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March 11-12th Winter Storm


Chicago Storm

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LOT...

 

SEVERAL CHALLENGES SURROUND THIS EVENT...THE FIRST OF WHICH ARE
PRECIP TIMING AND TEMPERATURE TRENDS. DESPITE THE PASSAGE OF THE
COLD FRONT TONIGHT HIGHS TUESDAY LOOK TO BE MILD WITH A RANGE FROM
AROUND 40 NORTH TO THE MID 50S FAR SOUTH. THE INITIAL AREA OF WARM
ADVECTION PRECIP WILL BE TO THE NORTH OF THE AREA THROUGH MUCH OF THE
DAY BUT THEN DEVELOP OR MOVE INTO THE NORTHERN CWA LATE IN THE
AFTERNOON. FORECAST SOUNDINGS SHOW ENOUGH DRY AIR TO ALLOW FOR
EVAPORATIVE COOLING TO THE POINT WHERE RAIN WOULD TRANSITION MIXED
PRECIP THEN QUICKLY TO SNOW. THE STRONGEST FORCING ARRIVES DURING
THE EVENING...ESPECIALLY DURING THE MID AND LATE EVENING AS THE
UPPER TROUGH DEEPENS. GIVEN THE MID LEVEL TEMP GRADIENT AND THE
EVOLUTION OF THE SYSTEM STRONG FRONTOGENETIC FORCING IS EXPECTED
DURING THE MID EVENING INTO THE OVERNIGHT HOURS. THE STRONG FORCING
AND STRENGTHENING OF THE SYSTEM WILL ALLOW FOR THE COLUMN TO COOL TO
PROVIDE A FAIRLY QUICK CHANGE OVER TO SNOW FROM NORTH TO SOUTH
THROUGH THE EVENING. FORECAST CROSS SECTIONS ALSO SHOW THE IDEA OF
AT LEAST LOWERED...IF NOT NEGATIVE STABILITY ABOVE THE ORGANIZED
FGEN ASCENT LEAVING THE POTENTIAL FOR CONVECTIVE BANDING. THE BEST
FORCING DOES MOVE THROUGH QUICKLY WHICH WILL LIMIT HOW MUCH OF THE
0.8 INCH PRECIPITABLE WATER VALUES THAT WILL BE REALIZED BUT THE
SIGNALS FOR BANDING/INTENSE PRECIP ARE CONCERNING. THE LOW TRACK
VARIES AMONG GUIDANCE AND GIVEN THAT THE UPPER FLOW PATTERN WILL BE
EVOLVING/PHASING BETWEEN NOW AND TOMORROW EXPECT TO SEE GUIDANCE
FLUCTUATE FURTHER. THIS WILL ULTIMATELY HELP DICTATE HOW FAR NORTH
MORE SIGNIFICANT PRECIP AMOUNTS WILL OCCUR WITH THE LATEST TRENDS
SHOW A MORE NORTHERLY TRACK PUTTING MORE OF THE AREA AT RISK. IN
TERMS OF AMOUNTS...WITH THINGS TRENDING FURTHER NORTH HAVE INCREASED
SNOW AMOUNTS ACROSS THE AREA. GIVEN ALL OF THE ABOVE THESE MAY
CHANGE FURTHER...WITH TOTAL AMOUNTS HINGING ON HOW QUICKLY A
TRANSITION TO SNOW OCCURS...ESPECIALLY FOR FAR SOUTHERN AREAS. WITH
THE STRENGTH OF FORCING INTENSE SNOWFALL RATES ARE LIKELY WHERE
BANDS FOCUS AND TURN TO SNOW. RIGHT NOW AREAS ALONG AND SOUTH OF
INTERSTATE 80 ARE FAVORED FOR THE GREATEST AMOUNTS. FAR SOUTHERN
AREAS SOUTH OF A PONTIAC TO RENSSELAER LINE WILL BE TRICKY AS THEY
WILL TAKE LONGEST TO CHANGE OVER AND MAY SEE REDUCED AMOUNTS AS A
RESULT.

