Rare May snowstorm bringing heavy snows from Colorado to Wisconsin

By: Dr. Jeff Masters , 2:42 PM GMT on May 01, 2013

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"Not the typical May forecast." That's the lead-in for today's National Weather Service forecast discussion for Minneapolis, where Winter Storm Achilles is expected to bring 6 - 9" of snow by Thursday morning. Snowfall rates as high as 1 - 3" per hour may occur in snow bands in East Central Minnesota this afternoon, and an 8 - 10" swath of snowfall is expected from South Central Minnesota into East Central Minnesota and West Central Wisconsin. With ratios of snow to liquid water an exceptional 5:1 or even 4:1 (normal is 10:1), the wet, heavy snow will be capable of downing power lines and tree limbs. However, the ground is warm, and accumulation on roads will be less of a problem than for the usual storm of this magnitude. The storm has already brought 7.3" of snow to Cheyenne, Wyoming, and 12 - 14" to locations 10 - 15 miles to the WNW of Cheyenne. Cheyenne's greatest May snowstorm on record was 18.3" on May 5 - 6, 1978. Denver, Colorado is expected to get 3 - 6" of snow from the storm; Boulder, Colorado has already received 8" of snow, Fort Collings got up to 9", and up to 28" has fallen in the Northern Rocky Mountains of Colorado.


Figure 1. Snow plasters trees in Fort Collins, Colorado, on May 1, 2013. Up to 9" of snow has fallen on Fort Collins from the storm. Image credit: wunderphotographer pkkeya.

A historic May snowstorm for some locations
According to the Minnesota Climatology Working Group, the greatest May snowstorm in Minneapolis is 3" on May 20, 1892, so today's winter storm has the potential to be the greatest May snowstorm in city history.

The 1.5" of snow that fell on Sioux Falls, South Dakota this morning was that city's first May snowfall since 1976, the first May snowfall of greater than one inch since 1944, and the 3rd highest May snowfall on record.

On Thursday, after the cold front from Achilles passes through Topeka, Kansas, up to one inch of snow is forecast to fall. May 3, 1907 was the only measurable snowfall at Topeka on record (3.2") during the month of May!


Figure 2. Snow on a Deserted Street in Dawson, Minnesota in Lac Qui Parle County on May 20, 1892. The storm brought Minneapolis its greatest snowfall on record, 3.0". Image courtesy the Minnesota Historical Society.

Jeff Masters

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Member Since: July 15, 2006 Posts: 174 Comments: 54434
Quoting Levi32:


Well look at it. The entire southern hemisphere has all of the anomalously warm water. It's ridiculous.





CFS is crazy?
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Quoting CybrTeddy:


I actually don't think this year might be a huge threat to the US East Coast unlike the last three seasons. Given there's some similarities between 2004 and 2007 with this hurricane season as I discussed a few days ago, I personally believe as your graph also indicates that the Caribbean islands, Mexico, and the Gulf Coast are the highest risks this year. To be honest, if I had to pick a US state.. I'd go with Florida or Texas this year.

That being said, these predictions and conditions are utterly meaningless if we don't get a storm at the right time with the right conditions. Remember when Isaac looked like it would clock Florida as a Category 2 hurricane? Didn't happen - instead it hit Louisiana just after becoming a Category 1.
Hard to avoid the east coast with a -PDO signal. -PDO largely explains why the east coast has been on the table the last few years.

I'd agree with a central American/Mexico threat and the Caribbean islands, which are always threatened. Wouldn't agree with Texas though. Anomalous ridging in the west means it's going to be hard to send a storm there. Just this Spring we've continued to see the cold poor into Texas and the SE. Should such a similar pattern continue it would be hard for a storm to make it into Texas. Of course, there's always the possibility, but that just doesn't sound like a favored track to me at the moment. Below I plotted the 500mb height anomaly for the days before during and after a hurricane made landfall along or near the Texas coastline. The storms I chose are Hurricane Alex (2010), Hurricane Alicia (1982), Hurricane Allen (1980), Hurricane Bret (1999), Hurricane Claudette (2003), and Hurricane Ike (2008).





The last two months have seen the exact opposite pattern...


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Quoting hurricanes2018:
Doubles
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Member Since: July 15, 2006 Posts: 174 Comments: 54434
Quoting FunnelVortex:


It's THEIR summer!


