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January 30-February 3rd Wave Train Part 2


Chicago Storm

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I guess the main concern would be if the WAA is underdone as has happened countless times. It's going to be an interesting battle...will the heavier precip rates keep it as snow in areas that are borderline.

Good points. One good example of the heavier rates keeping it as snow was the 2/7/13 paste bomb in northeast IL and southeast WI. Though there was some contribution from wetbulbing/evaporational cooling in that event in addition to excellent dynamic cooling via lift from the fgen and large scale lift from the upper trough. That was more of a marginal set-up than tomorrow aloft and at the surface.

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Well for what it's worth the day before the the big rainstorm on 1/10 and huge icing problem in parts of northern Illinois, the high was 25 at RFD. So it did start moderating, though the low that morning was -13. I think it's a concern for your area despite the moderation the past 2 days since it hit -13 a few mornings ago and -1 the next morning. After what happened on 1/10, I can say that was definitely discussed at the office yesterday as a big concern in our southern areas.

Yeah, I was thinking about that event as well. Thanks for the post!

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Iced over roads and salt washed away.

 

This was definitely a factor for us on 1/10. Throughout that evening, when precip rates went down, the salt they were spreading stuck around and was doing its thing. Under heavier showers the salt simply washed away and surfaces continued to ice.

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   Hoosier,

 

   3 Fridays ago, we were 33-34 and while the roads turned into water-covered skating rinks, there was zero accretion on twigs, cars, buildings, nothing.  If it was touching the ground itself, it was frozen.   Any elevation and it just dripped right off.   In fact, I don't recall any crust on the scraggly snow that was left.  But if you plowed a parking lot beforehand, you had a skating rink.  

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Just looking at 12z NAM thermal profiles, we're getting a little too close for comfort here. 775mb layer gets to 0 at the peak of the storm and 850s are hovering around 0.5. I've got to imagine the GFS is pretty similar, but will wait for text output before making any conclusions. Still snow, but very, very close to the pingers.  :yikes:

 

I'm also going to pin the ratios on this at about 8-9:1. So 5-8 is a good forecast for LOT as it stands.

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This was definitely a factor for us on 1/10. Throughout that evening, when precip rates went down, the salt they were spreading stuck around and was doing its thing. Under heavier showers the salt simply washed away and surfaces continued to ice.

Just heard that road temps in IN on the INDOT road sensors are not too cold, so hopefully above freezing icing won't be as big a problem this time.

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LOT

 

IT APPEARS THAT A HEAVY BAND OF SNOW WILL SET UP ACROSS  
NORTHERN ILLINOIS...FROM JUST NORTH OF THE TRANSITION LINE...TROUGH  
THE NORTHERN SUBURBS OF CHICAGO. A QUICK LOOK AT MODEL DERIVED CROSS  
SECTIONS INDICATE FAVORABLE CONDITIONS FOR HEAVY SNOW. THE MOST  
NOTABLE IS THE STRONG BAND OF MID LEVEL FRONTOGENESIS WITHIN  
PROXIMITY TO A DECENT LAYER OF NEGATIVE EPV. SIMILARLY...MODEL  
SOUNDINGS SHOW VERY STEEP MID LEVEL LAPSE RATES THROUGH THE  
DGZ...WITH EVEN A LITTLE CAPE NOTED FOR PARCELS LIFTED ABOVE 650 MB.  
GIVEN THE STRONG FORCING FOR ASCENT WITHIN THE BAND OF STRONG  
FGEN...WE COULD SEE SOME SNOW RATES AROUND AN INCH PER HOUR FOR AT  
LEAST A COUPLE HOURS SATURDAY MORNING AND PERHAPS SOME LIGHTNING  
AS WELL. ADDITIONALLY...THE LIKELIHOOD OF A NEARLY ISOTHERMAL  
LAYER BETWEEN THE SURFACE AND 700 MB AROUND 0 TO -4 DEGREES  
CELSIUS...SUGGESTS THE GOOD POSSIBILITY OF GOOD AGGREGATION OF  
SNOW FLAKES...WHICH WOULD ALSO SUPPORT HEAVY SNOW.
ALL IN ALL...WE  
HAVE DECIDED TO UPGRADE ALL OF NORTHERN ILLINOIS...BASICALLY ALONG  
AND NORTH OF I-80 TO A WINTER STORM WARNING FOR MAINLY HEAVY SNOW.  
THE HEAVIEST SNOW AREAS COULD RUN IN THE 6-10 INCH RANGE BY  
SATURDAY AFTERNOON. HOWEVER...A WINTER MIX IS POSSIBLE ALONG THE  
I-80 CORRIDOR ON SATURDAY MORNING...SO AMOUNTS COULD BE TAMPERED  
SOME THERE. THE ONLY EXCEPTION TO THE WARING UPGRADE IS ACROSS  
WINNEBAGO AND BOONE COUNTIES ACROSS NORTH CENTRAL ILLINOIS...WHERE  
AMOUNTS MAY REMAIN JUST UNDER 6 INCHES. FOR THESE TWO COUNTIES WE  
WILL GO TO AN ADVISORY.  

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TWC Video on this storm. Their in house model only has DTW mixing for few hours and is mostly snow. Same areas that were in sweet spot for jan 5th storm here in MI, in it with this one. Odd too that the structure and movement of the bands in this storm look similar to jan 5th also. No real wound up storm but still fairly strong

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