Pre-Christmas (Dec 21-23rd) Winter Storm

[SolidIcewx]

4 minutes ago, LansingWeather said:

GRR really late on their AFD, very interested in their thoughts. Must be tough for them too

I’m waiting to see that. DTX had some strong wording but I’m real curious to see the late night one

[LansingWeather]

2 minutes ago, SolidIcewx said:

I’m waiting to see that. DTX had some strong wording but I’m real curious to see the late night one

Haha, well it was kind of a dud. MAybe they just forgot to send it out.

[Geoboy645]

MKX just pulled the trigger on WS watches as well. The wording is some of the strongest wording that I have seen in a watch since probably 12/20/12.

[Kaner88]

Updated Winter Storm Outlook from the WPC, probabilities of warning-criteria snows.

[kevlon62]

Watch start times are interesting (some different takes in spite of coordination):

DVN 12/22 12 a.m.
LOT 12/22 6 p.m.
MKX 12/22 6 a.m.

[ILSNOW]

Chicago NWS Izzi

Issued at 305 PM CST Mon Dec 19 2022

Blizzard expected Thursday night into Friday...

Wednesday through Monday...

* Travel impacts expected to begin Thursday, mainly western CWA
* Rapidly deteriorating conditions Thursday evening as a ferocious
  arctic front rips across the area resulting in temperatures
  rapidly falling through the teens into the single digits
* Blizzard conditions will develop Thursday night, especially
  late, and continue through the day Friday
* Bitterly cold wind chills expected during the height of the
  storm, posing a significant threat to life for anyone who
  becomes stranded in the storm

After extensive collaboration with WPC and neighboring offices,
have opted to hoist a long lead time winter storm watch for
blizzard conditions Thursday night through Friday night.

Models and their respective ensembles have remained locked into
solutions depicting rapid cyclogenesis Thursday into Friday as
the cyclone tracks from southern IL to lower Michigan. Various
models depict explosive deepening of this low with central
pressure dropping 25-35mb in 24 hours. This type of explosive
intensification is quite rare in this region and is expected to
result in extremely powerful and potentially damaging winds late
Thursday night and especially Friday.

The deformation band with this cyclone is expected to be quite
intense owing to the extremely strong omega and weak static
stability/slantwise instability. Very steep mid-upper level lapse
rates do raise concerns about the potential for thundersnow even
later Thursday night into Friday morning. Expecting snow to liquid
ratios to average around 15:1, possibly 20:1 western CWA where DGZ
will be deeper. The one factor that *should* keep the snow:liquid
ratios somewhat in check is the very strong winds which would tend
to rip about the larger/fluffier dendrites.

Have seen some general downward trend in QPF values over the past
24 hours in guidance, but QPF generally still supports widespread
6" totals with even 1-2 foot totals possible associated with any
more intense banding/possible thundersnow. We are still very far
out and not planning to advertise snowfall amounts in public
products at this time, as much could change between now and then.
It is also worth stressing that the amount of snow that falls is
a secondary or tertiary concern among the hazards. The expected
temperatures will leave this snow extremely susceptible to blowing
around and even if only a couple inches of snow falls, a blizzard
would still be likely given the nature of the snow and magnitude
of the strong winds. This is one of the reasons for the early
winter storm watch.

Impactful winter weather, in the form of accumulating snow is
expected to begin in the western portions of the CWA during the
day Thursday. However, opted not to include this portion of the
storm in the winter storm watch as the threat level of this snow
will dwarf what will be expected during the blizzard portion of
the storm.

If current guidance is close to verifying, then conditions Friday
could rival the 2011 Groundhog Day blizzard, particularly in open
areas. Travel would become extremely dangerous and life
threatening, particularly in light of the bitterly cold
temperatures during the height of the storm.

Falling snow is expected to end Friday afternoon or evening, but
strong winds and blizzard conditions are expected to continue
Friday evening and only slowly abate through the night. Some
blowing snow will likely continue into Saturday with bitterly cold
temperatures through the holiday weekend.

- Izzi

 

[Chicago Storm]

Izzi went all out in his AFD.

I definitely would not have at this point.

[mimillman]

2 minutes ago, Chicago Storm said:

Izzi went all out in his AFD.

I definitely would not have at this point.

Man, understatement 

[Baum]

3 minutes ago, Chicago Storm said:

Well, he went all out. I personally wouldn't have gone there...

yup. Went full IZZI on a day 4 forecast. Now we know who to blame

[ChiTownSnow]

2 minutes ago, mimillman said:

Man, understatement 

 

4 minutes ago, Chicago Storm said:

Izzi went all out in his AFD.

I definitely would not have at this point.

RC said they were going to hit it hard.  I probably would have waited 45 more minutes for the GFS though.

If you take the amount of snow out of out of the equation, it makes more sense

 

[SchaumburgStormer]

5 minutes ago, ILSNOW said:

Expecting snow to liquid ratios to average around 15:1, possibly 20:1 western CWA where DGZ will be deeper. The one factor that *should* keep the snow:liquid ratios somewhat in check is the very strong winds which would tend to rip about the larger/fluffier dendrites.

Banking on higher ratios? 

[michaelmantis]

Without the wind potential my assumption is the NWS offices would hit this less hard and would have waited. 

The whole general thought (my words not Issi's) that "3 inches ve 9 inches doesn't matter with 55 mile per hour winds" really seems why they are sending the messages they are.

