The model forecasts for next week continue to follow the scenario discussed over the last couple of days: the next trough now moving across the Pacific into the Gulf of Alaska will dive down the North American west coast behind a strong upper level ridge building into the Gulf of Alaska, presenting a potential event for the HMT area aboutThursday. Yesterday's model runs favored the trough moving down the coast and over the HMT area around Thursday (11 Jan) before heading into the western CONUS and not digging off the coast, even in most of the ensemble model solutions. This would create a cold system with low snow levels in the HMT area but with
precipitation amounts that might be too marginal to consider for an IOP. The main difference among the 00z runs from last night is that the ECMWF model is more agressive in moving the trough inland as well, while the Canadian global model, on the other hand, has a solution that has far more of the trough off the California coast on Thursday, which would provide for more precipitation for the HMT area. However, it appears this may be caused by the Canadian run not leaving behind the southern end of the trough near Hawaii, as the other models do, and instead having a far more elongated, phased trough into the Pacific. The 00z Canadian ensemble tends to favor a somewhat more progressive solution although a few of the runs do keep more of the system off the coast (mainly towards southern California) than in the GFS ensemble. Beyond this system there is a tendency to keep the upper level ridge into the Gulf of Alaksa through next weekend (13-14 Jan), with perhaps another system following a somewhat similar track to the one next week. However, after about day 10, and a bit earlier on the ECMWF (which
I can only get out to day 10 for their deterministic run), there is a lot more spread in the ensembles, with some keeping a ridge in place but a number of the members breaking the pattern down and bringing systems into the West Coast (this would be from 15-22 Jan).
A look at the latest 12z runs coming in shows the following. The GFS is even somewhat more progressive in shifting more of the trough inland and while the timing for something in the HMT area is about the same, precipitation amounts forecast for Thursday are quite light, followed by an even weaker system coming down the coast the following week, so really not showing anything through 20 Jan. The Canadian global model still has more energy off the coast, albeit not as much as with the 00z run, but would have some potential for an event in the Thu to Fri (11-12 Jan) timeframe, and the NOGAPS has some support for more than the GFS (but not quite as much as the Canadian run). The 12z ECMWF run, just in, is in extremely good agreement with the GFS through 168 h (12z/Sat/13 Jan) with a quick-moving trough down the West Coast and that then moves inland and progresses slowly across the intermountain West. Both the GFS and ECMWF runs then would not support an IOP as the
precipitation amounts for the HMT area would be rather light. The 12z ensembles from the GFS generally support the GFS solution through next weekend. Longer term, beyond day 10, the 12z ensemble from the GFS has less spread than the 00z run and keeps a more persistent ridge into the Gulf of Alaska, so somewhat less favorable, it would appear, for very moist systems into the HMT area in the week period after 15 Jan at this point.
So right now would have to say we still need to watch for something in the Thursday 11 Jan timeframe, but it is likely to be marginal, at this point looking too marginal for an IOP, however, a cold event with low snow levels.