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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Looking foreward to the next storm!
Member Since: April 30, 2013 Posts: 5 Comments: 4316
Quoting LargoFl:
this could be bad news for us here in florida..as i walked the dogs this morning i saw patches of clear sky thru the broken overcast,with that LOW coming towards us in the gulf the last thing we need here..is daytime heating making the storms worse huh....stay safe and alert today folks.

Same exact thing I thought this morning when I was out.



Should be a fun one today.
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wow a Freeze all the way down into Texas?................FREEZE WARNING IN EFFECT FROM 5 AM TO 9 AM CDT FRIDAY...

THE NATIONAL WEATHER SERVICE IN FORT WORTH HAS ISSUED A FREEZE
WARNING...WHICH IS IN EFFECT FROM 5 AM TO 9 AM CDT FRIDAY. A WIND
ADVISORY IS ALSO IN EFFECT FROM 9 AM THIS MORNING TO 9 PM TONIGHT.

* TIMING...WINDS WILL INCREASE THROUGH LATE THIS MORNING WITH THE
STRONGEST WINDS EXPECTED LATE THIS AFTERNOON AND EVENING. WINDS
WILL DIMINISH LATE TONIGHT. TEMPERATURES ARE EXPECTED TO FALL TO
NEAR OR JUST BELOW FREEZING AROUND SUNRISE FRIDAY MORNING.

* WINDS...SUSTAINED NORTH WINDS OF 20 TO 30 MPH WITH GUSTS BETWEEN
35 AND 40 MPH CAN BE EXPECTED.

* TEMPERATURE...DROPPING TO OR JUST BELOW FREEZING DAYBREAK
FRIDAY MORNING...THEN WARMING ABOVE FREEZING BY MID MORNING.

* IMPACTS...LAWN FURNITURE...TRAMPOLINES...AND OTHER LIGHT WEIGHT
OBJECTS MAY BE BLOWN AROUND THURSDAY AFTERNOON. HIGH PROFILE
VEHICLES WILL EXPERIENCE BUFFETING. SENSITIVE PLANTS SHOULD BE
COVERED TO PREVENT DAMAGE FROM THIS LATE SEASON FREEZE.
Member Since: August 6, 2011 Posts: 4 Comments: 42845
Member Since: August 6, 2011 Posts: 4 Comments: 42845
Member Since: August 6, 2011 Posts: 4 Comments: 42845
Quoting GeoffreyWPB:


Can I watch it too?
LOL good morning..Nam has this low slipping down under florida thru the straights..hopefully it doesnt strengthen any during the day today,it really whacked mississippi etc with extremely heavy rains and a few tornado's...stay safe down there
Member Since: August 6, 2011 Posts: 4 Comments: 42845
Quoting LargoFl:
folks in the keys and miami had better watch this low carefully..


Can I watch it too?
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folks in the keys and miami had better watch this low carefully..
Member Since: August 6, 2011 Posts: 4 Comments: 42845
Heavy rain on my doorstep! So far all the rain forecasts for the P'cola area have been way overdone. It's now looking like it may make up for it today. I hate working in the rain. Have a good day all.
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Member Since: August 6, 2011 Posts: 4 Comments: 42845
Member Since: August 6, 2011 Posts: 4 Comments: 42845
Member Since: August 6, 2011 Posts: 4 Comments: 42845
this could be bad news for us here in florida..as i walked the dogs this morning i saw patches of clear sky thru the broken overcast,with that LOW coming towards us in the gulf the last thing we need here..is daytime heating making the storms worse huh....stay safe and alert today folks.
Member Since: August 6, 2011 Posts: 4 Comments: 42845
Morning, everyone. Evening, Aussie. It's a slightly wet 64 degrees. Radars shows no rain, but there's a slight drizzle coming down. High expected around 74 later on, and then the temps drop for tomorrow.

Breakfast's on the sideboard: egg casserole, blueberry and bran muffins, bacon and sausage, fresh fruit and apple or orange juice. Enjoy.
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Member Since: August 6, 2011 Posts: 4 Comments: 42845
Good Morning Everybody
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Good morning to all,evening Aussie.

The rainy days start today as a trough moves nearby the islands causing scattered showers and thunderstorms that may cause flash flooding. This weather is forecast to last until early next week.


AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
457 AM AST THU MAY 2 2013

.SYNOPSIS...AT UPPER LEVELS...A BRANCH OF THE SUB-TROPICAL JET
STREAM IS OVER THE LOCAL AREA. BY FRIDAY NIGHT THE JET STREAM WILL
CONSOLIDATE NORTH OF THE AREA AND HIGH PRESSURE WILL FILL IN OVER
THE SOUTHEASTERN CARIBBEAN AND WESTERN TROPICAL ATLANTIC OVER THE
WEEKEND AND EARLY NEXT WEEK. THE RESULTING RIDGE WILL SHIFT EAST
BUT FLOW WILL REMAIN ZONAL.

