1st May snow in 22 years? Potentially “historic” May snowfall possible Wednesday night

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Weather Denial

Yes Amy, somebody must have hacked my twitter and Updraft accounts.

This can’t be happening again right? It’s MAY!

The “Spring of 2013″ appears to be the wintery gift that keeps on giving. I’m laughing to keep from crying this spring at the Weather Lab.

Our next weathermaker is moving in with another shots of rain and yes….snow.

**I want to see another round of models runs overnight and Wednesday morning, but the suite of half a dozen of the more credible models we look at all seem to point in the same direction. Accumulating snow is a real possibility in the metro Wednesday night into Thursday morning.**

There. I said it.

In this Updraft we’ll walk through some scenarios for rain and snow in the next 48 hours, and search for a light at the end of the tunnel.

Did I mention 70s are in the forecast again by early next week?

3.0″ largest May snowfall on record in the Twin Cities

22 years since the last accumulating snow in the metro (May 5, 1991)

37 years since the last 1″ snow in the metro (May 2, 1976)

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Nice run of 70s:

Let’s start off on a positive note. Our 1st run of “true spring” weather in 2013 has been glorious. We’ve enjoyed 5 straight days of 70F+ since Friday, including the season’s 1st 80F Sunday (81 degrees).

Medicine Lake “Ice Chandeliers” put on a show

The warmer weather is breaking up ice on area lakes. Under certain conditions, the ice can crystallize into long pillars and break up like galss.

Check out this great video from Nadalie Thomas.

An April to remember: (Or forget?)

Even with our run of 70s, we’ll close the books on April more than -6F vs. average.. April is the 3rd consecutive colder than average month in the metro.

Since October we seem to have begun a new temperature trend in Minnesota with colder than average temps 4 of the past 7 months in the Twin Cities and Minnesota.

April -6.6F (preliminary)

March -5.6F

February -1.8F

January +1.3F

December +3.7F

November +3.4F

October -1.4F

Overall temps are running about -1F vs. average the past 7 months in the metro.

The 17.9″ of snow we shoveled this month goes in the weather books as the 3rd snowiest April on record.

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Next Up: Potentially historic May snowfall

I am still hoping for changes in the overnight and early Wednesday forecast models, but all signs point to at least some accumulating snow in eastern Minnesota Wednesday night into Thursday morning.

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Radars are lighting up with rain overnight into Wednesday morning. During the day on Wednesday, colder air works east through Minnesota…gradually changing rain to wet snow.

By Wednesday evening the rain snow line will work through the metro…and a narrow band of heavy wet snow will be in progress…most likely setting up either side of a Fairmont-Mankato-Twin Cities-Hayward line.

Here’s how much slush the NAM model thinks will fall from the sky.

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The Canadian (GEM) model paints a narrow sliver of accumulating snow that favors the eastern metro…with little accumulation in the west metro and central Minnesota.

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With warm ground and strong May sunlight…accumulations will be difficult during daylight hours. But once the sun sets, heavy snowfall rates should be enough to overcome warm ground…once you get the 1st layer of snow down.

Here’s’ the interesting language from the Twin Cities NWS forecast discussion.

AS ALLUDED TO EARLIER…SNOWFALL RATES OF 1 TO 2 INCHES PER HOUR ARE EXPECTED WITH THIS HEAVY BAND OF SNOW. CONTRARY TO POPULAR BELIEF…THESE RATES WILL OVERCOME THE WARM SURFACE TEMPERATURES…ESPECIALLY AFTER SUNSET…AND SHOULD BEGIN TO SEE WIDESPREAD ACCUMULATION OVERNIGHT. HOWEVER…THE GROUND WILL NOT FREEZE…SO THE SNOW WILL CONTINUALLY BE MELTING FROM BELOW.

THIS…TOGETHER WITH COMPACTION WILL PRODUCE SNOW TOTALS MUCH LESS THAN A SIMPLE ADDITION OF THE HOURLY RATES WOULD INDICATE. WITH THAT SAID…ONE MUST ACKNOWLEDGE THE COBB OUTPUT FROM THE NAM SUGGEST SNOWFALL TOTALS IN EXCESS OF 10 INCHES POSSIBLE FROM FAIRMONT…TO MINNEAPOLIS…AND RICE LAKE WI. THE SREF 30.09 PLACES THE HIGHEST PROBABILITIES ALONG THIS LINE AS WELL…WITH PLUMES SHOWING MEAN TOTALS OF 6-9 INCHES.

HOWEVER…STILL FEEL THESE TOTALS ARE TOO HIGH FOR REASONS MENTIONED ABOVE….AND ALTHOUGH HAVE HIGH CONFIDENCE IN A SNOW COVERED LANDSCAPE THURSDAY MORNING…DO NOT FEEL THAT SNOWFALL TOTALS WILL EXCEED 6 INCHES.

Well that’s comforting!

I’m inclined to agree with NWS that snowfall totals will not reach some of the higher model output so far. But with only 3″ needed to break the all time May Twin Cities snowfall record, it’s certainly possible that is in jeopardy by Thursday.

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Bottom Line: Expect rain to increase overnight into Wednesday. Rain will change to snow from west to east Wednesday…to all snow by Wednesday evening. Accumulations…and more “shovelable” slushy snow are quite possible by Thursday morning.

Stay tuned as we tweak the forecasts Wednesday.

Paul Huttner