January 22-23, 2024 | OV/GL Snow/Ice Threat

[Jpfalcon]

Snow/ZR Monday night into Tuesday morning for some.

 

[Cary67]

Keeping an eye on this. Rather snow then freezing rain.

[SNOWBOB11]

I’ve been watching this system. Slightly different setup being at the start of the warm up but having enough cold air in place for frozen precipitation.

[Hoosier]

With the recent extreme cold and the cold leading into this, I expect the ground temps to lag behind the 2m temps.  So ground icing may continue for a while even after the 2m temps get above freezing.

[StormfanaticInd]

I hate ice

[Hiramite]

Here are a couple early ice maps (FRAM est) just to give folks an idea of the areas at risk.

Please keep in mind the below info from Pivotal when posting or viewing Pivotal's Ice/Freezing Rain maps....

Freezing rain

The situation with freezing rain in many ways mirrors snow: we know a certain amount of liquid precipitation is forecast to fall as rain into subfreezing near-ground air, but that does not mean the accretion on a given surface will match the liquid equivalent. In fact, ice accretion is almost always less than the liquid equivalent precipitation (Freezing Rain QPF) in significant ice storms — sometimes less than half, if the precipitation falls in heavy bursts or temperatures are close to freezing. Our Freezing Rain QPF maps should never be used verbatim as forecasts of accretion; they are simply a starting point in making such a forecast.

For Plus subscribers and for some models, we have recently implemented the Freezing Rain Accumulation Model (FRAM; Sanders and Barjenbruch 2016) as a rough estimate of accretion thickness on elevated horizontal surfaces. This product predicts the ice-to-liquid ratio (ILR) empirically from a large climatology and is rather analogous to Kuchera for snowfall, except that wind speed and precipitation rate are also considered in addition to (wet bulb) temperature. Bear in mind ice accretion is even trickier than snowfall accumulation and varies widely by surface type, shape, exposure, and orientation, so we urge responsibility and context in using even FRAM for public-facing forecasts.

 

[Indygirl]

I’ve been watching local morning news. They’re talking up the possibility of freezing rain coming. I hope it’s not too bad….

[BuckeyeGal]

Normally I feel like the Canadians are a bit too cold, but given the temperatures leading up to this system.. think it's wise to err on the side of caution. This may cause some issues, especially where there's heavy snowpack.

[Hoosier]

The overnight ILX afd mentioned that the ground may have more ice than elevated surfaces and trees.  It's often the other way around, but because of the circumstances of transitioning out of some deep cold, it's quite possible.  This is where experience comes into play with forecasting as the models' freezing rain output generally only accounts for precip with air temps at/below freezing and doesn't factor in ground temps.  Also looks like it won't be a rapid rise to well above freezing temps for many areas (i.e. not going from 32 to 40 in a few hours), so the slow climb through the 30s should also slow down the amount of melting on the ground.

[Hoosier]

On January 10, 2014, there was an event in/around northern IL that appears to have some similarities to the upcoming one as far as the temps leading in.  The 2014 event shouldn't have been a big deal as most of the rain fell with temps above freezing, but it turned into a mess with bad road conditions, a lot of accidents, and the NWS needing to hold on to a freezing rain advisory even as temps warmed several degrees above freezing.

On 1/9/2014, which was the day before, the low in Chicago was -4 and the high was 27.  

The low tomorrow morning in Chicago could be similar to what it was on 1/9/2014, while tomorrow's afternoon high looks like it will be several degrees colder than it was back then.

I think we are setting up for something nastier than it would appear on the face of it.  For northern IL specifically, I think travel on Tuesday morning could still be tricky (especially secondary/untreated roads) even with temps probably above freezing by then.  

Edited January 20 by Hoosier

[Hoosier]

IWX and IND really ramped up their ice wording in the afternoon discussions, mentioning the impact of the cold ground.

[StormfanaticInd]

1 hour ago, Hoosier said:

On January 10, 2014, there was an event in/around northern IL that appears to have some similarities to the upcoming one as far as the temps leading in.  The 2014 event shouldn't have been a big deal as most of the rain fell with temps above freezing, but it turned into a mess with bad road conditions, a lot of accidents, and the NWS needing to hold on to a freezing rain advisory even as temps warmed several degrees above freezing.

