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 Wednesday, January 10, 2008

The Week in Review

It’s been a mixed bag of weather in the mountains of RMNP over the last week.  While southwestern Colorado received the bulk of the precipitation (4 – 6 inches of SWE), RMNP received between 0.75 – 2 inches of SWE, with the higher amounts occurring in the western ranges of the park.  Much of this new snow occurred with last weekend’s warm storm, which produced relatively low snow-density ratios for this time of year (6 – 8 inches of snow per inch of water equivalent).  In addition, post-frontal winds transported a fair amount of alpine snow to the sub-alpine regions, as observed by Eli in the eastern sections of the park (see Jan 10 Conditions report).  According to human and sensor observations, total snow depths are currently in the 1.5 – 3.0 feet range in the eastern sections of the park (see snow-depth plot below).

Temperature and wind speed have also been quite variable over the past week.  After experiencing warm temperatures with last weekend’s Pacific storm, colder air moved in behind the weather wave, which caused temperatures to bottom out on early Tues. (see plot below).  After a brief warm up on late Tues., the temperature dropped back to its weekly low, after the passage of another weaker storm on Wed.  Following each wave passage and minimum in temperature, the winds quickly increased to strong levels (see the start of Jan 8 and 10 below).  In the post-frontal environment, large-scale sinking air, increased thermodynamic stability, and a strong west-east pressure gradient perpendicular to the mountains (high to the west; low to the east), all act to produce an atmospheric mountain wave that accelerates the wind east of the Divide.

The Upcoming Week

Another weather system traveling in the mean northwesterly flow will move through the area on Fri.  The strength of this system, with respect to precipitation potential and temperature, will be similar to the previous storm (Wed.).  Higher elevation snow showers are forecast to occur throughout the weekend following the cold front passage on Fri. afternoon, particularly in terrain regions exposed to the northwesterly winds.  Moderate west-northwest winds near 25 mph gusting to 40 mph can be expected at times from Fri. – Sun.

Temperatures are expected to rebound on Mon. and Tue., before the next system brings another round of moisture, wind, and colder temperatures late Tues. – Fri.  The Mon./early Tues. timeframe may provide the best weather window of the week for alpine excursions.  Because the forecast strength and position of the Tues. – Fri. pattern have been variable between the different models, a watchful eye on the evolving forecast would be prudent if planning an outing during this time.

As alluded to in last week’s discussion, a high-amplitude ridge of high pressure is forecast to build off the west coast of the US and into Alaska during the next week.  With this type of pattern, the potential does exist for arctic air to move into the western US the following week (week of Jan 21).  The jury is still out on this one, as a significant amount of variability currently exists in the numerical forecast model output.  However, this significant weather situation bears watching, and will be updated in next week’s weather discussion.  If such a pattern verifies, very cold air and east-side snows will be in the cards.

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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