Cold Showers & Foothill Snow Ahead

March 21, 2018

7pm Wednesday

Weather was pretty boring today with light rain moving north out of California.  Thursday and Friday should be more interesting as we get into a typical spring “showers and sunbreaks” pattern.

A strong cold front moves inland tomorrow morning, lowering snow levels quickly from around 5,000′ to 2,000′ by afternoon.  Cool showers follow the front tomorrow night, Friday, & Friday night.  During this time models are advertising 850mb temps (the temp in Celsius around 5,000′) between -5 & -6 over us.  This isn’t a cold enough airmass to get sticking snow to sea level, but vigorous showers should at least get us a mix of rain/snow during the coldest times of day.  I think it’s unlikely we even get sticking snow down to 1,000′ in the metro area; although that could easily happen in the Coast Range and Cascade foothills (nighttime hours).  More likely if you live at/above 1,500′ you’ll get some sticking snow at times.

Snow Spring Headlines

This is not a real wet pattern.  Check out total snowfall through this entire event, forecast by RPM model

RPM Snow Accumulation

Now beyond Friday night we dry out once again with weak ridging in place for much of Oregon’s Spring Break.  Note the ECMWF model ensembles showing a drier pattern beyond Friday.  Many of the individual members give us several days of dry weather next week.

ecmwf_eps_precip

And of course that means temperatures will come back up above normal for the last week of the month.  Pretty good ensemble agreement on that, showing quite a rise after Tuesday.

ecmwf_eps_meteogram

By the way, with snow coming down into the foothills again, you might wonder how late in the season we’ve seen snow at PDX?  It was on THIS date, March 21s, 2012.

 

Those records just go back to 1938.  Downtown records go back much farther, but it gets trickier since hail/graupel was added into the “snow column” for observations back then.  I see a 0.3″, 0.1″, & 0.1″ on April 9, 1933, April 14, 1903, & April 14, 1924.  On all of those dates temps didn’t drop below 35 degrees.  On April 7th, 1933 there was a 1.4″ total.  But again, the low was 36!  Must have been deep hail or graupel.

Portland Snow Latest

Chief Meteorologist Mark Nelsen