Weekend Outlook Still Improving

April 17, 2012

I mentioned in yesterday’s post how lucky we have been to see two mild and dry April weekends.  Now we’re seeing increasingly positive indications that we could have the warmest weekend yet on the way. 

Models are still bringing a wet frontal system over us later Thursday through later Friday.  But then as new energy digs way offshore to our southwest, upper level ridging builds strongly just to our east Saturday & Sunday.  As of now, no model has any sort of significant rainfall over us this weekend, and most have none.  We will not be directly under the ridge; if we did, we’d see 80+ degree temps west of the Cascades.  Instead, high temps within 5 degrees of 70 seem to be most likely.  Maybe just below 70 on Saturday afternoon with increasing sunshine, then well into the 70s on Sunday, depending on how close the ridge is.  The ECMWF has the warmest atmosphere over us now, showing 850mb temps up around +12 or +13…that’s 75-80 in the Portland area.  GFS and GEM are cooler.  So we’ve gone 68 & 73 for now, still the warmest we’ve seen so far this spring.  You can see why the ECMWF is warmest in the images below; it has the ridging slightly closer.  These show 500mb height deviations from average for this time of year on the GFS, GEM, & ECMWF.  They are all the ensembles of each model too.  That’s many runs of the same model based on the same initialization time:

Beyond Sunday, models are actually in pretty good agreement that a sharp and cool trough comes down in the northwest flow for Monday and Tuesday.  This is a much cooler, but still drier than average weather pattern since the main energy remains to our north and east. 

Here is the same 500mb deviation chart for 8 days from now…next Wednesday afternoon, the 24th.  The GFS and ECMWF build a ridge just to our northwest in the eastern Pacific, but the GEM keeps more troughing close by:



Regardless, the pattern is very mild for spring through the next 7-10 days with not much rain after Friday morning.  There seems to be decent confidence in the many ensemble members of the ECMWF and GFS at least.  Here are today’s two charts of 850mb temps:





Chief Meteorologist Mark Nelsen