It’s real nice nowadays when we are able to predict the big pattern changes many days ahead of time. Example A is the December 2008 cold spell; we were quite confident and models were in agreement on the big freeze a good 8 days ahead of time. The December 2009 cold wave was well forecast too. Heat Waves have been advertised well ahead of time the past 5-10 years successfully as well. We still miss on the marginal events (36 degree rain or 5″ of 32 degree snow?), but we’re gradually getting even better with those.
This week is one of those times where we’re talking about a major weather pattern change many days ahead of time. We see a dramatic change from our record dry spell to unusually wet October weather. By Thursday, we will have had only 1 day with measurable rain in 83 days! Confidence has been growing the past 24 hours that this won’t just be a little bit of rain coming up but a big soaking. Take a look at the WRF-GFS model from the UW. It handles the mountain terrain far better than more coarse global models like the ECMWF and GFS. As mentioned on the previous post, it IS based on the GFS so it’ll always be similar:
That’s the 3 day rainfall from Friday morning to Monday morning…wow! Everyone gets at least close to 1″ in the driest parts of the western valleys; likely more. With the strong westerly flow running directly into the north-south facing Cascades, 4-6″ rainfall is possible on the parched soil!
Chief Meteorologist Mark Nelsen