Invisible Weather Trough Hits Prescott on Monday

22 January 2019   Dr. Curtis James
Surprise storm yesterday. 

An upper-level trough/surface trough swept across Arizona Monday, with an associated cold front, bringing wind gusts to 47 mph and brief wind-driven rain showers scattered across the region. Forecasts were calling for a 10% chance of showers and wind gusts up to 30 mph for Prescott, but this event proved to be more intense than forecast. The showers were not detected by the nearest NWS radars, so admittedly I was a bit surprised when it started raining at my location. The image below shows the NWS radar reflectivity from Flagstaff at the time rain was falling in the Prescott area...illustrating how the Flagstaff radar was blind to the showers over Prescott. This is because the lowest scans from the Flagstaff and Phoenix radars pass at least 5,000’ above us (Prescott is surrounded by terrain and lies 115 km away from the nearest radar). NWS radars are blind to the weather in the lower atmosphere in Prescott, which is why meteorology faculty at ERAU are submitting an NSF proposal tomorrow to acquire a local weather radar. 


     Conditions should improve this week as a high pressure ridge rebuilds over the Southwest, with temperatures above normal for the latter half of the week, although some brief cooling and breezes possible on Thursday as a week disturbance moves around the ridge from the northwest.  


C. James