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HMT Forecast Discussion: 6 March 2008 at 1945 UTC

The latest IR satellite imagery shows the remnants of the splitting shortwave trough making landfall across CA. Areal coverage of cold cloud tops is decreasing with time, and a dissipating band of weak precip is coming ashore in extreme northern coastal CA. As for the ARB, expect some high clouds to drift overhead today but no rain/snow.

The next progressive shortwave trough is clearly evident in the IR imagery crossing the 145th meridian between 30-50N. It will come ashore across the PacNW and N CA on Friday night into Saturday, temporarily flattening the West Coast ridge. Large-scale dynamics and orographic forcing will remain well N of the ARB, so no significant precip is expected in our area of interest.

All models increase the midtrop heights over CA later Saturday and Sunday, prolonging the dry wx across the ARB. Light warm-advection precip may extend as far S as Shasta in N CA toward the end of the weekend, although any significant rain/snow will likely remain focused across OR/WA.

The storm we have all been anticipating for Mon/Tue continues to look weaker and farther north in each successive GFS and EC solution. The current solutions show a quick-moving, shortwave trough and cold front making landfall across the ARB on Mon/Tue. The core of the dynamics and orographic forcing stays N of the forecast area. Midtrops heights promptly start rising again by later Tuesday, as the shortwave energy drops into the Intermountain West.

The GFS and EC are hinting at a storm toward the end of next week. We shall see!

Paul Neiman
NOAA/PSD