Updraft: December 7, 2012 Archive

Friday Flakes? Models boosting chances for heavy weekend snow

Posted at 6:01 AM on December 7, 2012 by Paul Huttner (1 Comments)
Filed under: Winter 2012-13

Friday Forecast: Light snow possible PM & evening from the metro south

Coating to 2" possible in and south of metro this afternoon & evening

Up to 3"+ possible well south of metro & along I-90 corridor

Better chances for accumulating snows Saturday night into Sunday

What the models are saying for metro snow chances...

NAM: 4" snowfall Saturday night & Sunday

European model: Up to 4" Saturday night & Sunday

GFS: Up to 6"+ totals through Sunday for metro??

Image: Caltech

The latest model runs are in, and all major models have dramatically increased snow potential for Saturday night & Sunday.

With less than 36 hours until the system arrives, the NAM model now cranks out as much as 4"+ snowfall (.42" liquid) for the metro Saturday night into Sunday, with heavier totals up north.

Image: NOAA NAM model via wxcaster.com

The overnight European run has jumped on the recent trends set by the GFS and NAM models, and lays out .35" liquid, which would translate into about 4" snowfall.

Image: Norwegian Met Institute

The GFS is even more bullish, suggesting 18 hours of snow that could pile up to over 6"+ in the metro by Sunday night from an impressive .74" liquid.

If the GFS output of .74" verifies in the metro, it would lay down some impressive snow totals. Check out the latest 120 hour GFS snowfall output, keeping in mind this would include any snow that falls Friday.

NOAA GFS 120 hour snowfall output via wxcaster.com

The GFS is by far the most aggressive with the incoming system. It may be over the top, but the latest trends actually bring the other models closer to the GFS solution.

Image: Iowa State University

These totals may (or may not) be aggressive, but the main point is that it now appears that Saturday night & Sunday system may be more "productive."

I want to see Friday's model runs before I totally buy into the notion of heavier snow Saturday night & Sunday, but the latest trends suggest we may see a "plowable" snow event this weekend.

Snow lovers may finally have something to cheer about by Sunday evening.

Stay tuned as the Friday model runs trickle in!

PH

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Winter Storm Warning: 1" to 2" tonight; 3" to 8" Saturday night & Sunday

Posted at 1:38 PM on December 7, 2012 by Paul Huttner
Filed under: Winter 2012-13

-Update 10pm Friday-

A few metro snow totals now trickling in.

MPX: Lakeville [Dakota Co, MN] trained spotter reports SNOW of M1.2 INCH at 09:30 PM CST --

-Updated 6:30pm Friday-

PRELIMINARY LOCAL STORM REPORT NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 612 PM CST FRI DEC 07 2012

0600 PM SNOW WINTHROP M1.0 INCH
SIBLEY CO, MN TRAINED SPOTTER

STILL SNOWING. VISIBILITY ABOUT TWO MILES.

Two snow systems for Minnesota next 48 hours

System #1 Tonight 1" to 2" in metro ending late tonight

Rush hour snow affected PM rush in some areas

MNDOT trafic cam at I-35 & Co. Rd. 42 show snow & slick highways in south metro
Image: MNDOT

-Latest Twin Cities radar loop

1st snowflakes have arrived at weather lab in west metro. Expect snow coverage increase in metro next 1-2 hours. twitter.com/MPRweather/sta...

— MPR Weather (@MPRweather) December 7, 2012

Image: Caltech

System #2 Bigger winter storm for most of Minnesota Saturday night & Sunday

3" to 8" likely in the metro by Sunday evening

6" to 12"+ likely for much of northern Minnesota by Sunday night

Winter Storm Warning includes most of Minnesota from Morris to the metro into northern Minnesota

-Twin Cities NWS multimedia briefing here

Image: Twin Cities NWS

Here comes "winter"

Finally.

The season's 1st major winter storm will roll into Minnesota with significant, even heavy snow Saturday night & Sunday.

The appetizer rolls in Friday PM & evening.

Here's the latest on the 2 systems.

System #1) The first snow system is favoring the southern half of Minnesota, basically from the metro south to the Iowa border.

Light to moderate snow is moving in from South Dakota, where visibilities have dropped as low as 1/2 mile at times. Snow will overspread the metro this afternoon, and may be a factor for PM rush hour, especially the tail end and tonight.

A general area of 1" to 2" is likely, with some 3" totals possible south of the metro.

Most of the snow should end by midnight.

System #2) Season's 1st Winter Storm for metro & much of southern Minnesota.

We've been talking about snow this weekend for a week in the weather lab. The models really locked onto growing snowfall totals Thursday, and by last night's (0z) run it was clear we had a significant winter storm approaching Minnesota.

Here's a breakdown of the weekend system.

System: A fairly strong "inverted trof" of low pressure moving in from the Pacific Northwest.

Timing: Snow should begin in western Minnesota by 6pm Saturday, and spread east into the metro between 9pm and midnight.

Duration: Snow should last in the metro until about noon Sunday. That would be aboue 12 to 15 hours of snow of varying intensity.

Moisture: Various models are printing out between .28" (Euro) to .53" (GFS) to .60" (NAM)

Snowfall Totals: The models estimate about a 13:1 snow:liquid ratio with this system. That would translate to an overall snowfall range of 3" to as much as 8" for the metro. I think most of the metro may end up between 3" and 6"...with the best chance of 7" to 8" in the north metro.

