The rain changed over to snow later than expected. Temperatures lagged further behind the cold front than models had it predicted. Most areas missed the heavy thump of snow that was plotted to happen during the switchover. This thump came down as rain. Snow is moving into the area now and temperatures are dropping, roads will coat with slush then freeze.
RADAR AT 7:15 AM
Temperature is 36 in Westminster
Radar did not detect rain/snow line well. The radar thought it was snowing when it was raining. Radar is angled up into the sky and captures precipitation thousands of feet in the air. At this height the snow had not melted just yet and radar believed it could make its way to the ground, when it didn't.
Freezing line at surface is lagging behind. This is what will turn slush to ice.
Radar at 8:40 AM
Temperature is 33 in Westminster
Moderate snow building into the air. It will coat the drier and colder areas of the road in slush. Freezing temperatures will move in as the snow stops to freeze slush. Snow will end before 10 AM for Carroll County and before noon for Baltimore and areas south and west.
Due to a later changeover, most areas will only see up to an inch of snow and less accumulation on the roads. Snow will finish up before 10 AM for most areas. Light slushy accumulation on roads expected to freeze up as temperatures drop. Deep freeze tonight as temperatures drop to the teens, perhaps single digits in some areas.
MARGINAL CONDITIONS
Models thought the cold layer would be thicker faster and the warm air would dissipate. This took longer than expected therefore the transition happened layer.
The cold air did move in at the upper level but the warm air in place and at the surface was stubborn. Snow melted as it went through cold layer into the warm layer. As the cold air advanced, the layer of cold air gets thicker and the warm air layer thins, the snow no longer melts and comes to the surface.
This is such a tough thing to forecast because the temperatures at the surface and aloft were extremely marginal and changing. It was above 40 degrees at midnight and now it's around freezing.
Comments