, but I'd be surprised if we get to the end of February without having at least one decent snow event.

The operational models 4-5+ days out are typically prone to big swings, but it seems like the very active Pacific jet/fast flow pattern this season has added more chaos than usual to the modeling, making them less stable and at times unusable in the medium range and beyond. Best advice is patience and hope we score some good snow events.

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.54” of ice. Going to be a big issue as this certainly won’t melt off before the wind starts. 

Where in DeKalb County are you? I can forward your report to the office for an LSR if you haven't yet.

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Yeah I was keeping an eye on my old DVN stomping grounds and saw the forecasts getting upgraded for FZRA. 

I've also noticed that here in the Northeast anyway, all the offices are forecasting snow ratio grids and deriving snow from that. And well modeling is not great with that (usually too high), and snowfall trends that way as a result.

My office started with just metro counties and west in an advisory, then expanded 1 tier south earlier today, then eventually CWA wide with 2 updates this evening. Finally we upgraded to warnings in part of the CWA then just a little while ago expanded the ice storm warnings we had issued late evening to now include most of Chicago metro except far north/northwest.

 

We have the same issue out here with the snow ratio grids used to derive the snow output. It's been less of an issue in this area this winter from what I've seen but last year we had several events with low snow ratios despite cold temps due to the lift being above the DGZ and over forecast snow amounts as a result of ratios being too high. We try to account for the ptypes in the snow amount forecast with the prob of weather type (powt) methodology (using modified bourgoin energy technique), so that when there's low hourly snow probs and/or 2m temps AOA 35, we don't accumulate snow that hour and it subtracts it out of the 6 hour snow grid.

 

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Funny you mention that. I just looked at ORD since we have interests there, and noted the same.  

I put together some select total ice accums as of 06z from regional ASOS sites (by adding up I6 groups in metars). Most impressive widespread ice storm in years in this area.

MLI: 0.47
DVN: 0.41
ARR: 0.32
VPZ: 0.30
DPA: 0.27
ORD: 0.22
RFD: 0.19
CID: 0.18
MDW: 0.15
PIA: 0.14
PWK: 0.09

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That warmth aloft is always hard to stop.
00z HRRR, NAM, and GFS all have sub-warning amounts for the southern half of NH. Scooter caution flags everywhere right now.

Was a red flag when we started off where I live in western Chicago metro as ZR/IP and not snow with SPC mesoanalysis off because of using RAP background which was too cold. Places well west and north in DVN CWA that were supposed to stay snow like CID and DBQ went over to ZR. Could see the mix line surging north on CC and knew it was all over. Good lesson today to err on the side of the warmth aloft being at least as aggressive as the most aggressive model.

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Some select ASOS ice accums as of 06z (by adding up I6 groups in METARs):

MLI: 0.47

DVN: 0.41

ARR: 0.32

VPZ: 0.30

DPA: 0.27

ORD: 0.22

RFD: 0.19

CID: 0.18

MDW: 0.15

PIA: 0.14

PWK: 0.09

 

 

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I'm an off-duty met from NWS LOT (Chicago). Haven't been following closely enough to know how the models have been depicting things over there, but just wanted to note that the NAM did by far the best with the warm nose here in northern IL and into eastern IA. The other models, including RAP/HRRR, were too cold aloft and not aggressive enough in pushing the warm nose steadily northward. We're now in a full on ice storm out here (I had close to 0.2" as of an hour ago where I live) and 2m temps flatlining around 31-32 with several more hours of steady precip to go.

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The piece of guidance that had this scenario depicted pretty close to how it's unfolded is the NAM. I think the challenge in this setup is that you can think of a physical reason why a blend of the guidance would work out and how heavy rates could slow or even stall the advance of a warm nose.

Today we had our hourly update guidance suite (RAP/HRRR) with the fake out colder trend, and since the background field for SPC mesoanalysis uses that, it also had 850 temps colder than reality. Unfortunately there's no public access to aircraft soundings that would give non NWS/FAA a better idea of trends.

It's tough to throw all the eggs into the basket of one model, but a good lesson to err on the side of a more aggressive push of the warm nose aloft. In hindsight, it all seems simpler and makes sense.

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Not who you asked but I’m in Momence. Grill and wooden porch stoop covered with a layer of ice. Dogs slipped running out to the backyard

Thanks, will pass your report on too. How are roads around there?

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Temp at my house is 30. Roads and sidewalks are skating rinks. Dynamite call by LOT leaving IKK out of the advisory. 

I relayed your report to the office. Did you happen to measure or estimate how much ice you've gotten?

 

Edit: Also, where about are you in Kankakee?

 

 

 

There are no absolutes, but normally I'd be very nervous completely discounting models that have the warm nose aloft farther north.  So probably not a bad idea to weight that in but to what extent is the big question.

Yup, what makes this such a tough call. 18z NAM didn't back down and has a big ice storm for much of the CWA. Comparing initialization and 21z to most recent mesoanalysis depiction of 850 0 line, it appears it'll be a bit farther north, though that doesn't mean it'll be wrong this evening. With earlier precip onset, we should at least start as snow.

Certainly have seen NAM be right on the warm nose before, though often in those cases it has support of RAP/HRRR, which instead this time have been generally ticking colder aloft. Maybe a blend is ultimately the way to go. Such a tough forecast and gonna come down to real time/nowcast.

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