Mid-winter bias of LFM-based MOS and NGM perfect prog temperature forecast

The Model-Output-Statistics (MDS) maximum temperature forecasts have exhibited a marked warm bias in mid-winter synoptic situations in which there exists a shallow cold air mass near the surface. This condition is frequently observed in the Rockies in association with intrusions of intense but shallow Arctic air nesses on the High Plains east of the Continental Divide. It is also observed in regions of trapped cold air in high western slope valleys. This paper will present recent examples of this phenomenon.