A Wet Day, And Month!

February 18, 2014

February 2014 is the wettest February we’ve seen in 14 years here in Portland!  Doesn’t seem like it has rained THAT much, but maybe it has more to do with all the dry Februarys.  Take a look:

MarkRain_February

The dashed line is the normal; just over 3.60″.  Yellow are the below average months and green above.  Notice since 2005 we’ve only had two wet Februarys.  And I think many weather geeks like me would agree that February has been a relatively quiet month the last 10 years too.  That sure changed this year!  More action this month than any other so far. Of course it isn’t too tough to do since for almost 2 months of the winter almost nothing happened weatherwise.

Chief Meteorologist Mark Nelsen


55mph in Portland; A Strange Windstorm Last Night

February 17, 2014

The peak gust at PDX of 55 mph was the strongest southerly wind gust (our storm wind direction) in 14 years!  Yet only 15,000 or so power outages in the metro area and Clark county?  How is that possible?  There’s more to this story.  Take a look at the peak gusts from last night’s system:

PLOT_Wind_Metro_PeakGusts

The center of town sure sticks out doesn’t it?   Except for a swath from Milwaukie to the Columbia River, peak gusts were all well below 50 mph.  For most of our area the gusts were no more than we’ve seen a few times this winter already.  We had very strong wind a few thousand feet up in the atmosphere overhead and some of that must have “mixed down” to the lowest elevations in the middle of town.

That  gust to 55 mph was the strongest at PDX since a windstorm in January 2000.

windgust

So was it stronger than the December 2006 storm which had a gust to 53 mph?  No.   That’s because the wind measuring equipment at NWS recording sites changed around 2007 from a 5-second peak gust to a 3-second peak gust.  There was about a 10 year period where Portland’s observation equipment used the longer duration gust requirement; basically the wind would have to peak for a bit longer to get that high value registered.  So the 55 today would probably be equivalent to a 46-48 mph peak gust during (the 5-second era) based on Wolf Read’s exhaustive comparison of past/present windstorm readings here:  http://www.climate.washington.edu/stormking/StormRanksASOSadjusted.html.   For comparison, the Davis line of instruments that many of us have at home, use a 2 second gust.  Those would tend to read a little higher than the 3 second gust.  Without all those numbers, the outage numbers probably tell an even better story.  During the December 2006 storm in which we saw widespread gusts 50-60 mph, almost 300,000 people in Western Oregon lost power!   Compare that with the 15,000 today.

Also note the 55 mph gust a few years ago in March was with a squall line from the west, and the 56 in 2007 was a downslope east wind type of event.

Tomorrow’s wind will be much more reasonable, with 35-40 mph gusts most likely peaking around midday with another bout of rain.

Chief Meteorologist Mark Nelsen


Best Skiing Of Winter On The Way

February 14, 2014

Take a look at our forecast for snow and snow levels on Mt. Hood for the next week:

MarkSnow_MtHoodFcst_2013

This is the snowiest forecast I’ve made so far this winter…funny that it took until the 2nd half of February to finally do it.  Well, I guess it’s not funny if you are s ski resort operator, but you know what I mean.  It should be obvious that out of the 3 day weekend Saturday is not the best day to ski.  That’s because we’ll see the first of two storms this weekend; and it’ll be a relatively warm storm with snow levels rising up closer to 6,000′ in the afternoon.  But don’t fret, the snow level will dip down around 2,000′ by Sunday morning as the cold front moves through.  So there should be a nice dumping of new snow on the ground Sunday morning with temps way down in the 20s.

Then on Sunday it should be mostly dry through midday to early afternoon…very nice ski conditions.

Sunday evening a much wetter and cooler storm arrives.  This one should be all snow in the mountains.  At this point I’m thinking we could see 15-20″ between Sunday evening and Monday evening!  It’s going to be a crazy Presidents Day on the mountain!  Beyond that, one more organized system later Tuesday and Wednesday, then much colder powder snow Thursday and some leftovers Friday.  So it’s very likely we’ll see 3-6′ of new snow in the Cascades between right now and when it dries out at the end of next week.  And a good chunk of that will fall with temps in the 20s…very good!  Best days next week will be Wednesday-Friday with the colder temps and not such intense snowfall.

For those of us in the lowlands, we’ve got the Saturday storm and the late Sunday storm on the way.  Tomorrow’s won’t give much wind to the valleys; and for the first part of it the flow is far too “southeasterly” to get good wind into the valley anyway.  Still, lots of rain with this one.

Then the Sunday night storm appears to be much more impressive.  The 00z models are a little weaker with the wind field and pressure gradient, so I’m thinking gusts around 70 mph at the beaches and 40-45 mph here in the valleys.  Neither is generally a damaging wind for either location, but a very wet and windy night!  In fact the rain looks quite intense for a few hours as the cold front passes from the northwest to the southeast across the area.  Looks like the type of setup that will give us localized urban flooding later Sunday night or for the Monday morning commute.

