Challenging Forecast

November 12, 2009

snapshotThe short term forecast is simple this evening.  Cold front plunges through tomorrow morning, then cold showers drop in behind.  This airmass is quite a bit more stable than previous post-frontal airmasses;  it’ll be tough to get heavy showers or thunderstorms.

Not much to talk about Saturday either, just cold with some brief sunshine, lots of higher clouds later.

Sunday through Tuesday is the real challenge.  Models (especially the GFS) have become more splitty and slower with the upper-trough to our west over the last 2 days.   Sunday we are on the southern edge of sloppy warm-frontal rain.  Light stuff and maybe some drizzle too.  Boring!  Monday the bulk of the rainfall may lift to the north.  Then Tuesday afternoon a secondary system develops well to the southwest and actually gives California a good dose of rain by Wednesday AM.  I see the 00z GFS now has NO rainfall over PDX from midday Sunday until Tuesday night!  That’s quite a change from 48 hours ago when it looked like a very wet period with even a possible windstorm setup Tuesday.

The split should “heal” a bit later next week.

Okay, I’m off for one day Friday.  So does that mean a surprise snowfall to relatively low elevations?  Could be.  Seems like each time Drew Jackson fills in for me we get some sort of weather event.

Chief Meteorologist Mark Nelsen

New Powder Alert

November 12, 2009

Drew’s new Powder Alert has been posted…link is above.

Feels Like December!

November 12, 2009

BlueBoxPass_pid742I see it’s 38 degrees and raining here at home this morning.  A friend up at 1800′ on the way up to Larch Mountain had 34 degrees and I assume at least a rain/snow mix earlier this morning…winter is getting close!  This is from a nice little upper disturbance passing overhead on it’s way to Idaho/Utah.  There isn’t as much precipitation as I expected, but we should make up for that tomorrow as a juicier and even colder system passes through tomorrow morning.  Now snow levels will actually bump up a bit at first, and then drop later in the day as colder air works in.  Models show the freezing level down around 2500′ in the afternoon/evening, which would put sticking snow down to around 1,500′.  Of course as always if we get a heavy shower it could go slightly lower.  The main message is that the December-like temps will continue.  Even with lots of sunshine Saturday it’ll be a real crisp day with fresh snow on the mountains around us.

Then it’s on to warmer west/southwest flow Sunday through Tuesday.  Lots of disagreement on models here.  A big change I see this morning is a strong El-Nino-ish split (sorry, now it’s like global warming where anytime we see a split it’ll have to be because of El Nino)  on the GFS at 6 and 12z models.  ECMWF not so much.  Unfortunately no models show a big deep low now for Tuesday or Wednesday.  I was a bit busy yesterday so I didn’t get a chance to post, but I know many of you saw the hint of some excitement during that time period.  Well, the models giveth and taketh away apparently.

So, other than some relatively low elevation snow coming up tomorrow, the weather looks pretty quiet for now…assuming the Monday-Tuesday trough splits some offshore.

This afternoon from about 3:30 to 6pm Shauna & I will be out at the Fred Meyer at 82nd and Foster Rd.  We’re raising money and donations (coats, school supplies etc…) for Marysville School that partially burned down Tuesday.  Come by and chat weather if you want…bring some pencils and Batman/My Little Pony lunchboxes too if you can…

Chief Meteorologist Mark Nelsen