2005-12-12 Daily Wx Forecast Discussion (1945UTC)
The persistent upper low will finally exit CA today and tonight, with only scattered light precip… mainly in the southern Sierra. In its wake, dry Nerly flow will cover the ARB through midweek, with midtrop ridging situated offshore.
Shortwave energy will chip away at the ridge the latter half of the week, with minoring-out vort spokes riding over the ridge into the Pacific NW and BC, and additional energy undercutting the ridge and establishing a Sern branch stream into Baja and extreme SoCal. Throughout, the ARB will remain at the epicenter of the split flow, with little in the way of wet weather.
The 12Z GFS shows a transitory shortwave breaking through the ridge during the weekend, with only a modest precip. event (at best) across the ARB. Ridging re-builds thereafter. In the 12Z ECMWF solution, the ridge remains locked across CA throughout the weekend. All in all, the outlook is considerably less optimistic for significant precip in the ARB than it was just a couple of days ago…. bummer!
Paul Neiman