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HMT wx forecast discussion: 12 February 2008 at 1945 UTC

Same outlook as yesterday: high and dry for the foreseeable future.

The latest satellite imagery clearly shows a prominent midlevel S/W trough riding over the EPAC ridge and making landfall across BC and the WA coast. A desiccated, thin comma-cloud tail extends SSWward from near the circulation center to a position just offshore of OR and extreme N CA before dying out. Meanwhile, the ARB is solidly in subsidence and is expecting another sunny and mild day today.

The newest model solutions still show the S/W digging vigorously SSEward into the Great Basin on Wednesday, as strong cold advection and a developing 300-mb jet become established on the back side of the wave. QPF is minimal at best on Wednesday across the ARB as the tail end of the midtrop vorticity max scrapes the Sierra Crest. All in all, the strong large-scale dynamics and enhanced moisture will remain E of our area. Perhaps the most noteworthy aspect of this storm for the ARB will be the brisk (and dry) N to NE winds that blow on the back side of the wave later Wednesday and Wednesday night, due partly to a developing large-scale pressure gradient of significant magnitude. Downslope mountain-wave dynamics may further intensify the NEerlies on Wednesday night.

The EPAC ridge amplifies in a big way on Thursday and beyond, so the dry wx shall continue unabated. Subsequent S/W troughs propagate into the diffluent upper-level flow across the EPAC, weaken, and make landfall in BC, the PacNW, or perhaps as far S as N CA through the middle of next week (~20 Feb). These systems will likely not yield much precip for the ARB. Thereafter, perhaps some zonal wave energy will finally reach CA.

Paul Neiman
NOAA/PSD