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

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