WINTER STORM WARNING IN EFFECT 3 AM FRIDAY TO NOON CST SATURDAY
Arlington Heights and O’Hare weather forecast for Thursday, January 11, 2024 YouTube Tips ⓘ
Period of light snow to end will end shortly after daybreak with accumulations generally under an inch.
Major winter storm likely (60%+) to produce a swath of very heavy snow (6″+) across much of northern IL predawn Friday through Saturday morning.
The worst impacts/dangerous to life threatening travel conditions are expected after dark Friday through early Saturday. Periods of blizzard conditions possible in open areas of northern IL (~30% chance of true 3-hour blizzard criteria).
Weather Radar in northeast Illinois was clear at 1:00 p.m.
See also Arlingtoncardinal.com/clouds
Here is a look at the weather beyond the storm: The coldest air of the season is expected to arrive towards Sunday and into next week. The coldest wind chills during this time may fall below -30 °F at times, especially Sunday and Monday nights! #ILwx #INwx pic.twitter.com/CuCjzu3eWX
— NWS Chicago (@NWSChicago) January 11, 2024
O’HARE FORECAST …
Thursday: Mostly cloudy, with a high near 33. West southwest wind 5 to 10 mph.
Thursday Night: Snow, mainly after 1am. Temperature falling to near 26 by 8pm, then rising to around 32 during the remainder of the night. West southwest wind 5 to 10 mph becoming east 10 to 15 mph after midnight. Winds could gust as high as 25 mph. Chance of precipitation is 100%. New snow accumulation of 1 to 2 inches possible.
Friday: Snow, possibly mixed with rain, becoming all snow after 4pm. The snow could be heavy at times. High near 34. Breezy, with an east wind 15 to 25 mph, with gusts as high as 35 mph. Chance of precipitation is 100%. New snow accumulation of 3 to 7 inches possible.
Friday Night: Snow. Patchy blowing snow after 10pm. Low around 22. Breezy, with a north northeast wind 15 to 20 mph becoming west 20 to 25 mph after midnight. Winds could gust as high as 40 mph. Chance of precipitation is 100%. New snow accumulation of 2 to 4 inches possible.
Saturday: Periods of snow showers. Areas of blowing snow. High near 22. Windy, with a west wind 25 to 30 mph, with gusts as high as 40 mph. Chance of precipitation is 80%.
Saturday Night: A 50 percent chance of snow showers. Mostly cloudy, with a low around 0. Breezy.
Sunday: A 30 percent chance of snow showers. Partly sunny and cold, with a high near 4. Breezy.
Sunday Night: Mostly cloudy, with a low around -9. Breezy.
M.L.King Day – Monday: Mostly cloudy and cold, with a high near 3.
Monday Night: A chance of snow after midnight. Mostly cloudy, with a low around -9.
Tuesday: Partly sunny and cold, with a high near 1.
Tuesday Night: Partly cloudy, with a low around -5.
Wednesday: Mostly cloudy, with a high near 17. Breezy.
SouthLakeMichiganDataPASTEHERE
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Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 129 PM CST Thu Jan 11 2024
.SHORT TERM… Issued at 318 AM CST Thu Jan 11 2024
Through Saturday…
Key Messages:
– Period of light snow to end will end shortly after daybreak with accumulations generally under an inch.
– Major winter storm likely (60%+) to produce a swath of very heavy snow (6″+) across much of northern IL predawn Friday through Saturday morning.
– The worst impacts/dangerous to life threatening travel conditions are expected after dark Friday through early Saturday. Periods of blizzard conditions possible in open areas of northern IL (~30% chance of true 3-hour blizzard criteria).
– Winter Storm Watch continues unchanged from previous forecast for areas near and north of the Illinois and Kankakee Rivers early Friday through mid day Saturday. If trends continue, much of this watch will need to be upgraded to a warning later today.
– Strong onshore winds off a still mild Lake Michigan will once again cut into snow accumulations near the immediate shore during the day on Friday, including east of I-90/94 in Illinois, and north of I-80/94 in Indiana.
Following the end of the early morning light snow, the focus quickly shifts to the next developing winter storm which is likely (60+% chance) to produce major impacts to commerce across a good majority of northern IL (highest impacts along and north of I-80 and away from the immediate Lake Michigan shore). The forecast for this storm system continues to be handled best by the more consistent global forecast models and ensembles (especially the ECMWF and its ensemble members). We therefore continue to steer the forecast in this direction. Currently, many of the higher resolution models such as the HRRR, NAM and RA Pcontinue to be northern and warm outliers with the system, and thus, their current iterations are not favored.
