mjwise

Just hit 0 here. We were at zero or below for 72 hours. If we don't nudge up to 1 here, we'll end up with about an 84 hour run at 0 or less. ETA: Hit 1 degree after exactly 72 hours of zero to subzero temps.

I have heard reports of stranded and abandoned vehicles in rural areas and that blizzard conditions prevailed overnight. ETA: Bottomed out at -14 at the airport, still -10 as of the 2pm observation. This will be my personal coldest daytime temp since January 1994 (-12) assuming we don't gain more than 5 degrees or so. For fun, I took an snow core yesterday from a relatively undisturbed part of my front yard and I measured 2.2" of liquid in ~12" of base.

Here's what it looks like at street level here before it gets dark. I don't have measurements, but our total compacted depth (all gained in the past week) is ~12". The bottom 2 inches was thick crust I needed to punch through. It's been all snow except for about 30 minutes of mixed SN/IP at about 8:30am. Sorry I didn't get a morning shot - buildings were plastered with snow from the weenie band but then temps went to 33 and most of it melted off the sides of buildings.

A not insignificant number of SREF members had rain getting all the way up to Madison for at least some of Friday in earlier runs today. QPF hasn't changed much, it was just running a blowtorch earlier.

Middle 3rd of the country is pasted with wind advisories or high wind watches. I haven't seen so many issued for some time. Air travel is going to be rough at best the next few days even outside of places that get snow.

Only about a 350 mile movement on the slp location versus the 12z run, where it was making for Wisconsin via Dubuque when the run ended...

The Euro is on board with that. The run ends below zero again.

Even within 24 hours it and the SREF are dodgy. As late as the 15Z run on Monday, the majority of the SREF members still said it would be a rain event on Tuesday afternoon in Dekalb. I put no stock in it 48 hours+ out.

The 12z Euro has us subzero for 72 hours straight here - Sun morn to Wed morn. The cold is not quite as sharp on the GFS but longer lasting with single digits starting late Sat. night and that or colder extending the sensible length of the run from there. Even the EPS shows us falling into negatives during the day on Sunday.

https://www.weather.gov/lot/chicago_precipitation_records

LOT agrees and just added Lee-Ogle-DeKalb-Kane-Lake-LaSalle to the WSW.

Up to a likely final total of 5.61" for the month in DeKalb and 9.24" for MJJ. 2.32" for the 24 hour stretch between early Friday morning and late Friday evening. May and June were dry but not as dry as points north and west have been. 3 90's for the year to date (6/24, 7/27, 7/28).

Here's a photo of the sun setting on the western side of the Kane county supercell before the main show last night.

This is the most lightning I've seen in years. Tons of cg strikes. Eta: hail!

SPC mesoanalysis is really off the charts in northern illinois area. 6.5kJ/kg SBCAPE, 5kJ/kg MLCAPE, LI -12, with swath of 2.1 inch PWAT aligned parallel with the convection. The only thing that could be a little stronger is shear. It's rare when you get a high end wind and potential high end flooding event out of the same complex.

It happened in the middle of July 2013 over the GL/OV. (Link - all the images are unfortunately dead) 850 temps were relatively pedestrian though so it was just an "average" heatwave when it happened.

Dekalb ASOS just clocked an 83 dew at 7:35pm. I went out for a casual walk and arrived home soaked (and not from rain!).

A gross 87/80/102 at the airport here. I think this is the first 80 degree dewpoint for DeKalb this year.

Looking hazy and intermittently smoky on the surface on the smoke HRRR for Northern Ill starting Sat morning all the way through Sun.

The SPC is a believer at least... https://www.spc.noaa.gov/products/md/md1506.html Mesoscale Discussion 1506 NWS Storm Prediction Center Norman OK 0305 PM CDT Wed Jul 12 2023 Areas affected...Northern Illinois and far southern Wisconsin Concerning...Severe potential...Tornado Watch likely Valid 122005Z - 122130Z Probability of Watch Issuance...95 percent SUMMARY...A tornado watch is likely across northern Illinois and possibly southern Wisconsin by 21Z. DISCUSSION...The air mass is recovering rapidly across northern Illinois in the wake of the morning MCS. An EML, advecting eastward amid 40-50 knots of mid-level flow has cleared out cloud cover and allowed for surface heating across eastern Iowa and northwest Illinois. Temperatures in this area have warmed into the low 80s with dewpoints remaining steady, or even climbing slightly, into the low 70s. Temperatures remain in the 60s across northern Illinois, but expect this warm front to lift quickly northeast through the evening as a result of surface heating north of this front and strengthening low-level flow in response to the deepening surface cyclone across eastern Iowa. Additional heating, combined with cooling temperatures aloft ahead of the approaching shortwave trough should result in 1500 to 2000 J/kg MLCAPE by this evening across northern and northeast Illinois. This instability will be co-located with a strong, veering wind profile (sampled by the 20Z LOT VWP). Expect a similar wind profile (featuring 200+ m2/s2 0-500m SRH) to remain along the outflow boundary/composite front through the evening. Supercells are expected to form along this boundary as ascent increases ahead of a digging mid-level shortwave trough and within the left-exit region of the upper-level jet. Southerly winds ahead of the surface low will provide sufficient low-level streamwise vorticity for a tornado threat. However, any storms which remain along or slightly north/east of the boundary, where more backed surface winds will be present, should ingest much higher SRH and will pose a greater tornado threat and even the potential for a strong tornado. In addition, large hail and damaging wind gusts will be possible. A tornado watch is likely by 4pm to cover this threat. ..Bentley.. 07/12/2023

That's a crazy stat to me. We have had 1 90 so far this summer, a 90 on 6/25. Granted, we have gotten 89'ed 5 (!) times, but still, even despite being ~300 feet higher, less urbanized and at a slightly higher latitude, I wouldn't expect that contrast between two sites separated by a <2 hour drive.

The GFS is also mixing to about 650-700mb to get that absurd surface output. It advertised that last year too, at time frames a lot sooner than 300hrs+, and it didn't remotely pan out then either. Whenever GFS 2m temps are spitting out 110+ in the midwest or GL, it's because it's got some broken mixing scheme going on.

DeKalb actually ended the month below normal per NOWData - at -0.2, month high was 90 on 6/25. We got 89'ed a hilarious 5 times, including four days in a row (6/1-6/4). Precip was 50% of normal.

Reminiscent of the August 11, 2014 Detroit flood event. Near tropical airmass + mild/moderate baroclinicity results in weak, diffuse, ambling surface low that can produce impressive rainfall. They tend to be poorly modeled. The ECMWF saw it for the most part but the GFS and NAM were clueless. 1.25" in Dekalb today. Most rainfall in a day in the last 3 months.

I spent the middle of July 1995 at a summer camp in an unair-conditioned dorm in southwest Ohio. It was a miserable week. We would take cold showers (well, as cold as they could get, which wasn't very) every night to get any kind of relief.