Update: 8-14" Possible (heaviest amounts south metro and southern MN)

Just got a look at the very latest guidance - comfort level is pretty high that much of the metro is going to pick up close to a foot of snow, an overall range of 8-12" for the metro by lunchtime on Monday. The best chance of 10-12", even 14" will probably set up over the south metro, with under 6-8" for the northern suburbs.


* 18z run shifts the very heaviest snow band just south of MSP, but it's still too close to call where that heavy band will set up.

Winter Storm Warnings are posted for Sunday into early Monday, try and get your travel plans and errands out of the way today, if at all possible. I still think travel conditions will go from very poor (morning hours Sunday) to treacherous (by Sunday afternoon/evening).

The heaviest snows come from midday Sunday into early Sunday night, when snow may be falling at the rate of 1-2"/hour. Sustained winds will reach 25-35 mph Sunday afternoon/night, close to blizzard criteria.

I say this with all humility and respect, but travel isn't recommended after midday tomorrow. The very worst travel conditions will probably be Sunday evening/night.

Cold enough for all snow - a little ice is possible near the Iowa border.

Another 1-2" may fall early Monday morning, but the brunt of the accumulation comes Sunday and Sunday night.



Latest Guidance. The intermediate 18z NAM run keeps the very heaviest snow band just south of MSP, with closer to 8-12" for much of the metro, and as much as 15-20" for Mankato and Rochester. We'll see if this is a fluke or a real trend in the models. Not sure how we see anything less than 6-8", but the best chance of a foot more more may be over the southern suburbs.

Risk Of A Foot And A Half Of Snow. The 12z morning run of the NAM suggested that the heaviest snow bands would set up almost directly over the Twin Cities, St. Cloud and Willmar Sunday and Sunday night, but the 18z afternoon run shifts the heaviest bands to the south. We'll see what the 00z run holds, whether the 18z run is a true trend, or a fluke.

Good News: We Won't See This Much Snow. But a foot or more may fall tomorrow into Monday morning, probably the second biggest snowfall of the winter season in the Twin Cities. 17.1" fell on December 10-11, 2010. Not sure we'll see that much, but a final number in the 8-14" range is certainly possible, the best chance of 12 or 14" coming over the southern suburbs.

Converging Model Solutions. All the models are grouped fairly tightly together, ranging from .8" to 1.2". Our confidence level is fairly high that we'll pick up at least 10", with an outside shot at 14" for parts of the south metro by Monday morning.

A Wide Swath Of Winter Storm Warnings. A huge hunk of real estate is in the warning, meaning it's imminent - it's coming, any doubt has been largely erased. All those green counties to our south are under flood warnings - last week's remarkable thaw melted most of the snow on the ground, resulting in some premature flooding.

Latest NAM Solution. 1.21" (a little more than last night's run) works out to 10-12", depending on the final snow/rain ratio.

Take A Deep Breath. One model is hinting at 17" for the metro area, with an average snow/rain ratio closer to 16/1 for the lifetime of the storm. I don't think we'll see 17" here in the metro, but some towns just to our south could wind up with 15-20" by Monday morning. Bottom line: it's going to be a pretty significant pile of snow by Monday, one of the snowiest President's Day in recent memory. Thank goodness many kids already have Monday off!

Timing The Storm. The heaviest "bursts" of enhanced upward motion and heavier snow at the surface arrive around midday Sunday, but the latest (12z) NAM model suggests the strongest upward motion Sunday evening, when snow may fall at the rate of 1-2"/hour.

Blizzard Potential. Latest models show sustained winds of 23 knots (about 25-26 mph) Sunday evening here in the metro area - but I'm concerned about the latest Bufkit analysis, which shows 40-50 mph sustained winds only 1,000 feet above the ground Sunday evening and early Sunday night. If some of that high velocity air works down to the surface we could have marginal blizzard conditions, especially over central and southwestern Minnesota, where the pressure gradient will be even tighter.

Midday Saturday Update From the National Weather Service (fairly technical, but I thought the die-hard weather freaks....and I say that with all love and devotion....might want to see this):

FOCUS TURNS TO NEXT SNOWSTORM FOR THE AREA. WATER VAPOR IMAGERY
SHOWING STRONG TROUGH LIFTING NORTHEAST ACROSS THE SOUTHWEST US.
BLENDED PERCENT OF NORMAL PRECIPITABLE WATER SATELLITE PRODUCT
SHOWS LARGE AREA OF OVER 200% OF NORMAL PRECIPITABLE WATER VALUES
MOVING ACROSS THE SOUTHWEST US. THIS SOURCE REGION THEN LIFTS
NORTHEAST AS THE NEGATIVELY TITLED TROUGH LIFTS NORTHEAST AND
GENERATE CYCLOGENESIS OVER EASTERN COLORADO LATER TONIGHT. THIS
WILL SPREAD THICKER CLOUDS INTO THE SOUTHWEST THIS EVENING AND
DEVELOP THE THREAT OF SOME LIGHT SNOW THERE BEFORE MIDNIGHT.
STRONG WARM SURGE...ESPECIALLY AT MID LEVELS LIFTS NORTHEAST AHEAD
OF THE SURFACE LOW WHICH MOVES ACROSS KANSAS TO IOWA BY SUNDAY
EVENING. STRONG FORCING ASSOCIATED WITH COUPLED H25 JET MOVING
THROUGH THE AREA SHOULD GENERATE STRONG FORCING FOR SOME HEAVY
SNOW. BOTH NAM AND ND GFS INDICATE HEAVIER SNOW BAND TO DEVELOP ALONG
AND NORTH OF THE MN RIVER VALLEY...AFFECTING MUCH OF CENTRAL MN
INCLUDING THE TWIN CITIES. CURSORY LOOK AT POTENTIAL HIGH SNOW
AMOUNTS VIA BJ COOKE TECHNIQUE INDITES AROUND 14 INCHES POSSIBLE.
THIS MATCHES PRETTY WELL WITH THE BUFKIT/CARIBOU SNOW
ACCUMULATIONS...ESPECIALLY OVER CENTRAL MN. THIS LEAVE A LARGE
AREA OVER OVER 10 INCHES ACROSS CENTRAL MINNESOTA INTO WEST
CENTRAL WI...WITH 13-15 INCH AMOUNTS POSSIBLE IN THE HEAVY SNOW
BAND. THIS BAND DEVELOPS OVER OVER THE METRO SUNDAY MORNING PER
GFS FRONTOGENESIS BAND AND MINUS 15C OMEGA FIELD. IT DEVELOPS OVER
CENTRAL MN AND PIVOTS ONLY SLOWLY TO THE EAST DURING THE DAY. THIS
SHOULD YIELD AT LEAST 1 INCH AN HOURS SNOWFALL RATES UNDER THIS
STRONGLY FORCED LIFT ZONE.