With the cool sfc temps from the CAD and near isothermal profile
aloft hovering near freezing through 600mb, initial round of
heavy precip may fall as sleet or snow mainly over higher
elevations of northeast GA this afternoon and evening. As warm
conveyer belt increases tonight, warm nose aloft warms to +2-4C
while sfc temps drop to or just below freezing. While GFS and EC
guidance, which handle CAD events poorly compared with hires CAMs,
were a little warmer, have carefully chosen sfc temp and dewpoint
guidance weighted toward CAMs and MDL National Blend of Models,
which has high weight of CAMs in first 24 hours of forecast.
Statistical and bias-corrected forecasts were much too warm and
handle rare, fast-changing events like this poorly and were not
used. Based on these sfc temps, p-types and snow/ice accumulations
were derived from top-down methodology and local studies, which were
then compared against and nudged by WPC Winter Weather Desk guidance
for a sanity check and better inter-WFO consistency. Results of
these forecasts used to drive winter storm warning and advisory
timing and areas. Appreciate coordination from WPC and surrounding
WFOs.
6z RGEM, gives us just 22-27” in my back yard!! Gonna need more beer! The 30” lollipop over Cashiers, looks delightful!
