The weekly
weather forecast for the high country of Rocky Mountain National Park,
Colorado. Researched and written weekly by professional meteorologist
and avid mountaineer, Dan "the weather man" Gottas.
May 7 weather forecast
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Thursday,
May 7th,
2009
The Week in Review
The weather in the high country
of RMNP continued to slowly transition
to spring over the past week.
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Two periods of snowfall
occurred on Friday, April 30th and
Saturday, May 2nd. About
a half inch of
liquid equivalence (~ 5 inches of wet snow) fell during each event.
Strong post-frontal winds
produced wind slab across the
alpine regions following each snow event.
Wind gusts above 50 mph continued for the remainder
of the week.
A period of warm temperatures
followed by a prolonged period
of extensive low- and mid- level cloudiness produced a very wet
snowpack near
and below treeline for most of the week.
During
that time, strong down-welling radiation from these clouds
greatly reduced or even reversed the net-radiative losses from the
snowpack
surface.
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(Click chart to enlarge)
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Eli Notes: Avalanches quickly covered these climber's tracks as they made a rapid retreat after what appeared to be a late-day start that had them climbing up the Dead Elk Couloir at noon on May 6th. We were aross the valley climbing on the slush and water covered rock of Hallett's Chimney which is far from being "in-shape" as an ice climb at the moment. Falling ice hazard was high in this narrow cleft from dislodging ice on all sides blown free in the strong morning winds and afternoon temperatures. We retreated with three 60m rappels from our high point.
By doing night climbs that end at sunrise or soon thereafter and choosing colder, higher altitude, and north-facing slopes; climbers can reduce the objective risks substantially of avalanches and falling ice/rock which are very active at the moment. Avoidance is always the best approach when it comes to death by avalanches and when the mountains are in their current shedding cycle, timing and route selection are the necessary foundations to a potentially successful mountain ascent.
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The
Upcoming Week
A strong jet stream is forecast
to persist across the
northern tier of states for the upcoming week.
This pattern will keep most of the active weather to
the north of
RMNP. However,
gusty conditions will
persist in the alpine regions for the remainder of the week.
The jet stream is forecast to
sag southward over Colorado on
Saturday. This will
allow moist,
low-level upslope flow to surge southward along the east side of the Rockies.
The depth
of this surge is currently forecast to evolve east and below mountain
top.
Aside from this brief period of
moisture, drier conditions
are expected for the high country.
This
will allow stronger net-radiative losses to occur skyward from the
snowpack,
which will help promote consolidation during the nighttime hours.
A larger wave of low pressure
is forecast to affect the area
by mid week. Pre-frontal
southwesterly
winds will kick in on Tuesday.
A brief
shot of cooler air will follow a cold front on Wednesday with only a
limited
amount of mid-level moisture.
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The
Dragontail Ridge and couloir at sunrise on May 6th, 2009.
Eli notes: Many sloughing avalanches; R3, D2 in size were reaching
Emerald Lake by noon on this day and all of the warm (E- S) aspects were highly
reactive after 9am with Avalanche Danger being HIGH by 11am on these Slurpee
consistency slopes. Notchtop Couloir, the South Face of Hallett, and similar slopes
should be avoided in these "not-corn" conditions.
The shedding season has officially begun in RMNP and at the moment,
steep snow covered slopes should be avoided as current avalanche danger is
CONSIDERABLE with danger reaching HIGH by 11am until 4pm each day, on all warm aspects.
Any cloudy nights will temporarily increase the
snowpack instability by blocking radiation losses and as a result avalanche danger will be increased. Clear skies are absolutely necessary for this snowpack to gain some temporary stability and eventually a stronger corn cycle.
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The NWS numerical forecast for
the mountains of RMNP over
the upcoming weekend is as follows:
Click chart
to enlarge
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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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