• Member Statistics

    15,773
    Total Members
    7,904
    Most Online
    mansour
    Newest Member
    mansour
    Joined
Sign in to follow this  
Frog Town

Overrunning Set-Up/Ice Storm 2/5-2/8

Recommended Posts

The RAP, and some other guidance, is ice storm warning worthy for the heart of the axis.

 

 

.

 

Share this post


Link to post
Share on other sites
2 minutes ago, Chicago Storm said:

The RAP, and some other guidance, is ice storm warning worthy for the heat of the axis.


.

had a November blizzard, Great clipper train, record cold...an ice storm worthy event wouldn't shock me...and then I need my 12-15" big dog, and I'll be ready for spring.

  • Like 2
  • Haha 6

Share this post


Link to post
Share on other sites

I'm a little surprised this setup didn't get a Winter Storm Watch. Isn't the criteria for that "Enough ice accumulation to cause damage to trees or powerlines?" Seems to me that plenty of models have shown support for that.

  • Like 1

Share this post


Link to post
Share on other sites

The waa in action... some model variance of course but general idea

 

18Z-20190204_NAMFLT2_925_temp-24-39-100-100.gif.ac69b5f767880b6e05d02edbc7124f25.gif

 

When I lived in LAF, we had a setup on 12/9/2007 (earlier I mentioned seeing thunder freezing rain on two occasions... this was one of them) that had a thick/very warm nose aloft but we were able to hang on to freezing/subfreezing temps at the surface for quite a while and received about a third of an inch of ice.  I don't think the warm nose back then was quite like this one as I don't believe 925 mb temps got that warm.  When you bring in 925 mb temps that are several degrees above freezing, it gets pretty hard to maintain the cold layer at the surface and even if you are at 32, the drops may have a hard time freezing even with lighter rates.

 

Share this post


Link to post
Share on other sites

There are so many variables to consider when figuring ice accretion and impacts...including air temp, antecedent conditions/ground temps, rain rate/drop temperatures, any other p-types mixing in.

For road impacts, air temps, road temps, and rain rate/temperature are all important...and stuff like this can be tricky.  For instance here in NW NJ, it was low 50s and sunny yesterday and 60 and sunny today.  But, our ground is still frozen and wet pavement was starting to freeze on my walk home with an air temp of 37 degrees.  It helps it's radiational cooling but is still impressive/surprising.  I know road temps in IL and IA today somehow got into the 40s, but you guys had two mild days after a brutally cold stretch, I'm guessing the ground is still mostly frozen...and it will be below freezing for about 24 hours before the ZR starts.  There will be some sun tomorrow so it's tough to figure pavement temperatures, though they likely won't be overly warm...likely awfully close to 32.

The airmass pressing in is decently cold and dry, but winds will be E when the ZR is ongoing and aside from the near shore waters Lake MI is well-above freezing.  Inland locales may hang on to 29-31 degree air for most of the ZR but the city and lakeshore will likely warm to 32-34 quickly owing to warm temps just aloft being dragged down by the heavy rates and a lack of sub-freezing air advecting in, due to the surprisingly warm waters in the middle of the lake. 

More than a few miles inland, mainly in Dupage, western Cook, inland Lake, McHenry, Kane, Dekalb (can extrapolate WSW a bit farther, and also perhaps into southern Walworth, Kenosha and Racine WI) there will be a narrow corridor that starts in the upper 20s when the ZR arrives and will take time to warm...and may not ever get above freezing well north of the surface low track.  The southern edge of this will be tricky because the warm layer is impressive so the drops will be warm with heavy rates...this will not accrete well if it's at or only slightly below freezing.  This is bracketed on the northern side by more sleet than ZR.  

