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April 20-21 late season snow potential


Hoosier
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1 hour ago, RCNYILWX said:

April 2019 showed well that very heavy rates overcome the August equivalent sun angle, so that's what we'll need to see continued support for to get noteworthy accumulations.
Looking back to those events, April 14th got going early before the peak sun angles to put down a good base of snow and keep the ground colder for continued accums under heavy rates.

April 27th didn't fully change over to snow until the afternoon and the rates were not as uniformly heavy, so overall road accums and impacts were less widespread than on April 14th.

For Tuesday it looks like the snow will have started by the morning, so that could point toward a more 4/14/19 like outcome *if* the heavy snow materializes.

I'm out of winter mode, so the only way this would be more tolerable is if ORD gets the amount needed to get to 50+" on the season.

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The wild card right now is on this side of the subforum, its mostly at night and a bit colder to boot. It could really be something if everything comes completely together.

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So, March and April 1923 were both colder than average.  That storm was on May 9.  When you compare this to the temperatures in March and April 2021, I'm not sure the leafout on May 9, 1923 would've been any farther along than it is currently.  Would be nice to see some pics from back then.

 

cd172_58_140_102_105_21.6_43_prcp.png.30fa60bf0f8b7b0540cb2d168673265c.png

 

cd172_58_140_102_105_21.7_35_prcp.png.0e706c93bff0093665e3bce8b42c97a1.png

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Do you have an early guess on what ratios may be like in the area?  It looks like the dgz is not particularly shallow and there is decent lift.  Obviously the marginal surface temps don't help but given what I mentioned above, I was thinking it may help to counteract the surface conditions to some extent so that maybe we end up with like 8:1 (maybe temporarily higher?) instead of something extremely waterlogged like 5:1? 
This would be an interesting case for ratios. BL temps look like they'd be 32-34 during the heaviest rates. 18z GFS Cobb output for actually showed raw snow ratios peaking at 11-16:1 due to the factors you mentioned, but little/no snow accumulation because surface temps never get below 34F. So I think something in the 8:1 range might be reasonable because you could end up with decent dendrites but the marginal surface temps knock down the effective ratio.

For the LOT CWA, the most recent operational solutions look less impressive than 4/14/19 from a large scale lift perspective. There could be decent low-mid f-gen but it might be more transient. Mid-upper lapse rates look good (7+C/km). PWATs are decent for a snow system peaking at ~0.6". This looks like a setup that could produce pockets of 2 to 4 inches of snow based off strongest banding placement and these areas could see some road impacts.

Downtown Chicago could see issues with accums for the same reason the recent November events didn't perform there, lake water temps are well into the 40s (52F today at Chicago shore), with a north-northeast wind direction forecast.

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49 minutes ago, Hoosier said:

So, March and April 1923 were both colder than average.  That storm was on May 9.  When you compare this to the temperatures in March and April 2021, I'm not sure the leafout on May 9, 1923 would've been any farther along than it is currently.  Would be nice to see some pics from back then.

 

cd172_58_140_102_105_21.6_43_prcp.png.30fa60bf0f8b7b0540cb2d168673265c.png

 

cd172_58_140_102_105_21.7_35_prcp.png.0e706c93bff0093665e3bce8b42c97a1.png

It was noted in the newspaper articles that vegetation was behind schedule so there was not excessive damage due to the storm. Here's a picture from grand circus park in Detroit, May 9, 1923

Screenshot_20210417-000010_Samsung Internet.jpg

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Buffalos biggest May storm:

1989

May 7th-8th…A late season snowstorm dropped up to twelve inches of snow across the western southern tier, Niagara Frontier and the Finger Lakes area. At Buffalo just under eight inches was recorded while at Rochester just over 10 inches fell. The snowfall established many new weather records for both cities. The snow covered the entire ten county area. The heavy, wet snow downed power lines and trees which took down more power lines when they fell. As lines fell, power poles were snapped. Nearly 13,000 customers were without electricity in much of Orleans and parts of northeast Genesee and western Monroe counties. Numerous scattered minor outages were also reported. Some roofs collapsed from the weight of the snow. Plows and salters were called out to clear roadways, though much of the snow was melting as it fell.

