GAN/MET/M1 - Intermittent PWD alarm

Intermittent backscatter alarms were tripping on the PWD suggesting something was blocking 
(dew) or getting into the measurement path (spider or ants).  Problem resolved 10/9 with 
no clear indication of the cause.

• pwd_pw_code_15_min
• pwd_id
• pwd_avg_vis_10_min
• pwd_cumul_snow
• pwd_pw_code_1_hr
• pwd_pw_code_inst
• pwd_avg_H2O_int_1_min
• pwd_avg_vis_1_min
• pwd_err_code
• pwd_cumul_water