A Wet Week Ahead; Chilly Start to Spring Break

March 18, 2013

A very nice looking low pressure center will be spinning up quickly the next 24 hours well offshore and head for northern Vancouver Island. Even with a forecast pressure around 985 millibars, it’s too far to the northwest to give us real strong wind either at the Coast or here in the Valleys. That said, gusts 60+ at the Coast and 30-40 mph are likely later Tuesday night and very early Wednesday morning just ahead of the cold front passage. We’ve seen very few (maybe only 1 or 2?) of these strong low pressure centers since late December, so it’ll be a refreshing change. Ahead of this we get a good 6-7 millibars easterly gradient developing through the Columbia River Gorge by sunrise. So those of you out in Corbett and Washougal expect to hear the wind roaring with gusts up around 50+ mph in the next 12 hours. Luckily this time of year the afternoon heating east of the Cascades doesn’t allow the high pressure to linger east side long so that wind will be gone by evening.

Plenty of rain with this system tomorrow and especially tomorrow night and Wednesday.  This is good news because:  1) We’re well below average January-March, and,  2) I just planted 100 Douglas Firs and they need a good soaking to settle in!

What caught my eye today and this evening is how cold the two upper-level troughs are going to be after the cold front passes through. The first comes through early Thursday morning, the 2nd late Thursday night and Friday morning. The NAM model has been “over-chilling” 850mb temps recently; not sure why. For example last weekend it was forecasting around a -7 or -8 and we bottomed out at -6 Saturday morning (or was it Sunday?). Anyway, it’s saying -7 to -8.5 now with a 2nd trough late Thursday night!  The GFS and ECMWF are a bit more reasonable in the -6 to -7 range.  That temp combined with showers could easily allow sticking snow down to 1,000′ or even a little below in the overnight hours.  The issue for Wednesday night is that we still have breezy southwest wind (onshore flow) and showers seem to taper off during the overnight hours.  Then on Thursday night surface high pressure is building in from the SW so we may not have much of any moisture.  It’s something to keep an eye on but I think lack of moisture is going to be an issue if you want anything more than a dusting down to 1,000′. 

Forget about sticking snow in the city of course…it’s too late for that unless we have some sort of solid and heavy precipitation with those chilly upper-level temps.

Friday between 2-4pm Spring Break begins for most Oregon schools and it appears to start chilly.  Not much rain this upcoming weekend but definitely cool.  Good for skiing! 

Models do imply more reasonable temps, but not necessarily dry beyond Sunday.  Here is the 18z GFS ensemble chart, click for a “non-gray” view:

tseries_850t_000-384_Portland

You can see temps go to average or a bit above for next week, so Spring Break may not be a total loss.  But what would that week be without some hail, gusty wind, and occasional downpours?  I spent every Spring Break week of my school career (except one) somewhere between Seattle and Salem and I think I remember 1, or MAYBE 2 that had some sort of sunny and warm weather.

Chief Meteorologist Mark Nelsen

 


Climate Tribes…Great Post By Professor Cliff Mass

March 18, 2013

I just read this wonderful (my opinion) overview of the stalemate/impasse in the global warming issue.  I think Cliff sums up the current situation quite well.  This is one of several reasons I rarely mention global warming in my nightly weathercasts.  In fact I can’t remember the last time I did!

http://www.cliffmass.blogspot.com/2013/03/climate-tribes.html

earth

Chief Meteorologist Mark Nelsen


Monthly ECMWF Maps

March 18, 2013

I’ve been a bit behind at work (and uninspired by the weather) lately, but I come bearing gifts.  Last night’s ECMWF monthly run:  4 maps, one for each week, showing the average 500mb (upper-air) pattern.  Yellow/red areas are higher than average (usually warmer), and bluish areas are troughy or cooler than average.

500za_week1_bg_NA

500za_week2_bg_NA

500za_week3_bg_NA

500za_week4_bg_NA

Here’s the 12z ECWMF ensemble chart too, showing the cool airmass later this week and then a rebound to average or a little above after that time:

tseries_850t_000-360_Portland

Chief Meteorologist Mark Nelsen