Thursday, July 27, 2017
The Steamboat Springs area finally received some beneficial rainfall from one of Southwest U.S. Monsoon surges that have been passing through the last few weeks. Around a half inch of rainfall was recorded in several locations around the city from Tuesday night through Thursday afternoon, with the town waking up to a rare steady rain Wednesday morning.
Activity will decrease today, but rain chances increase again later on Friday as the northern California low pressure system talked about in the last forecast begins it’s eastward trek across the Great Basin. Some energy ejects out ahead of the storm and moves over our area later Friday, increasing chances of rainfall Friday afternoon and evening.
After the ejecting wave passes, the northern California storm moves bodily into the Great Basin on Saturday, pushing the ridge of high pressure over the western states eastward. Another monsoonal surge appears on the the western periphery of the ridge, and embedded sub-tropical waves will once again increase the chances for locally heavy rainfall Saturday afternoon and evening.
Model disagreement makes Sunday’s forecast uncertain with the northern extent of the sub-tropical moisture battled by some dry air to our north. There could be another chance of locally heavy rain on Sunday or it could be drier than Saturday.
By Monday, there is model agreement that another robust surge of monsoon moisture and energy will begin and last through Tuesday. If the energy moves as far north as currently forecast, Steamboat Springs has a good chance of locally heavy rain for both days.
Longer range models have the western ridge retreating back westward as energy over the eastern two thirds of the country interrupts and reverses the eastward progress of the ridge. Much drier air is advertised for the rest of the work week and heading into the following weekend. This may spell the end of our monsoon season as the two week forecast has the strengthening westerlies of our next season moving southward. If this occurs, it will suppress any northward moving moisture and energy from the southern latitudes to our south.
Monday, July 24, 2017
The U.S. Southwest Monsoon will be re-invigorated tomorrow, a day faster than advertised in the last forecast. Currently, a storm off the West Coast has split, with the northern part of the wave forecast to move along the northern U.S. border during the week while the southern part loiters over the northern California coast until midweek.
Meanwhile, a well defined wave of energy from the tropics is currently moving northward in southern Arizona, and will conspire with some energy ejecting out of the northern California storm to bring a good chance of rainfall, some locally heavy, for the entire state of Colorado on Tuesday.
While this complex will move east of the Steamboat Springs area by early Wednesday, additional energy ejecting out of the northern California storm will keep a good chance of rain for Wednesday as well, though the chances are less robust than Tuesday. But stronger and sparser storms are possible later Wednesday and Wednesday night courtesy of a very weak cool front grazing our area from the wave moving along the northern U.S. border.
Eventually by Thursday, the northern California storm will penetrate inland and move northwest of Colorado, displacing the ridge of high pressure over the Rocky Mountains eastward. This keeps a weak monsoonal moisture plume over Colorado in the southerly flow on the west side of the ridge, for a continued chance of rains on Thursday.
Drier air is advertised heading into and likely through next weekend, though there is some mid and upper-level moisture that will likely not lead to significant precipitation, but may moderate the hot summer temperatures by partially blocking the sun.
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.
Monday, July 17, 2017
A storm off the coast of British Columbia has mixed with some cool air from western Canada, and a piece of the storm will travel across the northern U.S. border through today. Energy associated with this wave has flattened the dominant western ridge of high pressure that was over the Steamboat Springs area this past week and may provide a focus for a round of afternoon storms today.
Some drier air will follow for Tuesday as the western ridge tries to rebuild, though there will still be a slight chance of afternoon storms.
By Wednesday, the parent storm near British Columbia begins to move eastward, with energy ejecting out ahead of the storm nudging the flattened western ridge eastward and opening the door to a robust surge of monsoonal moisture from the south.
We should have a good chance of wetting rains on Wednesday and Thursday, including the overnight periods, with locally heavy precipitation possible, as embedded subtropical waves move through the moisture plume and phase with some passing energy from the eastward-moving British Columbia storm to our north.
Drier air is advertised to encroach on our area by the weekend in the westerly flow behind the passing storm to our north. Though we will still have a good chance of storms on Friday, the drying air should lead to a downturn in precipitation chances heading into the weekend.
Thursday, July 13, 2017
A building western ridge of high pressure has brought drier air to the Steamboat Springs area as of late yesterday afternoon. As discussed in the previous forecast, northern Colorado was close to the boundary separating drier air to our north and west from monsoonal moisture to our south, and Tuesday the boundary moved north allowing for another day of wetting rains. By Wednesday afternoon, drier and cooler air moved over our area as the boundary moved southward precluding significant precipitation.
The western ridge looks to dominate our weather through the weekend and into Monday. Hot temperatures and the possibility of daily afternoon storms are on tap as remaining low-level moisture is cooked by the strong summer sun as it recirculates under the ridge of high pressure.
Meanwhile, a storm off the coast of British Columbia mixes with some cool western Canadian air as advertised by the European ECMWF last week. As the storm moves to our north late in the weekend, a trailing cool front may be the focus of stronger storms later Monday and Monday night.
The storm will flatten and elongate the ridge of high pressure eastward, which opens the door to another monsoonal moisture surge in the southerly flow on the west side of the ridge. This one looks to hang around longer than the last one, with good moisture over our area through most of the work week. Some cloud cover will keep the hot temperatures at bay, and storm cells that move over our area will be capable of producing locally heavy showers.
Extended-range models are in disagreement with regards to the evolution of another weak wave moving to our north near the end of the work week. The European ECMWF is more aggressive in bringing the storm eastward, interrupting the monsoonal moisture tap a day earlier than the American GFS, as we head into a weekend advertised to be drier than the preceding work week.