March 2012 Is the Wettest March Ever In Portland

March 31, 2012

I just got back from vacation about one hour ago so of course the first thing I did was check the rain record. 

The wettest March on record in Portland (at PDX)  WAS 7.52″ in 1957.  As of 8:00 am, 7.53″ has fallen so far this month.

By the way, did you know a person can leave Hollywood, California at 3pm on a Friday, drive 16 hours and 10 minutes and be sitting here on the east side of the metro area blogging about weather at 8am Saturday? Amazing…that would be 2 kids, 2 adults, and a little compact car (efficient, but REAL tight).   That didn’t include more than 1 hour of sleep either; more on that on a later post. 

Due to that and the absolutely horrible weather outside right now, I’m going to take a nice long nap.

Chief Meteorologist Mark Nelsen


A Fresh Post

March 22, 2012

For warmer weather.  You can chat weather here while I’m on vacation for the next 9 days…Mark


Snow Totals: Thursday Morning

March 22, 2012

Did you get 1/2″ or more last night or this morning?  If so, put it in the comments below.  Keep discussing weather on previous posts.

1. Fresh snow received overnight.

2. Location

3.  Elevation if you are up above 500′ or so.

And don’t forget, the first time you post a comment, or use a different IP address, your comment is held for moderation.  It might be awhile since I’m on vacation for a week or so.  I’ll be checking in.  After that you can post anytime.  It may be a couple hours until I get to your comment.  This keeps the “spam issues” away.


Forecast Working Out Well; Historic Spring Snow In Valley

March 21, 2012

10:00am: 

Very impressive preformance by numerical weather models today!

Heavy snow in the foothills, very little in the lowest elevations around the Portland Metro area, heavy snow to the valley floor central and south valley too.

Right now the main action is from Salem to Eugene with the heavy snowfall…5-8″ down there!  As the NWS says, a historic spring snowstorm in the Valley.

More accumulation down south all  day, the precip changes back to snow (briefly) here in the Metro area sometime after 8pm, but with little additional accumulation.

Here in the Metro Area, it’s doubtful we’ll see anything other than a dusting overnight.  In fact temps stay above freezing down in Salem.  I don’t think we’ll have major issues for the Thursday Morning Commute.

Roads look clear enough, so I’m on vacation now through next week for Spring Break.

Chief Meteorologist Mark Nelsen


Snow Totals: Wednesday Morning Edition

March 21, 2012

Here we are again…almost Spring Break and…

Did you get 1/2″ or more last night or this morning?  If so, put it in the comments below.  Keep discussing weather on previous posts.

1. Fresh snow received overnight.

2. Location

3.  Elevation if you are up above 500′ or so.

And don’t forget, the first time you post a comment, or use a different IP address, your comment is held for moderation.  It might be awhile since I’m on vacation for a week or so.  I’ll be checking in.  After that you can post anytime.  It may be a couple hours until I get to your comment.  This keeps the “spam issues” away.


Snow Outlook Tonight-Thursday Morning

March 20, 2012

A big taste of winter FOR SOME AREAS the next 2 days; quite a challenging forecast!  Here are the nuts and bolts…

Steady precipitation (rain or snow) from now through late tomorrow night all areas over and west of the Cascades is an easy call, but high uncertainty on details; models are disagreeing a bit still.  Maybe it’s best to tell you what we DON”T expect the next day or so.

What we don’t expect through Thursday morning:
–          Strong or gusty wind.  It’ll be nearly calm from this evening through Thursday AM.
–          “Stormy” weather except way up in the mountains.
–          Flooding in the north/central Willamette Valley
–          A snowstorm in the Portland metro area.

What we’re confident with:
–          A ton of snow in the foothills near 1,500’ and above, Coast Range, and Cascades
–          Lots of rain, but we’ll probably avoid flooding due to snow in hills and quick cutoff of precipitation tomorrow night.
–          Afternoons just wet at the lower elevations, even if we get A.M. snow

The snow level gradually lowers late tonight to somewhere around 1,000’ in the Northern Willamette Valley, and possibly all the way down to the Valley Floor from Salem to Eugene.  Then it’ll rise during the “daytime heating” all day tomorrow through evening.  Possibly dipping down into the hills briefly again tomorrow night. 

FORECAST

Northern Willamette Valley (Portland), North Coast, and Columbia Gorge:
Zero-Dusting possible briefly tomorrow morning and maybe again late tomorrow night.
2-4” once you get up to 1,000’
Likely no commute issues tomorrow morning or evening.

Central/South Valley (Salem-Albany-Eugene):
1-3” lowest spots late tonight or tomorrow morning, possibly again tomorrow night.
5-7” once you get up to 1,000’…S. Salem Hills and Santiam Canyon might get nailed.
Could be messy morning commute in parts of Salem.

Near/above 1,500 (includes Coast Range, and Cascade Foothills):
-10-15” late tonight through Thursday morning.

When I have time later this evening I’ll blog about all the meteorological details…

9:00 PM UPDATE

Looks like sticking snow level is SLOWLY dropping as expected this evening, maybe approaching 1,000′ in the Cascade Foothills and somewhere just above 1,500′ over Portland based on KPTV temps.