Given the strong isentropic lift/WAA and some modest upright/convective instability during the heaviest precip, to go along with impressive PWATs of over 1", I can buy 0.50"+ of QPF (though over 0.75" will be a stretch IMO).  The lack of good cold/dry air advection and heavy rates, along with short duration, are arguments against a significant ice storm.  Given the heavy rates/warm drops on the southern fringe along with short duration and marginal surface temps, the modeled southern edge of the ice will likely be way too aggressive...I'd expect the more significant accretion to start 10-15 miles north of wherever the models have it, with the southern edge where it's marginal probably seeing a little glazing on some surfaces but much milder impacts.  This leaves a narrow corridor before it's more sleety to the north into WI (which will likely have its own travel impacts).  In that narrow corridor, drops won't be quite as warm due to deeper low-level cold and road temps may be cold enough for icing.  If the "normal" ice to liquid ratio of 1:2 is realized there would be enough QPF for a narrow corridor of tree damage, though with heavy rates and temps not that far below freezing the ratio may be worse than normal.  I think it's a narrow corridor that may actually see a legit ice storm with more severe travel impacts and tree damage...to the south, the heavy rates/warm drops along with marginal surface temps won't accrete well on trees or roads...this also goes for the city of Chicago and most of the immediate IL shoreline.  I like LOT/MKX not hoising an Ice Storm Warning yet...if they do (and I'd guess they will eventually if the expectation tomorrow afternoon is still for 0.50"+ QPF falling at or below 31 degrees) it will only be for a few counties. 

  • Like 9
  • Thanks 1

Share this post


Link to post
Share on other sites
3 hours ago, cyclone77 said:

Lol yeah I kind of like sleet when it's not at the expense of missing out on snow.  If the snow/sleet line were closer I'd definitely be rooting against sleet in that case.

I understand about sleet being frustrating when you are so close to a major thump, but like you said if it's not close, I'd chose sleet over ice any day. However, I have had some my best meltdowns here during multiple sleet storms. Well, maybe not as bad a meltdown as Beavis, but you know what I mean. All of that being said, the north shift is very pleasing to me, as looks like most of the ice stays north of the Hoosier state.

Share this post


Link to post
Share on other sites

LOT's Izzi on the evening update states concerns regarding an Ice Storm.....states concerns regarding T-storm potential. Good read for Chicago area folks.

Share this post


Link to post
Share on other sites
5 minutes ago, Baum said:

LOT's Izzi on the evening update states concerns regarding an Ice Storm.....states concerns regarding T-storm potential. Good read for Chicago area folks.

snippet from Izzi

 

Model guidance isn`t in perfect agreement on the placement of the
sfc freezing line and that has big implications on where the
greatest risk of icing will exist. Using the typically more
reliable models would lead me to believe that the great risk area
could be from Lee/Ogle/northern LaSalle counties east-northeast
into the western and northern suburbs of Chicago.

While I am concerned that there is a potential for ice accums of
at least 1/4" to 1/2", my confidence isn`t high enough in
placement or chance of occurrence to make any changes to going
headlines or forecast ice accums.

Share this post


Link to post
Share on other sites

To add on I thought this was interesting from the LOT update:

Quote
While I am concerned that there is a potential for ice accums of
at least 1/4" to 1/2", my confidence isn't high enough in
placement or chance of occurrence to make any changes to going
headlines or forecast ice accums. Will add a slight chance of
t-storms to the forecast for tomorrow night as I'm reasonably
confident that there will be some isolated to maybe scattered
t-storms around. Otherwise, plan to brief oncoming overnight shift
about these potential ice storm concerns and allow them a chance
to examine the full suite of model guidance and collaborate any
possible headline changes with neighboring offices, rather than
locking them in with any changes this evening. 

Looks like if we do see any warnings, it will be with the overnight updates.

Share this post


Link to post
Share on other sites
14 minutes ago, OHweather said:

There are so many variables to consider when figuring ice accretion and impacts...including air temp, antecedent conditions/ground temps, rain rate/drop temperatures, any other p-types mixing in.

For road impacts, air temps, road temps, and rain rate/temperature are all important...and stuff like this can be tricky.  For instance here in NW NJ, it was low 50s and sunny yesterday and 60 and sunny today.  But, our ground is still frozen and wet pavement was starting to freeze on my walk home with an air temp of 37 degrees.  It helps it's radiational cooling but is still impressive/surprising.  I know road temps in IL and IA today somehow got into the 40s, but you guys had two mild days after a brutally cold stretch, I'm guessing the ground is still mostly frozen...and it will be below freezing for about 24 hours before the ZR starts.  There will be some sun tomorrow so it's tough to figure pavement temperatures, though they likely won't be overly warm...likely awfully close to 32.

The airmass pressing in is decently cold and dry, but winds will be E when the ZR is ongoing and aside from the near shore waters Lake MI is well-above freezing.  Inland locales may hang on to 29-31 degree air for most of the ZR but the city and lakeshore will likely warm to 32-34 quickly owing to warm temps just aloft being dragged down by the heavy rates and a lack of sub-freezing air advecting in, due to the surprisingly warm waters in the middle of the lake. 

