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HMT Forecast Discussion: 8 March 2008 at 1945 UTC

The next in the series of weak, dry shortwave troughs has moved inland across the Great Basin. Midtrop heights will promptly rebound this afternoon and Sunday across CA in response to ridge building along the West Coast. Today’s satellite imagery shows mostly clear skies over CA beneath the amplifying ridge. Dry weather will continue through the weekend across the ARB, although light warm-advection precip may fall across the PacNW later Sunday and Sunday night. Enhanced cold cloud tops in the IR imagery offshore of the PacNW clearly mark this region of warm advection. Perhaps some high clouds will drift across the Sierras tomorrow.

The new GFS and EC solutions are still consistent with the handling of the progressive storm system for early next week. The shortwave is slated to make landfall along the West Coast for Monday evening into Tuesday while remaining mostly N of the ARB. Specifically, the large-scale dynamics and orographics primarily impact the PacNW, although the trailing cold front may generate some light precip along the N half of the Sierras Monday night into Tuesday. It should be noted that today’s 12z NAM solution is quite a bit more aggressive than the GFS/EC with grinding this shortwave through the mean ridge position. Moderate height falls, large-scale dynamics, and orographics affect the ARB, resulting in QPF values between 0.5 and 1.0 inch. I don’t much faith in this outlier solution.

All models then amplify the West Coast ridge yet again for the middle of next week, although unsettled wx may be in the offing toward week’s end and beyond.

Paul Neiman
NOAA/PSD