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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500mb pattern continues to stress entire southeast at high risk in particular florida. classic US mega years such as 1996, 2004, and 2005.

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From Cantore's Twitter account - perfect example of the new dual-pol and winter weather

Jim Cantore%u200F@JimCantore
Sleet in the middle RT @NWSDesMoines Rain/snow line showing up on radar...getting ever closer to Des Moines


Link
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714. Skyepony (Mod)
Recon went out & chucked a dropsonde at the Gulf of Mexico earlier. You can see the shear in the wind direction & speed. The wind shift is fairly low, between 700mb & 850mb. That is sort of hindering even for a shallow system.

Date: Near the closest hour of 16Z on the 1st day of the month
Highest Mandatory Level For Which Wind Was Reported: 400mb
Coordinates: 28.4N 86.9W (View map)
Location: 142 miles (229 km) to the S (172°) from Pensacola, FL, USA.
Marsden Square: 081 (About)

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1013mb (29.91 inHg) Sea Level (Surface) 23.6°C (74.5°F) 21.4°C (70.5°F) 140° (from the SE) 10 knots (12 mph)
1000mb 111m (364 ft) 23.0°C (73.4°F) 20.6°C (69.1°F) 155° (from the SSE) 13 knots (15 mph)
925mb 787m (2,582 ft) 18.6°C (65.5°F) 15.5°C (59.9°F) 160° (from the SSE) 20 knots (23 mph)
850mb 1,511m (4,957 ft) 16.0°C (60.8°F) Approximately 10°C (50°F) 125° (from the SE) 11 knots (13 mph)
700mb 3,132m (10,276 ft) 5.0°C (41.0°F) 3.4°C (38.1°F) 260° (from the W) 16 knots (18 mph)
500mb 5,800m (19,029 ft) -11.7°C (10.9°F) Reading unavailable when relative humidity is less than 20% 260° (from the W) 14 knots (16 mph)
400mb 7,460m (24,475 ft) -23.7°C (-10.7°F) Approximately -59°C (-74°F) 225° (from the SW) 27 knots (31 mph)
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Forming a little meso low
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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1013 PM AST WED MAY 1 2013

.UPDATE...AFTERNOON SHOWERS AND THUNDERSTORMS ACROSS NORTH CENTRAL
SECTIONS OF PUERTO RICO DIMINISHED RAPIDLY AFTER SUNSET LEAVING ONLY
PARTLY CLOUDY SKIES WITH ISOLATED SHOWERS MAINLY ACROSS THE
SURROUNDING COASTAL WATERS THIS EVENING. LATEST SATELLITE IMAGES
THIS EVENING DEPICTED AN AREA OF MOISTURE JUST TO THE EAST OF THE
LEEWARD ISLANDS. THIS FEATURE WILL CONTINUE TO MOVE WESTWARD
AFFECTING THE USVI AND EASTERN SECTIONS PUERTO RICO DURING THE EARLY
MORNING HOURS. FOR TOMORROW AFTERNOON...THIS MOISTURE IN COMBINATION
WITH DIURNAL HEATING AND LOCAL TERRAIN EFFECTS WILL PROMOTE A NEW
ROUND OF SHOWERS AND THUNDERSTORMS ACROSS WESTERN AND INTERIOR
SECTIONS OF PUERTO RICO. MODEL GUIDANCE SUGGESTS AN INCREASE IN
TROPICAL DEEP MOISTURE BY THE UPCOMING WEEKEND AND FOR EARLY NEXT
WEEK.
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Quoting BahaHurican:
Well, yeah... but we're not usually so red we're purple. We realistically expect a couple hits / brushes every year, but purple implies all hurricanes all the time... 2004 on speed.

NOT good.

Don't assume. :P

The Bahamas may very well be hit by multiple hurricanes this season...they may not. I debated making them purple for a very high chance of at least one hurricane hit there.
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Trouble.

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Quoting stormchaser19:


Are you surprised? Because always, i mean always the bahamas are in the business
Well, yeah... but we're not usually so red we're purple. We realistically expect a couple hits / brushes every year, but purple implies all hurricanes all the time... 2004 on speed.

NOT good.
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Quoting BahaHurican:
I'm taking u off my best friends list.



Are you surprised? Because always, i mean always the bahamas are in the business
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Quoting Astrometeor:


Better idea: Make your own landfall map and put North Carolina in the high-risk area.

I have no objections to that.
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Quoting BahaHurican:
I'm taking u off my best friends list.



Better idea: Make your own landfall map and put North Carolina in the high-risk area.
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Quoting TropicalAnalystwx13:

The Bahamas are very, very red. I debated making them purple.
But, SERIOUSLY...

I need to sit and do some analysis of conditions and analogues etc.... I am not at all liking the concept of a season so busy we need to be in the purple.... but if it's a valid possibility, I want to know in advance.
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Quoting TropicalAnalystwx13:

The Bahamas are very, very red. I debated making them purple.
I'm taking u off my best friends list.

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Quoting BahaHurican:
Uh.... so is the Bahamas in the red or the orange?

