Ice storm is on its way; map from the National Hydrometeorological Prediction Center

Posted on Sun, Feb 20, 2011 : 9:15 a.m.

The National Hydrometeorological Prediction Center's winter weather forecasts have detailed probability maps of severe weather. Here's one of the current ice storm forecasts, showing the likelihood of more than a quarter inch of ice.

An ice storm is on its way. This map shows the likelihood that the area will get more than a quarter of an inch of ice.

National Hydrometeorological Center

The full forecast, from 4:33 a.m. on Sunday, in all of its technical detail; I've edited only to decode abbreviations and move it out of all upper case.

Heavy snow is expected to occur along the track of a 700 mb low, forecast to progress out of Wyoming into South Dakota today. Snow develops in the zone of mid level theta-e advection and upper divergence maximum downstream across South Dakota, southern Minnesota, Wisconsin, and western Lower Michigan, which overlaps 850-500 mb frontogenesis in the area. The 00Z models and 06Z HPC QPFS support over an inch in the east center South Dakota / west central Minnesota, where the highest threat of 12+ inches of snow is depicted. The mid-level warm advection and embedded convective elements across southeast South Dakota / Iowa into southern Minnesota, northern Illinois, and southern Wisconsin leads to a precipitation type change over to sleet and freezing rain just north of the surface low track through the midwest, per the NAM/ECMWF thermal profiles. Desk output indicates (?) of a quarter to half inch liquid equivalent occurs as freezing rain, warranting a slight/moderate risk along the Iowa/Minnesota, Wisconsin/Illinois and Indiana/Michigan state lines.

If you want to decode more of these forecasts yourself, I found this National Weather Service forecast jargon list to be helpful.