Updraft: February 27, 2012 Archive

Next Winter Storm Takes Aim: Metro target this time?

Posted at 12:00 AM on February 27, 2012 by Paul Huttner
Filed under: Winter 2011-12, Winter storms

13.5" snowfall in Silver Bay Sunday!

Heavy snowfall totals in northern Minnesota Sunday

Next storm takes aim at central/southern Minnesota Tuesday-Wednesday

Winter Storm and Blizzard Watches/Warnings for Minnesota

Heavy snowfall likely for much of central Minnesota including metro!

Mixed sleet/ice/rain for southern Minnesota (significant icing possible)

1" to 2" liquid precip content by Wednesday PM?

6" to 12" widespread snowfall totals likely, with 1'+ totals possible

Next system taking shape:

It was 1 week ago that our weather pattern shifted into "active" mode. Since then 3 separate storm systems have clipped parts of Minnesota with snow.

We focused on northern Minnesota Sunday, now it looks like central and southern Minnesota, and greater Twin Cities Metro, are under the "Bull's Eye" this time.

System #4 is taking aim Tuesday & Wednesday, and it looks like a duzy.

We're still a good 24 hours away from the main body of the storm so the track may still change, but this could likely be the biggest snowfall this winter in the metro and much of central Minnesota.

Let's break down the system as it looks heading into early Monday.

The System:

A classic "Colorado Low" pressure system forming on the lee side of the Rockies in Colorado Monday. Colorado Lows tend to produce heavy snowfall totals for Minnesota, and can trigger lighting and thunder.

The Track:

There are still some slight (but important) differences in track forecasts for the low pressure center.

The 0Z NAM tracks the surface low from Sioux City, IA east through northern Iowa Tuesday to La Crosse by early Wednesday.

This track would favor all snow for the metro and bring the snowfall "bull's eye" from Willmar through the Twin Cities.

The 0Z GFS favors a more northerly track along the I-90 corridor from Worthington to Rochester.

This track allows warmer air to mix into the metro, and could change snow over to a mix of sleet or ice for several hours Tuesday night-Wednesday morning. It may also allow some "dry slotting" to taper snow intensity early Wednesday. This would reduce snowfall totals in the metro and place the snow "bull's eye" north of the metro from Alexandria to St. Cloud and Mora and Siren, WI.

The European model favors the more northerly GFS track.

Timing:

The GFS is faster and brings snow into the metro by just after midnight early Tuesday morning. The NAM holds off until around 6am Tuesday.

Duration:

Most models end snowfall from west to east Wednesday PM. (around 3pm for the metro)

When you subtract out a period of mixed precip (midnight-6am Wednesday) and a potential "dry slot" the total duration of snowfall appears to likely be around 27 hours.

If snowfall rates average .5"/hour during the storm...that would be a good 13" of snowfall.

Precip Totals:

The models are cranking out about 1.5" of liquid precip for this event in the metro and central MN.

Some may fall as a mixed bag of ice/sleet/rain in and south of the metro. In areas that see all snow, that could produce 15" at a 10:1 snowfall:liquid ratio...which seems likely for this event.

Bigger picture...

Regardless of precip type (rain/ice/snow) that much precip will be a blessing for drought stricken areas in the storms path!

With current snow cover and the coming storm, that could be 2" of runoff for rivers & lakes this spring.

Snowfall Totals?

So the big question for many is..."How much will I have to shovel/drive through?"

Take a look at the differences from the late Sunday night model runs!

GFS model favors 6" to 12" in metro with higher totals north

NAM model favors snow "bull's eye" of 15" in the metro!

I still want to see Monday morning's model runs for any track shifts and see how much warm air surges north ahead of the system. But at this point here's what I expect from the weather lab.

-Widespread 6" to 12"+ snowfall totals from Alexandria through St. Cloud south into the Twin Cities metro by late Wednesday.

-There will be some 12"+ totals (as high as 18"?) somewhere between the metro and Alex-St. Cloud.

-There still is a chance for 12"+ totals in the metro, if the storm follows the NAM's "southern solution."

Wind & Blizzard Warnings!

Forget about snowfall totals for a minute. There will be enough snow and wind in western Minnesota to generate blizzard conditions Tuesday into Wednesday.

