2005-12-05 Daily Wx Forecast Discussion (1945UTC)
Ridge conditions and dry weather will remain over the ARB today through early Wednesday.
The models are still showing a shortwave trough breaking through the West Coast ridge Wednesday and Thursday, although this forecasted disturbance is a bit weaker in the 12Z cycle simulations. As the shortwave rounds the ridge and then drops SEward along the CA coast Wednesday afternoon and Thursday, it may produce some light precip across the ARB with snow levels in the 5.5-6.5kft range. However, because the associated dynamics and orographics will both be modest at best, don’t expect heavy precip. The shortwave may cut off from the northern branch later Thursday/Friday. Interestingly, the 12Z GFS is the first model to suggest that the cuttoff circulation may stall W or NW of the ARB rather than to its S. If this is the case, light precip may persist into Friday. If, however, the cutoff drops S of the area (as has been progged by all other model solutions), the ARB would see drying downslope easterly-component flow at mid levels by Thursday night and Friday.
Midtrop heights should rise behind the departing shortwave by the end of the week, with the prospect of dry wx through the weekend. The long range models do still hint at the possibility of more modest shortwave energy breaking through the West Coast ridge after this weekend, but as of yet, there is no indication that a major zonal race-track of embedded frontal waves will develop.
Paul Neiman