Icing - Measurable Sleet with Freezing Rain Category

·         Consists chiefly of measurable sleet events, most often mixed w/freezing rain during the 6 hour forecast period.  

·         86% of the total events produced measurable sleet.

o        86% of the measurable sleet events mixed w/freezing rain

o        7% mixed w/snow

o        7% were all sleet

o        14% of the total events were all snow

o        14 total events


Due to the close proximity of the Atlantic and the Gulf of Mexico, an established inversion with a significant melting layer is prone to be maintained. This in part may explain the tendency for measurable sleet in Central North Carolina to be associated with freezing rain


Principal forecast issues


Vertical temperature profiles associated with the measurable sleet w/freezing rain category

o        characterized 25% of the soundings

o        33% of the soundings

o        these events were trending toward colder low level partials during the 6 hour forecast period likely due to cold air damming.

o        21% of the soundings

o        850/700 mb thickness values in the 1550s in this predominant p-type category can be associated with near freezing isothermal segments

o        when near freezing isothermal, then any melting layer aloft is very small and would lead to snow falling at the expense of sleet.


Prolonged Sleet - Tentative Findings