Mainly Dry Weekend

February 6, 2009

610day.03 Here's the 6-10 day 500mb height forecast along with the deviation from average.  It shows the general trend for next week.  An upper level ridge out in the Pacific…not too far offshore, with a trough over the Southwest.  Systems will pass over the top of the ridge, then drop down through or near the Northwest on their way down south.  This makes for unstable model forecasts.  Models constantly change focus on different shortwave troughs, making some more important than others (depending on the run).  This can make a huge difference in the forecasts since surface pressure patterns change.  For example, precipitation falling on Tuesday could be heavy enough to bring snow down to sea level, if we don't have too much warming with a southerly wind.  For now it doesn't look like that is the case.  In fact I notice that the southerly flow on Tuesday is slightly stronger on the 00z GFS tonight compared to 24 hours ago.  Not a huge change, but you get the idea.

In the short term…this weekend should be real nice.  Light rain from a weak front arrives Sunday evening.  Our RPM model and the WRF-GFS show very little snow/rain for Monday, so that's why I'm not talking much about that.

We'll see about the rest of next week, but none of the systems look especially juicy, but plenty of cool air spills through the Pacific Northwest.  My general mood is to keep a close eye on the maps, but nothing looks all that impressive for now…Mark Nelsen