Thanks to a very slow low pressure center moving onshore into southern California, a very unsettled pattern will continue for western Nevada through the weekend, with scattered showers and thunderstorms on and off throughout. Temperatures will drop to the mid-60s Thursday and stay there through Saturday before climbing to 70 on Sunday. For the next couple of days, snow levels could drop to near 8,000’, but should stay high enough to keep any snow off of the major mountain passes. Once the low finally moves off to the east at the beginning of next week, temperatures will rebound to the upper-70s to low 80s by mid-week.
Randal wondered: “How are average temperatures computed? Do they use the hundred year plus dataset, or is the average reset once a year or some other period?”
Locally, the NWS uses a 30 year rolling average, updated every year. For the numbers that go into the national climate database, they still use a 30 year rolling average, but they only update it at the end of every decade. They will have some new averages here at the end of this year (2010), so in essence we are really operating through the end of this year with 40 year old data