AT MID LEVELS...A LOW PRESSURE DROPPING SOUTH OVER THE WESTERN
ATLANTIC IN A LARGER LOW PRESSURE POOL WILL CAUSE MID LEVEL FLOW
TO BECOME MORE SOUTHWESTERLY...THROUGH SUNDAY. THEN BY TUESDAY A
RIDGE WILL EXTEND FROM THE WINDWARD ISLANDS TO PUERTO RICO AND
NORTH NORTHWEST INTO THE WESTERN ATLANTIC THROUGH MUCH OF THE
WEEK. MOISTURE AT MID LEVELS IS BEST OVER EASTERN PUERTO RICO AND
THE U.S. VIRGIN ISLANDS SATURDAY NIGHT AND EARLY SUNDAY MORNING.
IT MOVES SOUTHEAST BUT RETURNS OVER PUERTO RICO MONDAY NIGHT AND
TUESDAY...PERHAPS MORE VIGOROUSLY THEN PREVIOUSLY DEPICTED.

AT LOWER LEVELS...MODEST EAST SOUTHEAST FLOW BECOMES VERY LIGHT ON
FRIDAY AND SHIFTS TO THE SOUTH OR SOUTHWEST. BANDS OF MOISTURE
COME UP FROM THE SOUTH THROUGH TUESDAY AND THEN A BAND RETURNS
FROM THE EAST NORTHEAST WEDNESDAY NIGHT. WITH LOW PRESSURE
GENERALLY TO THE NORTHEAST OF THE AREA THE CARIBBEAN IS UNDER A
LONG RIDGE FROM THE TROPICAL ATLANTIC TO MEXICO.

&&

.DISCUSSION...SHOWERS BECAME MORE NUMEROUS DURING THE HOURS BEFORE
DAWN AS MOISTURE MOVES IN FROM THE EAST. THE MIMIC PRODUCT SHOWS
THE LEADING EDGE OF MOISTURE OF CLOSE TO 2 INCHES MOVING ACROSS
CULEBRA AND VIEQUES JUST A FEW HOURS BEFORE SUNRISE. SHOWERS ARE
LIKELY TO INCREASE DURING THE DAY AND DEVELOP OVER INTERIOR PUERTO
RICO...FAVORING THE INTERIOR AND NORTH PORTIONS OF THE ISLAND BY
THIS AFTERNOON AS FLOW AT 850 MB BECOMES SOUTH DURING THE DAY.
SOUTH FLOW OVER THE MOUNTAINS WILL PRESENT SOME DRYING AND IMPEDE
THE FORMATION OF SHOWERS AND THUNDERSTORMS FOR A WHILE ESPECIALLY
NEAR SAN JUAN...BUT EXPECT THE MOISTURE TO WIN OVER AND SEE SHOWERS
AND THUNDERSTORMS DURING THE LATE AFTERNOON. THE GFS DID NOT
DEEPEN THE MOISTURE AS MUCH AS EXPECTED FOR TODAY SO AREAS AROUND
THE FRINGE OF THE DEVELOPING SHOWERS WILL SEE QUITE A BIT LESS
THAN THOSE IN THE NORTHERN INTERIOR.

AT THE LOWEST LEVELS...UP TO 700 MB...MOISTURE WILL ARRIVE IN
BANDS FROM THE SOUTH AND SOUTHWEST ON SATURDAY AND CONTINUE UNTIL
TUESDAY. BRINGING HEAVY AFTERNOON SHOWERS THAT LINGER INTO THE
EVENING OVER MOST AREAS. BY SATURDAY SHOWERS WILL LIKELY CONTINUE
OVER THE SURROUNDING WATERS ALL NIGHT AND WILL DAMPEN THE
SOUTHWEST AND WEST COASTAL AREAS DURING THE MORNINGS...QUITE THE
OPPOSITE OF NORMAL FLOW HERE. CAPE WILL BE BEST TODAY AND TOMORROW
BUT WILL BE GENERALLY ABOVE 1800 J/KG EACH AFTERNOON UNTIL
WEDNESDAY. LOCALLY HEAVY RAIN WILL INCREASE EACH AFTERNOON THROUGH
ABOUT SUNDAY AND SOME THUNDERSTORMS WILL BE BETTER ORGANIZED AND
SLOW MOVING PRODUCING COPIOUS RAIN AND FLOODING...ESPECIALLY
SATURDAY AND SUNDAY. URBAN AND SMALL STREAM FLOODING IS EXPECTED
EACH DAY UNTIL THEN. THE WETTEST WEATHER SHOULD SEE ITS LAST HURRAH
ON TUESDAY...BUT SHOWERS WILL CONTINUE ALL WEEK.

