A climatology and assessment of impactful freezing rain events from 2010 to 2019 in the Baltimore/Washington CWA

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Maskell, Courtney P.
Freezing rain events represent a challenge to the forecasters at the Baltimore/ Washington Weather Forecast Office (KLWX WFO). Even a trace or glaze of freezing rain can put the Northern Virginia traffic to a standstill. Cases analyzed for this research had a significant traffic impact, determined using cost analysis data. In order to improve understanding and forecasting, a climatology of these events in the County Warning Area (CWA) was created for the 10-year period 2010 to 2019. The number of freezing rain events per winter season (November to March) varied between 0 and 11 events, with no pattern or trend. Freezing rain events occurred most frequently during January, which does not match the monthly distribution of cold-air damming (CAD) occurrence. A subjective and composite analysis of the synoptic scale weather features showed that the events can be placed in three categories: Front to the South (FTTS) (19 out of 30 total events), Great Lakes Low (GLL) (6 out of 30 total events), and 搊ther.� Both the composites and case studies of events from the FTTS events showed that shallow low-level cold air associated with CAD was entrenched east of the Appalachians with lower tropospheric warm air advection. Dynamic forcing from the upper-level trough and jet streaks are further to the north and south (respectively).