Tuesday, November 12, 2013
Signficant changes in the American GFS model over the last few runs has brought the model forecast closer to the European ECMWF forecast. The end result is that light precipitation won’t begin till Friday and a possibly significant winter-like storm develops by Sunday.
The first wave I was expecting to produce precipitation by Thursday morning looks drier and weaker and will likely only produce some slight cooling over our area. The second wave originally timed for Thursday night looks to hold off for 12-24 hours creating only light precipitation by late in the day Friday or overnight.
Weather will be seasonably cool and showery during the day Saturday as a strong wave amplifies along the west coast. Originally, the American GFS model has this wave traveling over the area as a much weaker and faster system, but the last few runs now agree with the European ECMWF model that the system will be much stronger and slower.
If the storm does not dig further to our west in subsequent model runs, I would expect the storm affect our area by Saturday evening and bring signficant precipitation by Sunday morning. The trough is expected to bring favorable mountain-top northwest flow to our area sometime on Sunday, enhancing snowfall rates, expecially near sunset. The storm will grow colder as it evolves from Saturday night through Monday morning, so snow densities will be decreasing, increasing the snow quality. I would guess a very tentative 6-12” or more by Monday morning on the hill.
The trough should be east of us by Monday morning, fringing rapidly warming and dry conditions through the rest of the week.
Another storm is currently forecast for the following weekend, but there is much uncertainty in the forecast for THIS weekend, much less NEXT weekend!
Monday, November 11, 2013
It appears model differences have largely been resolved for the pattern change beginning on Thursday, with the American ‘GFS’ (Global Forecast System) model coming into line with the European ‘ECMWF’ (European Center for Medium Range Weather Forecasting) model. As a side note, I publish these models in the numerical weather prediction section found under the ‘Models’ menu item.
A wave over northwestern Canada will progress southward bringing some cold air along the Front Range around Tuesday as it travels over the western ridge. Additionally, some energy from the eastern Pacific trough will move through the ridge late Wednesday bringing light showers and seasonably cool air to our area. While moisture is not plentiful, the favorable wind direction from the northwest and cooling atmosphere should be enough to produce 2-4” on the mountain by Thursday morning.
Another wave quickly follows allowing little break between systems. This slightly stronger and colder wave should produce an additional 4-8” on the hill by Friday morning.
Temperatures should warm on Friday before additional weak and very dry waves move across by Saturday morning and again Sunday morning. There may be some showers early Sunday morning, though any accumulations should be insignificant.
Another dry wave on Tuesday will mark the end of this pattern where weak waves travel around the dominant western ridge. Models indicate the eastern Pacific trough / western ridge couplet moving eastward by the end of next week signalling another pattern change.
Saturday, November 9, 2013
Even though our weather will be dominated by a ridge producing seasonably warm temperatures and dry weather this weekend and through early next week, how a complicated situation evolves in the eastern Pacific will determine our weather near the end of next week and beyond.
Current models are in agreement with both the trough in the eastern Pacific and the ridge over the western U.S., but differ in how energy moving westward from the western Pacific interacts with the trough.
A wave over northwestern Canada will progress southward bringing some cold air along the Front Range around Tuesday as it travels over the western ridge. Additionally, some energy from the eastern Pacific trough will move through the ridge late Wednesday bringing light showers and seasonably cool air to our area.
The forecast into next weekend is very uncertain. One model brings more energy over the top of the eastern Pacific trough and reinforces the trough carved out by the Wednesday shortwave producing winter weather by late in the weekend or very early in the work week. Another model forecasts far more interaction between these two disturbances, with the northern wave kicking the eastern Pacific trough eastward over our area by late in the week.
However the pattern evolves, both models eventually show winter weather returning to our area, increasing the likelihood of good early season skiing when the Steamboat Ski Area opens for Scholarship Day on Wednesday, Nov. 27th in 2 1/2 weeks.
Thursday, November 7, 2013
After a beautiful day today, a weak wave passes to our north on Friday, increasing clouds but likely yielding no or very light precipitation.
A second wave takes a far more western track and digs southward off the coast of California, pumping up a ridge over the Great Basin that should yield dry and warm seasonal temperatures through Monday.
The evolution of the the trough off the west coast will determine our weather mid-week, and models are struggling with the details. Currently, some energy is forecast to split from this digging wave off the coast and travel over the ridge before bringing cold air southward along the Front Range on Tuesday. Concurrently, some energy is ejected from the trough and travels over us late Wenesday or early Thursday, producing light precipitation.
Models are in disagreement with the pattern after this with regards to the trough of the west coast, with one keeping most of the energy off the coast and the other bringing it inland.
Wednesday, November 6, 2013
Another 3” of low water content snow was on my deck by this by 9am morning and should be the final deposit from this departing storm. Observations from the top of the Sunshine lift near Patrol Headquarters had just under 50” yesterday morning, and I expect that mark to be exceeded today.
A building ridge will produce moderating temperatures and dry weather through the weekend and likely most of next week. Weak waves do pass north of our area on Friday and again mid-week, but high clouds will likely be their only affect on our weather.
Models seem to be generally agreeing that the mid-week wave begins the process of moving the ridge eastward and allowing colder air to filter over the west coast. As is usually the case this far out, confidence is low, especially when the weather patterns are forecast to change significantly.