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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

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.

DLH .CLIMATE... Issued at 251 PM CST Mon Jan 28 2019 Record lows are possible this week. Below are records and current forecasts for select sites with a long history. Record Lows for Tuesday January 29... Duluth................-35 in 1951...Forecast...-21 International Falls...-41 in 1951...Forecast...-28 Brainerd..............-38 in 1965...Forecast...-25 Hibbing...............-34 in 1951...Forecast...-24 Ashland...............-35 in 1951...Forecast...-10 Record Lows for Wednesday January 30... Duluth................-25 in 1994...Forecast...-29 International Falls...-40 in 1950...Forecast...-36 Brainerd..............-40 in 1996...Forecast...-37 Hibbing...............-33 in 1951...Forecast...-33 Ashland...............-35 in 1950...Forecast...-19 Record Lows for Wednesday January 31... Duluth................-33 in 1982...Forecast...-32 International Falls...-35 in 1996...Forecast...-43 Brainerd..............-46 in 1996...Forecast...-40 Hibbing...............-41 in 1996...Forecast...-38 Ashland...............-33 in 1996...Forecast...-23

I know this is overdone...but Look at the -34 at Grand Forks, ND at 12 noon central time tomorrow on the 18z FV3.

DLH Area Forecast Discussion National Weather Service Duluth MN 251 PM CST Mon Jan 28 2019 .SHORT TERM...(This evening through Tuesday) Issued at 251 PM CST Mon Jan 28 2019 The focus remains on the extremely cold and historic air that will soon be moving into the Northland. This latest forecast has even colder wind chills than earlier forecast. Confidence is high for widespread dangerous wind chills. Wind Chill Warnings and Advisories have now been issued. An Arctic cold front will continue moving east through the Northland this afternoon through this evening, bringing an influx of extremely cold air out of Canada into the Northland into tomorrow. This will be a rare situation in which a deep upper level polar low will dive south into the Minnesota and Wisconsin region by tomorrow morning. This airmass will feature 850 hpa temperatures at least as cold as -40 degrees Celsius, with the coldest air across western into southern Minnesota. Gusty winds late tonight and Tuesday will cause widespread dangerous wind chills of 30 to 55 below zero across the Northland, with the coldest wind chills across central and northern Minnesota. Expect northwest winds of 10 to 20 mph gusting 20 to 30 mph. There will be little improvement of the winds and wind chills for the afternoon. The worst conditions will come Tuesday night through Wednesday morning. Air temperatures will plummet to 20 to 40 below zero. Northwest winds of 5 to 15 mph, and up to 20 mph along the Minnesota North Shore, will cause jaw dropping wind chills of 45 to 65 below zero which will continue well into Wednesday morning. These wind chills are on the order of an event that the Northland typically only sees at least once every 5 to 10 years. The latest comparable situations occurred in January 2014 and February 1996. Frostbite can occur within 5 minutes under these conditions! This overall forecast was by no means on the extreme side of model guidance. The temperature and wind forecasts were close to a consensus of available model guidance, especially the temperatures. That means there were other models that were significantly colder. It is possible we may need to forecast even colder temperatures with subsequent forecasts. If this were the case, the wind chills could be substantially, and incredibly, colder.

Point forecast at Rockford down to -30 for Thursday morning Hazardous Weather Outlook Winter Weather Advisory Wind Chill Warning Wind Chill Advisory This Afternoon: Snow likely, mainly before 4pm. Patchy blowing snow. Cloudy, with a steady temperature around 17. Wind chill values as low as zero. North northwest wind around 15 mph, with gusts as high as 30 mph. Chance of precipitation is 60%. Total daytime snow accumulation of less than a half inch possible. Tonight: A slight chance of snow before 8pm, then a chance of flurries between 8pm and 11pm. Patchy blowing snow before 8pm. Cloudy, with a low around -6. Wind chill values as low as -22. West wind 10 to 15 mph, with gusts as high as 30 mph. Chance of precipitation is 20%. Tuesday: Light snow likely with intermittent snow showers after noon. Partly sunny and cold, with a temperature rising to near -3 by noon, then falling to around -7 during the remainder of the day. Wind chill values as low as -30. Blustery, with a west wind 15 to 20 mph, with gusts as high as 30 mph. Chance of precipitation is 60%. Little or no snow accumulation expected. Tuesday Night: A chance of flurries before midnight. Mostly cloudy, with a low around -26. Wind chill values as low as -50. West northwest wind around 15 mph, with gusts as high as 30 mph. Wednesday: Mostly sunny and cold, with a high near -15. West wind around 15 mph, with gusts as high as 25 mph. Wednesday Night: Mostly clear, with a low around -30. Thursday: Mostly sunny and cold, with a high near -4. Thursday Night: A chance of snow. Cloudy, with a low around -9.

