The band of moisture with the potential system we had been watching has fallen apart quite a bit overnight with the model forecasts now delaying HMT area precipitation by several hours as well as lowering amounts some. The hi-res models (the Western WRF window run at 5km by NCEP and our 3 km WF run) still manage to crank out close to half an inch in some higher elevation spots (our 3 km run more like 0.5 to 1 inch max), but overall it looks like a good decision was made not to work this "event", especially given we are still early on in the program. So, will turn to the potential for anything in the future for the remainder of this discussion.
Overall the big picture has not changed substantially, but there are disagreements among the models regarding a "wandering upper level low" for later next week, and then some uncertainty in the longer range past day 10. Currently a high-amplitude upper level ridge is in place off the West Coast of North America extending northwards across central Alaska. A strong upper level low is located in the northwest Pacific with a strong zonal jet across the western Pacific south of this system. To the east of the upper level ridge is the trough we have been monitoring, and this is still forecast to dive south into the Intermountain West over the weekend and then shift eastward next week, with the upper level ridge if anything sliding more to right along the West Coast, keeping things quite dry in the HMT region. While there is the above-noted disagreement and uncertainty that I will elaborate on below, it should be noted that the deterministic run of the latest 12z GFS, as well as a number of the ensemble members, have a dry solution for the HMT region through day 15 (26 Jan), maintaining a strong upper level ridge near or just off the West Coast that effectively blocks any oncoming systems.
Now for the possible deviations from the above dry scenario. The one for next week involves what happens to the southern half of a lead shortwave trough that splits as it hits the western portion of the anchored upper level ridge later this weekend. All the models show some type of splitting as a piece of the wave rides over the ridge; the disagreement among the models is what happens more to the southern portion of the split, and this begins to show up by Mon/15 Jan. The GFS (12z and 00z runs) forms a closed low with the southern energy that drifts southward around 30N/140W, while the UKMET and ECMWF, and it appears to a lesser extent the Canadian and NOGAPS models, drive more of the energy farther eastward. The result in the 00z run of the ECMWF is an upper level closed low that is much farther north and drifting towards the coast by the end of the week instead of harmlessly way offshore (it should be noted that the previous run of the ECMWF was similar to the GFS). This closed low then reaches the HMT area by 00z/18 Jan. How much moisture is with it should the system actually evolve as in the ECMWF is uncertain, but there is a lot of moisture bulging northwards at this time near Hawaii. Beyond this time yet another piece of energy drops around this system, with the net result by day 10 in the ECMWF a broad elongated closed low extending from off the California coast east to Colorado. This is in stark contrast to the GFS deterministic run, which at the same time continues to maintain an upper level ridge just off the West Coast. The GFS ensembles have several members with more of a "wandering" but fairly small-scale upper level closed low next week, somewhat like the earlier run of the ECMWF, as do some members of the Canadian ensemble. Just to show the kind of variations in solutions back and forth we are likely to have with this kind of odd pattern for later next week, the 12z ECMWF goes back to a closed low farther to the west, more like the previous run and leaning towards the GFS, with the result that it is well off the West Coast midweek next week, although by late in the week a weak upper level low makes it to the south-central California coast. The 12z GFS ensemble has a number of variations on the movement of the small-scale closed low, all within the overall pattern of a mean upper level ridge off the West Coast. As noted in the telcon, substantial precipitation with such an event is unlikely, but it will be at least something to watch for next week. Also as noted in the telcon, perhaps the increase in spread beyond day 10, particularly in the Canadian ensembles, reflects some hope that a more substantial breakthrough of an undercutting jet could occur in the longterm.