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January 24 - 31 Cold Blast

MNstorms

By MNstorms,
in Lakes/Ohio Valley

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cyclone77

cyclone77

Posted
Posted

A lot of us grew up with the old wind chill chart, when it was sort of common to achieve -40 or lower wind chills during a harsh arctic outbreak.  I can remember in the '94 arctic outbreak they were forecasting -60 to -80 wind chills for northern IA.  On the modern scale (post 2001) seeing wind chills down near -60 show up on the models this far south is pretty astounding.  I found the old chart, and it looks like the wind chill potential using the old scale would be between -65 and -80 for the western sub.  

old-wc-chart.jpg

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Torchageddon

Torchageddon

Posted
Posted
2 hours ago, Jim Martin said:

0z HRRR being quite bullish on the Wind Chill temperatures for Wednesday Morning.

Absolutely ludicrous. I can't believe that's the HRRR's output. Large cities will be shutdown with that. That's a much colder run than my forecast point for Wednesday morning WC wise. Furnaces will be running continuously.

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cyclone77

cyclone77

Posted
Posted
6 minutes ago, Hoosier said:

00z Euro is obscene with Thursday lows.  Looks a hair colder than 12z overall.  Cedar Rapids gets to like -37.

Yeah it did one-up the 12z.  Also colder at 18z on Wed, with -22 to -24 similar to what the 03z RAP showed for northern IL/east IA.  Verbatim the new Euro has Waterloo hitting -39, Cedar Rapids -38, and DVN -37.  

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Hoosier

Hoosier

Posted
Posted
8 minutes ago, cyclone77 said:

Yeah it did one-up the 12z.  Also colder at 18z on Wed, with -22 to -24 similar to what the 03z RAP showed for northern IL/east IA.  Verbatim the new Euro has Waterloo hitting -39, Cedar Rapids -38, and DVN -37.  

Even managed a -27 in downtown Chicago.  That is like impossible to imagine with the UHI.

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beavis1729

beavis1729

Posted
Posted

DVN 

.LONG TERM...(Wednesday through Monday)
ISSUED AT 203 AM CST Tue Jan 29 2019

...Near record cold to record cold, with extreme wind chills remains
on track...

The strongest push of Arctic air will come through our area early
Wednesday morning, with the high gradually centering itself over
the CWA by Thursday morning. This entire period will be noted by
wind chills below -30. The coldest wind chills, with the combined
effect of -20s temperatures and sustained 10 to 18 mph winds will
be early Wednesday morning where wind chills in the north half
fall to the extreme range of -50 to -60. That extreme should last
through late morning, before being dominated by -35 to -45. The
south half should be -40 to -50 through Noon, then -30 to -35 in
the afternoon.

Wednesday night into Thursday morning, with high overhead and
radiation finally able to drop temperatures beyond the advection, we
will continue to face wind chill values of -25 to -45, but with
increasing variability after midnight, as winds become light.
Thursday morning, lows of -30 to -33 are likely along and north of I-
80, and over the Rock River valley in Illinois. This is possible all
time record levels!!  Just south, -15 to -25 are likely. I
specifically am not forecasting an all time low at Moline, for two
reasons. One, the urban heat island impact in light west winds, and
the second, also dealing in winds, the MLI airport really only sees
cold air drainage at the ASOS there when there is an extremely light
east to northeast wind, which taps drainage air. This is what
happened a few days ago, when we hit -22.  No matter the case, we
are within a couple degrees of all time cold!

Somewhat problematic for headlines, is that Thursday morning, wind
chills may or may not be extreme, as winds will be light. However,
ANY WIND, will bring extreme wind chills given the air temperatures
below -25 in much of the CWA. No changes expected in the wind chill
warning.

The sustained extreme cold with wind, followed by extreme cold with
lesser wind should continue to bring the advertised impacts which
include: vehicle problems(battery/tires/engine performance), 5-15
minute frostbite on exposed skin, water main breaks, burst pipes
inside homes/business, enhanced risk of fires from improper use of
home heating, pet/livestock impacts, and carbon monoxide poisoning
risk increase.  In general, we just are not routinely prepared for
dealing with this, and the widespread cancellations already declared
seem to give hope that the message is out.
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beavis1729

beavis1729

Posted
Posted

LOT 

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
604 AM CST Tue Jan 29 2019

.SHORT TERM...
323 AM CST

Through Thursday...

The long-advertised bitter and likely record cold is inbound this
morning, with the first cold front having advanced over the area
last night while the second much more substantial cold surge is
coming this evening. In terms of the cold, very little has changed
with the character of the forecast, with tonight through Thursday
morning the most dangerous time of cold. A couple all-time
records remain forecast as noted below. Wind chill headlines
continue as is. Forecast winds today have been increased some and
am concerned for areas of blowing snow, even potential ground
blizzard conditions in some rural areas this afternoon into
tonight. Will highlight this in messaging. Finally, the pattern
for nearly the past two weeks has been "every day it snows" (and
has 12 straight at Chicago), and feel that scattered snow showers
and/or flurries are a good bet from late morning on.

