Monsoonal flow interrupted for the weekend but returns mid next week
Thursday, July 20, 2017
Though the rainfall from the current Southwest U.S. Monsoon has only amounted to a few tenths of an inch over the past two days in the Steamboat Springs area, we will have more chances today and Friday for locally heavy rainfall, including the overnight periods.
Subtle waves of energy moving northward in the monsoonal moisture plume make local forecasting difficult, but current model forecasts have one of these waves phasing with some energy moving across the northern U.S. and traveling over our area later on Friday. This should give us our best chances for locally heavy rainfall Friday evening and overnight.
The westerly flow behind Friday’s wave will return drier air to northern Colorado for the weekend and into the early part of next week. Along with a building ridge of high pressure over the Intermountain West, there should be minimal chances for afternoon storms on Saturday, with a better chance on Sunday.
The drier air will stick around until Wednesday, keeping precipitation chances low, before a storm off the Pacific Northwest coast elongates to the south along the West Coast. This will promote southwesterly to southerly flow that is forecast to bring another monsoonal surge of moisture over Colorado. Some energy ejecting out of the West Coast trough of low pressure may provide a focus for stronger storms on Wednesday, with continued chances of more rains through the rest of the work week as the monsoonal plume of moisture remains mostly intact.
The evolution of the West Coast trough will dictate whether we see drier air for next weekend or a continuations of the moist conditions.