More than a few miles inland, mainly in Dupage, western Cook, inland Lake, McHenry, Kane, Dekalb (can extrapolate WSW a bit farther, and also perhaps into southern Walworth, Kenosha and Racine WI) there will be a narrow corridor that starts in the upper 20s when the ZR arrives and will take time to warm...and may not ever get above freezing well north of the surface low track.  The southern edge of this will be tricky because the warm layer is impressive so the drops will be warm with heavy rates...this will not accrete well if it's at or only slightly below freezing.  This is bracketed on the northern side by more sleet than ZR.  

Given the strong isentropic lift/WAA and some modest upright/convective instability during the heaviest precip, to go along with impressive PWATs of over 1", I can buy 0.50"+ of QPF (though over 0.75" will be a stretch IMO).  The lack of good cold/dry air advection and heavy rates, along with short duration, are arguments against a significant ice storm.  Given the heavy rates/warm drops on the southern fringe along with short duration and marginal surface temps, the modeled southern edge of the ice will likely be way too aggressive...I'd expect the more significant accretion to start 10-15 miles north of wherever the models have it, with the southern edge where it's marginal probably seeing a little glazing on some surfaces but much milder impacts.  This leaves a narrow corridor before it's more sleety to the north into WI (which will likely have its own travel impacts).  In that narrow corridor, drops won't be quite as warm due to deeper low-level cold and road temps may be cold enough for icing.  If the "normal" ice to liquid ratio of 1:2 is realized there would be enough QPF for a narrow corridor of tree damage, though with heavy rates and temps not that far below freezing the ratio may be worse than normal.  I think it's a narrow corridor that may actually see a legit ice storm with more severe travel impacts and tree damage...to the south, the heavy rates/warm drops along with marginal surface temps won't accrete well on trees or roads...this also goes for the city of Chicago and most of the immediate IL shoreline.  I like LOT/MKX not hoising an Ice Storm Warning yet...if they do (and I'd guess they will eventually if the expectation tomorrow afternoon is still for 0.50"+ QPF falling at or below 31 degrees) it will only be for a few counties. 

Nice writeup.  You laid things out nicely.

One thing I'd say about the lake temps is that while it's warm out toward mid lake, the progged low level flow just isn't very strong to advect that mid lake air toward the shore.  That is sort of a catch 22 though because a stronger tap into colder/drier air is generally more desirable in freezing rain setups.  That being said, I'd certainly bet on reduced impacts in the city proper due to what you mentioned about the heavy rates/warm drops and also some UHI. 

Share this post


Link to post
Share on other sites
9 minutes ago, Hoosier said:

Nice writeup.  You laid things out nicely.

One thing I'd say about the lake temps is that while it's warm out toward mid lake, the progged low level flow just isn't very strong to advect that mid lake air toward the shore.  That is sort of a catch 22 though because a stronger tap into colder/drier air is generally more desirable in freezing rain setups.  That being said, I'd certainly bet on reduced impacts in the city proper due to what you mentioned about the heavy rates/warm drops and also some UHI. 

That's a good point.  It will certainly be interesting to see what happens.  I think as is usually the case that accretion will be less significant/widespread than modeled due to a few negating factors, but there should be a narrow zone that is cold enough and gets enough freezing rain to be more problematic...just hard to avoid with the amount of QPF and some areas starting in the upper 20s. 

Share this post


Link to post
Share on other sites

The current cold air press out in the Plains seems a little more robust than progged.  This may not end up mattering down the line but perhaps could see an initial slightly southward displacement of the surface trough/wave?

  • Like 1

Share this post


Link to post
Share on other sites
7 minutes ago, HillsdaleMIWeather said:

0Z GFS accums are up too, more amped

Yuck! Since 06-07's constant ice we've had very little if any. We narrowly escaped Dec '13 by about 1/2 a county. We're actually over-due by all accounts. I just don't want to admit that we've been rolling the dice a long time and eventually snake-eyes are bound to show up..

Share this post


Link to post
Share on other sites
2 hours ago, OHweather said:

There are so many variables to consider when figuring ice accretion and impacts...including air temp, antecedent conditions/ground temps, rain rate/drop temperatures, any other p-types mixing in.

