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April 13-15 Snow Threat


Hoosier

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Multiple models have been hinting at it for a while and the 12z GFS is bullish.  Run to run model consistency could be better but it's still several days away.  Unclear how big of a snow maker this may be but I'd argue that the threshold for "significant" is much lower in the middle of April unless you're in the far northern tier.

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Yeah what a run on the GFS. Can actually see the front crash and the lakes influence over northeast IL looking at sfc temps valid 18z Sun and how it stays colder east of 39 and just stays cold. 

 

LOTS of gulf moisture/precip with great gulf trajectories for something significant if the cold air is there. 

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Yeah what a run on the GFS. Can actually see the front crash and the lakes influence over northeast IL looking at sfc temps valid 18z Sun and how it stays colder east of 39 and just stays cold. 

 

LOTS of gulf moisture/precip with great gulf trajectories for something significant if the cold air is there. 

 

 

One thing that bothers me in terms of realizing big amounts is that the 700 mb/500 mb lows remain open for the most part on the models.  I don't know for sure but I would suspect that most spring snowstorms have well defined/closed lows.  Can we get away with not having that in mid April? 

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Marginal temps near the lake off sounding data. Daytime event too, which would cut into rates...

 

 

 

Classic Geos...

 

Heaviest precip from 9-15z isn't quite a daytime event either this run. 

 

Here is even a 15z UGN sounding off this run. No problems at all, and 850s even cool throughout the day so don't really get what you're seeing.

 

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One thing that bothers me in terms of realizing big amounts is that the 700 mb/500 mb lows remain open for the most part on the models.  I don't know for sure but I would suspect that most spring snowstorms have well defined/closed lows.  Can we get away with not having that in mid April? 

 

Not sure, would have to look. But the gulf is wide open seen in the QPF amounts and the Euro has shown it with some runs too. 

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Classic Geos...

 

Heaviest precip from 9-15z isn't quite a daytime event either this run. 

 

Here is even a 15z UGN sounding off this run. No problems at all, and 850s even cool throughout the day so don't really get what you're seeing.

 

attachicon.gifugn sounding.gif

 

I was just going off of the twisterdata sounding I found. 

 

Temps should be warmer near the lake since the lake is cracking 40° now.

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I will be very curious to see where this exactly lines up, the GFS has been a bit inconsistent with location. Surprisingly the GGEM has been very consistent on a hit from Northern IN to Toronto following the favored path this winter, which the GFS did show on the 00/06z before shifting significantly west. The thing that worries me is the same thing Hoosier mentioned, the mid and upper lows do not close off and to be honest temperatures are not the best with this one especially at 850mb. Ideally you'd like temperatures at 850mb to be -4 or lower which they really aren't in WI, northern lower MI they are but the majority of snowfall occurs during the day time there. Yes, it can snow and stick during the daytime but you really need some good snowfall rates to allow that to happen. It will be interesting to see if we can lock in on a location with this one as there is a potential of a decent late season hit for someone the key will be the speed of the CAA.

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To all the 'non-eventers' want to give some reasoning or you guys just going to pass through trolling. I mean I honestly don't think this is a big event outside of the fact that it is mid April but at least I gave some quantitative reasoning as to why I think there are some limited factors. I didn't just mindlessly post 'non-event' and moved on.

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If I'm doing this right, Chicago has only had 7 one inch snows or greater from April 14 or later (includes 2 in May)...so it's been almost a once in 20 year occurrence.  The last time it happened was on April 14-15, 1980.

 

 

Note:  3.0" fell on April 11, 2007

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To all the 'non-eventers' want to give some reasoning or you guys just going to pass through trolling. I mean I honestly don't think this is a big event outside of the fact that it is mid April but at least I gave some quantitative reasoning as to why I think there are some limited factors. I didn't just mindlessly post 'non-event' and moved on.

100% agreed!

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poor run to run consistency, poor model consensus, 100 hrs out, marginal thermals, and terrible mid-april snow climo.