Blizzard watches/warnings will fly and travel will be downright dangerous in much of central and western Minnesota.

Stay tuned as we get a look at Monday's early model runs, and batten down the hatches for the potential for heavy snow by Tuesday!

PH

Winter (Slop?) Storm: Major uncertainties linger for metro precip type

Posted at 8:39 AM on February 27, 2012 by Paul Huttner (3 Comments)
Filed under: Winter 2011-12, Winter storms

Northward track shift in Monday AM model runs

Reduced snowfall output for Twin Cities from major models

Snow bull's eye shifting north now favoring central Minnesota

Winter storm/blizzard watches & warnings for Tuesday & Wednesday

Major uncertainties still for metro precip types

Precip starts as snow then trending toward mostly rain Tuesday PM/evening for the metro?

-Major 2" "rain event" possible for metro and southern Minnesota with localized street flooding??

Here we go again!

Let me say from the outset, this is going to be one tough storm to forecast for the Twin Cities metro.

It looks more likely today that central Minnesota is in line to pick up heavy snowfall with a widespread area of 6" to 12" including Wheaton, Morris, Alex, St. Cloud, Mill Lacs, Mora and Siren, WI.

Monday AM model trends suggest the Twin Cities is on the razor's edge of rain/ice/snow with the coming winter storm Tuesday & Wednesday.

Take a look at how the forecast models have crashed on metro snowfall output between Sunday PM and Monday morning. The NAM model plunged from 17.4" (Sunday 0Z run) in the metro to 1.5" by Monday morning!

The reason? A northward shift in storm track. The new tracks allow warm air to surge north. If that scenario verifies, snow will change to rain during the height of the storm, and much of the precip could fall as rain instead of snow in the metro!

12Z (Monday morning) NAM model brings 850mb freezing line north of the metro by Tuesday evening. This is often the "rain-snow" line.

Here are some trends in models early Monday.

-Still expecting a major winter storm for Minnesota Tuesday & Wednesday

-Latest model trends suggest a jog north in surface low, with rain snow line moving into the metro Tuesday

-Heaviest snowfall "bull's eye" favors central Minnesota; along a Morris-St. Cloud-Mille Lacs-Mora-Siren, WI line where 6" -12"+ could fall

-Models still favor a good 1" to 2" of liquid precip, which will benefit rivers & lakes in Minnesota regardless of precip type!

-At this point, I'm inclined to favor a mix of precip types for the metro, which will greatly reduce overall snowfall totals for the Twin Cities metro. (The latest GFS run suggests only 1.9" of snowfall at MSP Airport with this system, with around 1.2" of liquid precip!)

-There could be a huge snowfall "gradient" from north to south across the greater Twin Cities metro as warm air changes precip to ice/sleet/rain later Tuesday.

-Trends suggest enough warm air may surge north to change precip to all rain in the metro by Tuesday PM/evening!

The change to all rain during the height of the storm would reduce snowfall totals significantly for the metro.

Bottom line?

-Latest trends indicate a more "northward" trend with the track of the storm.

-Warm air surging north may change precip to a mix of sleet/ice or even rain in the metro

-Latest trends push heavy snow band (6" to 12"+) north & west of the metro

-Latest metro snowfall trends support lesser snowfal and higher mixed sleet/rainfall totals

-It looks like mostly rain with little snow accumulation along the eastern I-90 corridor (Albert Lea Rochester & La Crosse)

-Either scenario favors heavy precip totals over 1" of liquid Tuesday & Wednesday

Stay tuned!

Brown snow up north??

There are reports of "brown snow" from Sunday's system in northern Minnesota. Apparently, wind borne soil particles from dry areas in the Dakotas may have fed into the system, creating some brownish tint to some of the snow.

Here are the details from Jay Austin of the Large Lakes Observatory.
(Thanks to Jay Austin & Dr. Mark Seeley for passing this along!)

Hi Paul,

Got this email from Jay Austin at the Large Lakes Observatory in Duluth, also got a phone call from the tribal community up north. Both remarked about the brown snow falling across central and northeastern Minnesota, undoubtedly as a result of the dry, bare soil in the eastern Dakotas and western Minnesota where the strong winds picked up soil particles.....thought you might be interested........