Confidence continues to increase that this anomalously strong storm system (which bears a striking similarity to the heart attack snowstorm of Dec 15, 1987) will produce major impacts across much of northern IL into Saturday morning. While we have opted to hold off one more iteration before committing to a winter storm warning, if trends continue in this direction, an upgrade to a warning will be needed for most of the watch area with this afternoon`s forecast update.
Current thinking is that a transient band of intense frontogentically forced ascent developing within an convectively unstable layer later tonight will support a quick couple hour period of very heavy snow rates (1-2″ per hour) during the early Friday morning commute. While this period of heavy snow may only last an hour or two, the heavy rates could drop 1 or 3 inches of wet snow across the area through mid-morning on Friday. Following this “thump” of snow, lighter precipitation rates and lower impacts may ensue for a few hours (from mid to late morning into early afternoon). In fact, warming temperatures into the mid to upper 30s south of I-80 during the day Friday should support a transition over to just rain for a several hour period. We could even see rain at least briefly mix in with the snow as far north as the I-80 to I-88 corridors into midday Friday as temperatures briefly warm a bit above freezing.
Things will change in a big hurry after about 2 pm as the deepening storm system (very impressive sub 980mb low) tracks northward into northern IN. This is expected to induce strong dynamical forcing within what looks to be a very intense deformation band of precipitation along the northwesterly periphery of the surface low and near the 700 mb low track. The current favored track favors this band of heavy precipitation right across northern IL into the Chicago metro area. The heavy precipitation rates should favor much of this band falling as heavy low ratio (8-9 to 1) wet snow, with rates in excess of an inch per hour through the evening commute. While snow will also be favored along the Lake Michigan shore with this period of precipitation, there is some concern that the strong flow off the lake could once again limit accumulations right along the shore through early Friday evening.
Snow will continue Friday night into Saturday as colder air begins to spill into the area on strong northwesterly winds (gusts in excess of 40 mph at times). While the initial snow that falls into early Friday evening will be wet and likely not be supportive of blowing around much, higher ratio snow falling in the subfreezing airmass will support considerable blowing and drifting snow Friday night into Saturday, with near blizzard conditions and extremely dangerous travel likely across much of the area into Saturday, especially within open areas of northern IL. The current watch area continues to capture the highest risk area for major impacts well, so no changes are planned at this time.
KJB
&&
.LONG TERM… Issued at 205 AM CST Thu Jan 11 2024
Saturday night through Wednesday…
Key Message:
Dangerously cold temperatures and wind chills for several days next week.
Bitterly cold air will spread across the region this weekend and continue through the middle of next week. Subzero low temps are expected each morning Sunday through Wednesday with the coldest morning possibly Monday morning with lows in the -10 to -15 range for most of the area. Westerly winds in the 10-15 mph range with higher gusts at times will likely push wind chills into warning criteria of -30 for at least a few nights. In fact, if the current temp/wind forecast materializes, its possible that wind chills will remain below zero from Saturday evening through midday Wednesday for the entire area.
A weak system may bring some light snow to areas south of the cwa Sunday and the models show various weak impulses moving across the area through the middle of next week. Any one of these could bring some flurries or a chance of light snow but confidence is very low from this distance. cms
&&
.HYDROLOGY… Issued at 129 PM CST Thu Jan 11 2024
Key Messages:
* Increasing threat for rivers to reach bankfull mainly southeast of Interstate 55 (Vermilion, Kankakee, Iroquois rivers and Sugar Creek.
* Increased threat for ice jams and associated flooding on all area rivers from next weekend onward.
