A very slow moving storm system in the lower and middle portions of the atmosphere will combine copious amounts of moisture to produce heavy precipitation across the Front Range Mountains and Foothills as well as the Northeastern Plains of Colorado. The precipitation will start on Friday afternoon when numerous thunderstorms will develop across the area, and these storms and areas of heavy rainfall will continue through much of Friday night and Saturday elevating the possibility of flash flooding. Initially, snow levels will be high – above 12000 feet – but a cold front will push into northeastern Colorado early Friday morning, and this will allow for snow to fall at lower elevations. The snow level will be a tough call. The NAM and GFS model runs from this morning hint at snow levels dropping down to 8000 feet or slightly lower by mid day Saturday, meaning that frosty flakes could be in the air in the Foothills towns of Nederland, Ward, Black Hawk, and Rollinsville. With the recent warm temperatures, accumulations should be light, but higher up in the Indian Peaks the National Weather Service is calling for 8-18 inches of snow.
More significant is the threat of flash flooding. This slow-moving, moisture-laden storm with its associated slow-moving thunderstorms will result in areas of excessive rainfall and the possibility of flooding. Rainfall amounts vary wildly in the forecast models ranging from about 1 inch of liquid for the Northern Foothills on the NAM to 5 inches (yes, 5 inches) on the GFS. The latest dew point graphic from Unisys Weather shows very moist air streaming into Colorado from the east, and this moist air is fuel for thunderstorms and heavy rain:
Here is the latest precipitation forecast from the NWS Weather Prediction Center. It shows a bulls eye of substantial precipitation over Northeastern Colorado:
We’ll keep you updated as new information becomes available. Stay dry!