Updraft: February 19, 2011 Archive

A grand reprise of winter

Posted at 5:50 AM on February 19, 2011 by Craig Edwards (6 Comments)
Filed under: Winter storms

Old Man Winter may have dozed off for awhile, but he's got plenty of game left for February. Snow will crank up later today in the central Plains and expand north and east tonight. Here's the latest thinking from the National Weather Service, which paints the most likely area of heaviest snow from about Montevideo through the Twin Cities into Eau Claire, Wisconsin.

There will be a couple more model runs before the snowflakes light up on Doppler radar, but the trend appears to be a sharp cut off of the accumulating snow from about Alexandria to Rice lake.

A broad band of more than six inches of snow is likely, with a consensus forecast that more than ten inches of snow may occur in the Twin Cities.

From the Hydrometeorological Prediction Center of the NWS.

We were about due, with less than an inch of snow so far this month at both Minneapolis/St. Paul and Eau Claire. The average snowfall for February in the Twin Cities is around eight inches.

National Weather Service Twin Cities Winter Storm Updates.

(6 Comments)

Don't rush a good snow storm

Posted at 9:53 AM on February 19, 2011 by Craig Edwards (3 Comments)
Filed under: Winter storms

The latest computer model guidance, based on upper air observations taken at 6am, is holding firm on the potential for heavy snow from South Dakota through the southern half of MInnesota into Wisconsin. Snow will likely be mixed with sleet for a time early Sunday in far southern Minnesota.

Here's one of the computer model's projections for the position of the center of the surface low at 6PM on Sunday. Old school synoptic meteorology tells me this is in a great path to produce heavy snow from Marshall up to St. Cloud to the Twin Cities. Wind barbs are in knots. Expect winds of 20 to 30 miles an hour to blow and drift snow Sunday and Sunday evening.

There is no need to start altering snowfall predictions. The heaviest snow will likely occur from 9AM until about 10PM Sunday. More than twelve hours of moderate to heavy snowfall will tally up to ten plus inches of snow in some locations.
CE

(3 Comments)

Evening Update: Domebuster II? 10" to 17"+ totals possible

Posted at 6:38 PM on February 19, 2011 by Paul Huttner (1 Comments)
Filed under: Winter storms, Winter/spring 2011

Update 6:40pm:

Here's an eye opener.

The latest 18Z (noon) GFS run is cranking out an incredible 22.5" storm total snowfall at MSP Airport!

GFS snowfall total now = 22.5"!

For the record I think that number is on the extreme high side, and the next run may (hopefully!) reduce that total. I'm sticking with a general 10" to 17" snowfall range in the metro and much of central & southern Minnesota by noon Monday posted in my more complete discussion below.

Sure makes tonight's model run a little more interesting though!

More after about 9:30 to 10pm tonight when I've had a chance to sift through the new numbers.

PH

***orignal post 2:20pm Saturday***

Here we go again.

The latest forecast models are in, and all signs still point to another major winter storm "event" for much of central & southern Minnesota...including the Twin Cities metro Sunday.

Winter storm warnings are now in effect from 6am Sunday to 6am Monday.

NWS Winter storm warnings. (Click to enlarge)

Here are the latest details on the coming winter storm, which will slam the area Sunday.

The System:

Potent low pressure is developing today in Colorado. The low will deepen and move east into Iowa Sunday. The models remain consistent on the track, which is usually a heavy snow producer for Minnesota.

Timing:

It appears that a broad area of "lift" will rapidly develop in southern Minnesota after midnight, and snowfall will bust out from SW to NE overnight. Snowfall should get going in SW Minnesota (Pipestone to Redwood Falls) by around midnight, and begin the Twin Cities sometime between 2am & 6am.

As the low moves closer Sunday, snowfall will intensify during the morning hours Sunday. It looks now like peak snowfall intensity (rates of around 1" per hour) should be between noon Sunday and midnight Monday. Snowfall should be heaviest during those 12 hours Sunday PM & evening.

Lighter snow may continue into Monday morning before the snow tapers from north to south Monday.

Snow water content:

Moisture surging up form the south means the snow will be relatively wet during the first part of the storm. The NAM model is cranking out a snow:water ratio of 7:1 early Sunday PM. The snow should dry out as the storm progresses, with snow:water ratios approaching 20:1 late Sunday night & Monday.

Snowfall totals:

The forecast models are consistent so far in laying the heaviest band of snow on a rough Ortonville-Redwood Falls-Willmar-Twin Cities-Eau Claire line. This may extend on the north end as far as St. Cloud, and as far south as Mankato to the south.