For road impacts, air temps, road temps, and rain rate/temperature are all important...and stuff like this can be tricky.  For instance here in NW NJ, it was low 50s and sunny yesterday and 60 and sunny today.  But, our ground is still frozen and wet pavement was starting to freeze on my walk home with an air temp of 37 degrees.  It helps it's radiational cooling but is still impressive/surprising.  I know road temps in IL and IA today somehow got into the 40s, but you guys had two mild days after a brutally cold stretch, I'm guessing the ground is still mostly frozen...and it will be below freezing for about 24 hours before the ZR starts.  There will be some sun tomorrow so it's tough to figure pavement temperatures, though they likely won't be overly warm...likely awfully close to 32.

The airmass pressing in is decently cold and dry, but winds will be E when the ZR is ongoing and aside from the near shore waters Lake MI is well-above freezing.  Inland locales may hang on to 29-31 degree air for most of the ZR but the city and lakeshore will likely warm to 32-34 quickly owing to warm temps just aloft being dragged down by the heavy rates and a lack of sub-freezing air advecting in, due to the surprisingly warm waters in the middle of the lake. 

More than a few miles inland, mainly in Dupage, western Cook, inland Lake, McHenry, Kane, Dekalb (can extrapolate WSW a bit farther, and also perhaps into southern Walworth, Kenosha and Racine WI) there will be a narrow corridor that starts in the upper 20s when the ZR arrives and will take time to warm...and may not ever get above freezing well north of the surface low track.  The southern edge of this will be tricky because the warm layer is impressive so the drops will be warm with heavy rates...this will not accrete well if it's at or only slightly below freezing.  This is bracketed on the northern side by more sleet than ZR.  

Given the strong isentropic lift/WAA and some modest upright/convective instability during the heaviest precip, to go along with impressive PWATs of over 1", I can buy 0.50"+ of QPF (though over 0.75" will be a stretch IMO).  The lack of good cold/dry air advection and heavy rates, along with short duration, are arguments against a significant ice storm.  Given the heavy rates/warm drops on the southern fringe along with short duration and marginal surface temps, the modeled southern edge of the ice will likely be way too aggressive...I'd expect the more significant accretion to start 10-15 miles north of wherever the models have it, with the southern edge where it's marginal probably seeing a little glazing on some surfaces but much milder impacts.  This leaves a narrow corridor before it's more sleety to the north into WI (which will likely have its own travel impacts).  In that narrow corridor, drops won't be quite as warm due to deeper low-level cold and road temps may be cold enough for icing.  If the "normal" ice to liquid ratio of 1:2 is realized there would be enough QPF for a narrow corridor of tree damage, though with heavy rates and temps not that far below freezing the ratio may be worse than normal.  I think it's a narrow corridor that may actually see a legit ice storm with more severe travel impacts and tree damage...to the south, the heavy rates/warm drops along with marginal surface temps won't accrete well on trees or roads...this also goes for the city of Chicago and most of the immediate IL shoreline.  I like LOT/MKX not hoising an Ice Storm Warning yet...if they do (and I'd guess they will eventually if the expectation tomorrow afternoon is still for 0.50"+ QPF falling at or below 31 degrees) it will only be for a few counties. 

What are you thinking out this way? Temps are colder here and stay colder longer. I am really actually surprised DTX didn't go with a watch especially since they were burned on a similar setup just a couple of weeks ago, and if anything this one looks to have more moisture with it.

  • Thanks 2

Share this post


Link to post
Share on other sites
1 hour ago, Hoosier said:

The current cold air press out in the Plains seems a little more robust than progged.  This may not end up mattering down the line but perhaps could see an initial slightly southward displacement of the surface trough/wave?

OUN just came out with this.  Does this have a domino effect downstream (even shifting things by 10-20 miles) or is it meaningless?  Time will tell.

 

Area Forecast Discussion
National Weather Service Norman OK
1025 PM CST Mon Feb 4 2019

UPDATE...
Corrected temperatures in prelim numbers below.