Image: Iowa State University

The heaviest snow with this system will be north of the metro. I could see 6" to 12" including St. Cloud, Brainerd, Iron Range, Duluth and the North Shore by Sunday evening.

There's still some time and a few more model runs before Saturday's snow event...and thing could still change. At this point it looks like we'll see a nice coating of white around here by Sunday PM.

We're big boys and girls and used to snow in Minnesota, but this will be the first big snow for the metro so do expect some slick roads and snow covered travel this weekend.

Let it snow!

PH

Winter Finally Arrives: Snow resumes Saturday night; 3" to 7" metro range; heaviest north

Posted at 10:27 PM on December 7, 2012 by Paul Huttner (4 Comments)
Filed under: Winter 2012-13

Season's 1st "signifcant" winter storm for metro Minnesota Saturday night & Sunday

3" to 7" likely snowfall range in the metro by Sunday evening

Heaviest totals favoring north & northeast metro
(Models favor 3" to 5" at MSP Airport - more like 5" to 7" north metro)

6" to 10" likely along I-35 north of metro to Duluth by Sunday night

Winter Storm Warning includes most of Minnesota from Morris to the metro into northern Minnesota

-Twin Cities NWS multimedia briefing here

Much colder air follows the system - near 0F by Monday AM?

Heaviest snowfall totals north of the metro - wintery travel condtions pretty much statewide

Image: Twin Cities NWS

Several 1"+ snowfall totals with Friday's "appetizer" round

MPX: 1 WNW Prior Lake [Scott Co, MN] trained spotter reports SNOW of M1.1 INCH at 10:00 PM CST --

MPX: Lakeville [Dakota Co, MN] trained spotter reports SNOW of M1.2 INCH at 09:30 PM CST --

MPX: Shakopee [Scott Co, MN] trained spotter reports SNOW of M1.3 INCH at 01:00 AM CST --

MPX: 1 W NEW Prague [Scott Co, MN] trained spotter reports SNOW of M1.4 INCH at 12:05 AM CST --

Image: Caltech

Winter" finally arrives

Friday was the appetizer. The main course is served tonight.

The season's 1st major winter storm rolls into Minnesota with significant, even heavy snow Saturday night & Sunday. It may not be a "Domebuster" but looks like the first significant snow for the metro since late February.

We've been talking about snow this weekend for a week in the weather lab. The models really locked onto growing snowfall totals Thursday, and by Thursday night's (0z) run it was clear we had a significant winter storm approaching Minnesota.

Here's a breakdown of our 1st sginifcant snow system of the season.

System: A fairly strong "inverted trof" of low pressure moving in from the Pacific Northwest.

Image: Twin Cities NWS

Timing: Snow should begin in western Minnesota by 6pm Saturday, and spread east into the metro between 9pm and midnight.

Duration: Snow should last in the metro until about noon Sunday. That would be about 12 hours of snow of varying intensity.

Moisture: Various models are printing out between .33" (Euro) to .53" (GFS) to .47" (NAM)

Snowfall Totals: The models estimate about a 13:1 snow:liquid ratio with this system. That would translate to an overall snowfall range of 3" to as much as 7" for the metro. I think most of the metro may end up between 3" and 6"...with the best chance of 7" in the north metro.

Image: Iowa State University

The heaviest snow with this system will be north of the metro. I could see 6" to 10" including St. Cloud, Brainerd, and Duluth by Sunday evening.

NAM snowfall via wxcaster.com

What if? If there is a scenario where the models are off, the most likely scenario is that the storm edges a bit further north. With the metro on the southern end of the heavy snow gradient, this could conceivably reduce snowfall totals.

One more shot at a (hopefully) good model run by Saturday noon.

At this point it looks like we'll see a nice coating of white around here by Sunday PM.

We're big boys and girls and used to snow in Minnesota winters, but this will be the first big snow for the metro so do expect some slick roads and snow covered travel this weekend. Gusty winds will become a factor by Sunday PM.

Let it snow!

The magic of "snow crystals"

Snowflakes are among the most amazing creations in nature. The creation ice crystals out of "thin air" is one of nature's miracles.

It's great to see snow in our landscape again, but if you want a really up close look at snowflakes...snowcrystals.com is a must see.

I've had the distinct pleasure of interviewing North Dakota native and Caltech physics professor Dr. Kenneth Libbrecht a few times. His fascination with snowflakes began as a boy in North Dakota. He turned that into a career studying and growing snow crystals in a lab...and taking amazing photographs of his creations in the lab and natural snowflakes.

All images courtesy of Caltech and snowcrystals.com

It turns out different snow crystal types form at different temperature and humidity levels.

The morphology diagram tells us a great deal about what kinds of snow crystals form under what conditions. For example, we see that thin plates and stars grow around -2 C (28 F), while columns and slender needles appear near -5 C (23 F). Plates and stars again form near -15 C (5 F), and a combination of plates and columns are made around -30 C (-22 F).

Furthermore, we see from the diagram that snow crystals tend to form simpler shapes when the humidity (supersaturation) is low, while more complex shapes at higher humidities. The most extreme shapes -- long needles around -5C and large, thin plates around -15C -- form when the humidity is especially high.

Why snow crystal shapes change so much with temperature remains something of a scientific mystery. The growth depends on exactly how water vapor molecules are incorporated into the growing ice crystal, and the physics behind this is complex and not well understood. It is the subject of current research in my lab and elsewhere.

It's great to appreciate the snowflakes we see this weekend, and the microscopic detail and magic we can't see.

PH

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