Monday, March 12, 2012

March 12, 2012
 
Forecast valid: Mar. 12th (8:00 am) – Mar. 13th (8:00 am)
AVALANCHE PROBLEM
 
TODAY’S DANGER
MODERATE Considerable where wind affected.
DANGER SCALE
click for danger scale
DANGER TREND: The danger will remain steady with continued north winds through tonight.
 
WEATHER: Sunny this morning with increasing clouds this afternoon.  Highs near town in the mid 20′s except around 10 F through The Pass.  Northeast winds will continue today at 10-20 mph gusting to 30 mph near town. Winds in The Pass will be North 25-40 mph. Wind Chill Index
There is a chance of snow overnight tonight with low temperatures around 15 near town and 5 F in The Pass. Northeast wind 15 mph near town and winds in The Pass will be from the North at 15-30 mph. Expect 3-5 inches of snow Tuesday evening into Wednesday. GFS Meteogram
 
TRAVEL ADVISORY:  Fresh windslab will continue to form today through The Pass and in channeled terrain and exposed ridge lines near The Port. Commonly Thompson Pass and the Lowe River Valley redirect north winds to load slopes from east to west.
 
Yesterday skiers were finding whumpfs and were able to trigger small pockets of windslab on 40 degree west facing aspects. Windslab avalanches are often triggered from thin areas (edges) of the slab. Learn to identify hollow sounds, stiffness under your skis, and areas of denser snow over less dense snow indicative to windslab. 
 
Extended sun breaks may cause point release avalanches to release on steep, south-facing slopes in lower elevations.
 
AVALANCHES:
  1. Mar 11 - One D1 skier triggered slab avalanche on a west aspect above Tsiana River Bridge at 3,200ft. Two natural D1 slab avalanches on a SW aspect of lower Catcher’s Mitt at 2,500 ft. One D2 avalanche on the West face of Tones Temple running from Upper elevations to the 27 Mile glacier below.
  2. Mar 10 – Human triggered D1 slab avalanches reported near Benzene Alley. Size 1 windslab avalanche at MP 20.
  3. Mar 9 – Natural size 1 soft slab avalanche at 2,800ft on convex roll facing west. 
  4. Mar 8 – Human triggered size 1-1.5 wind slab avalanches kicked off on multiple aspects at all elevations.
  5. Mar 7 – Widespread point releases to size size 2, both cold dry new snow running far and also when the new snow was warmed by the sun. Size 2 slab avalanche on a SW shoulder at Mile 60.
Post your observations <here>.
Avalanches are sized using the destructive scale <here>.
 
 
VALDEZ
 THOMPSON PASS
 24 Hour 
0″
0″
March
22.1″
10″
Season Total
426″
636″
 Base
92″
132″
   
Snow load measured March 4, 2012 by NWS Valdez was 101.4 pounds/square foot. 
 
WEAK LAYERS:
  1. Interface beneath new windslab.
  2. Valentine’s Day near surface facets. Profile.
  3. Feb 6 surface hoar in the intermountain snow climate zone.
  4. Melt freeze layer in low elevations near the port. Francis Profile. Benzene Profile.
CONFIDENCE: Good.
 
Season Summary (written Feb 17) <here>
 
DEFINITIONS:
Snow climate zones:
  1. Maritime (Coastal) – from the Port of Valdez to Thompson Pass, all waters flowing into Valdez Arm and everything south of Marshall Pass.
  2. Inter-mountain (Transitional) – between Thompson Pass and Rendezvous Lodge.
  3. Continental (Interior) – the dry north side of the Chugach (north of 46 Mile, including the Tonsina River).
ELEVATIONS:
Lower – below 1500 feet
Mid – between 1500 and 3000 feet
Upper – above 3000 feet