We're talking about anomalies, not absolute temperatures.
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Yep ... front is a bit past Gris Fiord and moving in over the Llano River.

"Gris Fiord has a permanent population of at least 130 rugged individuals. It is one of the most northerly inhabited places in the world."

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Quoting Levi32:


Well look at it. The entire southern hemisphere has all of the anomalously warm water. It's ridiculous.





It's THEIR summer!
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Quoting Tropicsweatherpr:
Hi Levi. What do you mean when you said in a tweet that the CFS June forecast had a bizzare SST distribution?


Well look at it. The entire southern hemisphere has all of the anomalously warm water. It's ridiculous.





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Hi Levi. What do you mean when you said in a tweet that the CFS June forecast had a bizzare SST distribution?
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AccuWeather - Drought in West; Storms in Midwest, East, South

"...During the second half of the summer, the pattern will begin to change. Moisture from the Gulf and the Atlantic are likely to come into play allowing two things. One would be more liberally spread shower and thunderstorm activity, which would limit temperature extremes. The second would open the door for impact from one or more tropical systems."

"In the Southern states, it is possible the northwest flow of air could be disrupted long enough during the first part of the summer for impact from a tropical system.

Later in the summer, the frequency of storms from the northwest will diminish with a more typical flow of moisture from the Gulf of Mexico and the Atlantic setting up over the South. Not only would this bring rainfall to the Florida Peninsula and continue thunderstorm activity in the South in general, but it would increase the chance for direct impact from one or more tropical systems from the central Gulf Coast through the Atlantic Coast."
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Quoting FIUStormChaser:


new blow up of convection in the Gulf of Mexico?
Yup..And it should grow a bit, and do about the same as this mornings convection..
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Quoting 1900hurricane:

It's a bit higher out where those storms are firing.



Thank you, Sir. 2-3000? Not too shabby. And a good chunk of likely precip is at the Western edge, over the Llano river watershed.
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Quoting Jedkins01:



I think the GFS is taking a taking a algorithmic dump, an upper level low actually looking like that would be astounding.

If that does happen, it would be interesting though.
It could make things worse for folks that have had too much rain....162 hours out.
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Quoting TomTaylor:
That is pretty cool. Hopefully it verifies so we can observe it as well.

Had a question for you also, you mentioned on twitter that NOMADS doesn't provide full output for GFS at its native resolution (T574). Does this mean only the surface flux fields are offered at T574? Are things like 500mb heights, 250mb winds, etc. all at a lower resolution?


Yeah, only surface flux fields and some radiation fluxes at top of the atmosphere.
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Felt like an early summer day around Houston. Hard to believe its going to get blown away tomorrow. Looking at the WPC surface analysis, it looks like this boundary stretches almost all the way to Grise Fiord.
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Quoting Grothar:


new blow up of convection in the Gulf of Mexico?
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Member Since: July 17, 2009 Posts: 71 Comments: 26515
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Rainfall amount forecast for Zane in 12 to 18 hours:

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Quoting redwagon:


What's CAPE in TX right now? 1500? at most?

It's a bit higher out where those storms are firing.

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Quoting hydrus:
The GFS with another run showing the upper low that looks like a hurricane.



I think the GFS is taking a taking a algorithmic dump, an upper level low actually looking like that would be astounding.

If that does happen, it would be interesting though.
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First Heat advisories of the season I believe. (San Francisco Area)
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Quoting Levi32:
This is one of the coolest things I've seen on a model in a while. The 18z GFS forms mirror tropical cyclones on opposite sides of the equator in the Indian Ocean, which then appear to become "locked" together as if each were a lobe of a convectively-coupled Kelvin wave straddling the equator. So cool!

6MB GIF Animation
That is pretty cool. Hopefully it verifies so we can observe it as well.

Had a question for you also, you mentioned on twitter that NOMADS doesn't provide full output for GFS at its native resolution (T574). Does this mean only the surface flux fields are offered at T574? Are things like 500mb heights, 250mb winds, etc. all at a lower resolution?
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Quoting AussieStorm:

Need I say that all TC warnings have now been canceled.







