Update 1am Sunday:
North Platte, Nebraska radar loop detects cloud to ground lightning and heavy convective snow bursts busting out in central Nebraska at 1am. Expect "thundersnow" in Minnesota Sunday PM & evening.
Get ready for another potential "top 10" Minnesota "snow event."
The Saturday late evening model runs are in, and the trends support heavier snowfall with the coming snowstorm.
Based on the latest model trends I am now forecasting a range of 10" to 20" storm total snowfall for much of central and southern Minnesota, including the Twin Cities metro area.
This includes Ortonville, Granite Falls, Redwood Falls, Marshall, Willmar, Glencoe, the Twin Cities, Red Wing, and Eau Claire. Within this general heavy snow band area (especially west of the metro) the storm could produce some incredible snowfall totals over 20"!
Here are the highlights of the storm as we head into the overnight hours early Sunday morning:
Latest 00Z (6pm) model trends:
(Note: the 00Z model run is completed around 9-10pm)
The storm motion has slowed about 3-5 hours. Snow/ice should begin in southwest Minnesota between midnight and 6am. It looks like snowfall may begin in the metro roughly between 6am and 9am Sunday morning.
The 00Z storm track is ever so slightly further south. The NAM takes the surface low track through southern Iowa vs. central Iowa Sunday. The small shift should still place the heaviest snow band right over the Twin Cities metro area.
The surface low is developing rapidly along the lee slopes of the Rocky Mountains in Colorado. The topography of the mountains is perfect for deepening storms in the wake flow behind the mountains. Meteorologists call this rapid deepening of low pressure system "lee cyclogenesis."
The last two runs of the GFS and NAM have produced some eye opening snowfall totals.
The 00Z (6pm) NAM model is cranking out an incredible 1.54" liquid...and a storm total snowfall of 25.5" for MSP Airport! The latest 18Z (noon) GFS run came in at 22.5" for MSP!
While it would be easy to take these totals at face value (and they still could happen!), there are a couple of reasons why I think they may be on the high end of the snowfall range.
On reason is that the storm's geometry has the surface low evolving into more of an "open wave" late Sunday into Monday. This may stretch the storm a bit...and could result in lower snowfall rates late in the event.
Still, prior to the Domebuster storm, the models were cranking out around 17" of snow, and that's what we got (17.4") at MSP. It is possible we may see some 20"+ totals. My hunch is they will be west of the metro.
Why a 10" to 20"+ range?
The "banded structure" of heavy snowfall events produces surprisingly wide snowfall variations over relatively short distances. This is because "convective snow bursts" can deliver locally heavy snow totals in small areas, just like with summer thunderstorms.
You may recall the wide range of snowfall totals in the Dombuster storm of Dec 10-11th. There was literally a range of 10" to 23.5" in the metro with that storm. That kind of a range is possible again with this storm due to the relatively narrow heavy snow band and "banded structure" of the heavy snow bands embedded within the storm.
The peak snowfall rates with this storm appear to be slated between noon Sunday and midnight Monday. The latest NAM is cranking out some incredible snowfall rates of 2" to 3" per hour! This is likely the result of convective snowbursts or "thundersnow." These "mini thunderstorms" embedded within the overall snow area can really put down a lot of snow in a hurry!
Do not be surprised to see (oddly colored!) flashes of lightning and hear thunder with this storm, accompanied by intense snowfall bursts during the height of the storm late Sunday afternoon and evening. With wind, heavy snowfall and thunder things could get really intense for a few hours Sunday PM & evening!
Southern Minnesota event:
Note the rapid cutoff in snowfall totals once you get north of Hinckley & Brainerd. With the tight snowfall "gradient" on the storm's north edge and the slight southerly shift, MPR listeners and weather fans in Fargo, Duluth and points north may be delighted (or disappointed!) to see little or no snowfall from this realtively narrow (north-south) system.
2010-'11:Top 10 snowiest winters?
We've piled up 61.1" of snowfall so far this winter season in the metro.
This storm (another 13.3"+) should put the Twin Cities squarely in the top 10 snowiest winters on record.
Prepare for another storm of "Domebuster" magnitude Sunday into Presidents' Day. Travel may be possible early Sunday morning, but conditions will rapidly deteriorate Sunday afternoon and evening.
Icing is still likely along the I-90 corridor in southern Minnesota.
It looks like this is going to be another one for the books by Monday. Craig Edwards will have updates on MPR News stations and here in Updraft Sunday morning, and I will be back at it Sunday afternoon and evening.
Check out my earlier posts for additional detail on the storm.
Here are some resources to keep tabs on the "Sunday Snow Blitz."