First fall cold fronts move through the area Saturday and again next week
Thursday, August 21, 2014
Currently, mid and high level clouds from tropical storm Lowell off the Baja cost have overspread the area, keeping temperatures cool in the wake of a storm system that moved through the area late Tuesday and Wednesday. Cool temperatures should minimize the threat of showers today before a complex area of low pressure currently located off the northwest coast affects our area later Friday and through Saturday.
As this low pressure system moves west, another area of low pressure left behind from the Tuesday night storm in southern California will be forced to move northeastward and will travel over our state by late in the day Friday. There is some model uncertainty with regards to the exact track of this system and that will affect whether the rain comes earlier or later Friday, but periods of heavy rain appear likely sometime Friday afternoon through early Saturday morning.
Following closely on the heels of this system, the main fall-like storm from the northwest will first produce showers later Saturday and then produce rapidly falling temperatures and likely heavy rain again as the main front moves through late in the afternoon or evening. Rain is forecast to persist for a significant portion of the night before clearing early Sunday morning, and there may even be a dusting of snow at the highest elevations of the Colorado Rockies.
Sunday should be unseasonably cool in the wake of our first fall front, with lots of sun early and perhaps a stray shower late. At this point, further model disagreement about the evolution of a trailing wave makes the forecast very uncertain. The European ECMWF hangs this wave back before finally moving it over our area mid to late week, while the American GFS keeps this wave progressive, moving it over our area around Tuesday.
In either case, another rainy and cool day looks to occur sometime during the next workweek. After this storm passes, the forecast points towards dry weather and seasonably warm temperatures as westerly flow cuts off the very persistent and long-lasting monsoon, which has been producing steady rains since the beginning of July.