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 March 13, 2007

The Week in Review

While the recent surface temperatures and winds would independently indicate that winter still has a firm grip on the high country of RMNP, subtle visual characteristics in the sky clearly indicate that spring is springing.  The combination of increased levels of solar radiation associated with higher sun angles and the persistence of colder air aloft associated with a winter atmosphere have produce shallow moist convection (i.e., clouds of the puffy variety – aka cumulous) over the higher terrain during the afternoon hours of the past week.  While these cotton-ball conventions have done little by themselves to make headlines in the wacky world of weather, they are a sign or precursor of interesting weather to come.  In particular, enhanced precipitation processes often develop when the forcing associated with weather disturbances acts upon these destabilized lower atmospheric layers.

Over the past week, temperatures near treeline remained below the freezing mark, but moderated last Thurs. through Tues. (see plot below).  After reaching a high mark just below freezing on Tues., temperatures have once again dropped with the development of a west-northwesterly storm track over Colorado over the last couple of days.

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After a brief but welcomed reprieve from the wind over the weekend, the wind tunnel is back in moderate force.  Near treeline, sustained wind speeds over the past couple of days were in the 30-40 mph range and were gusting to 45-60 mph.  With the passage of weak and fast weather disturbances and the onset of moderate orographic forcing, snow has redeveloped over the high country.  The stabilization of the near-surface snowpack that evolved during the warming/drying trend of the last week has now been offset by the recent slab formation resulting from the new wind and snow of the past 24 hours.  Some of these new slabs may be forming on crusty or faceted surfaces.

The Upcoming Week

A strong jet stream will move over Colorado on Thurs. night and Fri. morning.  This combined with west-northwesterly flow near mountain-top level will force another round of snowfall, with the potential for around 0.5 inches of snow water equivalent (~ 6-8 inches snow) in the mountain of RMNP.  However, since a fair amount of thermodynamic instability exists in the lower atmosphere, locally higher snowfall rates and accumulations are possible, particularly Thurs. afternoon and evening.  With moderate winds accompanying the new snow, an increase in the avalanche danger can be expected on Thurs. evening through at least Fri.  The formation of new drifts and slabs of a foot or greater in depth are probable.

The next weather system is forecast to buckle the flow over the western US and form a deep area of low pressure over the desert southwest.

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On Sat. evening and Sun. the position of this system will produce a deep layer of moist southwesterly flow over Colorado.  While this flow orientation is not favorable for orographic precipitation production in the northern mountains, deep moisture, the passage of weak smaller-scale disturbances, and a thermodynamically unstable lower atmosphere (particularly during the afternoon in Sun.) will be enough to force periods of snow over the mountains.  Accumulations could be quite spatially variable, if enhanced regions of convection develop.

While some relatively weak upslope flow and precipitation is forecast to develop on Mon. along the Front Range (as the Southwest system moves east), the majority of the forcing will remain well south of our area.  As a result, a major winter/spring east-side precipitation event is not expected for our area with this system.  However, the depth of the weaker upslope flow (from the north-northeast) is currently forecast to extend up to mountain-top level, which may provide a relatively windless window to access some of the higher peaks for a winter-conditions ascent.

Temperatures near treeline are expected to be in the upper teens to low twenties range through Mon., with a warming trend into the twenties on Tues. through Thurs.  Winds will once again shift to a northwesterly direction on Tues. – Thurs., with higher speeds possible (particularly on Tues./Wed.) if a mountain-wave develops in the subsident northwesterly flow.

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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