DISCUSSION...
As the 00z models come in, it looks more likely that the warm
front will not lift as far north as soon as earlier expected. The
GFS is still holding out some hope of the warm front lifting to
near the northern border, but NAM, HRRR, RAP all show colder air
lingering longer in the central and north. Have started the trend
downward with the forecast max temperatures for Tuesday. This
still may be a bit too high across the north and central, but will
let the overnight shift investigate that more thoroughly. There
will likely be a relatively tight temperature gradient somewhere
across the forecast area tomorrow, most likely from east central
to southwest Oklahoma, so there is definitely some high bust
potential depending on where the front ends up tomorrow afternoon.

Share this post


Link to post
Share on other sites
37 minutes ago, Stebo said:

What are you thinking out this way? Temps are colder here and stay colder longer. I am really actually surprised DTX didn't go with a watch especially since they were burned on a similar setup just a couple of weeks ago, and if anything this one looks to have more moisture with it.

Yeah, you start low to mid 20s with dews in the 10s advecting in, with no big "warm" lake immediately to your east.  Detroit likely won't get above freezing until the vast majority of the precip falls if at all, and there will be a period of good accretion initially.   I think warning criteria ice accretion is pretty likely, though will obviously have to watch obs and make sure that cold push gets in there as modeled...though it likely will given how cold/dense the airmass is.  Same interesting questions about pavement temps and also warm drops/heavy rates, though if your air temps are 22-25 when precip starts (along with a deeper layer of cold at the surface) you should have a period of good accretion off the bat on trees and also significant travel impacts. 

The 0z HREF is colder than my initial thoughts for Chicago/IL.  As OUN's AFD above indicates the higher res stuff is likely leading the way with the low-level cold air seepage.  The HREF routinely kicks all other guidance's ass (badly) with CAD here east of the Appalachians...this isn't CAD but if it's leading the way so far it's likely worth giving more weight.  It has easily over 0.25" QPF falling before temps get above 30 just west of Chicago (and would be problematic even south of the I-88 corridor).  The short duration, winds off the water limiting the supply of cold/dry air to offset the latent heat release of the icing and warm drops/heavy rates still give me pause for IL, but if the colder guidance is right there will be a narrow corridor that gets a decent accretion with some tree damage.  If you're getting 0.25-0.50" QPF with temps below 30 and some more with temps 31-32, even if it's pouring and not accreting as well as it could that's still a lot of QPF falling at a cold temp as ZR...would be pretty surprised if there aren't a few counties west of Chicago (and maybe Cook for the NW corner) that end up under a warning...but wouldn't be too ambitious expecting significant impacts where it's sitting at 31-32 on the southern edge.

  • Like 1

Share this post


Link to post
Share on other sites

It'll be interesting to keep track of this...through 5z the HREF mean is not aggressive enough with the southern push in the Plains, but is a little too quick with the eastern push into WI/IL.

metars.thumb.jpg.b29056cd284adb8cbb2d1bc7225f692e.jpg

sfct_mean.conus.f00500.thumb.png.2011c665673e4203a681d3bb0bd0e464.png

  • Like 1

Share this post


Link to post
Share on other sites

Hmm. The NAM-3km and the GFS both have over 0.25" of ice accumulation for Toledo, but, as of yet, there has been no W.W.A. or W.S.W. issued for the southern tier of counties in Michigan or I-80 tier of counties in Indiana and Ohio. Maybe they are holding off due to uncertainty in impact, possible temperatures above freezing.

Share this post


Link to post
Share on other sites
3 hours ago, Chinook said:

Hmm. The NAM-3km and the GFS both have over 0.25" of ice accumulation for Toledo, but, as of yet, there has been no W.W.A. or W.S.W. issued for the southern tier of counties in Michigan or I-80 tier of counties in Indiana and Ohio. Maybe they are holding off due to uncertainty in impact, possible temperatures above freezing.

IWX says they're not planning to issue ANY headlines

Share this post


Link to post
Share on other sites

Well good morning. I can officially say, this Winter has just about brought it all the QC. Blizzard, Snowstorms, Record Cold, Very mild, w/ tornadoes, and now waking up to an ice storm warning.

 

ice.png

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, ams30721us said:

Well good morning. I can officially say, this Winter has just about brought it all the QC. Blizzard, Snowstorms, Record Cold, Very mild, w/ tornadoes, and now waking up to an ice storm warning.

 

 

And also thundersnow with that blizzard back in Nov.  :snowing:

06z models and latest HRRR runs have scaled back quite a bit of precip for the DVN cwa.  May have a tough time getting more than a tenth or two of glazing if those models are correct.  

  • Like 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.