Thursday, June 4th, 2009

Rocky Mountain National Park Weather Forecast

After a brief period of drier weather at the end of last week, cool and soggy conditions returned to the mountains of RMNP.
 

The Week in Review

The drier period last week was conducive to large diurnal cycles in temperature, which continued to strengthen the existing snow and produce favorable mountaineering conditions during the early morning hours.

The atmospheric juice moved back into the area last weekend, which produced extensive cloudiness, periods of precipitation, and relatively early daytime-thunderstorm initiation. 

In what has become a consistent vibe (and forecast error) during the spring of this year, the moisture and disturbed weather was slow to dissipate and move out of the area.  This pattern continued through beginning of this week until drier air moved back into the mountain elevations on late Wednesday.

Over the past week, the Estes Valley received about an inch of new precipitation.  Snow levels were mostly above 11 kft, except on Tue June 2^nd,  when a cooler airmass combined with northeasterly upslope flow (adiabatic cooling) forced the snow down to 9 kft.

Even though the skies have consistently resembled an early spring pattern, mean wind speeds have backed off considerably from their winter and early spring levels. 

Sustained wind speeds over the past week were mostly 5-20 mph above treeline, with occasional gusts in the 30 mph range.

The Upcoming Week

Yet another weather disturbance is forecast to affect the area this weekend (deja vu? - you betcha).  A full-latitude trough of low pressure, with support from the polar jet stream, will develop over northern Rockies.

Ahead of this system, mid- and high- level moisture will move back into the area on Friday helping to fuel afternoon thunderstorms.  Low-level upslope flow is forecast to develop east of the Divide overnight, however the depth of this is expected to remain well below the mountains of RMNP.

Above this upslope layer, the jet stream will force drier air over the mountains during the nighttime hours and during the day on Saturday (read good for climbing conditions). 

However, strong southwesterly winds are expected during this time, with a mountain-wave signature (i.e., locally stronger accelerations) showing up in some of the forecast models during the early morning hours.

On Sunday, moisture will once again increase as the circulation axis passes over CO.  This will once again increase the risk for thunderstorm development.  High elevation wind speeds should be less than those on Saturday, with the jet position shifting east.

For the rest of the week, the pattern is forecast to remain more like spring than summer.  With weak low pressure continuing over the northern inter-mountain west, periods of mountain cloudiness and precipitation are likely, and temperatures will remain on the cool side.

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