Maybe u could do like the NHC and just draw a couple of coloured lines along the axis of the really tiny islands...

The Bahamas are very, very red. I debated making them purple.
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702. MTWX
Quoting hericane96:


Worst rain we've had since Hurricane Isaac. Some people had to be rescued in Moss Point. WLOX.com for more info.


Totals according to radar are in the 6-8" and counting!!!

Link
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Quoting TropicalAnalystwx13:

You should draw a landfall probability map like I did earlier.

Repost for those who may not have seen it:

Uh.... so is the Bahamas in the red or the orange?

Maybe u could do like the NHC and just draw a couple of coloured lines along the axis of the really tiny islands...
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Quoting TomTaylor:
What resolution are the remaining variables disseminated at? For example, when I look at a standard GFS 500mb plot, what resolution am I looking at?


You're looking at 0.5° (2.5° extended range) for everything published on the web that I know of except for some of the special products Dr. Maue and I offer. The native grid is ~0.2° (0.625° extended range).

It's important to realize that the GFS is integrated on the T574 grid for all variables. The maps we all look at are interpolated from their original T574 grid to a 0.5° lat-lon grid. I wish NOMADS would just publish all of the data in its native format alongside the standard lat-lon grids.
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Quoting Astrometeor:
The scary thing is the bolded part of the warning:



JACKSON MS-HARRISON MS-
750 PM CDT WED MAY 1 2013

...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 945 PM CDT FOR
SOUTHEASTERN HARRISON AND SOUTHERN JACKSON COUNTIES...

AT 746 PM CDT...LOCAL LAW ENFORCEMENT OFFICIALS CONTINUED TO REPORT
FLASH FLOODING OVER THE WARNED AREA. EVACUATIONS ARE OCCURRING IN
THE MOSS POINT AREA NEAR SHORTCUT ROAD...MACPHELAN ROAD...HIGHWAY
63...AND FREDERICK STREET DUE TO FLOODING ALONG A BAYOU AND DRAINAGE
CANALS.

LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO ST. MARTIN...
OCEAN SPRINGS...MOSS POINT...GULFPORT...GAUTIER...ESCATAWPA AND
BILOXI

PRECAUTIONARY/PREPAREDNESS ACTIONS...

ADDITIONAL RAINFALL AMOUNTS OF 2 TO 4 INCHES ARE POSSIBLE IN THE
WARNED AREA IN THE NEXT HOUR.


Worst rain we've had since Hurricane Isaac. Some people had to be rescued in Moss Point. WLOX.com for more info.
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Quoting hydrus:
Yup..And it should grow a bit, and do about the same as this mornings convection..
I gotta admit this morning's blowup looked pretty impressive.
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Rain off and ON in WPB all night!!:)
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Quoting Grothar:


Hey TA.

Look at this. Is this yours that I found on the web?


!

lol
Quoting CybrTeddy:


As you can clearly tell, my relative inability to read into patterns is my strongest weakness. My strongest area of cyclone forecasting is cyclogenesis. I just tend to avoid what I don't understand.
No worries...steering is rather simple though. Just a matter of looking for troughs and ridges and understanding the flow around them. Once you got that you're set really. Forecasting involves a bit more, but even then you are doing the same thing just interpreting different model solutions and understanding their individual biases to arrive at what you think will be the most likely outcome.
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Evening all. This is the first time in a while I've been free - or awake - enough to get on the blog. It's been a hectic couple of weeks at work.

Meanwhile the weather here has been phenomenally good: clear skies with a great variety of clouds, brisk easterlies due to high pressure in the area, with cool air temps in the evenings to offset the increasingly hot daytime temps. Good stuff, I say...

I've been looking at this Gulf system and wondering how much precipitation [if any] we are likely to get from it. It seems strange to see a low traversing the GoM from the west, even at this time of the year.
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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
827 PM EDT WED MAY 1 2013

.UPDATE...
CHANCES FOR SHOWERS AND POSSIBLY A FEW THUNDERSTORMS WILL PREVAIL
THROUGH THE NIGHT AS WEAKNESSES IN THE MID LEVEL FLOW CONTINUE TO
PUSH ACROSS THE AREA. LATEST IR SATELLITE IMAGERY SHOWS AN MCS
SITUATED ACROSS THE SOUTH CENTRAL GULF OF MEXICO MOVING SOUTH
TOWARD THE YUCATAN CHANNEL. LATEST SHORT TERM MODELS INCLUDING
LOCAL MODEL DATA DEPICTS A FEW ASSOCIATED SHOWERS AND
THUNDERSTORMS PUSHING EAST AND INTO THE EASTERN GULF WATERS BY
EARLY TOMORROW MORNING. KEPT CHANCE POP ACROSS THE ENTIRE AREA
THROUGH THE MORNING HOURS. UPDATE WILL BE SENT SHORTLY.
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Quoting Grothar:


Hey TA.

Look at this. Is this yours that I found on the web?


Lol!!!!!
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Quoting TropicalAnalystwx13:

They were too tiny so I just decided to leave them uncolored lol.

