HMT Forecast Discussion 1945Z Th 28 Feb 08
Overall conditions appear unfavorable for IOP candidates for the next week or more. The best opportunity at present is from full-latitude mobile Pacific trough near 150W. This feature is forecast to move steadily toward the coast over the next 48h, with a surface low developing and moving newd toward the Queen Charlottes by late Friday the 29th. The trough aloft crosses the HMT late Friday night and Saturday morning. Unfortunately, there is no low-level WAA with this complex, and the sea-level geostrophic wind becomes difluent as the associated sfc frontal system approaches the coast. What this implies is that the system will be relatively dry at and south of the latitude of the HMT, though topographic forcing for pcpn on the higher terrain will be favorable. I don't see any reason to depart significantly from the GFS and EC on overall trends with this system, but I think up to 0.75" pcpn is possible at higher elevations in the ARB, with max pcpn 0.5" more likely. Heavier pcpn will fall on the Siskiyous and northward.
Looking farther ahead, models indicate ridge buliding smartly into the Pacific NW and a resumption of troughing over the central US. All this bodes poorly for any IOP potential for the next 7 days or so.