HMT Forecast 1/14/2008 19:45 UTC
This morning has evidence of good radiational cooling over the ARB with fog in some areas and temperatures ranging over a wide extent from 49F at KBLU to +5F at KTRK. No precipitation was likely received since yesterday at this time. The moisture situation in the Pacific has taken a turn for the worse as we have lost many of the strong circulations this morning and associated moisture plumes are dissipating. The progged low off the CA coast at 31N 145W remains in place, the circulation center at 41N 180W has dissipated with the major plume from Indonesia now drawn up into an area of convection in the mid-Pacific. Its potential for reaching the CONUS now looks to be doomed.
In the near term, the current potential event that will be in the area tomorrow morning is still expected to miss the ARB passing mainly to its north. No model brings precipitation into the area and the SREF (03ut) even has 0% probability of rain or snow over any portion of the ARB . The NAM shows short wave passage roughly at 18UTC 1/15 and one is hard pressed to even identify a wave in the GFS or EC models.
Beyond this, the area looks to be ruled by severe dry conditions until possibly the Sunday 1/20 timeframe when the arctic cold outbreak that was discussed in detail yesterday still shows a possibility of wringing out some moisture (it certainly does not advect any into the area), but today the models are pretty stingy on bringing snow to the region. It would be snow if it occurred as the EC model brings in a 526 thickness over the ARB on 1/22. Along with this, the off shore ridge appears to adopt a strong positive tilt that directs any Pacific moisture rivers well up into AK and down into central Canada steering them well away from the ARB.
Beyond this, the ensembles have no precip in the ARB until 1/21 (Monday) 12utc at the earliest and in this case it is only a couple runs. There appears to be another potential cold air outbreak on or about 1/30, again not an optimal situation for the experiment if it even does bring precip into the ARB. Today's ensemble 500-height forecasts however, show less tendency for the ridge to retrograde, keeping it pretty much set up off the CONUS coast with high amplitude out for the full 384 hours (1/30) with a very strong cold low pressure circulation stationary over Hudson's Bay.
Dan Birkenheuer ESRL/GSD