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HMT wx forecast discussion: 8 February 2008 at 1945 UTC

Dry and mild conditions will prevail today and tomorrow across the Sierra Nevada, as midtrop ridging just offshore of CA provides dry, subsident W to NWerly flow aloft. The ridge will flatten later tomorrow and Sunday, as S/W cyclonic vorticity spokes take aim at the PacNW. The leading S/W is presently visible in the satellite imagery moving Eward across ~155W between 40-50N. The ARB will remain well S of any dynamics and precipitation associated with these transient disturbances. Hence, expect the dry wx to persist on Sunday.

Building geopotential heights at midlevels will once again occur offshore of the West Coast early next week, so do not expect any wet/white wx in the Sierra through Tuesday February 12th. Thereafter, the next in the series of S/W troughs is progged to come ashore Tuesday night and Wednesday. Unlike yesterday’s GFS model runs that kept this S/W well N of the ARB, last night’s solutions dig this wave into the Great Basin, although with no significant precip in the ARB. The EC model digs this wave with more vigor in the NWerly flow along the West Coast (as in yesterday’s EC runs), with the possibility of precip and low snow levels in the ARB. Given the history of this winter to date, I believe the EC solution is a distinct possibility. However, it is questionable whether either scenario will yield conditions favorable for an IOP.

Another cold, digging wave may be in store for the ARB toward the end of next week.

Paul Neiman
NOAA/PSD