HEADLINE REASONING...MANY AREAS MAY ULTIMATELY SEE AN ADVISORY LEVEL
EVENT BUT THERE IS SOME POTENTIAL FOR WARNING CRITERIA SNOWS WHICH
COULD FALL IN A SHORT AMOUNT OF TIME. THEREFORE DO NOT FEEL GOING
RIGHT TO AN ADVISORY IS THE BEST OPTION AT THIS POINT. AFTER
COORDINATION WITH NEIGHBORING OFFICES WILL HOIST A WINTER STORM
WATCH FOR THE SOUTHEAST THIRD OR SO OF THE AREA OR FROM PORTER
SOUTHWEST TO LAKE...KANKAKEE...AND LIVINGSTON COUNTIES AND POINTS
SOUTH. DEBATED INCLUDING AREAS A LITTLE FURTHER NORTH FROM THE
SOUTHERN CHICAGO METRO BACK TO OTTAWA/MENDOTA BUT DO NOT HAVE ENOUGH
CONFIDENCE IN ENOUGH OF A NORTHWARD SHIFT WITH UPCOMING RUNS TO DO
THIS AT THIS POINT. OVERALL ITS A MINIMAL CONFIDENCE WATCH. 

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Not saying the current very amped up 18z run of the NAM is right, but the last somewhat similar southwest type system to impact the area on 2/4-2/5 ended up farther northwest with good snows than the globals had been advertising and the NAM didn't do a bad job with it.

Sent from my SCH-I535 using Tapatalk

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DTX warning area is terrible.... What model indicates a real difference between Flint and Detroit right now?

If you looked at the euro, you wouldn't think they even issue watches north of 94. While the NAM is probably way too far NW, most people didn't believe (including me) the 18z NAM yesterday. Todays 12z NAM/GFS/RGEM all came north and looked closely identical to yesterdays 18z NAM.

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Not saying the current very amped up 18z run of the NAM is right, but the last somewhat similar southwest type system to impact the area on 2/4-2/5 ended up farther northwest with good snows than the globals had been advertising and the NAM didn't do a bad job with it.

Sent from my SCH-I535

 

Higher-resolution models should have a better handling of the system compared to the globals, correct? You would think at least..

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In all seriousness, I think the answer lies somewhere between the NAM and the Euro, probably closer to the Euro. The GFS actually is pretty close to my expectation right now.

 

euro has been pretty consistent about 2 factors over the last 5 or 6 runs:   1) placement of snow axis, running from central IL thru northern OH.   2) the heaviest snow is really not that heavy, (relatively speaking, highest amounts not much more than 6" until it gets east of the subforum).   

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Looked at the Euro a bit ago again.  It looks a bit strange to me how it blows up so much precip relatively close to the low.  With very little in the way of banding further north deeper into the cold sector.  Almost looks like convective feedback to me, with so much heavy precip pretty close to the low. 

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Higher-resolution models should have a better handling of the system compared to the globals, correct? You would think at least..

I don't know if I'd say better handle because it's hard to put a lot of trust in a NAM run even at this range. With that being said I think the Euro and GGEM are too far south and specifically the Euro has been too low on QPF here with some recent snow events, as pointed out by cyclone may be an issue with northern extent of cold sector qpf on Euro. The answer probably does lie in between the 2 extremes and 3-6" is more of what I'm expecting for the Chicago metro.

Using the location of the upper level potential vorticity anomaly hook which has worked in other events this winter to foretell more of a northwest track of the surface low does offer that possibility here as well when looking at the 250 mb PVU surface on the 12z GFS and the 12z UKMET.

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That must be another member in my area. Maybe Tuanis did.

 

I've seen enough. I'm enjoying the melt & warmer temperatures. My house is ready to be done with the snow & cold.

Unfortunately my gut tells me this is coming north from what the euro is showing.

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