IOP #4 Winds Down
Weather Status: IOP #4 looks to be in its final phase with the last few rain/snow bands ending early Monday (7 Jan 12UTC [04L]). National and HMT models are all pointing at about another 0.5 to 1 inch for the ARB. BLU is still without power but snow estimates are about 4 ft. Boreal ski area up I-80 had 5.5 ft; Heavenly Valley had 5.5 to 8 feet with unofficial reports to 9 ft. Huysink had 7.5 inches of liquid. Attention now focuses on new waves that will impact the ARB this week. The first will begin early Tuesday (8 Jan 12UTC [04L]) with a fast moving system, a forecast IPW plume, and a warm advection period. QPF for the event will be a bit over an inch of liquid, so the event will exceed the minimum criteria for an IOP. Question remains on the height of the freezing level. NWS is estimating about 5000ft, below BLU. This impending precipitation event has been identified as IOP #5. In less than a day following, another event, this one with a fast moving system and a classic IPW river, will move into the ARB late Wednesday (10 Jan 06UTC [9/22L]). The jury is still out on this event as QPF totals only about a half an inch from the GFS. Given the ingest of tropical air these amounts could increase in subsequent forecasts. After these two systems the long range outlook indicates an inactive period for at least a week.
Summary: IOP#4 ends 7 Jan 12UTC (04L); IOP#5 starts Tues 8 Jan 12UTC (04L) - heaviest precipitation 18-00UTC (10L - 16L) - ending Wed 9 Jan 12UTC (04L); next system late Wed-Thurs (9 - 10 Jan).
Observation Status: BLU still has no power so no surface observations are available. Same story at Big Bend. Cazadero came back on line Saturday afternoon but went out again early Sunday. Chico is still out. Radar crew will attempt to redeploy to radar site Monday (7 Jan) subject to accomplishment of snow removal. Once on site crew will start generators to restore power to surface instrumentation. Radar crew will start up HYDROX radar for IOP#5 by 8 Jan 12UTC (04L) planning to run until 9 Jan 12UTC (04L). New radar crew will travel to ARB if Wed-Thurs event looks more significant. Travel would be Tuesday, with crew overlap on Wednesday, and radar operations on Thursday. A decision will be made on Monday as to necessary travel for relief radar crew. SHS RAOBs will go into action for IOP #5 at 8 Jan 12UTC (04L) with last sonde tentatively planned for 9 Jan 06UTC (8/22L). RNO and OAK will start special sondes on 8 Jan 15UTC (07L) ending on 9 Jan 06UTC (8/22L). Owing to speed of system and more compact horizontal scale ALL SONDES WILL BE LAUNCHED AT 3 HOUR INTERVALS.
Decision summary: IOP#5 - Radar in operation 8 Jan 12UTC(04L); SHS sondes commence at 8 Jan 12UTC (04L); RNO and OAK special sondes begin at 8 Jan 15TC (07L)...sondes to be launched at 3 hour intervals...tentative ending time for all sondes 9 Jan 06UTC (22L).
Product Status: All model products available; all observation products available except at sites noted above.