Wednesday,  December 30th, 2009

Rocky Mountain National Park Weather Forecast
 

A deep freeze returned to the mountains of RMNP over the past week.

The Week in Review

High amplitude ridging along the west coast of North America allowed cold arctic air to surge southward along the Rocky Mountains. 

Although not quite as severe as the cold snap that occurred during the beginning of December, temperatures still bottomed out near a chilly -5 F for a two day period near treeline.

About 0.6 inches of new liquid equivalence fell in the form of a few inches of snow over the past week.  While this new light load did little by itself to change the avalanche risk, strong northwesterly winds produced significant drifting and new slab on favorable lee- and cross-loaded slopes. 

With continuously cold conditions, a shallow snowpack depth, and generous air space between snow crystals in the lower snowpack, weak faceted snow has remained beneath these stronger new drifts and slabs.  This combination continues to exhibit strong signs of instability.

The snowpack across the Park remains near average levels for this time of the year, with 5-6 inches of snow water equivalence in about 2-2.5 feet of snow. 

From a climatological perspective, this amounts to about a quarter of the average total winter accumulation, which typically peaks near the end of April.

The Upcoming Week

Over the upcoming week, the storm track will guide weather disturbances from the Pacific Northwest to the northern Rockies.  Three low amplitude waves are forecast to move swiftly eastward across CO on Thu (12/30), Sat (1/2), and Mon (1/4).

Collectively, these storms are forecast to produce a minimal amount of new snow, with up to 0.5 inches of snow water equivalence (~ 5 – 8 inches of snow).  Moderate to strong northwesterly flow is forecast near mountain top with each system, which will produce significant blowing and drifting snow.  Expect additional slab development and an elevated avalanche risk on lee- and cross-loaded slopes.

Beyond Monday’s system, an active weather pattern is forecast to develop over the eastern Pacific.  This will maintain storminess over the Pacific Northwest, and drier and warmer conditions over the intermountain west, including CO, under strong ridging conditions.

Click image to enlarge

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