Hoosier

Noticed the 12z Euro had more MUCAPE than the GFS.  Not a huge value by any means, but would probably suggest a bit more of a threat than the GFS.

The timing of this would be atypical, but not unheard of.  Severe threat could begin by daybreak in IL.

So you want snow, beavis?  Just head to the Los Angeles metro area.  

Seriously though, I wonder how often something like this happens out there.  Especially the blizzard warning.  Not familiar with that area at all.

URGENT - WINTER WEATHER MESSAGE
National Weather Service Los Angeles/Oxnard CA
340 AM PST Thu Feb 23 2023

CAZ053-054-232100-
/O.CON.KLOX.WS.W.0002.000000T0000Z-230224T1200Z/
/O.CON.KLOX.BZ.W.0001.230224T1200Z-230226T0000Z/
Ventura County Mountains-Los Angeles County Mountains-
Including the cities of Lockwood Valley, Mount Pinos, Acton,
and Mount Wilson
340 AM PST Thu Feb 23 2023

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 4 AM PST FRIDAY...
...BLIZZARD WARNING REMAINS IN EFFECT FROM 4 AM FRIDAY TO 4 PM
PST SATURDAY...

* WHAT...Winter Storm Warning through late Thursday with low
  elevation snow, strong winds and very cold wind chills. For the
  Blizzard Warning, heavy snow, winds gusting up to 80 mph, and
  near zero visibility. Total snow accumulations from 6 to 12
  inches likely between 2000-4000 feet up to 2 and 5 feet of above
  4000 feet. Isolated amounts to between 7 and 8 feet at higher
  elevations. Major mountains passes will be affected by
  significant snowfall.

* WHERE...Ventura County Mountains and Los Angeles County
  Mountains.

* WHEN...For the Winter Storm Warning, until 4 AM PST Friday.
  For the Blizzard Warning, from 4 AM Friday to 4 PM PST
  Saturday.

* IMPACTS...Travel could be very difficult to impossible. Very
  strong winds could cause extensive tree damage.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If you must travel, keep an extra flashlight, food, and water in
your vehicle in case of an emergency.

Travel should be restricted to emergencies only. If you must
travel, have a winter survival kit with you. If you get stranded,
stay with your vehicle.

The latest road conditions from CalTrans are available by calling
1 800 4 2 7 7 6 2 3.

Assuming the strength of the low for early next week holds up, should get a decent wind event in the sub.  And it's coming in strong, not a late bomber pulling into Canada, which will get the typically less prone southern sub into the game for high winds.

Lapse rates suck come Monday, but despite the poor instability, I expect at least an isolated severe threat to materialize in the Ohio Valley and potentially up to the southern Lakes.  Very strong wind fields with good signals for a line or broken line of storms moving rapidly across the region.  Damaging winds would certainly be the main threat, but I wouldn't rule out an isolated tornado.  Directional shear isn't the greatest but there's some modest turning in the profiles, while speed shear is very good.  This may get going relatively early in the day on Monday as well... maybe even potentially carrying over from the Plains.

5 hours ago, Cary67 said:

Relatively speaking what's the odds of having a significant ice storm versus a heavy snowfall? 

Kind of depends on how you define heavy snowfall and significant ice, but assuming you have reasonable definitions for each, the snowfall is going to be more likely in general (maybe a different story as you head into the southern US, but not sure).  So many failure modes for getting significant ice compared to a heavy snow.  Although you wouldn't know it this year for a good portion of the sub lol

2 minutes ago, cyclone77 said:

lol 958mb at hour 216.

And still primarily a rainer 

Would be wild on the west side of the low as it peaks in MO/IL.  Extreme 850 mb winds.

Obviously have to take this particular solution with a 1000 grains of salt, but I think it is an indication that the pattern could produce something pretty significant for somebody.

Sub 960 mb.  Holy ****

00z Euro going ape.  965 mb low near STL.  

Not sure I've seen that modeled before.

Alluded to this in the storm thread, but figured I'd bring it over here for more detail.

While the storm of 2/22/2023 will largely be forgettable for Chicago, this calendar day managed to pull off a combination that is quite uncommon. 

1) have a high in the 30s

2) have 1"+ of precip

3) have less than 1" of snow

The above combination has now happened only 14 times since 1884-85 (the first year that snow records are available), so it's about a 1 in 10 year occurrence over the long haul. 

For some comparison to a different season, Chicago has officially hit 100 or higher a total of 65 times.  That is over 4 times as much as what occurred today.  Of course it's not exactly apples to apples -- you either hit 100 or you don't, and that's that -- while this requires all 3 conditions of highs in the 30s, 1" precip, less than 1" of snow to be met.  But you get the idea.

Here is the list of all calendar days with highs in the 30s, 1"+ precip, and less than 1" of snow in Chicago.  All of these would've largely been a cold rain or some combination of rain and freezing rain.  Snow amounts for each date are listed last.  Everything else is self explanatory.

11/10/1898:  36/33, 1.20", 0

4/16/1921:  36/31, 1.97", 0.1"

11/29/1930:  38/18, 1.19", 0.1"

3/12/1939:  35/31, 1.10", T

2/6/1942:  35/35, 1.98", T

4/19/1947:  39/36, 1.40", 0

1/18/1949:  35/17, 1.11", 0.2"

3/26/1959:  39/35, 1.40", 0

12/11/1983:  38/33, 1.03", 0

12/27/1988:  39/15, 1.03",  0.1"

4/4/2003:  39/32, 1.22", 0

2/16/2006:  37/22, 1.09", T

3/24/2016:  39/30, 1.09", T

2/22/2023:  36/33, 1.20", 0

Almost everywhere in northern IL is at least a degree or two above freezing now.  

