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. 

Warning:  Climbing Life and it's contributors accept no liability for your decisions based on the information contained in this site.  Weather conditions change very quickly and unpredictably, especially in this part of the world, and the actual conditions you find may vary wildly from what we have forecast.   

Issued 11-14-07 2:30pm MDT  

The Week in Review

For the middle of November, a very tranquil weather pattern persisted through last Sunday in the mountains of RMNP.  Warm temperatures, relatively light winds, and occasional cloudiness have been the norm.  As alluded to in the November 13th Ice Conditions Report, the temperatures in the Loch Vale area were warm enough to cause consistent dripping from the ice formations.  With the warmer diurnal cycles of temperature that have been recently occurring, only a few hours during the early morning have had the potential for freezing temperatures.  The presence of clouds during these hours, as observed by Eli, helped to prevent a hard freeze from occurring.  Small cloud drops/ice crystals absorb longwave radiation, which is emitted from the earth’s surface, and re-radiate part of this absorbed energy back toward the earth. As a result, the insulating property of clouds acts to limit the amount of cooling that can occur between the cloud and the ground, during nighttime hours.  This effect is maximized with lower-altitude, higher-water-content clouds and increased cloud depth.  For example, high-altitude, thin cirrus clouds will have only a minimal effect on limiting near-surface temperature loss, whereas saturated air based at the surface (i.e., fog) can limit the overnight temperature loss by only 2-4 degrees Fahrenheit.  In contrast, during some of the potentially coldest winter days, this effect can occasionally work towards the ice-climber's advantage by preventing the ice from becoming overly brittle at very low temperatures.  In addition to the warming effect of clouds, wind can produce enough turbulence to mix cooler, surface-based air with relatively warmer air above the surface, and prevent the build up or layering of colder air near the surface.

Not unlike the state of weather affairs over Colorado the past three weeks, Monday’s storm system was a dud.  A persistent large-scale high-pressure anomaly over the western US significantly weakened Monday's disturbance, as it moved into the Intermountain West.  Only very light precipitation developed over RMNP, as a mid-level front moved across the region.  Observations across most of mountains of the Front Range, including reports from Eli near Loch Vale, indicated less than an inch of accumulated snowfall.  On Tuesday, moderate winds returned once again to the higher terrain along the Front Range.  Wind measurements from Niwot Ridge (located in the Indian Peaks just south of RMNP) indicated sustained winds near 40 mph, with wind gusts in the 60-70 mph range from the west.  It is likely that larger-scale terrain features with a north-to-south orientation (such as the Indian Peaks) experienced windier conditions, with the development of a mountain wave.  What little snow that did fall, was immediately scoured or sublimated away in areas exposed to the wind.  The tail end of a stronger disturbance moving through Wyoming and Montana produced another dusting of snow on Tuesday evening and into Wednesday morning.  While Wednesdays temperatures will be cold enough for ice formation, the atmosphere will gradually start to warm up again as the week progresses.  As of today (Wednesday), the winds above treeline have slowed down into the 20-30 mph range with gusts in the 30-40 mph range.

Forecast Discussion

Over the last week, convection has intensified and become better organized over the western tropical Pacific Ocean.  Partially in response to this, jet-stream-level disturbances have also intensified over the mid-latitudes of the Pacific Ocean.  This increased activity is forecast to produce periods of rain and snow for Washington and Oregon from Thursday through Sunday.  For Colorado, expect more of the same tranquil weather all the way through Monday, with dry, seasonably warm, and occasionally breezy conditions persisting.  However, a change in the storm-track configuration is on the horizon.  A high-amplitude ridge of high pressure is forecast to develop off the coast of North America on Tuesday.  Such a scenario would allow a storm system to develop over the Intermountain West, bringing colder temperatures and a chance of precipitation to Colorado.  Beyond Tuesday, there is again great uncertainty as to how the pattern will further evolve.  But, several indicators are at least suggesting that a northwesterly storm track may evolve far enough south to bring more frequent chances of colder and snowier weather to the mountains of Colorado.  Cross your La-Fingers.

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.