San Juan North
==============

Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, crossloaded, crusts, 
drifted, drifts, facets, human triggered avalanches, paths, precipitation, shears, 
slab, slabby, slabs, surface hoar, weak layers, wind slabs, windloaded

                 Issued 01/28/2009 7:47 AM by Simon Trautman

   Weather Discussion

   Northwest flow is bringing snow to the Northern and Central Mountains.

   Although most of the available moisture is north of Colorado, a series
   of shortwaves in combination with jet support will enhance the
   potential for precipitation. Snow began falling around 3 AM in
   Steamboat, and is expected to move south of I-70 early to mid-morning.

   The Northern Mountains will see the heaviest precipitation today, while
   the storm will intensify in the Central Mountains this evening after
   dark. At this time models indicate the track will just brush the San
   Juan's...however, if the jet moves a little to the south we may see
   more precipitation than forecast in the North San Juan.

   Weather Forecast

   Fields           Wednesday        Wednesday Night  	Thursday
   Temperature (°F) 15 to 20         5 to 10          	13 to 18
   Wind Speed (mph) 15 to 25         20 to 30         	10-20 G35
   Wind Direction   NW               NW               	NW
   Sky Cover        Mostly Cloudy MC Mostly Cloudy MC 	Overcast OV
   Snow (in)        Tr to 3          Tr to 2          	0 to 2

   Snowpack Discussion

   In the alpine winds have been moderate from the NNW.  Expect recent
   loading on E-SE-S aspects, and touchy new wind slabs as a result.

   Storm totals between Thursday and Monday were roughly 20" to 30",
   favoring the south end of the zone. There were localized areas of
   higher accumulations, so expect to find variable snow amounts from one
   drainage to the next. Strong and persistent southerly winds howled
   Sunday and Monday. The very strong winds loaded paths lower than usual,
   with drifts 3' to 4' thick in some spots. Wind drifted storm snow on
   all aspects is slabby, and observers reported some good propagation and
   shooting cracks.

   The drifts are sitting on a variety of older snow. There were near
   surface facets on northerly slopes, and some smooth crusts and old bed
   surfaces well above treeline. Fortunately, the storm snow came in warm
   and bonded fairly well to the old snow. The interface still bears
   examination. There are older weak layers in the snowpack, too. Remember
   back when we talked about surface hoar for several days? It is still
   there, and observers report clean, easy shears on it.
   
   Tuesday a party triggered a slab 1 to 2 feet thick on a slope test. On
   Monday morning a skier triggered a shallow, soft slab avalanche on an
   open, southeast aspect near Coal Bank Pass.Natural avalanche activity
   has been limited to long-running loose slides or shallow slabs on
   windloaded north and northeast aspects.

   Avalanche Danger

   The avalanche danger for the Northern San Juan zone is CONSIDERABLE on
   NE-E-SE-S-SW aspects near and above treeline. Wind loaded slopes have
   unstable slabs, and human triggered avalanches are probable. The danger
   is MODERATE on all other aspects and elevations. You may encounter
   crossloaded or drifted slopes, and should steer clear of them if they
   are steep.