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December 25-29th Storm Disco


Chicago Storm

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With the way the models are bouncing around it's definitely gonna take another day or two to pin down the best glazing potential.  A lot of the precip forecast displays from various models indicate more sleet than freezing rain in the transition areas, but those probably aren't the most accurate.  

 

The lack of snow cover over most of the region is a bit of a concern.  Snow cover can help delay WAA to some extent at the surface, but we won't have that pretty much anywhere in the impact area.  The only tool to maintain a subfreezing surface layer is the dry easterlies on the south side of that big high pressure.  

 

Whatever glazing we get will probably be significantly less than what we would have received if a substantial snow pack was in place region wide.

 

I'm thinking for most of us it will be either sleet or rain.

 

 

Thanks...and good point about lack of snowcover. 

 

Just going to post this as an example...here's a forecast sounding for South Bend at 18z Monday.  Besides the ridiculous low level winds, look at the temperature profile.  It has sfc temps a little above freezing but about -2C as close up as 950 mb and colder just above that.  Also note that the lowest km still has winds out of the east.  I guess I'm wondering how realistic that is or if it would be more like 31-32 at the surface given those temps just off the deck. 

 

post-14-0-12228300-1451115570_thumb.png

 

 

One thing is for sure...a couple degrees colder and this would get extremely ugly.  I guess you can say that about a lot of ice setups though.

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE ST LOUIS MO

247 AM CST SAT DEC 26 2015

.SHORT TERM: (Through Tonight)

Issued at 245 AM CST Sat Dec 26 2015

Confidence continues to increase that a high impact and

potentially historic flooding event will unfold this afternoon

through Monday. Life threatening flash flooding along

creeks/streams and other low lying areas is expected, along with

major to historic flooding on area rivers. The forecast itself has

not changed much at all with widespread rainfall amounts of 4-8

inches across the southeast half of the CWA. There was a slight

northwest adjustment to the heaviest axis of rainfall in the 00Z

guidance, but this did not impact headlines.

Showers and thunderstorms are quickly developing to our southwest

and advecting northeast toward the CWA as the warm front begins to

lift north. Believe coverage will become widespread by this

afternoon as a perfect recipe for heavy rainfall aligns overhead.

Key feature is a back building anticyclonically curved upper level

jet that will enduce an ageostrophic response, increasing

frontogenesis and therefore upward vertical motion. The focused

forcing and flow aloft parallel to the frontal zone, favors training

convection. Can`t rule a few strong or severe storms occuring this

afternoon and evening along and south of the front as well. The

heaviest rainfall from this prolonged event will occur from this

afternoon through Sunday morning with a broad area of 3 to 5 inches

occurring. The convective nature of this precipitation could

produce locally higher amounts, especially if training persists.

CVKING

.LONG TERM: (Sunday through Friday)

Issued at 245 AM CST Sat Dec 26 2015

The front should sag south on Sunday, shifting the axis of

heaviest rainfall to the southern third of the CWA.

The final wave of potentially heavy rainfall will occur Sunday night

into Monday as a strong closed upper low and the associated

vertically stacked system lifts north/northeast through the middle

Mississippi River Valley. Due to the warm air aloft and track of the

system, believe the prospect of any wintry preciptiation remains

very low. Generally have painted another 1 to 3 inches of rain with

the system itself to come up with event total rainfall amounts of 4

to 8 inches.

 

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FWIW, I was poking around on the CIPS site using various domains and came across 12/3/1990.  Anyone remember that storm? 

 

 

Madison got 17 inches out of that one.Day time storm. Traffic was snarled to say the least!

 

But system was more of an open wave not a slow moving cut off coming out like this one. .Fear this one will have too much sleet to get a that kind of snow in Madison.,GFS 000Z track however encouraging!

 

There was supposed to be an earth quake in the mid west that day to rival one in 1816.Instead we got 17 inches of snow.

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New LOT AFD offering reasoning for a west track.

 

LAST EVENINGS RAOBS INDICATED A STRONG JET STREAM MAXIMUM OF AROUND

150 KT DIGGING SOUTH ACROSS THE WESTERN U.S. WHICH WILL CUT OFF A
CLOSED LOW ACROSS THE DESERT SOUTHWEST/MEXICO BORDER BY TONIGHT.
THIS WILL EVOLVE NORTHEAST IN RESPONSE TO ANOTHER JET MAXIMUM
DIGGING UPSTREAM. A CUTOFF FEATURE SUCH AS THIS LOW AND BEING
FAIRLY FAR SOUTH IN LATITUDE TENDS TO END UP BEING SLOWER THAN A
MEAN MODEL SOLUTION AND WE HAVE SEEN THAT OVER THE PAST COUPLE
MONTHS WITH SYSTEMS LOCATED EVEN FURTHER NORTH. SUCH A SLOWER
EVOLUTION WOULD RESULT IN A FURTHER WEST TRACK AS THE SYSTEM LIFTS
NORTHEAST WHICH IS ADVERTISED BY THE PREFERRED EC...NAM...AND
SREF MORE SO THAN THE GFS...ITS ENSEMBLE...AND THE GEM. THE
OVERALL TREND IN A MEAN OF ALL THESE GUIDANCE HAS ALSO SHIFTED
SLIGHTLY SLOWER AND FURTHER WEST WITH THIS SYSTEM...FURTHER
SUPPORTING LEANING THIS ROUTE. IN ADDITION...THE STRONG CANADIAN
HIGH PRESSURE OVER THE NORTHERN PLAINS THAT COULD OFFER SOME
BLOCKING AND SUPPORT A FURTHER EAST TRACK IN THE LOW IS TRENDING
SLIGHTLY FURTHER NORTH...AGAIN FAVORING LEANING WEST.

 

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