FWIW, the 18z HRRR shows H85 temps of -36C over northern IL around 4z Wed, or 10 PM central time on Tuesday. Here are the 18z HRRR temps, as far out as they go (6z Wed). If this is anywhere close to correct, it's good news, as ORD and RFD won't have the dreaded midnight high when Tuesday turns to Wednesday.

DVN .CLIMATE... ISSUED AT 251 AM CST Mon Jan 28 2019 Record lows for January 29th... Burlington........ -19 in 1966 Cedar Rapids...... -24 in 1966 Dubuque........... -26 in 1951 Moline............ -19 in 1966 Record lows for January 30th... Burlington........ -20 in 1899 Cedar Rapids...... -22 in 1951 Dubuque........... -25 in 1951 Moline............ -14 in 1966 and previous years Record cool highs for January 30th... Dubuque............ -3 in 1996 Moline............. -2 in 1951 Record lows for January 31st... Burlington........ -20 in 1996 Cedar Rapids...... -21 in 1996 and previous years Dubuque........... -24 in 1996 Moline............ -21 in 1996 Coldest January low temperatures... Burlington........ -24 on 1/14/1957 Cedar Rapids...... -29* on 1/15/2009 Dubuque........... -32 on 1/07/1887 Moline............ -27 on 1/16/2009 1/02/1979 1/05/1884

Wind Chill Warning from LOT URGENT - WINTER WEATHER MESSAGE National Weather Service Chicago IL 136 PM CST Mon Jan 28 2019 ILZ003>006-008-010>014-019>022-INZ001-002-290345- /O.UPG.KLOT.WC.A.0002.190130T0000Z-190131T1800Z/ /O.NEW.KLOT.WC.W.0001.190130T0000Z-190131T1800Z/ /O.NEW.KLOT.WC.Y.0003.190129T1000Z-190130T0000Z/ /O.CON.KLOT.WW.Y.0006.000000T0000Z-190129T0000Z/ Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-DeKalb-Kane-DuPage-Cook- La Salle-Kendall-Grundy-Will-Lake IN-Porter- Including the cities of Rockford, Belvidere, Woodstock, Waukegan, Oregon, Dixon, DeKalb, Aurora, Elgin, Wheaton, Chicago, Ottawa, Oswego, Morris, Joliet, Gary, and Valparaiso 136 PM CST Mon Jan 28 2019 ...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 6 PM CST THIS EVENING... ...WIND CHILL ADVISORY IN EFFECT FROM 4 AM TO 6 PM CST TUESDAY... ...WIND CHILL WARNING IN EFFECT FROM 6 PM TUESDAY TO NOON CST THURSDAY... * WHAT...Light snow and areas of blowing snow this afternoon. Dangerously cold wind chills expected. Wind chills 20 to 30 below Tuesday and as low as 55 below zero expected Tuesday night through Thursday morning. * WHERE...Portions of northwest Indiana and north central and northeast Illinois. * WHEN...For the Wind Chill Warning, from 6 PM Tuesday to noon CST Thursday. For the Winter Weather Advisory, until 6 PM CST this evening. For the Wind Chill Advisory, from 4 AM to 6 PM CST Tuesday. * ADDITIONAL DETAILS...Plan on slippery road conditions. The hazardous conditions could impact the morning or evening commute. The dangerously cold wind chills could cause frostbite on exposed skin in as little as 5 minutes. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Wind Chill Warning means the combination of very cold air and the wind will create dangerously low wind chill values. Frostbite can occur quickly and even hypothermia or death if precautions are not taken.

I guess this was kind of expected...but, unfortunately, the GFS appears to be backing off on the severity of the airmass a bit. Coldest H85 temps on the 12z GFS for N IL are now around -35C, compared to -38C a couple of days ago. Even more concerning is that the duration of the extremely cold H85 temps is quite a bit shorter than it looked a few days ago...meaning that the timing of everything will need to work out even more perfectly. Not pointing this out to raise alarm or anything, as this will still be a special event. But when going for all-time records, every degree counts.

Looks like the front just passed through De Kalb. Temp dropped from 32 to 28 over the past hour. 33 at ORD.

For here, it's -22 Wed morning, -14 for the high on Wed, then -26 Thu morning. If the models don't deviate from what is currently progged on the GFS and Euro, I could see both of our points dropping another 1-2 degrees.

