IOP-12 will begin 00 UTC Monday Feb. 27 (4 PM PST Sunday). Light precip is expected to start over the ARB from warm air advection in the warm sector of an advancing cold front/upper wave. Heavier precip is expected from both orographic lift and baroclinic lift processes beginning around 06-09 UTC. Rain will taper off early Tuesday after the frontal passage. Snow levels start out rather high, 7-8 kft, and then descend to perhaps 5 kft as the trough axis passes and the ARB comes under the influence of cold air advection.
The SMART-R and XPOL radars will begin ops at 00 UTC Monday. Soudings from Sloughouse will also begin at 00 UTC. The first OAK supplementary sounding will be 03 UTC. Supplementary soundings will continue to Tuesday 09 UTC (OAK) and Tuesday 12 UTC (Sloughouse). The end of IOP-12 is expected to be around 12 UTC Tuesday, although if the rain tapers off significantly before then the radars could suspend data collection earlier. Total QPF for IOP-12 could be as high as 5.5" at BLU.
There will be a break in the precip as short wave ridging occurs from late Tuesday to early Thursday. Another wave with QPF perhaps 2" will occur on Thursday. Its possible that another IOP will be declared on the Thursday storm. That decision will not be made until perhaps Tuesday.
Instrument Status Issues:
The faulty transmitter from the Colfax S-band profiler is now back in Boulder and its condition is being evaluated. More might be known by later this afternoon. However, it appears unlikely that the profiler will be back in operation for IOP 12.
The faulty temperature and relative humidity sensors at Blue Canyon have been replaced and the data are now being displayed on the HMT-West 2006 web page. As a result of this repair, snow depth data at Blue Canyon is now also being displayed again.
The untelemetered rain-gauge and associated data logger at Yankee Jim Crossing has been destroyed beyond repair as a result of vandalism (gun-fire). Data acquisition stopped on 27 January.