A Brief Downturn

September 8, 2006

A very straightforward forecast this evening!

Weak cold front and upper level trough offshore this evening.  It moves into the Northwest overnight.  I expect at least a trace of rain anywhere north of Salem.  Maybe .05" at PDX and .20" wettest west slopes of Cascades & Coast Range (my "rainforest" house included).  Yesterday there was debate in the models as to whether it would be an open wave or a closed upper-level low tracking across the Northwest Saturday.  Now it is pretty clear that we’ll see just the open wave moving overhead.  That means a quick end to any rain.  MM5-UW Cross-sections show almost no saturated air overhead by Sunday morning with light north-northeast flow.  That means a quick return to sun for Sunday midday at the latest, if not right at sunrise.

Ridging for at least early-mid next week an easy call too.  As you folks have noticed, a wide variety of solutions beyond Thursday.  12z ECMWF has a very chilly closed low dropping south out of Canada, but none of the GFS models show that, so I’m ignoring it for now.  More likely the ridging just backs off a bit, like yesterdays ECMWF.  That brings cooler air overhead and to our east, but no moisture of any consequence.

Enjoy the "big rain" for tomorrow…I don’t see any other wet stuff for at least another week…Mark