Wet Season Arriving

October 25, 2018

6pm Thursday…

When I think of typical October weather, today would pretty much cover it.  Not a real soaker, but gray and rainy at times.  We’ve picked up about a quarter-inch of rain so far in much of the metro area:

Rain Metro Today Databound

I’ve been expecting a decent amount of rain during the next week, but models are a bit wetter today.  Check out the 7 Day precipitation forecast from the ECMWF, that’s through next Thursday

ECMWF Precipitation Accumulation

Pretty wet!  If this occurs, October will go down as a wet one even though we had two weeks of sunshine in the middle of the month.  This points out how things can change quickly in late October as the wet season arrives.  Notice a few spots in the Coast and Cascade ranges with 6-8″ of rain; this will provide the final soaking to finish off what was left of this fire season.

Sunday could be a particularly active weather day with frequent showers, downpours, and thunder/hail.  It’s a cool and unstable airmass moving overhead that day.  By Monday morning we’re back to that chilly airmass we saw in early October; expect snow down below Timberline Lodge but not quite sticking to the passes.  You see the dip in snow level here:

ECMWF Snow Level From 850mb Temps LONG TERM

By the middle of next week strong high pressure offshore will somewhat shut down the rainfall, or at least slow it to a trickle as we enter November.  One weak system will slide over the ridge on Halloween and that COULD give us a rare wet Halloween evening, we’ll see.  Most of the past 15 years we’ve seen dry conditions during that critical Trick-or-Treat time 5-8pm.

Halloween Weather History

Looking farther ahead, the weather pattern still looks mild and slow later next week and that first weekend of November.  You see the upper-level ridging and mild conditions on the ECMWF ensemble 500mb heights on Saturday the 3rd

m500za_f216_bg_NA

There are hints of a cooler pattern just beyond that, maybe 12-14 days from now.  We’ll see, that’s a long way off.  For now I’m still confident that we don’t see a stormy pattern through the first week of November.

Chief Meteorologist Mark Nelsen