Saturday, February 19, 2011

00z NAM Report

-NAM is colder
-Precip is slightly more south.

Concern of Freezing Rain change to Rain

Recent forecasts have been predicting a changeover in portions of the Great Lakes from Frzg Rain to Rain, but a run of the SREF somewhat objects to this.
Below is the SREF take on the chance for freezing rain turning into rain.
In the image around one day from now, we see a somewhat elevated risk of freezing rain turning into rain. The most risk centered around the Wisconsin/Illinois border.
3 hours later, the probability of freezing rain into rain has gone down and is much less disorganized. That leads to thinking that changeover may not be as predominant as thought.
Another 3 hours further, the risk for changeover continues but is more disorganized and now practically nonexistent.
These images are leading me to believe that the GFS model is incorrect. The SREF handled the Blizzard of 2011 well, as well as the ECMWF.
But the SREF has handled all storms in short-range quite well, so there is much reasoning behind new thinking.
Current thinking by The Weather Centre is the following:

SREF Evaluation: Mean Snowfall Accumulations

This is an evaluation of mean snowfall accumulated over 12 hours. The model is the SREF.
Below is where we'll start off, with the SREF image of about 30 hours out from now.
We see heavy snowfall totals centered around the Dakota areas, with upwards of 15'' in 12 hours.
A blizzard is expected in the Dakotas.
We also see precipitation beginning to spread eastward into the Great Lakes and putting down widespread 4-6'' totals in 12 hours.
Below is the next 12 hours image from the SREF.
12 hours later, we see heavy snowfall being projected in the Upper Midwest, particularly Minnesota into Central Wisconsin, even back into New York. The Dakotas will still be in bands of heavier snowfall.

Mesoscale Discussion #108

As strong low pressure moves eastward, heavy snows with rates of up to 2 inches/hour are possible.
Snows located in back end of storm as main circulation of upper low moves off.
Further analysis: Not warranted.

Overall Storm Forecast

Here at the Weather Centre, we do project low pressure to move across the Midwest through North Illinois and the Ohio Valley. Icy conditions will be present across Chicago and areas around Illinois 1-80 westward through the Midwest. People north of the highlighted ice region will receive quite a snowfall, possibly over a foot. And areas south of the projected low pressure will get rain.

Large Winter Storm to impact the US on Feb. 19-23

A major winter storm is forecast to hit the Plains, Midwest and Great Lakes starting tonight.
This storm is still not being handled well by the computer models nor the SREF. The Weather Centre team will be working round the clock to provide as much info as possible.
Extreme ice accumulations will occur in the South Great Lakes west into the Plains. Areas may receive up to 1 inch of ice. People south of the warm front projected will receive rain.
There are 3 colors in the snow area. The light blue band is where people could receive over a foot.
Make sure you stay safe as this storm arrives.