Thursday, July 6, 2017
A ridge of high pressure centered over the Great Basin will be nudged eastward this weekend by incoming Pacific energy. The weak southerly to southwesterly flow on the west side of the ridge will allow the monsoonal moisture pooling around the Sonora Desert to move northward, increasing mid and upper level moisture over the Steamboat Springs area for Friday and Saturday. The additional moisture will create high-based afternoon and early evening storms that will produce more gusty and erratic wind than rain, and possibly some dry lightening, as the lower levels of the atmosphere remain quite dry.
By Sunday, the Pacific energy traveling over the top of the ridge will interrupt the fledgling monsoonal flow from the southwest, with drier air moving over the area in weak westerly flow. There will still be the possibility of afternoon storms though, as the meager low-level moisture is lifted by the strong surface heating of mid-summer and interacts with some of the grazing Pacific energy to our north.
On Monday, more Pacific energy again pushes the western ridge eastward into the Great Plains, and a better monsoonal tap of moisture appears around Tuesday. While mid and upper level moisture is carried northward by southerly flow on the west side of the ridge, low level moisture may also receive a boost from a tropical storm moving westward south of Baja. Northern Colorado will have a much better chance of wetting rains starting around Tuesday and extending through the work week and into next weekend, as moisture falling from any storm will not encounter the very dry lower-level air present for this weekend.
Longer-range models, as of today, want to keep the monsoonal flow around after next weekend as well, hopefully leading to a far wetter July as compared to June as tropical waves of energy move northward over the Sonora Desert and eventually across the Great Basin.
Monday, July 3, 2017
The wave of energy discussed in the last forecast has moved east of the Steamboat Springs area, and drier air has moved in behind the departing disturbance. There may still be a chance of some afternoon or evening sprinkles later today.
Temperatures will warm further for Independence Day and the work week as a ridge of high pressure builds over the western US. Moisture to fuel any afternoon storms will be sparse for most of the work week as generally light northwest flow keeps hot and dry air over our area.
By the end of the work week and heading into next weekend, incoming Pacific energy is forecast to nudge the western U.S. ridge eastward, placing the ridge axis over the spine of the Rocky Mountains. The weak southerly to southwesterly flow on the west side of the ridge will allow the monsoonal moisture pooling around the Sonora Desert to move northward, though the northward extent of this moisture surge is uncertain.
The robustness of the moisture surge may also be moderated by the incoming Pacific energy traveling over the top of the western U.S. ridge and digging southward into the eastern third of the country. The cooler air to our east may nudge the western ridge back westward which would interrupt the fledgling monsoonal flow over Colorado.
The end result is the hot and dry conditions forecast for the work week will be followed by some increasing moisture and the chance of afternoon storms heading into weekend.
Thursday, June 29, 2017
A trough of low pressure over the northern plains has brought cooler temperatures to the Steamboat Springs area today. A trailing wave will bring the last cool front in this series through the area overnight, leading to a chilly morning with even the possibility of some frost. The National Weather Service forecast for the Park Range even has the mention of snow flurries for tonight! Still-tender plants in low-lying areas might need to be protected tonight and Friday night with the unseasonably cool temperatures.
As the trough moves eastward, a ridge of high pressure will return to the western states, bringing drier air and strongly warming temperatures for the weekend.
Meanwhile, another Gulf of Alaska storm has mixed with some subtropical moisture and will weaken as it crosses the Great Basin on Sunday. By the time the trough moves over Colorado later Sunday into Monday, the increased moisture and upward motion associated with the trough will bring increasing chances of showers, with the associated clouds moderating the hot temperatures.
A western ridge rebuilds behind the early week storm, bringing hot temperatures for Independence Day. There may be a chance of some afternoon showers, but they should be isolated and brief.
By midweek, the numerical models disagree with the evolution of the western ridge. The American GFS insists on further amplification, bringing even hotter and drier weather to the western states for the rest of the work week, while the European ECMWF has a weakening ridge which allows some Pacific energy to move inland. This would result in more seasonable temperatures with the possibility of afternoon showers starting around midweek.
Monday, June 26, 2017
A ridge of high pressure over the Intermountain West will allow temperatures to rise above normal for today and Tuesday with very little chance for precipitation. A storm currently in southern British Columbia will mix with some cool western Canadian air as correctly forecast by the American GFS last week and bring a series of cool fronts through the Steamboat Springs area starting Wednesday and persisting through the first part of the weekend.
These fronts will be dry, with some breezy westerly to northwesterly afternoon winds. Temperatures will be close to or slightly below normal leading to gorgeous and comfortable summer days with cool nights for the rest of the work week and heading into the weekend.
A transient ridge of high pressure is forecast to translate over the western states for the second half of the weekend, allowing hot temperatures to return around Sunday and heading into the new work week. There is also a weak subtropical disturbance moving through this ridge, leading to a slightly better chance of clouds and possibly some precipitation on Sunday.
With summer weather firmly entrenched, I’ve been looking at the longer-range forecast models to get an idea of when our summer monsoon season might arrive. While there currently is some moisture pooling around the Sonoran Desert, it appears it won’t get here until around the following weekend when southwesterly flow is predicted to become better established over the western states.
Thursday, June 22, 2017
Some cooler air will wash over the Steamboat Springs area starting early Friday and extending through the weekend, and possibly again around mid-next week. For the rest of today, similar to yesterday, there may be a chance of a mostly windy afternoon storm. The locally strong and gusty winds around these storms are caused by evaporating precipitation (virga) which cools the air before it reaches the ground. This cooler air creates strong downdrafts which then spread out horizontally when colliding with the surface.
For Friday and Saturday, a couple of waves moving southward along the western flank of a storm in the southern Canadian Plains will introduce cooler air over our area, knocking temperatures back towards the normal range and making for some very pleasant early summer days. These cool fronts will be dry, and with less moisture predicted to be in the atmosphere as compared to the last few days, precipitation chances will be close to nil.
Temperature will warm a bit Sunday, but the warming will occur in earnest on Monday and Tuesday as a transient ridge brings hot temperatures over the western states. We may have a slightly better chance of afternoon storms then as some energy from a tropical wave interacts with energy from a storm in the Gulf of Alaska and moves over our area later Monday and Tuesday.
By Wednesday, significant differences appear in the numerical forecast models, with the American GFS having the Gulf of Alaska storm mixing with some cool western Canadian air before digging it into the Great Basin. This forecast is a change from the last few days and would bring a series of cool fronts through the area for the end of the next work week. The more consistent European ECMWF, however, keeps this storm further north and faster moving which leaves most of the cool air north of our area.