There is something funny to me about watching the low level circulation of a tropical cyclone shooting out away from the convection, maybe I'm just a geek, I don't know, but it always makes me laugh...
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The GFS with another run showing the upper low that looks like a hurricane.
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Quoting KEEPEROFTHEGATE:


What's CAPE in TX right now? 1500? at most?
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Quoting FLWeatherFreak91:
yep, but check out that little tiny thunderstorm that just popped up in the midst of the dry upper level air. A good sign there is plenty of low level moisture and lift.



Yeah total PW is still very high. Also that disturbance generating strong thunderstorms in actual direr air over Texas will swing over the gulf with time is well. Mid level lapse rates are much steeper over there, at least some of that is expected to overspread Florida.
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Quoting Dakster:


What are we talking about?

I'm late to the blog today.
Greetings Dak...Most of us were discussing 78L, which was producing a large cluster of storms with intense lightening over the gulf. It put down over 800 strikes in 15 minutes.
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Quoting mermaidlaw:
Wow, right after I posted #611 the rain finally picked up. I will take the rain here,we need it. It is light rain at the moment.
Thank you Jed!


No problem :)

Unfortunately you guys missed the bulk of the rain the last couple days. You guys need it just as much as the Tampa Bay area. Hopefully you guys will get into the action tomorrow.
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This is one of the coolest things I've seen on a model in a while. The 18z GFS forms mirror tropical cyclones on opposite sides of the equator in the Indian Ocean, which then appear to become "locked" together as if each were a lobe of a convectively-coupled Kelvin wave straddling the equator. So cool!

6MB GIF Animation
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Shadows at sunset give more definition to the visible sat pics.

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another meso low looks to be forming south of biloxi
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Quoting bigwes6844:
i think if im right Ernesto was the storm first that had that issue last year right?


Yeah, and some issues with trade winds
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Quoting Chicklit:
wow...the blob went to mush


But lets wait for the low itself to come into the gulf, shall we?
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Wow, right after I posted #611 the rain finally picked up. I will take the rain here,we need it. It is light rain at the moment.
Thank you Jed!
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Member Since: July 15, 2006 Posts: 174 Comments: 54434
Member Since: July 15, 2006 Posts: 174 Comments: 54434
625. MTWX
Quoting barbamz:


Yes, really awesome three new cams, moderated in order to follow the action in the harbour. And it seems they change audio channels, too. I'm still waiting for lightning and boomers though ;-)

I'm now on cam 2

http://portevergladeswebcam.com/


Edit: And now I see the rain on cam 3. Nice new toy!


You guys have ruined me! I can't quite watching!! The tracker on Google Maps is awesome too!
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Quoting stormchaser19:

When you have more inestable atmosphere is more favorable for Thunderstorm development,In unstable conditions, a lifted parcel of air will be warmer than the surrounding air at altitude. Because it is warmer, it is less dense and is prone to further ascent.

When you have a unestable atmosphere at the time you have a TC is like if you remove a problem when this is trying to put his act together
i think if im right Ernesto was the storm first that had that issue last year right?
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1.2 inches in 24 minutes.....in May
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Quoting KEEPEROFTHEGATE:
there she blows.
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Quoting Chicklit:
wow...the blob went to mush
yep, but check out that little tiny thunderstorm that just popped up in the midst of the dry upper level air. A good sign there is plenty of low level moisture and lift.
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Quoting Jedkins01:
There is a serious flood threat in southern MS right now, rain continues to pile up from persistent heavy thunderstorms.

Just in from the coast, the 1% chance event for a 3hr duration rainfall is in the 6-8" range. There appear to be a few isolated areas estimated with 6-7" of rainfall in the last 3hrs, especially just to the NW of Van Cleve, MS, and south of Lucedale.
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Member Since: July 15, 2006 Posts: 174 Comments: 54434
Went down alot since yesterday in the GOM
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Once again, its raining like hell east of Ft Myers, it needs to stop, or all the vegies are gone,,,,,this is frigging unbelievable
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Quoting mermaidlaw:
Hello everyone. I think I finally just saw a sprinkle at my house here in Spring Hill, FL. Well maybe...I did see a bird.:)
I do have a question: Why does the radar show rain over me when we are not getting rain? Thanks to all that can answer.
I hope everyone is safe, and has a wonderful night!


It may appear rain is over you but it is not. I've seen it happen before myself, sometimes you can just be unlikely to where the radar is either not high enough resolution to show that you aren't getting any, or its not quite over you.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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