Not gonna get a lot of ice melting off while 33-34 though, especially now with it being nighttime.  

8 minutes ago, sbnwx85 said:

Fun to look at though. 

Indeed.  Even half of that accreting in the main band would probably be like a 1 in 100 year event for a given location.

5 minutes ago, Cary67 said:

Definitely hoping that bump in temps materializes because my area is a mess.

Gonna be a race as far as how much ice can melt before the winds pick up.  One thing I'd say is that it seemed like the wind potential had trended downward a bit when I last checked into it.  50+ mph gusts would've been really bad.

1 minute ago, Chicago Storm said:

Closing in on 100k without power across N IL.

I keep imagining if the icing was farther south to encompass more of the metro.  Yikes.

22 minutes ago, OHweather said:

Ice accretion is fun...definitely an interesting one today with places getting over a quarter inch of accretion with air temps at or slightly above freezing for some or all of the freezing rain.

Basically, wet bulb temp, wind speed, and precip rate determine how efficiently freezing rain will accrete. Higher precip rates don't accrete as efficiently due to more of it running off before freezing...though on the flip side very light freezing rain or drizzle can accrete at a better than 1:1 ratio to the liquid amount. Otherwise, it's a battle against latent heat release. If air temps are slightly above freezing you can accrete (as many saw today) if the wet bulb temperature is below freezing due to evaporational cooling. However, when the rain freezes it gives off latent heat which warms the surrounding air, so wind is also very important to the equation. Stronger wind whisks away the latest heat given off and can continue advecting in drier air. Strong winds can also increase accretion efficiently due to giving each given rain drop a greater chance at encountering an elevated object (since the drops move more horizontally as they fall when wind is stronger). 

Typically, it's a battle against the latent heat release and often that battle doesn't last very long if the winds are light and the dew points aren't that low, but in a set-up like this with an actual cold high to the north advecting in a drier airmass it all balanced out fairly well. I'm guessing the efficiency of the ice with temps at or slightly above freezing was not well forecast...we also under-did accretion here in NE Ohio to the point where we had a few power outages east of Cleveland, and much like farther west temperatures had to get firmly above freezing before accretion stopped. 

 

This is an excellent summary.

I think this event will also be remembered for the relative lack of impact on most roads throughout the bulk of the event (maybe things will get a little more questionable now with the loss of daytime).  It's a good reminder that it really doesn't matter how mild the winter has been overall or in the lead-up to the storm when it comes to getting icing on elevated/colder objects, but it is a factor for road impacts.

Obviously  but 18z GFS had an insane ice storm toward the end of the run.  Some areas get freezing rain for like 36 hours.  Catastrophic may not be a strong enough word.

1 hour ago, Chicago WX said:

True. But seems the models usually underplay temps when you're on (close to) the line. LAF went the other way. Bad beat for them.

Sucky day for anybody working outside in LAF.  You already knew it was going to suck farther north.  

4 minutes ago, Chicago WX said:

Models pulled the rug on MSP. Hate to see it. Still a solid storm, but what might have been.

Also, models were awful with temps looking at LAF. They're at 39˚ currently. Most models had them in the 60's right now. 12z Euro had them in the low 60's all afternoon. Woof. 

EDIT: zone forecast for today. 

It's torching just south of there in Crawfordsville.  Tricky when you're near a large gradient.

10 minutes ago, cyclone77 said:

Chunks of ice are hitting the east side of the house as the wind is now starting to knock off some of the ice from high up in the front tree.  Glad temps weren't a degree or two colder or we'd have been hit pretty good.  Hoosier's point about the dews being a bit lower than freezing is interesting, never thought about that.  

Up to 0.90"

Not totally sure, but it seems like it makes sense.    All else being equal, something like 32/29 seems like it would be better for accretion than 32/32.

28 minutes ago, cyclone77 said:

0.87" rain so far, which is more than I figured we'd get.  Also some glazing on the trees about 30ft+ up, but none below that.  

That is a neat observation.

One of the ugliest wx days I can remember in a while.  Stuck at 34-35 degrees all afternoon with mod-hvy rain.  I'd take heavy snow in April over this any day.  Today is just nasty with no redeeming value since it's too warm for ice.

3 minutes ago, Chicago Storm said:

Based on pictures I've seen, even with borderline temps and heavy rates, ice accrual has been fairly efficient across portions of Northern Illinois.

Gotta think that dews staying 2-3 degrees below freezing (at least per ASOS sites) and the brisk winds have been helping the cause.

Whatever areas end up on the northern side of the freezing rain zone with little/no sleet will have the worst ice and tree/powerline impacts.  Those areas may remain a tick colder at the surface than the southern part of the freezing rain zone, plus the warm layer aloft won't be quite as warm.

7 minutes ago, madwx said:

the pinging has become constant here.  if this carries on for the next 6 hours or so I'll get a feel for what LAF experienced during GHD1

The number to beat is 4" of sleet.  

4 minutes ago, madwx said:

That euro fantasy storm will trend drier and weaker.  

By default.  It basically has no other choice but to trend weaker in this case.

29 minutes ago, bdgwx said:

A 974mb low near Little Rock, AR?

What is the deepest a mid-latitude cyclone has gotten in Arkansas?

About 976 mb, back in February 1960.  The record low pressure at Little Rock is around 980 mb.  So basically, the Euro is pushing the boundaries.