&&

.AVIATION...
VFR THRU MORNING EXCEPT OCNL MVFR IN SHRA AT TNCM/TKPK AND
PSBL AT TISX/TIST. MOISTURE WL SPREAD WESTWARD FM LEEWARD ISLANDS TODAY.
DEVELOPING SHRA/TSRA MAINLY ACROSS E AND N PR. SCT MVFR/ISOLD IFR DURING
SHRA IN AFT AT TJSJ/TIST/TISX/TNCM/TKPK WITH WIDESPREAD MTN OBSC.
MAY ADJUST THESE TAFS FOR TEMPO PDS. LLVL WIND BLO FL050 S-SE 5-12
KT VEERING TO SW AND INCRG ABV.

&&

.MARINE...MARINE CONDITIONS CONTINUE TO IMPROVE EXCEPT FOR
INCREASING SHOWERS AND THUNDERSTORMS. WINDS WILL BE RATHER LIGHT
ON FRIDAY AND SATURDAY...BUT THEN INCREASE THROUGH THE END OF NEXT
WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 87 76 / 40 10 70 0
STT 84 75 85 79 / 30 40 40 20
Member Since: April 29, 2009 Posts: 75 Comments: 15024
Quoting islander101010:
exiting africa? what the heck its not even hurricane season yet
It will probably go poof soon.
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exiting africa? what the heck its not even hurricane season yet
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THIS HAZARDOUS WEATHER OUTLOOK IS FOR WEST CENTRAL AND SOUTHWEST
FLORIDA.

.DAY ONE...TODAY AND TONIGHT.

...THUNDERSTORM IMPACT...
SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP TODAY...SOME OF
WHICH COULD BECOME STRONG THIS AFTERNOON AND EVENING. THE MAIN
HAZARDS FROM THE STRONGEST STORMS THAT DEVELOP WILL BE DAMAGING
STRAIGHT LINE WINDS...LARGE HAIL...FREQUENT LIGHTNING AND HEAVY
RAINFALL.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

...THUNDERSTORM IMPACT...
SCATTERED TO NUMEROUS THUNDERSTORMS WILL BE POSSIBLE THROUGH THE
WEEKEND...WITH FREQUENT LIGHTNING...HEAVY RAINS...AND GUSTY
STRAIGHT LINE WINDS BEING THE MAIN HAZARDS WITH THE STRONGEST
STORMS THAT DEVELOP.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS SHOULD MONITOR THE WEATHER AND SELF ACTIVATE IF NEEDED.
Member Since: August 6, 2011 Posts: 4 Comments: 42845
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Member Since: August 6, 2011 Posts: 4 Comments: 42845
lets see if the sun comes out today around here......
Member Since: August 6, 2011 Posts: 4 Comments: 42845
Good Morning Folks!..7-day for Tampa Bay area............
Member Since: August 6, 2011 Posts: 4 Comments: 42845
Good morning/afternoon/evening all

Such a calm morning here on the island. Not a leaf moving, no chickens calling, no traffic....

I think I'm up too early!

Lindy
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for these temps to be this warm already wow
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getting ready to exit africa
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Quoting VR46L:


Your Welcome!

Are you just a season™ blogger haven't noticed you around since last Atlantic season !
lol u can say that! i normally tend to ride the blog on may 1st until november around thanksgiving. i tend to peak at the blog ever so often during the winter but i love hurricane season time. but yes im out from hibernation mode
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785. VR46L
Quoting moonlightcowboy:


Welcome. Understood, agreed. Certain products do certain things better or worse than others. There is different data interpretation, differently displayed channels or outputs that will vary from product to product. You just have to stay with it and figure some things, eventually discerning the ones that are more dependable, accurate over time.


I actually have been playing around with the root directory of where those images you posted are some really nice imagery on there Thanks

Member Since: March 1, 2012 Posts: 0 Comments: 7011
Quoting VR46L:


Wow Thanks for the info ... I do usually look at some of that info but was lazy still early here .. The one image I really Dont like is this one ...Could be a desert and it sees moisture
LOL



Welcome. Understood, agreed. Certain products do certain things better or worse than others. There is different data interpretation, differently displayed channels or outputs that will vary from product to product. You just have to stay with it and figure some things, eventually discerning the ones that are more dependable, accurate over time.
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783. VR46L
Quoting AtHomeInTX:


Yeah 2a.m. Usually more awake but I'm about to call it a night. Got the satellite tv guy coming tomorrow. I guess I gotta let him in. :) Everyone have a great night/day/afternoon.