So now my expectations should be anywhere from 2-12 inches of snow with wind for 36 hours?!?! ;-)

[TheRegionRat]

I'm interested in the ratios now.  Sounds like we won't be delivering beer on Friday.  

[Malacka11]

Can I just take the ICON to the bank and be done now

[ChiTownSnow]

2 minutes ago, Malacka11 said:

Can I just take the ICON to the bank and be done now

Yup..

[RCNYILWX]

As much as the high end Kuchera ratios are overdone (24:1+ in western IL/eastern IA on last night's insane 00z GFS), banking on 10:1 ratios is also underdone. With the exception of 1967, Chicago's #2 through #5 snowstorms all relied on above to well above climo (~12:1) ratios.

There are red flags in this setup per today's guidance related to the timing of the low rapidly deepening and wrapping up. That said, by far the most reliable NWP we have, the ECMWF, has 1-1.25"+ QPF for the southeast 2/3 of the Chicago metro (and the ECMWF is not known to have a high bias with QPF).

If that verifies, then the ratios will easily verify above 10:1. An average of 15:1 would be attainable, and perhaps maxing out at 20:1 in mesoscale banding. The high winds only do so much to lower ratios. Well aligned strong omega with the DGZ, a deep DGZ, and steep lapse rates from the current ECMWF idea would compensate to result in near to above 15:1 ratios.

Unless the system ends up well weaker and east of the current ECMWF/EPS consensus (which is possible but a lower probability outcome at time), this will be a very high impact storm.

[janetjanet998]

ILX pulled the trigger 

 

INCLUDING THE CITIES OF GALESBURG, TOULON, PEORIA, LACON, EUREKA,   CANTON, PEKIN, BLOOMINGTON, NORMAL, RUSHVILLE, HAVANA, LINCOLN,   CLINTON, BEARDSTOWN, PETERSBURG, WINCHESTER, JACKSONVILLE,   SPRINGFIELD, TAYLORVILLE, AND DECATUR   332 PM CST MON DEC 19 2022     ...WINTER STORM WATCH IN EFFECT FROM THURSDAY MORNING THROUGH   LATE FRIDAY NIGHT...     * WHAT...BLIZZARD CONDITIONS POSSIBLE. SNOW ACCUMULATIONS OVER 3   INCHES POSSIBLE. WINDS COULD GUST AS HIGH AS 50 MPH.  

[Chicago WX]

18z RGEM goes through Indiana. Solid hit for many. Nothing extreme, but solid.

[Hoar_Frost]

Even a couple of inches of snow with such high winds during a high-impact holiday travel period in a city that is home to one of the busiest airports in the country will cause many problems.  If one of the snowier solutions plays out, that'll just exacerbate those problems.  I can understand why LOT is hitting it hard early.  

[SolidIcewx]

Let’s see what gfs brings

[Nelson]

FXUS63 KMKX 192135
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
335 PM CST Mon Dec 19 2022

.LONG TERM...
(Issued 335 PM CST Mon Dec 19 2022)

Wednesday through Monday:

Confidence continues to increase in a potent winter storm later
this week that could bring blizzard conditions to southern
Wisconsin. There is high probability for significant winter
impacts in the region, with the focus now on narrowing down the
timing and location for the most impactful weather. This storm
will have ample moisture and forcing for significant snowfall,
with confidence increasing for 6+ inches. Latest model ensemble
snow probabilities show the higher end numbers right across the
forecast area. This is not surprising, as latest guidance shifted
a bit back towards the southeast with the low track, knocking out
any mixed precip or rain potential in the southeast that was
showing up earlier. Ensemble probabilities are on the high end
for wind gusts of 40-50 mph during the height of the storm later
Thursday into Friday night. Some guidance is showing the potential
for gusts to 60 mph, though not ready to bite on these higher
numbers yet.

Given the potential for this storm to have high end impacts,
decided to pull the trigger on a Winter Storm Watch Thursday
through Friday night. Warm advection aloft ahead of the storm will
likely result in the snow starting by Wednesday evening, but the
worst of the weather is expected to hold off until Thursday. There
is still a lot of time for the track/timing of this storm to
change. When/where the low deepens and the track of the low will
likely continue to waffle a bit from model run to model run, so
keep up with the latest forecast as the finer details will
continue to be worked out.

Another concern with the late week system will be the cold wind
chills on the back side of the storm, with 15 to 25 below possible
later Friday into Friday night.

[SchaumburgStormer]

GFS looks west. Low right in central IL at 72

[mimillman]

1 minute ago, SchaumburgStormer said:

GFS looks west. Low right in central IL at 72

No, It’s virtually the same 

[A-L-E-K]

points for a carbon copy run

[ChiTownSnow]

Just now, mimillman said:

No, It’s virtually the same 

And still moving due east

[SchaumburgStormer]

1 minute ago, mimillman said:

No, It’s virtually the same 

You're correct, I was looking at an older run. 

[SolidIcewx]

I don’t even want to leave to go home until I see the model done. Good ole dry slot

[ChiTownSnow]

Good hit

[weathafella]

Qpf seems more paltry than I would expect.  Trying to figure it out…

[Chicago916]

Everytime I see the GFS or other models backing the low west over Lake Michigan it reminds me of mesolows, except we might be dealing with a sub 980 mb low. Oof.