Success! A Cool & Cloudy Day

October 7, 2010

We took a gamble yesterday evening (also mentioned on Wednesday’s post) that a strong southwest surge of marine air this time of year means a major cool down and probably marine clouds all day.  Our RPM showed low clouds only to the Coast Range, but the UW WRF-GFS showed a big surge right into the Valley after 8am.  So I forecast a high of 63 at PDX today and mentioned cloudy, cool, and even a few sprinkles possible.  This is one of those times that everything turned out just right.  I was working on the chicken coop and kid’s fort (almost done!) from 9am-noon.  It went from scattered mid-level clouds to a gusty southwest wind and then totally overcast by noon as the cool air surged in.  The cooler air had a huge effect on the temperatures today.  We were still 62 at PDX at 2am, and even now at 4pm we’re only 63 degrees!  That’s down 17 degrees so far compared to Wednesday!

Moving on, two things to talk about…pretty decent weather for Friday and a relatively stormy weekend.

Friday:  I think tomorrow may be one of those cases (like today) where a close look at the models can improve a forecast.  There seems to be quite a break between the dying front moving across the NW tip of Oregon tomorrow morning and the now-delayed heavy rain with a cold front tomorrow evening.  Light south wind, a warming atmosphere, and quite a bit of afternoon sun should push afternoon temps up to at least 70…maybe as high as 74 with good mixing.  I don’t think “mostly cloudy” is going to be correct for tomorrow.  I prefer partly cloudy and warm with just a chance of a shower in Portland in the morning.

This Weekend:  Two very nice deep low pressure centers and their associated frontal systems swing onshore 24 hours apart.  The first low moves onto the British Columbia coast north of Vancouver Island Saturday around daybreak.  Then a 2nd low hits the same area around daybreak Sunday morning.  Our coastline should get quite a surge of southerly wind ahead of each of those.  So very windy later Friday night and later Saturday night at the beaches.  Peak wind gusts will probably be in the 40-50 mph range with both of those.  Between those expect just breezy southerly wind.  Here in the Valleys, southerly wind will just be breezy (no gusts above 30 mph) both nights.    As for rain…it looks real juicy!  Check out the Water Vapor image forecast for Saturday night…around 50 mm. = almost 2″ precipitable water surging onto the Oregon Coast.  You can clearly see the curl of the 2nd low headed towards Canada.  Quite a moisture tap all the way back into the Central Pacific.  The result?  It’s going to get briefly warm and humid this weekend.  Our RPM is quite heavy with the rainfall…showing 1.00-1.60″ here in the Valleys.  Might be a little high, but I think all of us will get at least 1.00″.

Beyond Sunday, back to nice ridging and dry/cool Fall weather Monday-Wednesday at least.  So a good soaking and then sunshine…something for everyone.

Chief Meteorologist Mark Nelsen