Within the heavy snow band I now expect a general area producing snowfall totals between 10" and 17" including the Twin Cities metro!

NAM model lays heaviest snow band right through Twin Cities metro.

As you can see on the map, snowfall totals will taper on the northern end toward Duluth and south into Iowa.

The NAM is cranking out a (scary!) 17" total for MSP Airport by the time the storm ends Monday. This may be on the higher range of things...but it is not out of the question that we may see similar totals to the "Domebuster" storm in December that produced 10" to 20" snowfall.

NAM: 1.25" liquid yields 17" snow total at MSP Airport!
(click to enlarge for better view)

At this point my best estimate is that most snow totals in the heavy snow band will range between 10" and 17" by Monday noon. It is possible we could see some snowfall totals in excess of 17".

Wind driven snow:

Northeast winds will build into the 15-30 mph range as the storm intensifies Sunday. This will be a wind whipped snow. Expect blowing and drifting in open areas, especially Sunday night.

Ice south:

Mild air above freezing in the lowest 5,000 feet of the atmosphere will surge into southern Minnesota briefly Sunday. This may create a wintery mix of sleet & ice in Worthington, Mankato, Albert Lea and other towns along the I-90 corridor. Expect snowfall to be reduced accordingly, but the ice will make for treacherous travel.

Thundersnow?

The upper air dynamics with this storm, and the fact that ice may move close to the southern metro at times may combine to create thundersnow in parts of southern Minnesota. Do not be surprised to hear a clap of thunder Sunday PM or evening, followed by a "burst" of heavier snow.

Bottom line & travel:

-This will be a major winter weather "event" for central and southern Minnesota Sunday into Presidents' Day.

-This could be the 2nd biggest snowfall of winter for many Minnesota locations. (MSP Airport picked up 17.4" in the Domebuster storm in December!)

-Travel should be okay tonight into the wee hours Sunday...but travel conditions will deteriorate rapidly Sunday morning. Travel will be very difficult to dangerous Sunday PM into Monday morning. You may want to get those "errands" done today and tonight!

Craig Edwards and I are watching the developing storm closely and will have extra updates tonight and Sunday as the storm ramps up on MPR news stations and here in Updraft.

We've set the table so to speak...now let's wait to see one more major model run tonight before the flakes start flying early Sunday morning. I'm still looking for a scenario that will produce less snow with this system, but right now I can't find one. Maybe tonight's model run will shed more light.

Prepare accordingly and stay tuned!

PH

(1 Comments)

Latest Models: GFS 22.5"...NAM 25.5"!

Posted at 9:50 PM on February 19, 2011 by Paul Huttner (9 Comments)
Filed under: Winter storms, Winter/spring 2011

I'm working on a longer version of this post, but I wanted to get the headline out there.

It looks like I'm going to raise my snowfall forecast for the metro and much of southern Minnesota for a 2nd time.

I am now leaning toward a storm snowfall total of between 10" and 20" by Monday noon for much of central and southern Minnesota, including the Twin Cities metro.

This includes Redwood Falls, Willmar, The Twin Cities, Eau Claire & Red Wing.

The 00Z (6pm) NAM run is in. The model is cranking out an incredible 1.54" liquid...and a storm total snowfall of 25.5" for MSP Airport!

The latest 18Z (noon) GFS run came in at 22.5" for MSP.

The models are producing incredible snowfall rates of up to 2" and 3" per hour Sunday late PM & evening!

The other trend is to slow the storm about 3-6 hours. It looks like snowfall will begin in the metro between 6am & 9am Sunday.

More soon....

PH

(9 Comments)

Storm Update: 10" to 20"+ snowfall totals could rival "Domebuster"

Posted at 11:09 PM on February 19, 2011 by Paul Huttner
Filed under: Winter storms, Winter/spring 2011

Update 1am Sunday:

North Platte, Nebraska radar loop detects cloud to ground lightning and heavy convective snow bursts busting out in central Nebraska at 1am. Expect "thundersnow" in Minnesota Sunday PM & evening.

Black dots indicate lightning on North Platte, Nebraska radar loop.

***
Get ready for another potential "top 10" Minnesota "snow event."

The Saturday late evening model runs are in, and the trends support heavier snowfall with the coming snowstorm.

Based on the latest model trends I am now forecasting a range of 10" to 20" storm total snowfall for much of central and southern Minnesota, including the Twin Cities metro area.

This includes Ortonville, Granite Falls, Redwood Falls, Marshall, Willmar, Glencoe, the Twin Cities, Red Wing, and Eau Claire. Within this general heavy snow band area (especially west of the metro) the storm could produce some incredible snowfall totals over 20"!

