Chicago Storm

A lot of the higher end guidance from last evening has come in warmer and a bit north this morning. One thing that hurts is that the SFC flow becomes more easterly, instead of being more northerly...which will help bring in more modified air. So there is high bust potential today...and at this point I'd say its more likely than not.

The RAP, and some other guidance, is ice storm warning worthy for the heart of the axis. .

Did I mention, lol? .

lol is lol. .

Indeed "warmer" and north. If that trend continues, likely can write this one off for much of the area.

Tue-Wed looks fairly good, and I could see an axis of ≥0.25" ice accrual across portions of the area. Wed-Fri is much more iffy...Could be snow, ice or rain.

The presence of CAPE on some guidance suggest TSFZRA being quite possible.

In addition to the above, ORD tied the record low max temp yesterday of 1 (1971).

1.7" at ORD and 1.9" here from yesterday and last nights clipper.

Other Chicago cold stats... Coldest Windchills: 1. -60 1/10/1982 2. -59 12/24/1953 3. -58 1/20/1985 4. -53 1/17/1982 5. -52 1/30/2019 5. -52 2/9/1933 7. -50 1/18/1994 8. -48 1/16/1977 9. -48 1/18/1930 10. -44 1/15/1994 Coldest Noon Temps: 1. -21 1/10/1982 2. -18 1/30/2019 3. -17 1/20/1985 4. -16 12/24/1985 5. -15 2/9/1933 5. -15 1/22/1936 5. -15 1/16/1982 8. -14 1/18/1994 8. -14 1/6/2014 10. -13 1/16/1977 Coldest Low Temps On Record: -27 1/20/1985 -26 1/10/1982 -25 12/24/1983 -25 1/16/1982 -23 1/30/2019 -23 1/19/1985 -23 1/17/1982 -23 12/24/1872 -22 1/21/1984 -21 1/31/2019 -21 1/18/1994 -21 12/23/1983 -21 12/22/1872 -21 2/9/1899 Coldest High Temps On Record: -11 1/18/1994 -11 12/24/1983 -10 1/30/2019 -10 1/25/1897 -8 2/9/1899 -7 1/16/1977 -6 12/23/1983 -6 1/29/1966 -6 2/9/1933 -6 1/4/1884

ORD is back up to 0, which ends the streak at 53 consecutive hours below freezing (If I counted correctly.) This makes it the 4th longest such streak on record. Most Consecutive Hours Below 0: 1. 98 Ending 12/26/1983 11AM 2. 66 Ending 2/4/1996 2PM 3. 60 Ending 1/11/1982 8AM 4. 52 Ending 1/31/2019 11PM 5. 48 Ending 1/21/1985 8AM 6. 45 Ending 1/19/1994 2PM 7. 44 Ending 1/6/1988 1PM 7. 44 Ending 1/16/1994 12PM 9. 43 Ending 1/17/1977 1PM 10. 42 Ending 1/17/1982 11PM

No doubt the winds were the issue. ORD had winds of 5-15mph all night, as did other metro OBS sites, which kept temps from dropping much. As you said, with no CAA associated with the winds, there was nothing to significantly drop the temp. Out west, the wind situation was much better...though there were still issues. You would see temps drop quickly with calm winds, only to have winds kick up to 5mph and temps rise...with that progression having occurred for a while at many OBS sites. There was just enough gradient on the northeast side of the ridge, preventing winds from totally going calm out west, and be much lower in to metro...which would have lead to much colder temps everywhere with perfect radiational cooling conditions. Probably would have seen sites like SQI/RPJ/FEP/ARR/DPA end up near -40.

DPA and ORD can't really be compared, even when removing the newer development around ORD. It is very developed around ORD overall, with dense business parks and dense suburban areas surrounding, and ORD is also much larger overall. With DPA it's a small airport...It has a "large" rural like area just to the north heading towards Wayne, and then also south with Fermilab, and also to the east in less populated northern portions of West Chicago. If anything, PWK is a much better comparison to ORD. PWK has dense suburban area and dense business parks to the north, east and south. Only real difference is the narrow forest-like area along the Des Plaines river just west. This is why PWK and ORD often have similar temps on the hotter days in the warm season and colder days in the cold season.

Have had light snow here for the past several hours.

Tied for 4th longest streak on record.

BCK and CMY in WI both stopped reporting temps last night after hitting -38. However, ARX has posted on their page that BCK hit -45 this morning.

Not that I fully believe it, but the ECMWF/GFS/NAM melt just about the entire snowpack around here by Monday evening.

The ECMWF continues to be north of all guidance for this last clipper today. Looking at radar it looks like that further north track is the way to go, with all other guidance being a bit too far south. Additionally, the ECMWF is the driest of all guidance, so that is something to watch as well. Looks like a 1-4" event area wide of the LOT CWA.

-30 RPJ.

-33 SFY now. That's a dark-horse no one mentioned.

-26 RFD. 2F from breaking the all time record low temp there.

-31 MLI a bit ago.

ORD -20 finally.

-31 SFY.

ORD is DOA for the record... Might not even exceed the low from last night (-23) at this rate. As for further west, there has been a real struggle to keep winds calm. Sites such as SQI/RPJ/ARR go calm and temps drop, then winds pick back up and the temp rises. The issue will likely continue for a while longer, before the ridge pushes in more towards morning. It's pretty clear that will be too late now though, so the state record is safe and it might be hard to find many sites that get below -30.