Thursday, May 28th, 2009

Rocky Mountain National Park Weather Forecast

By sunny Colorado standards, the weather over the mountains of RMNP was mostly characterized by gloomy and wet conditions over the past week.

The Week in Review

A large plume of subtropical moisture combined with weak atmospheric weather disturbances to produce extensive cloudiness and periods of precipitation.  With the steepest lapse rates existing east of the Divide, the atmosphere organized on convective scales most extensively over the eastern foothills and plains where 1 – 2 inches of liquid fell.

Less precipitation fell in the Estes Valley, with 0.85 inches of liquid measured over the week.  Almost two thirds of this amount fell during the afternoon and evening after Eli completed his solo stroll of the Notch Couloir on the morning of May 25^th.  

During that time, the wind-profiling radar in the Estes Valley measured the snow level between 10-11 kft, with 0.5 inches of liquid captured on the ground.  This likely equated to about 3-5 inches of new wet snow up high.

The addition of rain water to the existing snowpack below 11-12 kft, the overall cooling of the airmass to near the freezing point, and the diurnal minimums in cloudiness during the morning hours, have collectively worked to further consolidate the snowpack over the last few days (May 25-27).

As we start transitioning into a drier weather regime (on 5/27), the alpine snow and ice climbing conditions should really become prime, with strong nocturnal radiational losses acting in conjunction with an existing cool airmass to create firm morning snow and thickening high-elevation ice. 

Corn cycles should also evolve during the mid-morning hours on consolidated aspects exposed to solar radiation.

(Click  charts/photos  to enlarge)




Joanne Helmuth napping on the summit of Longs  Peak after a climb of the North Face  aka 'Cables Route'.

The Upcoming Week

The very moist pattern of last week has come to an end, as the airmass dries and warms under a building ridge of high pressure over the intermountain west.  The associated weather over RMNP during this time will be favorable for producing good mountaineering conditions.

Over the next week, the surface radiation budget over the higher terrain will favor strong nocturnal losses to space and freezing surface conditions.  This will promote firm early morning snow conditions and perhaps some additional high-elevation ice formation.

One of the key atmospheric parameters that drive this cycle is moisture.  The drier the overlying column of air is, the stronger the radiation losses from the surface.  The most ideal conditions occur when these radiation effects coincide with colder airmasses.  The cooler airmass that evolved over the last few days combined with the current drying trend will likely produce some of the best conditions of the week over the next couple of days (5/27 – 5/29).

Over the next week, column water vapor values are forecast to be near or below 8 mm over the mountains of CO.  While these values aren’t bone dry by CO standards, they are plenty dry enough to produce favorable mountaineering conditions. 

However, moisture is expected to increase on Sat 5/30 and Sun 5/31, with the greatest amount of overnight cloudiness forecast to occur overnight on Sun.  Drier air is once again forecast to return to the area on Monday (6/1).

There will be enough heat and moisture during the afternoon hours to produce showers and thunderstorms.  Expect this activity to be greatest over the weekend, with the forecasted increase in large-scale moisture

The NWS numerical forecast for the mountains of RMNP over the upcoming weekend is as follows:

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