Thursday, September 7, 2017
A trough of low pressure approaching the Pacific Northwest will split today, with the southern piece forming a meandering closed low off the California coast and the northern piece moving eastward across the U.S. - Canadian border. The northern portion will move the ridge of high pressure currently over the western states east of the Steamboat Springs area by Friday afternoon, with weak southerly winds behind the ridge and ahead of the closed low off the West Coast directing moisture toward Colorado and smoke from the local wildfires to our northwest away from the city.
However, the southerly flow is not strong, so it is unclear how much smoke will be scoured from the area, though an improvement in air quality is very likely. Additionally, the weak flow will limit the amount of moisture that moves over our area, so the afternoon storms that may occur Friday, Saturday and possibly Sunday afternoons may produce more wind than rain.
By early in the work week, the western ridge partially reforms behind the eastward-moving wave forecast to be to our northeast, and this reintroduces drier air and weak northwesterly flow for northern Colorado. Therefore, if the local wildfires to our northwest are still producing smoke, we may once again have some smokey and hazy days next week.
Another Pacific wave approaches the West Coast midweek, and dislodges the California closed low. Models disagree on how strong the Pacific wave will be, but agree that the remnants of the closed low will move across the Great Basin and approach our area sometime around the end of the work week.
At this point, I would expect the possibility of some light showers ahead of the closed low near the end of the work week, with a much better chance of wetting rains around next weekend if the closed low moves over our area.
Monday, September 4, 2017
The cool front for today I mentioned in the last forecast has weakened for the Steamboat Springs area as most of the energy will travel to our east along the west side of a deep, closed low pressure system over Hudson Bay. The minimal cloudiness we see now represents the leading edge of the front, but it now appears no rain will be produced from this weak surge of cooler air.
Probably the most significant impact of the front will be cooler temperatures for Tuesday and Wednesday morning with slightly cooler afternoon highs.
Upstream Pacific energy combined with some energy loitering off the California coast will conspire to nudge the western ridge of high pressure eastward and allow moisture to modestly increase over Colorado by around Thursday in weak southwest flow.
It looks like our best chance for showers will be Thursday and Friday before additional Pacific energy splits as it approaches the West Coast near the end of the work week. The northern portion of the split travels across the northern U.S. border during the weekend, reducing the atmospheric moisture a bit for a downturn in rain chances for the weekend, but increasing them early in the next work week as another shallow cool front is forecast to move through northern Colorado.
The gorilla in the room is Atlantic hurricane Irma, and though it won’t directly affect our weather, it will certainly be national news as the week wears on. Current forecasts have the major hurricane affecting Florida by mid-weekend, validating the earlier trends of the European ECMWF model over the American GFS model.
And even though forecasting the track of the hurricane over a week out is very low probability, current non-hurricane specific models bring the hurricane north through Florida and along the southern East Coast early in the work week before turning it northwestward towards the Ohio River Valley by midweek.
Friday, September 1, 2017
Some clouds are still hanging around Steamboat Springs in the the northwest flow behind last night’s cool front. But drier air will overspread the area later today and on Saturday and Sunday as the western ridge of high pressure rebuilds, leading to dry sunny weather with warm to hot days and cool nights. Some morning fog may be present Saturday, as it was today, as the low levels of the atmosphere are still moist from yesterday’s rainfall.
Over the weekend, a Pacific wave traveling over the top of the ridge will mix with some cold air over Hudson Bay, some of which may bring the season’s first frost to northern Vermont. The wave will eventually elongate into a trough of low pressure over the Midwest by midweek, and this brings a seasonable cold front through northern Colorado sometime on Labor Day. Cooler air should filter into the area by Monday afternoon, with some showers developing later Monday and possibly extending into early Tuesday.
The cooler airmass will lead to noticeably cooler minimum temperatures for Tuesday and especially Wednesday, though the western ridge rebuilds behind the departing trough and brings drier air and warming daytime temperatures for the rest of the work week.
Additional Pacific energy approaches the West Coast by the end of the week, though there is uncertainty with regards to the timing. The American GFS has energy and moisture pushing into the ridge by mid-next weekend, leading to the return of showers, while the European ECMWF is slower.
Meanwhile, and of no direct consequence to our weather, the Atlantic storm Irma has reached hurricane status and looks to develop into a powerful storm that may threaten the Eastern Seaboard soon after next weekend, especially if it eventually phases with the eastward propagating Midwest trough.
Monday, August 28, 2017
While a powerful storm spins in the Gulf of Alaska, and hurricane Harvey inundates the western Gulf Coast, a ridge of high pressure is dominating the western U.S. weather, bringing cool nights and above average daytime temperatures with only the slightest chance of light afternoon showers. This pattern will persist through midweek before a couple of waves of energy ejecting out of the Gulf of Alaska storm manage to dent the ridge and bring some moisture to the Intermountain West.
The first wave around Wednesday will hardly be noticeable except for an increase in clouds and perhaps a better chance of a weak afternoon shower. The second wave for Thursday and Thursday night looks more significant, and we should have a good chance of showers later Thursday and Thursday night that may extend into early Friday morning.
The western ridge rebounds behind the departing disturbance by Friday afternoon. It appears the ridge axis will move a bit further to the west as cool air begins to encroach upon the northern Midwest, though there is uncertainty as to how far west the cooler air reaches late in the long Labor Day weekend. The weather in Steamboat Springs will return to the usual late summer pattern of warm to hot dry days and cool nights for at least the first part of the weekend, with the possibility of some slight cooling by late in the weekend and early next week.
Thursday, August 24, 2017
A building ridge of high pressure over the western states will dominate the weather in Steamboat Springs this week. Ahead of the ridge, a storm that has just crossed the west coast near Vancouver, British Columbia will travel eastward across this northern U.S. border early this weekend with little impact on our sensible weather.
Current cloudiness is caused by the remnant low pressure area over California that threatened, but did not impact, Monday’s eclipse viewing for northern Colorado (check out my account of the remarkable spectacle). Some remaining pieces of the storm are moving over our area today, but it looks like the threat of storms will stay mostly to our south for the rest of the afternoon.
While there will be some ridging tomorrow, the western ridge builds in earnest behind the eastward moving Vancouver storm on Saturday. Much drier air will contribute to warm to hot days and cool nights that are typical for late summer in Colorado.
Around midweek, some energy from the Pacific moves inland as it battles the dominant western ridge. There is uncertainty with respect to the evolution of this battle, but some increasing moisture is likely, leading to the chance of storms by midweek and lasting for a few days. At this point, anything more than possibly brief heavy rain looks unlikely before the western ridge is advertised to rebuild for the following weekend.