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53 minutes ago, RCNYILWX said:

This would be an interesting case for ratios. BL temps look like they'd be 32-34 during the heaviest rates. 18z GFS Cobb output for actually showed raw snow ratios peaking at 11-16:1 due to the factors you mentioned, but little/no snow accumulation because surface temps never get below 34F. So I think something in the 8:1 range might be reasonable because you could end up with decent dendrites but the marginal surface temps knock down the effective ratio.

For the LOT CWA, the most recent operational solutions look less impressive than 4/14/19 from a large scale lift perspective. There could be decent low-mid f-gen but it might be more transient. Mid-upper lapse rates look good (7+C/km). PWATs are decent for a snow system peaking at ~0.6". This looks like a setup that could produce pockets of 2 to 4 inches of snow based off strongest banding placement and these areas could see some road impacts.

Downtown Chicago could see issues with accums for the same reason the recent November events didn't perform there, lake water temps are well into the 40s (52F today at Chicago shore), with a north-northeast wind direction forecast.

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Yeah it's hard to imagine downtown not struggling more than farther inland.  As far as I can tell, mid lake water temps are in the mid 40s with warmer conditions closer to shore as you mentioned.  The airmass aloft looks cold enough for snow all the way to the shore but could envision it remaining 2-3 degrees above freezing there for much of the time.

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Yeah it's hard to imagine downtown not struggling more than farther inland.  As far as I can tell, mid lake water temps are in the mid 40s with warmer conditions closer to shore as you mentioned.  The airmass aloft looks cold enough for snow all the way to the shore but could envision it remaining 2-3 degrees above freezing there for much of the time.
The dreaded white rain lol. Speaking of ratios, looks like the WeatherBell Kuchera output is back on the juice.

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58 minutes ago, Hoosier said:

I have nothing to back this up but for some reason I have a feeling we are going to get a Euro run that goes a little nutty with widespread double digits or something.

The gfs and ukmet  went southeast clipping Detroit.  The Canadian was stronger than actually throws the biggest knows West to Detroit so I would expect the euro to have a blend and keep the 6-10 totals the 12z had.

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DVN point has snow going back to rain on Monday morning lol.  Pretty unfortunate that they seem to be forced into using some sort of blend and not issuing a correct/actual forecaster based forecast.  Pretty embarrassing really.

Tuesday
Rain and snow showers likely, becoming all rain after 10am. Mostly cloudy, with a high near 41. Chance of precipitation is 70%.
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IWX is indeed all in:

SPC UPPER AIR SOUNDING CLIMATOLOGY, CIPS ANALOGS AND GEFS M-CLIMATE RETURN 
INTERVAL ALL SUPPORT AN EVENT THAT MAY POSSIBLY BE CLASSIFIED AS A
50 YEAR OR 100 YEAR EVENT. A VERY STRONG ANOMALOUS SIGNAL WILL SET
UP TUESDAY. HAVE SIGNIFICANTLY UNDERCUT MODEL BLEND GUIDANCE GIVEN
DIABATIC PROCESSES TUESDAY INTO TUESDAY NIGHT. TEMPERATURES SHOULD
FALL DURING THE DAY TUESDAY WITH RAIN CHANGING TO SNOW. THE ECMWF
WHICH IS A LITTLE SLOWER THAN MOST OTHERS, REALLY BURIES NORTHWEST
INDIANA INTO LOWER MICHIGAN WITH 6" TO 10" OF SNOW. THE 2-DAY
RECORD SNOWFALL DURING THE SECOND HALF OF APRIL IS 9.9" IN 1961.
CURRENT THINKING IS 4 TO 8 INCHES OVER NW INDIANA WITH LESSER
AMOUNTS SOUTHEAST.
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34 minutes ago, IWXwx said:
IWX is indeed all in:

