The weekly weather forecast for the high country of Rocky Mountain National Park, researched and written by professional meteorologist and mountaineer:  Dan "the weather man" Gottas. 

Issued Thursday February 28, 2008

The Week in Review

The westerly storm track, which developed last Thurs. through Tues., brought a period of moist and temperate weather to the western US, including the mountains of RMNP. 

With this type of storm track, the western-most mountain ranges of the US are usually the precipitation winners (e.g., in the Sierra Nevada, 4–7 inches of snow water equivalence (SWE) fell at the higher elevations).  In Colorado, the western-most ranges were able to squeeze out 2-3 inches of SWE - specifically, upwards of 2-3 inches in the San Juan’s and 2.5 inches in the Elk and Park ranges.  In RMNP, the western ranges (e.g., Never Summer) received 1 – 1.5 inches of SWE, while the eastern sections (e.g., Wild Basin and Bear Lake) managed to scavenge only 0.5 inches of SWE from the leftover moisture scraps.  Deja vu?

Another characteristic of westerly storm tracks is relatively mild temperatures for Colorado.  The faster speed and lower amplitude of the weather disturbances associated with this pattern prevents colder continental air, which resides to our north, from participating in the storm process.  Temperatures at 10 kft have recently demonstrated this effect, with about five freeze-thaw cycles occurring over the past week.  The main benefit of these temperature cycles is to strengthen and stabilize the snow pack, particularly in the near-surface layers.  This is particularly true for aspects that receive some degree of solar radiation during the day.  On steeper and locally colder, north-facing aspects, the higher sun angles and warmer temperatures of spring will be required to begin the stabilization process on these slopes.

Since the passage of the most recent storm on Tues., the pattern has evolved back towards the northwesterly storm track that has been characteristic of this year’s winter and consistent with La-Nina climatology.  As a result, temperatures have cooled and the winds have increased to moderate northwesterly speeds (30-40 mph gusting in the 40-50 mph) over the last couple of days above treeline.

The Upcoming Week

Two storms riding on a northwesterly track will affect the mountains of RMNP over the next week.  With this, winter conditions will once again return to the high country starting on Sun.

Ahead of the first storm system which is forecast to move in on Sun., a surge of warm air will move into the region on Sat.  Temperatures are forecast to reach near 40 F at 10 kft.  Moderate west to southwesterly winds will accompany this warm surge above treeline, with gusty conditions mixing down to lower elevations as the daytime heating commences.  If you’re looking to play in warm weather this weekend, Sat. is your day.

Clouds and snow will develop over the high country overnight on Sat./Sun.  With this, the winds will shift to a northwesterly direction.  With the moisture depth forecast to be mostly below 18 kft, significant accumulations are not expected.  In addition, east-side upslope is not expected to accompany this system, which will further limit the accumulation potential over the eastern sections of the park.  Current quantitative precipitation forecasts are between 0.25 – 0.50 inches of SWE near and just east of the Divide.  The new snow loads solely associated with the falling snow should not substantially increase the avalanche danger.  However, when combined with the forecasted moderate winds, increased avalanche danger can be expected in locations susceptible to loading and slab formation under northwesterly flow.  Temperatures near 10 kft are expected to drop into the low to mid teens F on Sun., which will amount to nearly a 30 F degree swing from Sat.

Snow showers will continue into Mon. morning, but this activity is expected to taper during the day.  Northwesterly winds will continue through the day on Mon., with the potential for high winds, if a mountain wave develops - conditions will be conducive for this development as subsidence moves into the area on the western side of the weather disturbance.  Temperatures will begin to moderate on Mon., and continue to warm on Tues., with highs once again forecast to reach the freezing mark by Tues. afternoon ahead of the next weather system.  Winds are expected to decrease to moderate levels on Tues. and turn to a westerly direction.

The second storm system is currently forecast to move in on Tues. evening.  This system has a greater precipitation threat associated with it, as it is forecast to be accompanied by deeper moisture and an east-side upslope component.  However, the precipitation forecast for this event will be very sensitive to the wave position as it moves in.  A watchful eye on the detailed forecast is recommended over the next several days, if a honed precipitation forecast is required.  Temperatures are expected to be colder with this system, with single digits once again a possibility above 10 kft.  The potential for moderate to strong northwesterly winds will once again threaten the higher terrain on Thurs., as the weather wave passes to the east of the area.

In the long-range forecast, a reprieve from the wintery conditions is expected the following weekend (3/8-3/9), with the potential for more winter weather developing by the middle part of the following week.

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.

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