Satellite imagery this morning depicts the lobe of polar air
marching southward from Canada into the Upper Midwest. Observed
last evening in central Canada with this were a dynamic tropopause
below 700 mb, sub 500dm 500 mb heights, and 850 mb temperatures
near -40C. This will advance southeastward toward the area today
with little to no moderation. As this supports deepening of the
surface low over the central Great Lakes, cold advection will
persist and on a unidirectional westerly wind profile. Given
steep low-level lapse rates in this regime, even with some clouds,
see nothing to prevent winds gusting to 30 mph regularly this
afternoon and evening, possibly even 35+ mph sporadically. Given
yesterday`s blowing and drifting snow, at times producing very low
visibility especially in north central Illinois, would envision
similar problems today and maybe even to a higher degree
especially in and near any snow showers that may develop. If just
a tad higher winds, would strongly consider a Winter Weather
Advisory, but feel the WSW for the wind chills and an SPS for the
blowing snow will convey the message just fine.

As for the potential for falling snow, there are multiple small
scale impulses upstream seen on satellite. In just the broad
scale DPVA and low-level CAA pattern, there should be some daytime
enhancement with isolated to scattered snow showers and flurries
in this especially given the readily ability to saturate with
respect to ice. The cloud depths are shallow so not expecting
heavy snow showers, but with the gusty winds could temporarily
push down visibility sharply in some places.

Temperatures will hold steady on these winds with little if any
rebound today. These support the Wind Chill Advisory for today.
For duration below zero interests, it is possible some places dip
below this morning then briefly top zero before heading into the
deep cold this evening. The 925mb temperatures will drop to near
record low levels of -34C tonight using ILX sounding climatology.
While do think there will be some clouds including into the
overnight over far northern Illinois, advection will mainly drive
temperatures. Clouds could still impact a few degrees so
naturally there is uncertainty in specifics. Have only made
subtle tweaks and have Rockford right at their all time record low
of -27, while Chicago metro -18 to -24. It really is amazing to
have the wind speeds we will have with those temperatures, and as
such wind chills still fall out -45 to -55 by Wednesday morning.
This is dangerous, extremely rare cold and continues to be the
center of our safety message for this event.

While less wind on Wednesday, cold advection continues, and highs
still look to be negative double digits for most of the area. Have
both Rockford and Chicago at their all time record cold high
temperature, and again for the calendar day there will be heavy
dependence on what midnight temperature is namely at Chicago, and
that`s going to be close to -11.

The signature of the high pressure moving over northern Illinois
Wednesday night continues to be consistent and sets the stage for
ideal radiational cooling with a near to record low starting
point into the night. So all time record lows continue to show
potential with widespread -20s and some -30s in favorable places.
The -30 forecast for Rockford still looks good, with 75 percent of
available 00Z guidance forecasting a record low at Rockford. For
Chicago, about 15 percent of models forecast an all time record
low at ORD. Favorable locations in north central Illinois, could
easily push -35 to -39 for lows with all the ingredients lining
up.

In terms of impacts, the wind chills will be lessening by Thursday
morning due to the light or even calm winds in some spots.
Nonetheless, record cold is obviously impacting enough, so the
Wind Chill Warning duration looks really good. Clouds should start
moving in Thursday and many locations are likely to remain below
zero through the day. Light snow will be possible by afternoon as
the elevated baroclinic zone starts to move overhead, with better
chances after dark.

MTF
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beavis1729

beavis1729

Posted
Posted

While I think Chicago and Rockford will be comfortably safe from the "midnight high" on Wed morning, some of the models are showing that it may warm up enough on Wed afternoon to prevent breaking the all-time record low maxes (-11 Chicago and -14 Rockford)...before temps tank again at sunset. 

Yesterday, I thought we'd have a 90% chance of this record being broken at both ORD and RFD...but right now I'd say 60-70%.

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Hoosier

Hoosier

Posted
Posted

So one of the questions with assessing record low potential for tonight around the area is what the thermal structure in that lowest part of the atmosphere looks like.  925 mb temps are progged in excess of -35C into IL, which is astonishing and near record territory.  If you have that value at 2m, that is -31F.  We are not talking about good radiational cooling conditions tonight with the kind of pressure gradient in place and perhaps some clouds, so the low levels will remain mixed but to what extent?  Do we have dry adiabatic up to 925 mb or weaker lapse rates?  

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Hoosier

Hoosier

Posted
Posted
26 minutes ago, beavis1729 said:

While I think Chicago and Rockford will be comfortably safe from the "midnight high" on Wed morning, some of the models are showing that it may warm up enough on Wed afternoon to prevent breaking the all-time record low maxes (-11 Chicago and -14 Rockford)...before temps tank again at sunset. 

Yesterday, I thought we'd have a 90% chance of this record being broken at both ORD and RFD...but right now I'd say 60-70%.

I'd figure about a 10-12 degree diurnal recovery at ORD, so hope it tanks like crazy tonight to give some wiggle room.

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Hoosier

Hoosier

Posted
Posted
4 minutes ago, beavis1729 said:

And here it comes...

Grand Forks ND at 11 AM central: temp -25, winds N 29 G 43, wind chill -59.

Coldest wind chill so far: -61 at Flag Island ND, -27 with NW wind 25 mph.

Gonna be keeping a close eye on how that is performing upstream relative to models.

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