I’ve had a few emails wondering why the push for snow to our south  to lower elevations vs. up here in Portland. 

1. The dividing line, a stationary front, will linger somewhere around Roseburg to Bend through tomorrow night.  All areas to the north of that line COULD see snow if precipitation rates are heavy enough to drive the snow level all the way down to the surface.

2.  Models (all except the NAM) keep the heaviest precipitation from Salem to Roseburg.

3.  So the best chance for the lowest elevations to see snow is somewhere south of Portland to somewhere north of Roseburg.  Assuming models are handling things correctly.

The 00z RPM and WRF-GFS are similar to earlier runs, although both were SLIGHTLY farther south with the heavier snow.  Check out the 24 hour snowfall off the WRF-GFS from 5am tomorrow through 5am Thursday.  I really like the 11″+ at Junction City!

And the Salem forecast sounding still goes with a snow profile for 7am tomorrow:

The Portland sounding is only 1-2 degrees warmer in the morning, thus the forecast of 2-4″ in the West Hills and a trace in the lowest elevations.  A 2-3 degree error in temperature forecast will make the difference between no snow in Portland and 2″!

The NAM continues to push precipitation much farther south, in fact the UW-MM5-NAM has Portland and areas to the north mainly dry tomorrow!

Our RPM has shifted the better chance for sticking snow in the Salem and Portland areas from late tonight to tomorrow night instead.  It also totally cuts off precipitation after midnight tomorrow night, then a light southwest wind kicks in.  That tells me Thursday morning’s commute will probably be fine with several hours of temperatures above freezing even if we get snow around 10pm-midnight tomorrow night.

I’m staying with my forecast above…we’ll see how it goes.

Theoretically, I’m driving my small car (with snow tires removed) tomorrow at 9am to Reno, Nevada for the start of a 10 day vacation…hmmm.  We’ll see.

Chief Meteorologist Mark Nelsen


No Wind, But Tons of Rain & Snow On The Way

March 19, 2012

Yes, I realize the title is incorrect because of course there will be SOME wind.  But the highlight of weather this week will be a huge amount of rain (for March) in the lowlands and maybe the heaviest snow of winter in the Cascades, possibly in the foothills and Coast Range too.

Here’s the setup:

A cold front is heading towards us this evening; it’ll spread steady rain inland overnight.  Oh, and maybe 8-12″ snow in the Cascades.   The front, with its steady precipitation, slides to our south tomorrow.  Thus we just get lighter showers most of tomorrow.  Tomorrow will not be a washout, just off/on light rain.

The real action kicks in tomorrow night as the front slides a bit farther north, to around Eugene.  Between tomorrow night and Thursday morning, the front sits right over that area.  It’ll be the focus of the heaviest precipitation as you can see in the 3 day rain forecast graphics from our model, the RPM:

It shows a 6″ rainfall (or melted snow) from Coos Bay up into the Central Oregon Cascades and the WRF-GFS:

Note the red areas indicate forecast rain totals greater than 5″!  I love the Pacific Northwest; the red area is only maybe 20 miles away from little or no rainfall in the shadow of the Three Sisters around Redmond.  Now flooding in March is not unheard of, but very unusual.  If these rain totals actually occur, we may see some flooding to our south, even on larger rivers. 

What about snow?  During the Tuesday night – Thursday morning period that stationary front will be quite a sharp dividing line between about a 6,000′ snow level around Medford to near sea level (at night) north of Eugene.  In the central/northern Willamette Valley, we’ll have calm or very light north wind, heavy and steady precipitation, and a freezing level between 1,500 & 3,000′.  Sound familiar?  It is, like what we saw at the Coast last week.  Check out the Salem cross-section on the 4km WRF-GFS:

It shows near 32 degree temps all the way down to the surface Wednesday morning and close on Thursday morning, and barely above freezing during the day Wednesday.  The soundings show a snow profile as well.  Portland’s forecast sounding is just slightly warmer, but still very close to snow. 

WHAT DOES THIS MEAN?  Some of the lowest elevations COULD see sticking snow Wednesday morning and/or Thursday morning, but as with the Coast last week, we probably won’t have a real good idea until a few hours before.  A bigger, and screaming message is that areas up around 1,000′ and above in the Coast Range, central/northern Willamette Valley, and Cascade Foothills may get hammered with their biggest snowfall of the season.  It’s possible.  IF these models are correct, most or all of the precipitation for about 24 hours in those locations at/above 1,500′ will be snow.  That could be 12-18″!    Here is our 72 hour snowfall forecast from the RPM model, showing light 1-2″ totals in the Valley:

Here is the WRF-GFS snowfall forecast for 5pm tomorrow afternoon through 5pm Wednesday afternoon.  5″ in the south Salem hills?  Interesting eh? 

 

Now all of this is based on 12z runs…I should point out the NAM has the front farther south with less precipitation over us and slightly warmer air.  So there is quite a bit of uncertainty with the whole plan I’ve just set out above.  If later model runs come in with the front sitting farther north (more rain and less snow over Portland), or farther south (no snow and lighter precipitation), that will make for big forecast changes.

There is some good news…much drier and decent March weather Thursday PM through the weekend as more energy heads south into California.

Chief Meteorologist Mark Nelsen


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