Update 4 am: Snow eases south, picks up later

4 am Update:

Okay, I never can sleep during big storms anyway so here's a quick overnight update.

At 3:20am I measured 5" of snowfall in Deephaven at the weather lab. We have been under an intense band of snowfall producing 1" per hour for the past 2-3 hours in the Lake Minnetonka area.

Radar trends indicate (and the latest model runs support) a lull in snowfall working through southern Minnesota and into the south metro. There may be a let up in snowfall in some areas early Saturday morning...but I expect snowfall to fill in again as the storm reaches peak intensity Saturday.

[image]

NEXRAD shows a (temporary?) lull in snowfall working into south metro at 3:45am.

The late night NAM model cranked out an insane 28.1" snowfall total! This would rival the Halloween Mega Storm if it verifies...but I do not buy that total just yet. What we refer to as "short term radar and satellite trends" or "nowcasting" suggest a lull in the action for a few critical hours early Saturday morning that could keep snowfall totals in check.

(Click for bigger image)

For now, I am still forecasting snowfall totals of between 10" and 20" as a range for the greater metro area and much of western Wisconsin.

Still, the storm now appears to be coming in 2 or three intense waves of snowfall intensity...and the second wave late Saturday morning through midday could be the most intense. Forecast models suggest (and satellite trends may support) a period of intense snowfall with possible thundersnow producing prolific snowfall rates of up to 3" to 4" per hour spinning up toward the metro around 8-9am.

Potential "snowbursts" AM & PM?

(Click to enlarge)

If that happens we could pick up a lot of snow in a hurry!

The NAM model then suggests another lull in snowfall intensity...with another 1" to 2" per hour burst late in the afternoon.

Bottom line: The storm will come in waves, and it really doesn't matter at this point exactly how much snow falls...there will be enough snow and wind to produce blizzard to near blizzard conditions in much of southern Minnesota Saturday.

Stay tuned to MRR News stations (KNOW 91.1FM in the metro) Saturday. Craig Edwards will have hourly updates, and the latest snow totals and model runs through the morning and I will pick things up with hourly updates after noon as we follow the storm through the day.

Be safe, and enjoy the snow if you can!

PH

Evening Update:

Ice and snow progressing northeast as expected tonight. It still looks like a wintery mix could begin anywhere between about 8pm and 10pm in the metro...then change to all snow and pick up in intensity after midnight.

I set up the Twin Cities radar loop to show snow, ice and rain. Latest radar update here.

We could have 6" of snow on the ground already by early Saturday morning in many areas.

Latest model trends all support high snow totals...in the 15"+ range. I'm sticking with a forecast snow total range of 10" to 20" for the metro and western Wisconsin by Saturday evening.

Travel should be fine around the metro until 9pm or so...then al bets are off. Get home early, or be ready for snow (and maybe a little ice) if you are going to be out later tonight.

PH

Doppler Update 4:30pm :

Sioux Falls doppler showing mixed bag of rain, ice and snow busting out and moving NE into southwest Minnesota during the 4pm hour.

[image]

Moisture surge should reach the metro between 8pm & 10pm tonight. A possible wintery mix should quickly change to all snow and intensity will increase rapidly after midnight.

Just when you thought it was safe to think about maybe lowering snowfall forecasts...the 18Z (noon) NAM model run cranks out a 19" snowfall total for the metro!

That's the highest output of any numerical forecast model so far. I think that's probably on the high end of the range...but it supports the notion of a 10" to 20" forecast in the max snowfall band.

PH

All systems are go for a MAJOR winter storm in Minnesota tonight and Saturday.

It looks like this storm will deserve all the pre-storm hype we can pile on, as a powerful mix of snow, wind and bitter cold locks in over Minnesota and the Upper Midwest this weekend.

Here's the latest (and hopefully best) thinking at this point...and some headlines on the storm.

-Winter storm warnings are up for the metro, blizzard warnings for much of SW MN, inclding counties just southwest of the metro!

Winter storm warnings are flying for the metro. Blizzard warnings include Mankato, Redwood Falls, Marshall and Worthington.

-The biggest emphasis and IMPACTS with this storm will be heavy snow, wind causing severe blowing and drifting snow, and bitter cold behind the storm. There may be near blizzard conditons in much of Minnesota Saturday and Saturday night! We all love to focus on inches...but travel conditons will be the same (travel difficult to impassable) Saturday regeardless of 10" or 20" of total snowfall.

-Snow will spread into SW Minnesota this afternoon, and should begin in the metro sometime between 9pm and midnight.

-The snow will pick up in intensity after midnight, and snowfall rates could exceed 1" per hour from midnight through about 9-10 am Saturday. There could be convective snowbursts or "thundersnow" with this storm overnight into early Saturday. Snowfall rates can approach 2" to 3" per hour in thundersnow.

Nam model snowfall output indicating 1"+ per hour for many hours...and a total of 18.9"!

(Click for much more easily readable image)

-Snow will continue through much of Saturday PM before winding down late PM.

-Strong winds between 25 and 40 mph will kick up Saturday into Saturday night, causing severe blowing and drifting of relatively dry powdery snowfall. There will be blizzard or near blizzard conditions in much of Minnesota Saturday and Saturday night. (Blizzard criteria = sustained winds of 35 mph and visibilities at or under 1/4 mile in falling or blowing snow.)

-The storm will likely mix with freezing rain along the I-90 corridor...and sleet in south central Minnesota.

-Storm total snowfall accumulations could approach 10" to 20" for much of east central Minnesota and western Wisconsin by late Saturday...including the Twin Cities metro area. This has the potential to be the biggest snowfall since the Halloween Mega storm in 1991 for some locations.

NAM model continues to lay out the heaviest snow band (up to 16"+?) right across the Twin Cities metro Saturday.

Model runs with "Cobb Technique" snowfall output...10" to 18"?

This will be a major winter storm...and possibly (hopefully!) the biggest storm this winter season. I expect travel to be extremely difficult (impassable?) outside the metro by Saturday PM & evening. I also expect numerous road closures and MNDOT may have to pull plows off the roads Saturday in some areas.

A top 10 storm?

For the record, I do not think this storm has the capacity to rival the Halloween Mega Storm for overall snowfall totals.

But, if we get 15" in the metro with this storm, it would be the 11th biggest snowstorm in Twin Cities history. Here are the top snow storms in Twin Cities history courtesy of the Minnesota Climate Working Group.

Top Thirteen Largest Snowfalls for Twin Cities:

1. 28.4 inches: October 31 - November 3, 1991 (Halloween Blizzard)

2. 21.1 inches: November 29 - December 1, 1985

3. 20.0 inches: January 22 - January 23, 1982

4. 17.4 inches: January 20 - January 21, 1982

5. 16.8 inches: November 11 - November 12, 1940 (Armistice Day)

6. 16.7 inches: March 3 - March 4, 1985

7. 16.7 inches: March 11 - March 14, 1940

8. 16.5 inches: December 27 - December 28, 1982

9. 16.0 inches: January 20 - January 21, 1917

10. 16.0 inches: March 8 - March 9, 1999

11. 14.7 inches: March 31, 1985

12. 14.3 inches: November 29 - November 30, 1991

13. 14.1 inches: March 22 - March 23, 1952

If the snow total with this storm exceed 16" it will in fact be the biggest snow since the Halloween Mega Strom of 1991. That's a tall order, but it looks like at least possibility with this storm. A 15" snowfall would make this the biggest snow in the metro in 11 years, since March of 1999.

Bottom line: A major winter storm will bring snow, wind and then bitter cold to Minnesota during the next 48 hours. Be ready!

PH