Hoosier

Exciting stuff from DVN Discussion for Wed and Wed night...A greatly deepening cyclone tracking from the west central plains at noon, to the west basin of Lake Superior by Thu morning, becoming negatively tilted and deepening to under 975 MB along the way, to drive high winds acrs the region Wed afternoon and night. Plume of 50-75+ KT H925 to H85 MB southwesterly wind layer still on track to surge acrs the CWA from late afternoon and especially the evening thru 07z or so, with ongoing challenge of how much will translate to the sfc with ongoing warm layers aloft and stratus clouds. If these strong LLVL jet winds verify, even marginal mixing should produce high end advisory to around wind warning criteria 57-63 MPH. A more enhanced mix by a band of thunderstorms or even a fine line of showers may tap into the higher wind stream aloft and produce isolated swaths of 70 to near 80 MPH winds. If this scenario looks to unfold, convective severe T-storm warnings may still need to be issued embedded in the High Wind Warning. LLVL CAPE values of only 200 to 600 at best may limit stronger updrafts or the intense LLVL shear(0-1km 40-50 KTs) may shred them apart limiting discrete storm development. While the more discrete low topped supercells(if they form) with tornado potential and intense down-drafts will hopefully arch northeastward at tremendous speeds over 60 MPH just off to the northwest of the CWA Wed evening, it appears a fine line of showers with/or even isolated embedded thunder will still sweep eastward acrs the western CWA after 00z Thu, SREF timing crossing the MS RVR around 03z, and out of the CWA off to the east by 06z or 07z. These may mix down the warning criteria winds or enhanced higher gusts. Then there are signs of a sfc wind veer more southwest and deeper adiabatic mix with arrival of a dry slot from west to east after 04z, which may produce more widespread gusts of 55 to 65 MPH. Both of these processes are taken into account for with the warning upgrade from the watch and timing tweaks. There will be higher end Advisory winds taking place either side of the warning criteria wind surges, lasting well into the overnight. The western sector may need to be cancelled early, but for simplicity sake all wind warnings and advisories to end at 12z Thu morning. Foresee trouble with high profile vehicles Wed evening, tree damage on powerlines for outages, and will have to watch for downed power line sparking wildfires in cured grassy areas, especially when the dry slot arrives later Wed night.

NWS PAH has the path plotted on their event page.

A little odd that LOT left the Indiana counties out of the wind advisory. I have to assume it will be coming eventually because everything I'm looking at supports it.

Although there is no instability farther east, would not be surprised to see some isolated damaging gusts with that band of shallow showers. Some of the background/synoptic gusts will be flirting with or exceeding 58 mph anyway, and it won't take much downward momentum with those showers to make that happen.

The High Wind Watch from DMX mentions southwest gusts up to 70 mph. Impressive to see that given there is no marine influence to help enhance winds.

Using filtered storm reports, this was one of the most active days of 2021

Things are pointing to at least EF-4, whether it's what we can tell based on damage photos (yes, there are some limitations at just looking at pictures) but also various radar data. I also feel like we can use the death toll as a proxy. Generally speaking, you are not going to get the kind of death count we are looking at from anything under EF-4, unless maybe it's a freak circumstance such as an outdoor event being hit or nothing but trailer parks, which we don't have in this case.

On 12/15, this year will become the 19th time that Chicago's seasonal snowfall total is sitting under 1". Here are those years and what the final snowfall total ended up being, along with a B or A to signify whether the final total was below or above average. 14 out of 18 had less snow than average. And of the 4 that were snowier than average, 2 were barely snowier than average. 2020 - 48.8" A 2012 - 30.1" B 2011 - 19.8" B 2003 - 24.8" B 2001 - 31.1" B 1999 - 30.3" B 1998 - 50.9" A 1993 - 41.8" A 1990 - 23.5" B 1984 - 39.1" A 1965 - 24.9" B 1948 - 14.3" B 1943 - 24.0" B 1939 - 31.0" B 1938 - 33.9" B 1923 - 27.6" B 1918 - 28.8" B 1912 - 19.0" B

Very puzzling to not even have a marginal risk on the day 3 outlook, and could definitely argue for a slight. I wonder if part of this is because of the geographic area we are talking about. A December severe threat is pretty rare there. If the exact same parameters were forecast in the Ohio/Tennessee Valley, would there have been a risk area introduced?

I feel like beavis is going to blow like Mt. Vesuvius pretty soon. A diehard winter lover can only take so much of this.

Yeah it looks pretty eventful out that way. Some severe threat too.

The 00z GFS doesn't have any snow in Chicago until the 20th. That would tie the record for latest measurable.

I wouldn't be as definitive as some are, but I think it's greater than 50% chance of it being EF-5. I am probably more interested in whether it broke the Tri-State tornado record for path length. That is almost an unthinkable record in my book. It's like DiMaggio's hitting streak being broken.

Here is the NWS Paducah page for this event. Sounds like they are bringing in the best people to assist with the damage survey. Watch this space: https://www.weather.gov/pah/December-10th-11th-2021-Tornado

There is about 50 kts down as low as 950 mb on Wednesday evening with not much stability in the low levels. Winds should be rocking pretty good.

Yeah. Came close to happening in LOT.

*former. I'm still the boss around here though. j/k

I see. 1982 had 9 days of 60+ though so that should be on that list. Don't mean to be nitpicky.

Although certainly trivial in comparison to what happened farther south, the tornado that was confirmed in the LOT cwa was noteworthy because of the month. On a more local level, it is the latest in a year that a tornado has occurred in Lake county IN (previous latest was November 13) and the first DJF tornado on record for Lake county IN. Here is more info from the event page that LOT put together: Tornadoes during the month of December in the NWS Chicago County Warning Area are exceptionally rare. Roughly 99.6% of all tornadoes in our area occur outside the month of December, and rough math suggests December tornadoes occur about once every 20 years. Additionally, the Cedar Lake to Crown Point tornado was... The first December tornado since 12/4/1973, and only the 4th tornado to occur during the month of December The latest tornado on record in a calendar year. The other three happened on 12/3/1955, 12/8/1966, and 12/4/1973. Severe weather is also exceptionally rare during the month of December. Since 1950, there have only been 9 days during which severe weather was reported in the month of December (roughly 0.7% of all 1220 severe weather days). December 10, 2021 is also the 6th latest day on which severe weather was reported in our forecast area behind 12/23/2007, 12/23/2015, 12/24/1965, 12/27/2008, and 12/28/1982.

You did that funny. Like, every year that is on the 65+ list should also be on the 60+ list, but it's not.

lol

Got it 3 times in like 15 minutes. Twice on a big group message like that and one individual.

Record high for Chicago on the 16th is only 60. That will be broken easily and right after midnight.

It certainly isn't something you want to rely on.

Depending on what kind of info comes out about the super long tracked tornado in the upcoming days, we may want to consider having a separate thread for it for easy reference. Could include images, historical context, cleanup progress, rebuilding progress, etc. We may be dealing with something that is pretty historic overall (it certainly is for the state of Kentucky).