Bermuda, Azores, Cape Verde Islands, Newfoundland - Medium chance

Lesser Antilles - High (North), Medium (South)


Hey TA.

Look at this. Is this yours that I found on the web?


Member Since: July 17, 2009 Posts: 63 Comments: 23727
Quoting hydrus:
Yup..And it should grow a bit, and do about the same as this mornings convection..


Certianly looks healthy out in the Gulf.

Did anyone else notice a surface feature asscoiated with the first complex of convection come ashore near Ft.Myers earlier this evening?
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Quoting TomTaylor:
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...




As you can clearly tell, my relative inability to read into patterns is my strongest weakness. My strongest area of cyclone forecasting is cyclogenesis. I just tend to avoid what I don't understand.
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Quoting SFLWeatherman:


That's 1008 mb on the graphic right, in that small font?

Doesn't that suggest that the low that is expected to form may be somewhat tropical in nature?
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688. JLPR2
Quoting TropicalAnalystwx13:

You should draw a landfall probability map like I did earlier.

Repost for those who may not have seen it:



That's comforting, I'm seeing a trend with people marking High risk for the Antilles. :\

Really don't need a storm this year.
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Quoting KEEPEROFTHEGATE:


Water temps have gone up 4 degrees here in the last few days. But another cold front coming they'll probably go down again.

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Quoting SFLWeatherman:


maybe work its way down from the upper low tomorrow
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Quoting SFLWeatherman:
Did you all see this!!!:)

Wait hold on is this two separate systems?
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Member Since: July 15, 2006 Posts: 165 Comments: 52274
The scary thing is the bolded part of the warning:



JACKSON MS-HARRISON MS-
750 PM CDT WED MAY 1 2013

...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 945 PM CDT FOR
SOUTHEASTERN HARRISON AND SOUTHERN JACKSON COUNTIES...

AT 746 PM CDT...LOCAL LAW ENFORCEMENT OFFICIALS CONTINUED TO REPORT
FLASH FLOODING OVER THE WARNED AREA. EVACUATIONS ARE OCCURRING IN
THE MOSS POINT AREA NEAR SHORTCUT ROAD...MACPHELAN ROAD...HIGHWAY
63...AND FREDERICK STREET DUE TO FLOODING ALONG A BAYOU AND DRAINAGE
CANALS.

LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO ST. MARTIN...
OCEAN SPRINGS...MOSS POINT...GULFPORT...GAUTIER...ESCATAWPA AND
BILOXI

PRECAUTIONARY/PREPAREDNESS ACTIONS...

ADDITIONAL RAINFALL AMOUNTS OF 2 TO 4 INCHES ARE POSSIBLE IN THE
WARNED AREA IN THE NEXT HOUR.
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Hey Tom, with the current pattern, you are expecting a hurricane season like this:
(2010) Season


If not show me your analog year
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Quoting KEEPEROFTHEGATE:


The moment of truth is coming very soon when it will splash to the water.
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Did you all see this!!!:)

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Quoting Tropicsweatherpr:


What happened that the Lesser Antilles islands are not colorized.

They were too tiny so I just decided to leave them uncolored lol.

Bermuda, Azores, Cape Verde Islands, Newfoundland - Medium chance

Lesser Antilles - High (North), Medium (South)
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Member Since: July 15, 2006 Posts: 165 Comments: 52274
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Quoting TropicalAnalystwx13:

You should draw a landfall probability map like I did earlier.

Repost for those who may not have seen it:



What happened that the Lesser Antilles islands are not colorized.
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Quoting Tropicsweatherpr:


Still hanging there.
Member Since: July 15, 2006 Posts: 165 Comments: 52274
Quoting TomTaylor:
Yeah, I saw yours. Like it for the most part. In fact, I don't really think it's worth drawing one since I pretty much agree with everything already on there. How did you draw it though? Looks like you are going beyond the capabilities of what Paint offers lol.

Powerpoint and Photoshop. Got help from a friend as well.
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Levi where's your landfall probability map? ;)
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Quoting TropicalAnalystwx13:

You should draw a landfall probability map like I did earlier.

Repost for those who may not have seen it:



That map is quite a bit like last year.
Member Since: October 20, 2012 Posts: 7 Comments: 2866
Quoting TropicalAnalystwx13:

You should draw a landfall probability map like I did earlier.

Repost for those who may not have seen it:

Yeah, I saw yours. Like it for the most part. In fact, I don't really think it's worth drawing one since I pretty much agree with everything already on there. How did you draw it though? Looks like you are going beyond the capabilities of what Paint offers lol.
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Quoting KEEPEROFTHEGATE:


Still hanging there.
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Quoting TomTaylor:
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 at 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. Here's what the 500mb height anomaly looks like 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...



You should draw a landfall probability map like I did earlier.

Repost for those who may not have seen it:

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Quoting Levi32:


Yeah, only surface flux fields and some radiation fluxes at top of the atmosphere.
What resolution are the remaining variables disseminated at? For example, when I look at a standard GFS 500mb plot, what resolution am I looking at?
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Member Since: July 15, 2006 Posts: 165 Comments: 52274

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.