Season’s first real flakes Tuesday, wide metro snow range likely

And so it begins:

9.3 inches — average November snowfall total at Minneapolis-St. Paul International Airport

Nov. 18 — average first inch at MSP

Nov. 5 — likely first inch in 2013

Image: snowcrystals.com

The season’s first real wintery weather episode still looks to be on track Tuesday p.m. and Tuesday night. This won’t be “Snowmageddon” or “Domebuster”  status, but it will be the first real taste of winter weather for most Minnesotans. A Winter Weather Advisory is in effect from 4 p.m. Tuesday until 9 a.m. Wednesday.

Image: Twin Cities NWS

There are still (always?) some unanswered questions about the incoming system. And the relatively narrow, 50 mile wide snow band with this one adds a higher degree of difficulty to the forecast for the Twin Cities. Check out NOAA’s NAM model forecast snowfall showing a very narrow snowfall band stretched right across the metro.

Image: NOAA via wxcaster.com

A slushy coating – to 5 or 6 inches?? 

That could literally be the range in snowfall totals across the greater Twin Cities metro area by Wednesday morning.

As the surface low moves north, the infamous “rain-snow line” will hover near the Twin Cities Tuesday afternoon before colder air changes precipitation to all snow by Tuesday evening.

Image: NOAA via IPS Meteostar

As always, tonight’s late model runs and Tuesday morning’s runs may shed more light. This system is not like some of our bigger winter storms in January that produce a large snow shield stretching from Grand Forks to the Twin Cities. A 50-mile zig or zag in the track of the surface low or dry air intrusion could change everything.

So caveats aside, here’s my best crack at the incoming weather system at this point.

Probable sequence of weather events Tuesday

  • Rain develops in southwest Minnesota late morning to lunchtime.
  • Rain and moves into the Twin Cities metro before the afternoon rush Tuesday. (Most likely between 1 p.m. and 4 p.m.)
  • Rain mixes with sleet, and changes to all snow during rush hour Tuesday p.m. (Most likely between 4 p.m. and 7 p.m.)
  • Warm pavement and above-freezing temperatures means roads should be mostly wet for afternoon rush Tuesday, but roads may get slick as temperatures fall to near freezing Tuesday night.
  • Snow continues, moderate to heavy at times, Tuesday night.
  • Snow tapers off just before or by around a.m. rush Wednesday.
  • Wide range of snow totals across the metro. Very narrow band of heaviest snow could be only 5 to 10 miles wide.

Snowfall totals if current track and temperature trends hold.

  • Most of the metro will probably end up in the 1 inch to 4 inch range for snowfall by Wednesday a.m.
  • Heaviest snowfall band appears to favor south and east Twin Cities metro neighborhoods at this point, a possible narrow band with some 4- to 6-inch totals.
  • We could see a range of a slushy 1 inch snow in the far northwest Twin Cities metro area around Rogers to as much as 4- to 6-inch totals in south and east.

Storm impacts and action

  • Be ready for rain changing to sleet and snow Tuesday afternoon and evening.
  • Tuesday p.m. rush hour will be wet, with roads becoming increasingly slush and snow covered Tuesday night.
  • Snowfall will begin to taper by Wednesday a.m. rush, but near freezing temperatures will mean icy conditions underfoot Wednesday morning.

Here’s a nicely detailed graphic that pinpoints expected precipitation and temperatures from the Euro model.

Image: Euro via Weatherspark

Stay tuned as we tweak snowfall totals based on late night and Tuesday a.m. model runs!

Here’s the official verbiage from the Twin Cities office of the National Weather Service:

URGENT – WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
218 PM CST MON NOV 4 2013

…SNOWFALL LIKELY TUESDAY AFTERNOON AND TUESDAY NIGHT…

A WIDESPREAD AREA OF MODERATE TO HEAVY PRECIPITATION WILL MOVE INTO SOUTHWEST MINNESOTA TUESDAY AFTERNOON AND QUICKLY SPREAD NORTHEAST INTO WESTERN WISCONSIN BY 6 PM. TEMPERATURES ON THE WESTERN EDGE OF THIS AREA OF PRECIPITATION WILL COOL QUICKLY AS THE PRECIPITATION MOVES IN…ALLOWING RAIN TO QUICKLY TRANSITION TO A NARROW BAND OF MODERATE TO HEAVY SNOW. WITHIN THIS BAND OF SNOW…IT IS POSSIBLE MANY AREAS COULD SEE 3 TO 5 INCHES OF SNOW…WITH LOCALLY HIGHER AMOUNTS OF 6 INCHES BY EARLY WEDNESDAY MORNING.

…WINTER WEATHER ADVISORY IN EFFECT FROM 4 PM TUESDAY TO 6 AM
CST WEDNESDAY…

THE NATIONAL WEATHER SERVICE IN TWIN CITIES/CHANHASSEN HAS ISSUED
A WINTER WEATHER ADVISORY FOR HEAVY SNOW…WHICH IS
IN EFFECT FROM 4 PM TUESDAY TO 6 AM CST WEDNESDAY. THE WINTER
STORM WATCH IS NO LONGER IN EFFECT.

* SNOW ACCUMULATION: 3 TO 5 INCHES…WITH AMOUNTS AROUND 6 INCHES POSSIBLE.

* TIMING: RAIN WILL OVERSPREAD THE AREA FROM THE SOUTH EARLY TUESDAY AFTERNOON WITH A TRANSITION TO SNOW OCCURRING TUESDAY AFTERNOON AND EVENING. THE SNOW WILL TAPER OFF LATE TUESDAY NIGHT.

* IMPACTS: THE FIRST HEAVY SNOW OF THE SEASON IS POSSIBLE DURING THE TUESDAY AFTERNOON COMMUTE. IN ADDITION…IT IS LIKELY TO BE A WET SNOW AND ANY TREES WITH LEAVES LEFT ON THEM MAY BE STRESSED…LEADING TO BROKEN TREE LIMBS AND ISOLATED POWER OUTAGES.