SPC UPPER AIR SOUNDING CLIMATOLOGY, CIPS ANALOGS AND GEFS M-CLIMATE RETURN 
INTERVAL ALL SUPPORT AN EVENT THAT MAY POSSIBLY BE CLASSIFIED AS A
50 YEAR OR 100 YEAR EVENT. A VERY STRONG ANOMALOUS SIGNAL WILL SET
UP TUESDAY. HAVE SIGNIFICANTLY UNDERCUT MODEL BLEND GUIDANCE GIVEN
DIABATIC PROCESSES TUESDAY INTO TUESDAY NIGHT. TEMPERATURES SHOULD
FALL DURING THE DAY TUESDAY WITH RAIN CHANGING TO SNOW. THE ECMWF
WHICH IS A LITTLE SLOWER THAN MOST OTHERS, REALLY BURIES NORTHWEST
INDIANA INTO LOWER MICHIGAN WITH 6" TO 10" OF SNOW. THE 2-DAY
RECORD SNOWFALL DURING THE SECOND HALF OF APRIL IS 9.9" IN 1961.
CURRENT THINKING IS 4 TO 8 INCHES OVER NW INDIANA WITH LESSER
AMOUNTS SOUTHEAST.

wow..they are all in!

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8 hours ago, Hoosier said:

Good stuff.  Thanks.

A lesser known, less widespread, but even more impressive snowfall hit May 21st 22nd 1883. It is by far the latest measurable snowfall Detroit. It appears that the accumulating snow was confined to Southeast Michigan and Ohio. Reports include 5" at Detroit, 3" at Toledo, and 1.5" at Cincinnati. Due to this being in the early days of weather records there is not too much written about the storm other than what was the newspaper's, but it was noted that the snow did cause damage to the fully leafed trees.

 

Detroits top 10 largest post-Apr 20 snowfalls on record...140 years of record...indeed this could be historic.

6.0" - May 9, 1923

5.0" - May 21/22, 1883

4.3" - Apr 23/24, 2005

3.0" - Apr 29, 1909

1.7" - Apr 23/24, 1967

1.5" - May 13, 1912

1.2" - Apr 20, 1947

1.0" - Apr 22, 1911

0.5" - May 10, 2020

0.5" - Apr 20, 1943

0.5" - May 10, 1902

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1 hour ago, IWXwx said:
IWX is indeed all in:

SPC UPPER AIR SOUNDING CLIMATOLOGY, CIPS ANALOGS AND GEFS M-CLIMATE RETURN 
INTERVAL ALL SUPPORT AN EVENT THAT MAY POSSIBLY BE CLASSIFIED AS A
50 YEAR OR 100 YEAR EVENT. A VERY STRONG ANOMALOUS SIGNAL WILL SET
UP TUESDAY. HAVE SIGNIFICANTLY UNDERCUT MODEL BLEND GUIDANCE GIVEN
DIABATIC PROCESSES TUESDAY INTO TUESDAY NIGHT. TEMPERATURES SHOULD
FALL DURING THE DAY TUESDAY WITH RAIN CHANGING TO SNOW. THE ECMWF
WHICH IS A LITTLE SLOWER THAN MOST OTHERS, REALLY BURIES NORTHWEST
INDIANA INTO LOWER MICHIGAN WITH 6" TO 10" OF SNOW. THE 2-DAY
RECORD SNOWFALL DURING THE SECOND HALF OF APRIL IS 9.9" IN 1961.
CURRENT THINKING IS 4 TO 8 INCHES OVER NW INDIANA WITH LESSER
AMOUNTS SOUTHEAST.

What a turn of events this would be. Can't do nothing but laugh 

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8 hours ago, RCNYILWX said:

Here's the reasonably realistic looking Kuchera output from Pivotal. 130ab70186afaa39d8eb6ac443ff2ce9.jpg&key=ead97d18a6325acd344b2e5b3516af2de00043bb63d155d7fc604027bf0096c2

 

 

 

Late season lock it in for South Bend, please. Last year we had about 3” on 4/17/20 and I thought that was really amazing. A beautiful, wintry scene around 11 am. Then it looked like spring again by 4 pm. 

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