beavis1729

Agree, has been confounding to say the least.

Crazy. Will be fun to see the HRRR temps over the next couple of days.

And the 06z GFS shows -37C in the same area. Pretty amazing. It seems pretty certain that -35C H85 temps or colder will occur in parts of IL. If so, you'd have to think that LOT's forecast lows could be a bit conservative on Wed morning (generally -20 to -23)...but of course it makes sense to go conservative for now, then they can always bring temps down a bit over the next 12-24 hours if the models hold on to this. Unfortunately, it looks like the core of the coldest air moves out quickly. I now think that Wed morning will probably have both the coldest temps and the strongest winds in the Chicago area. Rural areas of N IL may be different. The radiational cooling on Thu morning may be better, but H85 temps will have warmed significantly by then...to around -25C. Will be interesting to see how this plays out.

Verbatim, this would break the all-time record low wind chill in IA and IL...although it's probably overdone a bit.

INL hit -46 this morning...wow.

Who knew it would eventually be so handy.

Record coldest wind chills by state on the new scale, as best I can tell: MN: -66 at Duluth, 1/10/1982 IA: -64 at Waterloo, 12/24/1983 WI: -59 at Eau Claire, 1/10/1982 IL: -60 at Chicago, 1/20/1985

No, that was a different location in 2014...I think it was RPJ (Rochelle, IL). The -30 was not deemed official.

Agree with your thoughts. I think the midnight high is more of a risk. It looks fairly likely that temps will stay below -11 on Wednesday afternoon. We’ll see what the 0z runs show tonight.

Yes, ORD has significant UHI, along with all of the Chicago suburbs. An example is this morning, when ORD only hit -6 but many rural areas of northern IL were in the -10s and -20s. ORD doesn’t radiate well at all. It’s not quite as bad as NYC...but that’s not saying much...

Wind chills off the charts...

Good info. Unfortunately, it looks like clouds and/or wind could prevent temps from dropping as low as they otherwise could, given the airmass in place. I hope I am wrong. Still a bit too far away to pin down the details. If any locations can clear out or have lighter winds, then things could definitely get out of hand. Either way, wind chills will be extreme, possibly down to -50 in northern IL. On 1/6/2014, I believe wind chills bottomed near -45. At this point, I would guess the following lowest temps by state: IL -30, IA -35, WI -35, MN -40.

If I'm reading the scale right, 12z GFS still showing H85 temps around -37C in northern IL...and it’s only 90 hours away.

-15 here, wow.

LOT AFD, long-term from Izzi Tuesday through Friday... Record breaking and potentially historic outbreak of cold still appears to be in the offing for the middle of next week. Greater than normal degree of forecast uncertainty in temperatures, due in large part to models showing all time records being broken and in some cases shattered. Generally made only very small tweaks to the temperatures from the model blend, due to the uncertainty. It is worth noting, that this model blend includes bias-corrected grids which still reflect a bias correction warmer from the unseasonable warm spell back in late Dec and early Jan and also contains a MOS component which tends to have some weighting toward climo, which obviously midweek temps will not look anything like climo. Typically, in record breaking temperature situations, a blend of the raw 2m model temperatures verifies best and those values are colder than our official forecast and approach or break all time records for ORD and MDW. The GFS, GFS-FV3, GEM, and ECMWF 12z operational runs all continue to drop 850mb temps to below -30C & in the case of the GFS to- 40C. To put this into perspective, using the SPC sounding climo page, the coldest 850mb temp even observed in IL (ILX, DVN, RAN, and PIA and dates as far back as 1949). Over the past couple days there have been some minor run to run variations in how low 850mb temps bottom out, but there has been a good deal of consistency of 850mb at least reach -30C. Even the 51 member ECMWF ensemble has 850mb temps reaching -30C over northern IL. Assuming we have a fresh snow pack from Monday`s system, the stage would be set for temperatures to really get out of hand and end up colder than currently forecast. Initially, moderate to strong northwest winds look to send wind chills bottoming out in the -35 to -50F range late Tues night into Wednesday. Some minor improvement in wind chills is expected Wed night into Thursday morning, due primarily to diminishing winds. Also worth noting that the 35 to 50 below wind chills are based on the somewhat conservative official forecast temps, but should the colder raw 2m model temps verify we could see wind chills approaching 60 below in the coldest areas and with most of the CWA reaching close to 50 below. There is still time for model guidance to back off on the intensity of Arctic air mass. Keeping that in mind, I felt quite comfortable with the more conservative temperature forecast. It is much easier and preferred to slowly trend a forecast closer to all time records this far out, rather than jumping out forecasting all time records only to later have to back off on those extremes if model guidance trends less severe with the cold. To put this cold into perspective some, during the past 20 years, Chicago has only had a sub zero high temp twice and only 22 times in the past 100 years. Our current forecast has air temps below zero between 40 and 60 hours across most of the CWA, which a much longer period of sub-zero wind chills. While still very cold, temps do look like they will begin to moderate Friday. - Izzi && .CLIMATE... Here are the record lows and record cold highs for next week`s cold... Tue Jan 29 Wed Jan 30 Thu Jan 31 Chicago Record Low -16 (1966) -15 (1966) -12 (1985) Record Low Max -6 (1966) 3 (1966) 1 (1971) Rockford Record Low -20 (1966) -19 (1966) -18 (1966) Record Low Max -9 (1966) -3 (1951) -3 (1996) Chicago All Time Record Low: -27 (Jan 20, 1985) All Time Record Low Max: -11 (Jan 18, 1994 & Dec 24, 1983) Rockford All Time Record Low: -27 (Jan 10, 1982) All Time Record Low Max: -14 (Jan 18, 1994 & Jan 6, 1912) - Izzi

Yeah, the 12z GFS generally held serve on the arctic outbreak, although verbatim it's a bit shorter in duration than what has been shown over the past few days. Strange outcome...because you'd think that with the Monday storm being more north, it wouldn't be able to pull the cold air down as far south as before...yet it still did. Heck, I'll take a -12/-22 day at ORD, to set the all-time low max. You'd think Thursday 1/31 has the best chance of doing this, as it will likely not have a midnght high going into the day...but of course it could warm up later in the evening of 1/31 if the arctic air mass begins moving out. It makes 1/18/94 and 12/24/83 even more remarkable to think about, both with highs of -11. At this point, it doesn't look like the all-time record low will be set. Of course it was always a long shot due to UHI and needing a million things to go right...but it actually looked possible over the past few days. Still nice to see the sub-480 thicknesses on the GFS, though.

Yep, fair point...but hard to deny the trends across the board.

Right...and it means that the furthest south of all models is now tracking the low over the IL/WI state line. Not good trends for the Chicago area. In addition to missing out on the heaviest QPF axis, the ratios will be much worse, since temps won't be as cold. If trends continue, Chicago will be lucky to see 2" out of this, with temps warming into the 30s after the snowfall. What used to be a clipper parade has now turned into essentially one meaningful clipper...and now this one clipper may not even produce...and now the arctic outbreak next week is being muted. Not a good day for winter weather lovers here. Better in MN/WI. While these shifts are not too unusual 3-6 days out (and perhaps we're guilty of getting too excited too far out), it's still frustrating.

Trends are definitely concerning. I guess the good news is that this is a rather unusual system/track, and the models could be having difficulty due to the unique situation and/or poor sampling in the source area. Of course this may just be weenie thinking...but we'll see.

Ugh, not good. What about 0z Euro ensembles and the 6z Euro op?

Yeah, this cold front seems to be packing more of a punch than originally thought. DVN just issued a Wind Chill Warning.