Quick Snow Update

January 8, 2013

Here are my latest percentages…

MarkSnow_PortlandOutlookPercentages

As you can see, we’re not real excited about the chance for sticking snow here at the lowest elevations the next few days.  Mainly due to lack of moisture.  It sure looks cold enough from late Wednesday night through early Saturday, but this “event” looks even weaker than that light snowfall some areas saw just before Christmas.

9:45pm Update…

There may be some confusion on those numbers above, those percentages are all “stand-alone” numbers.  I figure a 10% chance of a snow day for schools in the metro area, about a 30% chance of enough snow to affect the commute Thursday morning or evening, and a 50/50 chance of any of us in the lowest elevations around the Portland/Vancouver metro area seeing a dusting.  You need more than a dusting to have any affect on the commute, thus a lower chance.

That graphic is specifically for the Portland area. For those of you in Salem and farther south, I’d give it about a 70% chance of a dusting and 50% chance of AM or PM commute issues.  I see some models are spinning up a weak surface low pressure area and dropping it into western Oregon during the morning Thursday.  This isn’t a new development, models have been consistently pointing more moisture into SW Oregon.  Here’s the WRF-GFS 24 hour precipitation from 4am Thursday to 4am Friday.  There’s enough precipitation there to give at least a dusting to the central/southern Valley.  This could be a situation where a cluster of showers moves into the Valley and drops 1-3″ from Salem southward Thursday morning and the metro area stays dry…we’ll see.  Soundings appear cold enough too:

or_pcp24_60_0000

I lowered our 7 Day forecast temps a bit based on a minor change the past few runs…the upper level ridge is going to be a bit closer to us than what we were looking at 24 hours ago (slightly closer).  The effect is a bit more offshore flow at times, although week.  The ridge is not in a position to give us any sort of strong east wind (or even much) like we saw last week, but a little more continental/drier air means lower nighttime temps and daytime highs only around 40 or so.

I’m also ignoring the 00z GFS deciding to ram an upper-level shortwave right through the ridge on Saturday and down into California.  That was a weird development and leaves us dry with chilly offshore flow.  The NAM still has some very light rain/snow over us Saturday with the freezing level around 2,000′, although we are on the edge of the precip area.  Our RPM only goes through Friday evening.  The 00z GEM is similar to the NAM.  Other than that, it appears we are heading into a long-term ridgy period again.  The 00z GFS has no rainfall for a 9-10 day period starting Thursday evening!

Chief Meteorologist Mark Nelsen


Follow

Get every new post delivered to your Inbox.

Join 300 other followers