Snow levels look to be somewhere in the surface to 1,000′ level late next week.  Don’t get too excited, it’s going to be one of those “snow in the barkdust” setups where we see areas of patchy snow in the morning then it’s in the low-mid 40s in the afternoon.  At least right now it’s looking that way.  Plus the bar was set pretty high one week ago when we had 3 different snow storms!

Have a good weekend and enjoy the wind/rain.  I’m working tomorrow…it’ll be Day 14 due to Superbowl, snow, and a day to cover this weekend.  Finally a day off Sunday, so I will only blog if Sunday’s storm looks stronger.

Chief Meteorologist Mark Nelsen


Flood Watch for Western Oregon

February 13, 2014

There is a flood watch out for all of Western Oregon tonight through Sunday evening as several wet weather systems move through.  That means the NWS is “watching” to see if conditions will warrant flood warnings for specific rivers.  A watch is for a large area, a warning is for a river.

MarkWarnings_FloodWatch

WHAT IS LIKELY:

-Localized flooding or “urban flooding” if at some point we get heavy rain all at once.  Right now I don’t see that in the next 2 days at least.  We’ll watch closely

-Two rivers in our viewing area are forecast to possibly rise above flood stage, both minor flooding and in farm/rural areas.  Descriptions from NW River Forecast Center gives you the idea.

 

Pudding River: Above 22 ft, Expect minor flooding of low-lying agricultural lands and access roads along the river.

 

Luckiamute River:  Above 27.0 ft, Expect flooding of low lying and agricultural lands in the vicinity of Sarah Helmick State Park, Highway 99W, and Parker Road. Some secondary roads and rural access roads may be flooded at this point. Flooding along Buena Vista Rd near the confluence with the Willamette is also likely, especiallly if the Willamette is running high.

 

 

WHAT IS NOT LIKELY RIGHT NOW:

-Widespread river flooding for the entire area

-No repeat of 1996 floods

-A big snowmelt event

-Willamette River in Salem and Portland flooding; there is tons of room in reservoirs for flood storage due to the current drought.  Just one lake, Detroit Lake, is forecast to rise 30 ft. as Detroit Dam holds back all the water and keeps it out of the Willamette River system.

This could change if models decide to keep heavy rain over us for a longer period later in the weekend or next week.  But hopefully this gives you an idea of what’s going on right now.

Chief Meteorologist Mark Nelsen


Avalanche Kills 2 in Wallowas

February 11, 2014

It’s been 4 years since we’ve seen someone die in an avalanche here in Oregon, but it happened today.  In the southern part of the Wallowas two cross country skiers were killed in an avalanche.  There have only been two other deaths since at least 1998 according to the avalanche.org website:

MarkAvalanche_ORstats

Most likely because we don’t have a lot of the real steep avalanche terrain like up in Washington and in the Rockies.

A nice surface low is getting very close to the Washington coast this evening, and we should feel the strong south wind soon here in the valleys; not crazy strong, but real windy.  I’d guess a peak gust of 38 mph at PDX.

MarkWarnings_Wind_Coast_Valleys

The coast is getting slammed with 50-60 mph gusts now and will probably get a little stronger, still, it doesn’t get exciting out there until the gusts are in the 70-80 mph range.

Looking ahead…lots of rain and mountain snow.  I don’t see any one “big storm”.

Models still show cooler troughiness next week and snow levels maybe a little below 2,000′ somewhere around Sunday.  Then a colder trough with snow levels at least down to 1,500′ next Thursday/Friday.  The new ECMWF is a little cooler with potential snow almost to sea level.  But, it’s the annoying “showers in northwest flow” pattern where some folks get an inch or so in the morning and then it melts in the afternoon.   The bar has been set pretty high after last week!

Beyond that, it looks milder again.  To sum it up, you could say winter is likely over except for some occasional close calls with low elevation snow.  No sign of a late season arctic blast.  But I’ll wait to pull out everyone’s favorite graphic until after the cold trough next week.

Chief Meteorologist Mark Nelsen


Storm Summary Posted

February 10, 2014

It’ll be permanent, I put it as a PAGE above…feel free to comment on the event up there.  Any other comments can continue here:

Chief Meteorologist Mark Nelsen


ECMWF Maps: Mild, Cool, Mild

February 10, 2014

Spent most of today cleaning up emails and dealing with post-storm stuff.  I’m working on a page detailing how the storms went last week forecast-wise.  The 4 weekly maps from last night’s ECMWF run are almost the same as they have been for a week, or maybe even 10 days.  Mild westerly flow this week, cooler flow then real chilly trough next week.  Then the last few days of February into early March ridging comes back

500za_week1_bg_NA

500za_week2_bg_NA

500za_week3_bg_NA

500za_week4_bg_NA

The 00z GFS seems to support that idea with snow levels down to the “hilltop level” about 10 days from now, then milder again.

tseries_850t_000-384_Portland