Winter Storms Studies along the Front Range of Colorado during FROST

During the winter of 2013, Colorado State University and NCAR joined forces to carry our the FROST project, Front Range Observations of (Winter) Storms. CSU contributed the CSU-CHILL National radar facility and a radiosonde unit. NCAR contributed their X-band radar and various ground based observations at their Marshall Field site. FROST marked the first extended operation of the CHILL's X-band component, sporting a 0.3 degree beamwidth antenna pattern, utilizing the CHILL's advanced, offset Gregorain design antenna.

Numerous winter storms were observed in FROST, particularly in March and April. Three significant storms were observed in April alone, which marked the 4th snowiest April in the last 100 years along the Front Range of Colorado. Nearly every event featured strong banded precipitation, in addition to weak embedded convection near the echo top. These generating cell regions were ubiquitous and were denoted by high reflectivity and near zero differential reflectivity, producing well identified fall streaks through the general upslope forced echo. Weaker reflectivity and very large Zdr surrounded the generating cell features.

Several interesting polarimetric patterns will be presented including rain snow transitions and ice crystals transitioning to aggregates. Differential phase observations at X-band are robust and used to identify areas of dendrites preceding the onset of aggregation.