Sure looks like we'll set some Leap Day precipitation records this year.

Mark

From: Jay Austin
Date: Sun, Feb 26, 2012 at 8:42 PM
Subject: brown snow?
To: Mark Seeley

Hi Mark-

Something that you and Paul Huttner might be interested in (couldn't find his contact info online- pass this on if you'd like)- the snow that fell this morning in Duluth had a very distinct brown tinge to it, compared to the very white snow that fell earlier in the week. Is this associated with a dust storm somewhere? Noticed this in several places around town, so it seems like it was pretty widespread.

No Frank Zappa jokes, please.

jay-

PH

(3 Comments)

Storm Shifts North: Metro "Slop Storm"? St. Cloud & Duluth heavy snow!

Posted at 5:18 PM on February 27, 2012 by Paul Huttner (3 Comments)
Filed under: Winter 2011-12, Winter storms

Winter Storm Warnings kick in Tuesday

Blizzard Warnings for western MN & eastern Dakotas

Storm track shifts north - again!

Heavy snow band from Wheaton-Morris-Alex-St. Cloud-Brainerd-Duluth (8" to 16" possible!)

Mixed precip types looking more likely for the metro

Starting as snow in the metro Tuesday AM - mix to all rain PM/evening?

Heavy rain possible (Up to 1"+?) Tuesday evening from the metro south!

Localized street ponding & flooding Tuesday night in the metro and south

Good news for easing MN drought regardless of eventual precip types!

Northward Shift Holds:

**That's the main headline as we head into Monday evening. The northward shift I talked about in this morning's model runs has held firm in the PM (18Z) model updates.**

Local NWS offices have acknowledged the northward model shift, but are (understandably) reluctant to let the notion of heavy snowfall go for the greater Twin Cities...even as the Duluth office has expanded winter storm warnings northward to account for the northern track shift.

Here at the Weather Lab I'm leaning more towards a "snow sandwich" for the metro. Precip begins as snow Tuesday AM...changes to a mix Tuesday PM then all ran by Tuesday evening. It may go back to all snow by around 3am Wednesday, but by then a dry slot could shut off heavy precip, keeping snow totals down.

NWS seems to be betting on some "dynamic forcing" with intense precip rates that could keep precip mostly snow in the metro...and that could happen. But right now I'm just seeing too strong of a push of warm air above freezing in the lowest mile of the atmosphere to be overcome by drawing down colder air form aloft.

Honestly, I'm a little freaked out that NWS has not gone stronger toward the mostly rain solution fore the metro. Like they say in those PGA golf promos; "Those guys (and gals) are good."

I'm going to be looking again hard at my forecast tonight before the snow flies to see if there is a trend toward keeping mostly snow in the forecast for the metro. Right now I appear to be the outlier on the low side of snow forecast totals, leaning more toward mostly rain.

Time will tell.

Here the latest breakdown of the system pending tonight's final model runs before the snow starts to fly!

Track:

The system has shifted track again to the north, supporting Monday AM model trends. 24 hours ago some models tracked the surface low through northern Iowa. Now the GFS and NAM agree on a track from Sioux Falls to the Twin Cities.

Timing:

Expect snow to break out after midnight tonight in southwestern Minnesota and work east. The GFS brings snow into the metro by sunrise, the NAM holds off until later Tuesday AM.

Precip type:

It looks like all snow at the onset of this event. Snow will begin to pile up early Tuesday morning in western and central Minnesota and continue all day.

In the metro, snow should begin in the morning and stay all snow until afternoon.

By Tuesday 2-4PM there should be a changeover from snow to mixed precip (sleet?) from the metro south... and then a gradual change to all rain later in the afternoon.

Heavy rainfall?

There are indications that the heaviest precip may fall as rain from the Twin Cities south at the height of the storm Tuesday night.

The NAM is cranking out as much as 1.5" of rain in the metro and south along I-35 Tuesday night!

If that happens, there will likely be localized street flooding and ponding of water from rain & snow melt in the metro and south Tuesday night.

Snowfall totals:

As you would expect, the northern track shifts the heaviest snow band to the north.