Posting various AFDs for posterity. DLH Arctic air streams into the Northland tonight with overnight lows generally between 10 and 30 below zero. Winds are expected to remain elevated overnight due to cold air advection keeping the low-levels mixed along with a tightening pressure gradient. Resultant wind chills of 30 to 55 below zero are expected overnight. With the prolonged period of dangerously cold temperatures and wind chills, have decided to issue a Wind Chill Watch from 06Z tonight through 15Z Thursday. Dangerously cold temperatures and wind chills will continue through the day Tuesday. Afternoon highs will struggle to reach 20 below along our western border and will climb into the middle single digits below zero in our eastern zones. Winds will strengthen as the pressure gradient tightens during the day with wind chills in the 40s below zero west and to around 20 below zero east. .LONG TERM...(Tuesday night through Sunday) Issued at 421 AM CST Mon Jan 28 2019 The period will start off very cold, especially Tuesday night into Thursday. The Northland will see very low temperatures and dangerous wind chills Tuesday night, wind chills that are not very common even for northern Minnesota. The area will be between high pressure centered over the Dakotas and low pressure well off to the east Tuesday night and this will lead to sustained wind speeds between 8 and 15 MPH for most areas. The wind combined with overnight lows from 25 below to 35 below zero will create wind chills from 45 below to 60 below zero. The lowest wind chills will occur over the western half of the area. High temperatures Wednesday will only be from 5 below to around 10 below over northwest Wisconsin and from 10 below to 18 below over northern Minnesota and wind chills will only improve to 25 below to 40 below during the afternoon. As the upper low moves further east, a surface ridge will move over the area Wednesday night. The ridge will be over most of the Northland by 12Z Thursday and winds will be lower than Tuesday night, and may go calm in spots. Despite the coldest air aloft moderating Wednesday/Wednesday night slightly, Wednesday nights lows will be colder in spots than Tuesday night due to good radiational cooling conditions. Low temperatures will drop to 25 below to around 30 below for most of northern Wisconsin and from 30 below to around 45 below over much of northern Minnesota. Wind chills will be from 30 below to around 50 below but wind speeds will be quite a bit lower than what occurs Tuesday night into Wednesday. More sun is expected on Thursday, outside of the South Shore area. Highs will rise into the single digits below zero and wind chills will be less of a concern by Thursday afternoon. The surface high will continue through the Northland Thursday night with lows in the teens below zero to around 25 below and with lighter winds, wind chill values from 20 below to 35 below are expected.

FWIW, the 6z FV3 shows temps and wind chills significantly colder than the GFS. For example, temps near -40 in far NW IL with wind chills in the -60s. I wish I could believe it, but have to admit that it's overdone.

Wow. This town is located at 50N. Per Wikipedia, their all-time record low is -58F, and their normal January low is -13F. So, this morning's low is 40 degrees below normal. https://en.wikipedia.org/wiki/Greenstone,_Ontario

The progged -65 wind chill is SE MN is based on a temp of -35, with 16 mph winds.

LOT .LONG TERM... 319 AM CST Tuesday through Sunday... Certainly the main story continues to be the well advertised period of dangerously and potentially historic cold temperatures from Tuesday evening through Thursday morning. The latest forecast still has the Rockford area very near their all time record low of minus 27 Tuesday night and a couple degrees colder than that Wednesday night. The forecast daytime high Wednesday around minus 15 for RFD would beat their all time record coldest high of minus 14. The forecast lows for Chicago presently look a few degrees above their all time record which also is minus 27 but the forecast daytime high Wednesday around minus 14 would beat their all time record coldest high of minus 11. For both locations, the all time record that looks most in jeopardy would be the all time coldest average temperature for one day which is around minus 18 at both sites. As an aside, the daily records for both locations look to be crushed on Wednesday and Thursday. Aside from all the talk about numbers, wind chill headlines also deserve a mention. Was not sure how best to handle wind chill watch, advisory, and warning decisions based on the different onset times from northwest to southeast across the forecast area. For all locations the key period of warning level wind chills, meaning below minus 30 degrees, would be Tuesday evening to about noon Thursday. This matches the watch that was issued this morning. This does not mean to imply that the daytime Tuesday or the afternoon of Thursday will be balmy in any way. Wind chill advisory headlines may very well be needed both before and after the warning period. This is especially true toward the northwest third of the forecast area which likely will need an advisory starting Tuesday morning. For Thursday afternoon, highs look to be in the single digits both below and above zero but winds look relatively light with a ridge moving overhead. Beyond the cold period...on Thursday night both the GFS and ECMWF now want to show a quick shot of light snow associated with a weak shortwave aloft and a bit of warm advection at lower levels. Obviously it is too early to give this significant attention with the bigger concerns in the near term, but anticipated QPF amounts presently would not suggest this would warrant additional headlines later in the week.

Agree. Low center is right over Chicago instead of Waukegan. Makes a huge difference. Verbatim, 18z GFS shows about 0.6” of liquid at ORD, and around 0.7” at the WI/IL border. Assuming 13:1 ratios, would imply 8-10” in these areas.

Minot ND is 40 degrees now, and should be -30 Wednesday morning. My point was lowered to -24 on both Wednesday morning and Thursday morning. High of -14 on Wednesday.

What a strange track on the NAM. I guess the Euro is doing this too, to some extent. The storm was modeled for the last 6 days to come down from the NNW and then head due E...and now, just before the event, we get a NE hook showing up on the models. Not saying this to complain...but this storm has been bizarre to say the least.