Winter’s dress rehearsal, PM mix to all snow by evening

Here we go! Welcome to winter 2013-’14’s first salvo.

It’s not Snowmageddon 2013, but our well advertised rain and sleet to snow system is still on track as it moves into Minnesota today and tonight. The wintry mix rides in with a low pressure system that’s producing snow in the Black Hills and streaking across South Dakota.

You can track the precip here as the system moves in today.

Latest Sioux Falls, S.D., radar loop

Latest Twin Cities radar

The rain snow mix changes to all snow by this evening in the metro.

Here’s the Twin Cities National Weather Service “graphicast” estimate on timing today and tonight.

(Image: Twin Cities NWS)

A rain/sleet mix should change to all snow in the metro between around 5 p.m. and 7 p.m. tonight. Roads will likely be mostly just wet for the afternoon rush, but as snow intensity increases and temps fall to near freezing, roads will get slick tonight.

How much snow? I’m leaning 1 inch (far northwest metro) to 4 inches as a metro range, but I could see a narrow band of 3 inches to 6 inches from Worthington to Mankato, to Lakeville in the south metro.

Here’s the Twin Cities NWS notion of snowfall accumulations through tonight.

(Image: Twin Cities NWS)

One interesting way to look at accumulation is to use many models in a so called “ensemble” forecast. Here’s a look at the chance for snowfall of 2 inches or more from the National Oceanic and Atmospheric Administration’s Weather Prediction Center, and the explanation of the 32 member ensemble that includes NOAA’s Short Range Ensemble Forecast, the North American Mesoscale System, Global Forecast System models and the European and Canadian model products.

(Image: NOAA Weather Prediction Center)

The operational WPC Winter Weather Desk (WWD) creates 24-h forecasts of snowfall and freezing rain accumulations for each of three consecutive 24-h periods (days) extending 72 hours into the future. These products are shared with the NWS Weather Forecast Offices (WFO) in a collaborative process resulting in refinement of the accumulation forecasts. After the 24-h snowfall and freezing rain accumulation forecasts are finalized, the WWD issues its public products: a limited suite of probabilistic winter weather forecasts

A multi-model ensemble is utilized to create a distribution of values around the WPC accumulation at each grid point. The typical constituency of this ensemble is as follows:

 21 NCEP Short-Range Ensemble Forecast (SREF) members
1 NCEP North American Mesoscale (NAM) 12Z (day) or 00Z (night) operational run
1 NCEP Global Forecast System (GFS) 12Z (day) or 00Z (night) operational run
1 European Center for Medium-Range Weather Forecasts (ECMWF) latest operational run
1 Canadian Model (CMC) latest operational run
1 ECMWF latest ensemble mean
1 NCEP Global Ensemble Forecast System (GEFS) latest ensemble mean (6-h SLRs)
5 NCEP GEFS members, randomly selected

32 Total members

Here’s a look at one model’s snowfall output for tonight. NOAA’s overnight run from the  North American Mesoscale model lays out the heaviest snowfall from southwest Minnesota toward the southern metro.

(Image: NOAA via wxcaster.com)

Here’s the NAM updated morning run…which shifts the snow band slightly south. To my eye 1″ to 4″ still looks like a pretty good metro range…with the best chance for 4″ totals in the south metro. Looking at snow intensity trends in South Dakota this morning, I can still see a narrow band of 3″ to 6″+ that may creep up into the south metro.

Image: NOAA via wxcaster.com

This will be a good day to vote or get shopping done early and sit back and watch the snow fly tonight!

  • Dana Moore

    already over 5 inches in Marshall!