Right now it looks very likely that the heaviest snow band (all snow for the duration of the event) will run from west central Minnesota (Browns Valley, Wheaton Ortonville & Morris) through central Minnesota (Alex, St. Cloud, Mille Lacs, Mora) into north central Minnesota (Brainerd, Hinckley, and Duluth.)

In these areas anywhere from 6" to 12"+ is likely, with some totals possibly up to or exceeding 18"!

NAM confirms northward snow trend.

In the metro I am expecting a shot of 1" to 3" of snow Tuesday morning before the changeover to sleet/rain. We may pick up another inch or so on the back side of the system Wednesday.

Overall I would say a range of 1" to 4" looks likely for the metro, with the best chance of 4" in the northwest metro. (Anoka, Maple Grove, Buffalo) Snowfall totals should increase accordingly as you move up I-94 towards St. Cloud, where a foot of snow is quite possible.

If the warm air push is not as strong, or the track jogs south again in tonight's model runs I may have to increase snowfall totals for the metro.

Needless to say, stay tuned to see what tonight's model runs do as things can still change!

Next update by around 11pm tonight!

PH

(3 Comments)

Still On Track: Mostly rain metro; Heavy snow north; 50s by Monday??

Posted at 10:16 PM on February 27, 2012 by Paul Huttner (1 Comments)
Filed under: Winter 2011-12, Winter storms

1.1" NAM model precipitation output for MSP Tuesday & Wednesday
(mostly falling as rain!)

0.7" NAM snowfall output for MSP

7" to 15"+ snowfall likely from Alex to Brainerd and Duluth!

Northern track confirmed on Monday evening model runs

Winter Storm Warnings in effect for much of central Minnesota

Blizzard Warnings for western Minnesota

Still On Track:

The Monday night models confirm my earlier thinking today about the track of Tuesday's storm. It looks like yet another case of a near miss for snowfall in the metro this "winter."

Meanwhile this storm will be serious business from the eastern Dakotas right through central Minnesota to Duluth. Heavy snowfall totals and wind will make for difficult travel in much of the region. Sustained winds of 35 mph may create blizzard conditions from near Morris to along I-94 near Alexandria Tuesday night into early Wednesday.

Heavy snow band stays north:

Snowfall totals and coverage still look similar to my earlier posts today, meaning the heaviest snow will fall from Morris to Alex, near and north of St Cloud, through Brainerd to Duluth.

A cool foot could pile up in these areas by late Wednesday.

Metro leans mostly rain: Some "backside" snow?

If anything the evening NAM nudged the system slightly further north/west. That means the warm air may get here about the same time as the precip.

It appears snow or a mix could move into the metro by morning or early afternoon Tuesday, and quickly change to mostly rain. The NAM model raises temps to 33 degrees by 11 am Tuesday, then to 38 by 3-4pm at MSP Airport...and keeps temps above freezing through Tuesday night.

That should mean rain... and mostly wet streets for the greater Twin Cities during most of this event.

We may pick up a quick coating of snow before the changeover early Tuesday, and another shot of snow from the backside "wrap around" Wednesday in the colder air behind the system. I now expect mostly rain with this system...but the metro could pick up 1" to 2" on the systems back side Wednesday.

February rain storm?

One of the more interesting facets of this system is the amount of rainfall that the storm may dump on the metro and areas of southern Minnesota.

Various model runs have been cranking out 1" to 2" of liquid precip with the storm. Monday night's NAM trimmed this to 1.1" for the metro.

GFS model: Up to 2" of rain for metro??

If we get an inch (or two?!) of rain and 38 degrees on top of the .5" water content snow cover from last Monday's metro storm, there's going to be rapid runoff and water in the streets by later Thursday.

Look for some big puddles and the potential for rare February local street flooding from the metro south by Tuesday PM rush and especially Tuesday evening & overnight!

Oh yeah, and there may be enough "lift" to generate some thunder later Tuesday and Tuesday night!

To top it off, the GFS is hitning at a major warm surge Sunday & Monday. Temps may push into the 50s by Monday!

The Grateful Dead might have said it best about this "winter" in Minnesota. "What a long, strange trip it's been!

PH

(1 Comments)