Thursday,  December 16th, 2009

Rocky Mountain National Park Weather Forecast
 

A significant warm up and a dose of new snow characterized the weather over the past week.

The Week in Review

The arctic airmass of the previous week gave way to a much milder Pacific airmass on Dec 10 – 13, resulting in a 30 degree F warm up.  Daytime high temperatures have been in the 20’s F near treeline since.

A weather disturbance rolled in on Dec 14 bringing some much need precipitation with it.  During the period when precipitation was detected (by higher signal-to-noise ratio returns) at the nearby wind-profiling radar in Estes Park, the Bear Lake snow pillow measured about 0.6 inches of liquid equivalence (6-8 inches of snow).

With the passage of the trough axis, as denoted by the wind shift from west-southwest to northwest, all of the ingredients came together to form a strong mountain wave. 

These included a strong down-slope pressure gradient, northwesterly flow, subsiding air, and strengthening thermodynamic stability.

Last week's weather events in RMNP.

click charts  and photo to enlarge

Next week's pressure movements for North America. 

The Upcoming Week

In the short term, moist northwesterly flow near mountain top will produce periods of light snow through Saturday, with little in the way of accumulations expected.  Winds will remain at moderate levels with the favorable northwesterly direction, and temperatures are expected to cool by 4-8 degrees F.

With tropical convection forecast to intensity and reorganize over the tropical Pacific, the formation of a teleconnection pattern over the Eastern Pacific Ocean and western US is a strong possibility by early next week – somewhat similar to the cold pattern we experienced two weeks ago.

While the current dynamical models do a relatively poor job forecasting these tropical modes, there is an increasing consensus across different temporal runs and models that another highly amplified pattern will evolve in response to the tropical forcing.  While there is still a large degree of uncertainty in forecast details (see US and European solutions plot), the probabilities are increasing for another arctic surge along the US Rockies.

The initial cold front could arrive as early as Tuesday or Wednesday (Dec 22/23), and would be accompanied by east-side upslope snows.  If the pattern remains sufficiently amplified, additional surges of cold arctic air and snow would follow later in the week. If and when the cold air dives south of our region, the higher-elevation westerly component winds will subside.

A look into the uncertain weather future continues to maintain a high-amplitude ridge along the west coast of North America.  Such a pattern would reinforce colder and snowier than average conditions for the locals that lie east of the Divide, including RMNP.

Detailed 7-Day Forecast

NWS Forecast for the 12,000 foot level near Longs Peak 

The link above will take you to the National Weather Service forecast for the 12,000 foot level near Longs Peak.  These forecasts are derived from computer-generated numerical forecasts, and are updated shortly after 3:30 am, 9:30 am, 3:30 pm, and 9:30 pm local time.  In the lower right-hand corner of the page, one can view forecasts for other locations in the Park by clicking on the desired location in the terrain map.

Do-It-Yourself Weather Forecast Links

Weather Observations and Forecasts

The link above provides a list of web links to various sites containing a variety of meteorological data and information.  Collectively, these resources can be used to monitor and study current weather conditions, as well short-term, medium-range, and climate forecasts