Cool front for tonight weakens ahead of some late work week moisture
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.
Nice weekend ahead of cold front for Labor Day
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.
Best chance of moisture this week around Thursday
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.
Quintessential Colorado late summer weather on tap
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.
Some moisture midweek through the weekend
Sunday, August 20, 2017
A wave traveling over the top of a ridge of high pressure in the Gulf of Alaska has split, with the northern part of the split moving across Montana and the Dakotas tomorrow. The southern end has taken up position off the California coast, and the southwesterly flow ahead of that area of low pressure will encourage northward transport of moisture over the Steamboat Springs area around midweek and heading into next weekend.
There may be some sprinkles this afternoon, though any storms are likely to produce far more wind than rain as the lower atmosphere is quite dry and any precipitation will largely evaporate before reaching the ground.
For Monday, eclipse day, models have generally trended towards a more cloud-free solution for northern Colorado and southern Wyoming. The wave to our north will drag a couple of weak cool fronts through northern Wyoming tonight and early tomorrow. There may be some clouds ahead of and along the fronts, though current forecasts have the fronts east of Casper, Wyoming by noon on Monday. Therefore, skies will be improving through the late morning, hopefully in time for an unobstructed view of the 2017 solar spectacle.
Areas to our south may not be quite as fortunate, though models have trended drier with their noon forecast as well. There will be a chance of some storms across all of Colorado by the afternoon or early evening, most numerous to our south.
After a dry Tuesday, pieces of energy are forecast to eject northeastward from the California low, reaching our area around midweek even as a brief ridge of high pressure builds over the Rockies. There is uncertainty with respect to the interaction between the low to our west and the ridge of high pressure over our area, with models trending weaker with the surges of moisture and energy. The end result is an uptick in chances for storms starting around Wednesday and lasting into the first half of the weekend, though the threat of more than brief heavy rain currently looks small.
By around Thursday, a strong storm crosses the southern British Columbia coast and travels along the U.S. - Canadian border over the weekend. This will sweep the ridge of high pressure and the California low eastward, with the unsettled weather ending by mid-weekend and being replaced by Colorado’s quintessential late summer weather with warm, dry days and cool nights.