Good Night At Home
Member Since: March 1, 2012 Posts: 0 Comments: 7011
782. VR46L
Quoting moonlightcowboy:


That CIMSS chart for SAL is not the best way to look at dust or dry air = SAL. It tends to be interpreted, perceived as a dust product and clearly overshoots its intentions. There is actually very little dust in the eATL. For a better look at dust use EUMETSAT's dust product.



And, for dry air/moisture use a simple water vapor product. For dust, one should generally use the mid-level water vapor products - the layer dust resides. The orange area in this chart, however, is not dust - it's dry air.

A few weeks back much of the MDR was dry, but you can see in the following two charts that the region has gotten more moist. And, it will continue to moisten with trade winds settling down, getting more surface lift with warming daytime temperatures, as well as the ITCZ getting higher climatologically. Notice there is more dry air in the mid-level than in the upper levels.

Mid-Levels



Upper Levels



Wow Thanks for the info ... I do usually look at some of that info but was lazy still early here .. The one image I really Dont like is this one ...Could be a desert and it sees moisture LOL

Member Since: March 1, 2012 Posts: 0 Comments: 7011
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780. VR46L
Quoting bigwes6844:
yhanks it really shows me to get pre pared early this year


Your Welcome!

Are you just a season™ blogger haven't noticed you around since last Atlantic season !
Member Since: March 1, 2012 Posts: 0 Comments: 7011
Quoting VR46L:


Good Morning Folks !!

Nice image ! But still needs a bit of latitude .. but the Sal is rather weak at the moment and only imapcting the east Atlantic



That CIMSS chart for SAL is not the best way to look at dust or dry air = SAL. It tends to be interpreted, perceived as a dust product and clearly overshoots its intentions. There is actually very little dust in the eATL. For a better look at dust use EUMETSAT's dust product.



And, for dry air/moisture use a simple water vapor product. For dust, one should generally use the mid-level water vapor products - the layer dust resides. The orange area in this chart, however, is not dust - it's dry air.

A few weeks back much of the MDR was dry, but you can see in the following two charts that the region has gotten more moist. And, it will continue to moisten with trade winds settling down, getting more surface lift with warming daytime temperatures, as well as the ITCZ getting higher climatologically. Notice there is more dry air in the mid-level than in the upper levels.

Mid-Levels



Upper Levels

Member Since: Posts: Comments:
Quoting VR46L:


Good Morning Folks !!

Nice image ! But still needs a bit of latitude .. but the Sal is rather weak at the moment and only imapcting the east Atlantic

yhanks it really shows me to get pre pared early this year
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Quoting AtHomeInTX:


Yeah 2a.m. Usually more awake but I'm about to call it a night. Got the satellite tv guy coming tomorrow. I guess I gotta let him in. :) Everyone have a great night/day/afternoon.
night at home
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Quoting VR46L:


Guess its pretty late where you are ?


Yeah 2a.m. Usually more awake but I'm about to call it a night. Got the satellite tv guy coming tomorrow. I guess I gotta let him in. :) Everyone have a great night/day/afternoon.
Member Since: Posts: Comments:
775. VR46L
Quoting AtHomeInTX:


Good morning VR.


Guess its pretty late where you are ?
Member Since: March 1, 2012 Posts: 0 Comments: 7011
Quoting VR46L:


Good Morning Folks !!

Nice image ! But still needs a bit of latitude .. but the Sal is rather weak at the moment and only imapcting the east Atlantic



Good morning VR.
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Quoting bigwes6844:
its going slow i know. u remember why about the africa storms?


Can't seem to find it. May have been on twitter.
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772. VR46L
Quoting bigwes6844:
WOW!


Good Morning Folks !!

Nice image ! But still needs a bit of latitude .. but the Sal is rather weak at the moment and only imapcting the east Atlantic

Member Since: March 1, 2012 Posts: 0 Comments: 7011
its going slow i know. u remember why about the africa storms?
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Quoting bigwes6844:
yeah i was tryna figure out if the MJO is causing this already thats amazing


I think they were discussing that earlier on the blog. Somewhere. WU seems to be acting up for me tonight.
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Quoting AtHomeInTX:


Wow! Doesn't look like it's still May with them lined up like that.
yeah i was tryna figure out if the MJO is causing this already thats amazing
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Quoting bigwes6844:
yep did u check my image of africa? take a look at it . one word shocking its on this page


Wow! Doesn't look like it's still May with them lined up like that.
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Quoting AtHomeInTX:


Hi Wes. Welcome back! Don't know if I'm ready or not but the season is approaching anyway. :)
yep did u check my image of africa? take a look at it . one word shocking its on this page
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Quoting bigwes6844:
hey ya at home im back for another active season. im ready to do this


Hi Wes. Welcome back! Don't know if I'm ready or not but the season is approaching anyway. :)
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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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