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 December 19, 2007
The Week in Review
Over a majority of the last week, the weather in the mountains of RMNP has been consistent – consistently windy, that is. While last Friday’s storm system turned out to be a dud with respect to new precipitation, it held true to the forecast when it came to ushering in cold temperatures during its tenure and ramping up the winds following its passage. On Fri. night and Sat. morning, temperatures in most mountain locations were in the single digits below zero Fahrenheit. Decreasing trends in model-forecasted precipitation for Fri. became evident on Thurs., and only up to 0.1 inches of snow water equivalence (SWE) was measured at multiple locations along the Front Range by Friday evening (a dusting to an inch of new snow). As the storm system moved east of our area on early Sat. morning, the west-northwesterly wind tunnel became established, causing frequent wind gusts in excess of 50 mph.
The remainder of the past week was characterized by continued periods of moderate to strong westerly winds and gradually moderating temperatures. As such, areas exposed to the wind have once again been scoured, while deposition zones (both lee and cross oriented to the wind) continue to load with new snow in the form of sensitive slabs and drifts. In addition, slow but consistent settlement in the snowpack below treeline has occurred since last Sat., with an average decrease in snow depth of about 3 inches. This decrease in snow depth is attributed mostly to settlement rather than to snow loss (e.g., due to sublimation), since the SWE of the snowpack has remained virtually unchanged.
The first in a series of weather disturbances embedded in a west-northwesterly storm track is moving over Colorado today (Wed.). Weak dynamical forcing and meager moisture have greatly limited the precipitation threat with this system, however, the orographic forcing along the higher terrain of RMNP and Indian Peaks has been strong enough to support light snow, as evidenced in radar data. Little in the way of accumulating snow is expected with this activity, as it tapers off during the evening hours.
The Upcoming Week
An active weather pattern is on store for the western US over the next week. As the most recent computer-model data indicate, three disturbances will affect RMNP between this Thurs. and next Wed. These disturbances will be riding on a swift west-northwesterly storm track, making their timing somewhat difficult to forecast.
The first system will begin to spread snow into mountains on Thurs. night, and will last through Fri. Snowfall will be of light intensity throughout most of the storm, but the extended duration of the precipitation may allow several inches of new snow to accumulate (~0.5 inches of SWE is currently forecast). Another respectable drop in temperatures will occur, after the cold front passes through the area on Fri. afternoon (15-20 F drop when compared to pre-storm temperatures).
The second system is forecast to move into the area on Sunday. Only light snow accumulations are expected with this storm, with around 0.15 inches of SWE currently forecast. This system will be equally as cold as, or a bit colder, than the Fri. system.
The third system is currently forecast to move in late Mon. night / early Tues. morning. This system has potential for producing another several-inch snowfall event, and may also be the coldest of the three storms. Of course, being a week out, these details come with a considerable amount of uncertainty.
With respect to winds, expect the recent moderate/strong speeds to temper as the periods of precipitation move in. As usual, the post-frontal environment is most favorable for the strongest winds. Because of the configuration of the first system, strong post-frontal winds are currently not expected. However, moderate post-frontal winds may develop behind the second and third systems, on Mon. and Tues. respectively.
Beyond next Tues., medium-range forecast indicators show unsettled weather continuing through the end of next week.
Happy Winter Solstice to all!
Detailed 7-Day Forecast
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
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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