Another Tough Forecast

December 6, 2005

Everything is proceeding according to plan, except there is more than one plan…

Very dry (and colder) air is entering the metro area this evening via the Gorge.  And a weakening weather system is approaching from the west.  Easterly gradient increases rapidly to around 10mb. in the Gorge tonight and should easily produce 65 mph gusts in the usual spots (Corbett, Mt. Zion, Rooster Rock), and 45 mph gusts Washougal, Camas, Troutdale, Gresham.

But the question of the day…will there be moisture to produce some sort of frozen precip Wednesday?

Of the 5 models I’ve looked at (UW-MM5…3 versions, GFS, ETA):  2 are dry…nothing ever makes it here, 3 have very light precip…less than .15".  Obviously, if it’s dry…we just stay cold and windy tomorrow.  If moisture arrives (anywhere between 8am-5pm depending on model), will it be enough to cool temperatures to freezing, or only do that right in the Gorge?  And it also appears to be marginally cold enough above us to possibly allow snow to make it all the way down, which would eliminate the freezing rain threat, but give many areas a dusting.  What a mess.  Best guess forecast would be real light precip midday or so, which means anyone could see flurries, but solid freezing precip (sticking or freezing to ground) may stay confined east of I-205.  Frozen precip of any sort is very unlikely south of Wilsonville or north of Kalama.

Either way a real windy and chilly day!  All maps return us to cold high pressure east side and gusty gorge winds through the beginning of next week.  This is a one shot deal tomorrow and Thursday AM.  We’ll see what shows up 8-9pm on the new model runs.  If they are all dry, then it’ll be an easy forecast.

(Additional note at 11pm:  Our own model we run here plus the new GFS, & 1 version of the MM5-UW keep it dry…so I am definitely leaning towards dry now.  RRK gusted to 48 mph and Corbett to 57 the last couple hours, the cold/dry air is definitely moving in…)