On 1/9/2014, which was the day before, the low in Chicago was -4 and the high was 27.  

The low tomorrow morning in Chicago could be similar to what it was on 1/9/2014, while tomorrow's afternoon high looks like it will be several degrees colder than it was back then.

I think we are setting up for something nastier than it would appear on the face of it.  For northern IL specifically, I think travel on Tuesday morning could still be tricky (especially secondary/untreated roads) even with temps probably above freezing by then.  

We are supposed to drop to -5 tonight. The ground will frozen solid for this event. This is setting up a potentially dangerous situation on the roads Monday night and Tuesday 

[MesoscaleBanding]

ILN taking notice of the ice potential as well

[NWOhioChaser]

Yeah not liking this threat for early in the week. Ice during the morning commute always not welcome. 

[beaver56]

It could be one of those situation schools will cancel and by 2 pm you will wonder why because of the warm up.

Edited January 20 by beaver56

[Hoosier]

The main knock against this setup -- and it's not a trivial one -- is the high pressure slipping off the east coast, which sets up southerly low level flow at the surface.  That is usually not conducive to prolonged/heavy icing as there is nothing to lock in and replenish the cold/dry air.  There is a high that comes in from the north later on, but its main influence will be felt in the northern tier to the north of where most posters on this board are from.  

That aside, most every other factor is quite favorable.  Precip rates generally look light, perhaps eventually becoming moderate at times for some areas, which will minimize runoff and help with accretion efficiency.  There will be a bit of a breeze, but not too strong which is actually a good thing for ice in this particular situation as it should tend to slow down the northward pace of the WAA compared to having a stronger southerly flow.  And as already mentioned, the prolonged antecedent cold is very favorable for causing problems with ground icing.  The antecedent airmass also looks fairly dry, so it will take a while to get dewpoints above freezing and completely exhaust the wetbulbing process.  

[Hoosier]

 

[BuckeyeGal]

This.. is starting to get really concerning. I'll also mention that the 3k NAM, which isn't included in this little mashup, was considerably south of the operational NAM.

[BuckeyeGal]

ILN:

Quote

.LONG TERM /MONDAY THROUGH SATURDAY/...
NBM derived weather for Mon night has a not insignificant area in
CWA with a snow or wintery mix that is plainly not based in reality.
Thicknesses that would support a mix of snow are well into MI, and
through the whole of the overnight period. While surface temps
during the day could possibly tip to near 40 degrees in the far se
CWA, the rest of the region will be in the low to mid 30s during the
day. By evening, readings will drop to or below freezing for much of
the CWA and remain there until about 09Z Tues with a slight warming
to above freezing by daybreak. However, these temperatures measured
at 6` will not be indicative of what`s happening at the actual
ground level. Warm air without a significant wind is not enough to
scour out entrenched cold air.

All this being said, rain will become an increased likelihood by
daybreak Tuesday, especially over west central OH, east and se IN,
and along and west of the I-75 corridor. Being 60-72 hours out this
is by no means a solid forecast. However, the conditions are ripe
for a freezing rain event during the predawn hours of Tuesday. Will
trend the forecast in this direction and expect to increase this
potential with each passing morning/afternoon forecast update.

 

[BuckeyeGal]

2 hours ago, beaver56 said:

It could be one of those situation schools will cancel and by 2 pm you will wonder why because of the warm up.

This. I see a lot of delays, at the very least.

[Hoosier]

29 minutes ago, BuckeyeGal said:

This.. is starting to get really concerning. I'll also mention that the 3k NAM, which isn't included in this little mashup, was considerably south of the operational NAM.

The Euro seems like it trended more icy overall compared to previous runs.  It has been one of the warmer models.

[snowlover2]

Really glad i don't have to worry about driving to work Tuesday morning. Anything but ice.

[Crowbar]

Told my neighbors, who both teach up here in different districts, that there may be a delay on Tuesday.  Don’t expect cancellations up here, but delays may be in order 

[StormfanaticInd]

[StormfanaticInd]

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