Discussion:
The hydrologic forecast for the next several days is complicated for the area due to uncertainty in precipitation types, precipitation amounts, and river levels during the upcoming period of very cold weather. Rainfall over the last several days, generally southeast of I-55, has increased soil moisture and river levels. With the next system tonight through and Saturday, a period of rainfall is also expected, with the highest liquid precipitation totals likely occurring again across to the southeast. As we enter the period of very cold temperatures Saturday into Sunday, attention will shift toward concerns for river ice and frozen soils. Although a period of temperatures averaging <0F for several days is often followed by widespread river ice and at least a few ice jams, elevated river conditions can increase the production of river ice further. With cold weather expected to remain in place for most of next week, a prolonged period of river ice generation will exist, along with the potential for significant frost depth penetration in area soils. Accumulated precipitation on Friday prior to the changeover back to snow on Friday afternoon will be the most important factor relating to crests on rivers and streams. The HREF LPMM indicates 0.75-1.25 inches, with the heaviest axis from generally Ottawa to Chicago. The NBM mean is slightly higher with 1.25-1.50 and a 10th to 90th percentile range from 0.9 to 1.75 inches. The NBM`s heaviest axis is slightly different, from generally Paxton to Chicago. The highest overlap in QPF locations includes the Vermilion River Basin, the lower Kankakee River Basin, and the Thorn Creek Basin. To the south, in the headwaters of the Kankakee River Basin, precipitation is likely to remain liquid for a longer period of time, but more uncertainty exists in the QPF. River forecasts from NCRFC currently assume approximately 1.0 inches averaged across the Kankakee and Iroquois river basins, which yields multiple locations nearing or exceeding bankfull. This assumption appears reasonable based upon the mentioned model uncertainties. If some of the high rainfall totals occur, a few rivers may see minor flooding, but the chance for more significant flooding (moderate or major) appears very low (<5%) at this time. By late weekend into early next week, temperatures will quickly become favorable for the rapid formation of river ice area-wide. Mild temperatures during December and early January may initially slow the development of ice due to river temperatures of 35-40F. Water temperatures will likely cool quickly, with rapid river ice formation likely by Monday. Isolated freeze-up ice jams will be possible across the area, but may be more likely southeast of I-55. Elevated river levels from recent rain and forecasted rain will likely increase frazil ice production. Ice-prone areas in the Kankakee River Basin will need to be watched carefully next week as even small increases in water level due ice jams will cause flooding due to elevated river levels. River ice flowing from tributaries into the Illinois River, in additional to river ice that forms locally, may cause impacts to shipping. Ensemble temperature forecasts suggest a low chance of high temperatures consistently exceeding 20F through next week, which may signal an extended period of river ice problems. WSL && .AVIATION... For the 18Z TAFs... The primary aviation weather concerns through the 18Z TAF period are as follows: * Accumulating snow showers late tonight through Friday with periods of moderate to heavy snow expected * MVFR cigs today going IFR for late tonight and Friday * Gusty easterly winds Friday Gusty snow showers will move in from the west late tonight, roughly around 09Z at Chicagoland sites, closer to 08Z at RFD. Snow will then continue to fall through the remainder of the period. Bouts of moderate to heavy snow will be possible with the best potential looking like the early morning. Periods of IFR to LIFR vsbys look rather likely. Rain may attempt to mix in during the late morning and afternoon. However, confidence on precipitation type during this time is admittedly low. Westerly winds will back to SW this afternoon, flipping over to SE early this evening then onto easterly tonight. Wind speeds near or below 10 kt will ramp up through the night tomorrow with 20+ kt gusts expected by the onset of snow. Gusts out of the east to near 30 kt are anticipated for much of the morning and afternoon. Additionally, MVFR cigs will continue to hang overhead today before dropping to IFR late tonight with low-end IFR cigs expected for the better part of Friday. Doom && .MARINE... Issued at 205 AM CST Thu Jan 11 2024 A strong area of low pressure will move from south/central IL Friday morning to central lower MI by Saturday morning. Easterly winds will steadily increase early Friday morning with gales to 35 kt possible, especially across the IL nearshore waters. Winds will shift to the northeast Friday afternoon as the low approaches and may diminish in strength for a short time into early Friday evening. As the winds turn northwesterly Friday evening, speeds and gusts will rapidly increase with gales to 45 kt expected and the potential for storm force winds, especially across the IN nearshore waters. The strongest winds will likely diminish by mid morning Saturday with gusts into the 30kt range persisting into Sunday. Current gale watch for the IL nearshore and storm watch for the IN nearshore look on track and no changes planned this morning. Much colder air will spread across the region this weekend into next week and if the winds remain strong enough, freezing spray will likely develop Saturday night and Sunday. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Winter Storm Watch...ILZ003-ILZ004-ILZ008-ILZ010-ILZ011-ILZ019- ILZ020-ILZ021...3 AM Friday to noon Saturday. Winter Storm Watch...ILZ005-ILZ006-ILZ012-ILZ013-ILZ023-ILZ103- ILZ104-ILZ105-ILZ106-ILZ107-ILZ108...6 AM Friday to noon Saturday. IN...Winter Storm Watch...INZ001-INZ002...6 AM Friday to noon Saturday. LM...Gale Watch...IL nearshore waters...3 AM Friday to noon Saturday. Storm Watch...IN nearshore waters...midnight Saturday to noon Saturday. && $$ Visit us at weather.gov/chicago Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/NWSChicago www.twitter.com/NWSChicago www.youtube.com/NWSChicago