Thursday,  October 6th, 2011

Rocky Mountain National Park Weather Forecast

Unseasonably warm and calm weather conditions persisted across the mountains of RMNP over the past couple of weeks.

Week in Review

However, with the seasonal shift into fall, the jet stream in the northern hemisphere has been gaining strength and continues to migrate southward.

How the storm track evolves over the coming months across CO will depend on many competing regional to global meteorological forces.

Last year, a strong La Nina event in the tropical Pacific dominated the circulation patterns across the entire Pacific basin and forced a persistently windy and snowy northwesterly storm track across RMNP.

Over the past couple of months, La Nina has made an encore appearance, but in a much weaker state than last years event at this time.

An ensemble collection of many different forecasts suggest that a weak La Nina will continue into the upcoming winter season.

Does that spell for a repeat performance of last year’s wintery barrage?  Not necessarily.  In fact, weak La Nina’s have historically been accompanied by another tropical oscillation, namely the Madden-Julian (MJO).

The MJO can dramatically alter the western US storm tracks as it slowly propagates from the Indian to Pacific Oceans on its 30-60 days eastward trek around the entire equator.

The first instance of an MJO during this newly revived La Nina event is currently occurring and is likely energizing the current west coast storm system that is forecast to drop significant snows across the mountains of southwest CO.

If the MJO indeed persists through the upcoming winter, get ready for a varied and potentially wild roller coaster ride of weather.

The Upcoming Week

The first true taste of winter is on tap for the upcoming weekend, as a strong west-coast storm system ejects northeastward across CO.

Two waves of energy will force widespread snows across the CO mountains. The first will focus the greatest amounts across the southwest and central mountains on Thu, while the second will generate easterly upslope snows along the northern Front Range on Sat.  The current forecast has 0.5 – 0.75 inches of liquid-equivalent accumulation over RMNP from Thu – Sun.

Temperatures will become notably colder, with 20s F forecast at 10 kft after the initial frontal passage on Fri.  Prefrontal southwest winds will be in the 40s mph on Fri. The new snowfall on Sat will be colder and lower density, with easterly-component winds.

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.

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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.