 

i'm pumped

 

 

That last point especially. I've only experienced one accumulating April snow after the 10th.

Plus only 0.5" in the last 5 weeks, doesn't sway me to saying this will be noteworthy event.

 

Another thing going against anything significant is rising soil temperatures.

 

http://www.greencastonline.com/tools/SoilTempMaps.aspx

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THROUGH THE REGION. THIS WILL THEN PLAY INTO PRECIP TYPE AS A

RETURN TO WELL BELOW NORMAL TEMPS WILL BE LIKELY NEXT WEEK...WITH

SOME POTENTIAL FOR EITHER A RAIN SNOW MIX OR EVEN ALL SNOW BOTH OF

WHICH APPEAR TO BE POSSIBLE MULTIPLE TIMES DURING THIS PERIOD.

NOOOOO!!!!!!

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Sorry to say Geos :P...but it looks like someone will be seeing several inches of snow with this. The band placement changes run to run, model to model, but consensus for someone to get a mid-April snowstorm is quite high at this stage. BTW...rates make all the difference this time of year. If you get heavy snow, it would stick in June :lol:

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One thing that bothers me in terms of realizing big amounts is that the 700 mb/500 mb lows remain open for the most part on the models.  I don't know for sure but I would suspect that most spring snowstorms have well defined/closed lows.  Can we get away with not having that in mid April? 

 

At the same time, these tight temperature gradients can produce some pretty impressive frontogenesis precipitation.

 

How much of that is snow depends on how much/fast the cold air advects in and how strong the secondary piece of energy is.

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I can understand why some would have their doubts about this event.

 

The fact is what the GGEM/GFS shows is not a climatologically favorable event, which is good enough reason for doubt. Not to mention the fact that it's still 120 hours out AND that these secondary lows typically don't work out.

 

That said, to declare it a non-event this far out is also laughable. Those folks will be the very ones lucky enough to shovel out of 15" of cement.

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Sorry to say Geos :P...but it looks like someone will be seeing several inches of snow with this. The band placement changes run to run, model to model, but consensus for someone to get a mid-April snowstorm is quite high at this stage. BTW...rates make all the difference this time of year. If you get heavy snow, it would stick in June :lol:

 

So does flake size.

 

It will be much easier to get those golf ball-sized dendrites falling at 1"+ per hour rates to accumulate than the pixie dust/spitting snow at 1"+ per hour rates.

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If I'm doing this right, Chicago has only had 7 one inch snows or greater from April 14 or later (includes 2 in May)...so it's been almost a once in 20 year occurrence.  The last time it happened was on April 14-15, 1980.

 

 

Note:  3.0" fell on April 11, 2007

Chicagos numbers are surprisingly low.

 

Detroit 1"+ snowstorms on or after April 14th. Several more instances had amounts under an inch as well, and several others were 1"+ a day or two before April 14th.

 

May 21/22, 1883...5.0"

April 14/15, 1885...1.5"

April 15, 1893........2.5"

April 14/15, 1904...1.6"

April 29, 1909........3.0"

April 22, 1911........1.0"

May 13, 1912........1.5"

April 17, 1921........4.5"

April 14, 1923........2.2"

May 9, 1923...........6.0"

April 16, 1943........2.0"

April 19/20, 1943...3.5"

April 16, 1947........1.9"

April 19/20, 1947...1.6"

April 16/17, 1961...3.0"

April 23/24, 1967...1.7"

April 14/15, 1980...1.3"

April 17, 1983........3.4"

April 23/24, 2005...4.3"

April 18, 2011........1.6"

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So does flake size.

 

It will be much easier to get those golf ball-sized dendrites falling at 1"+ per hour rates to accumulate than the pixie dust/spitting snow at 1"+ per hour rates.

Yes. Its something that really doesnt matter in winter...but in April it does. If you recall, a majority of our accumulation on April 24, 2005 occurred from 10am to 3pm in heavy snow.

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