Winter storm warnings are still flying, and blizzard warnings have been expanded into southwest Minnesota Sunday!

NWS expands blizzard warnings!
(click to enlarge)

NAM places heavy 10" to 20" snow band over metro & much of southern Minnesota.
(click for bigger image)

Here are the highlights of the storm as we head into the overnight hours early Sunday morning:

Latest 00Z (6pm) model trends:
(Note: the 00Z model run is completed around 9-10pm)

Timing:

The storm motion has slowed about 3-5 hours. Snow/ice should begin in southwest Minnesota between midnight and 6am. It looks like snowfall may begin in the metro roughly between 6am and 9am Sunday morning.

Track:

The 00Z storm track is ever so slightly further south. The NAM takes the surface low track through southern Iowa vs. central Iowa Sunday. The small shift should still place the heaviest snow band right over the Twin Cities metro area.

Lee Cyclogenesis:

The surface low is developing rapidly along the lee slopes of the Rocky Mountains in Colorado. The topography of the mountains is perfect for deepening storms in the wake flow behind the mountains. Meteorologists call this rapid deepening of low pressure system "lee cyclogenesis."

-Snowfall totals:

The last two runs of the GFS and NAM have produced some eye opening snowfall totals.

The 00Z (6pm) NAM model is cranking out an incredible 1.54" liquid...and a storm total snowfall of 25.5" for MSP Airport! The latest 18Z (noon) GFS run came in at 22.5" for MSP!

NAM: 25.5"!
(click to enlarge)

Models trending ever higher with snowfall.
(click for bigger easily readable image)

While it would be easy to take these totals at face value (and they still could happen!), there are a couple of reasons why I think they may be on the high end of the snowfall range.

On reason is that the storm's geometry has the surface low evolving into more of an "open wave" late Sunday into Monday. This may stretch the storm a bit...and could result in lower snowfall rates late in the event.

Still, prior to the Domebuster storm, the models were cranking out around 17" of snow, and that's what we got (17.4") at MSP. It is possible we may see some 20"+ totals. My hunch is they will be west of the metro.

Why a 10" to 20"+ range?

The "banded structure" of heavy snowfall events produces surprisingly wide snowfall variations over relatively short distances. This is because "convective snow bursts" can deliver locally heavy snow totals in small areas, just like with summer thunderstorms.

You may recall the wide range of snowfall totals in the Dombuster storm of Dec 10-11th. There was literally a range of 10" to 23.5" in the metro with that storm. That kind of a range is possible again with this storm due to the relatively narrow heavy snow band and "banded structure" of the heavy snow bands embedded within the storm.

Snowfall rates:

The peak snowfall rates with this storm appear to be slated between noon Sunday and midnight Monday. The latest NAM is cranking out some incredible snowfall rates of 2" to 3" per hour! This is likely the result of convective snowbursts or "thundersnow." These "mini thunderstorms" embedded within the overall snow area can really put down a lot of snow in a hurry!

Do not be surprised to see (oddly colored!) flashes of lightning and hear thunder with this storm, accompanied by intense snowfall bursts during the height of the storm late Sunday afternoon and evening. With wind, heavy snowfall and thunder things could get really intense for a few hours Sunday PM & evening!

Southern Minnesota event:

Note the rapid cutoff in snowfall totals once you get north of Hinckley & Brainerd. With the tight snowfall "gradient" on the storm's north edge and the slight southerly shift, MPR listeners and weather fans in Fargo, Duluth and points north may be delighted (or disappointed!) to see little or no snowfall from this realtively narrow (north-south) system.

2010-'11:Top 10 snowiest winters?

We've piled up 61.1" of snowfall so far this winter season in the metro.

This storm (another 13.3"+) should put the Twin Cities squarely in the top 10 snowiest winters on record.

Top 10 metro season snowfalls.
(click to enlarge)

Bottom Line:

Prepare for another storm of "Domebuster" magnitude Sunday into Presidents' Day. Travel may be possible early Sunday morning, but conditions will rapidly deteriorate Sunday afternoon and evening.

Icing is still likely along the I-90 corridor in southern Minnesota.

It looks like this is going to be another one for the books by Monday. Craig Edwards will have updates on MPR News stations and here in Updraft Sunday morning, and I will be back at it Sunday afternoon and evening.

Check out my earlier posts for additional detail on the storm.

Here are some resources to keep tabs on the "Sunday Snow Blitz."

-Twin Cities radar loop
-Twin Cities NWS (latest warnings)
-Twin Cities NWS storm page

Stay safe!

PH