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HMT Forecast Discussion 1945z 1 March 2008

There was 0.06" between 12 and 18z this mrng at KBLU, and there may be a bit more pcpn this aftn as another weak band of clouds and showers passes thru. However, pressures are rising at the surface over the Northwest, indicating the building ridge sfc and aloft over and just off the West Coast. There will be another weak wave pass to the N of the ARB M-Tu 3-4 March, but this should bring only a few high and middle clouds over the ARB.

As noted in yesterday's discussion, this feature (or part of it) will dig southeastward or southward midweek next week. There remains quite a bit of difference of opinion amongst the different models and ensemble members about whether this will cut off over the Southwest or will remain connected to the main midlatutude waveguide and give a major storm to the East. The hi-res GFS run from this mrng follows the latter scenario. In any case, the only hope for the ARB is for the ridge along and off the Coast to flatten and shift inland to allow Pacific systems to penetrate sufficiently far south to be of interest. The first inkling of that is next weekend when the ECMWF from this morning brings a wave across OR and Nrn CA of sufficient strength for a little pcpn on northern CA. A couple of the Penn State Ewall GFS ensembles are indicating a possibility for a stronger system early the week after next (say, near Tu 11 March). However, there is large ensemble spread by this point. In summary, I consider chances of an IOP candidate to be < 10% before M 10 March and < 30% before Th 13 March.

John B.