ECMWF Monthly Run

December 19, 2013

The 4 weekly maps from last night’s ECMWF run show some sort of ridging wanting to remain just off or along the West Coast through the next 4 weeks!  Not a good sign for those wanting some weather action in January.  But just one run of one model of course.  Enjoy the pretty colors:

500za_week1_bg_NA

 

500za_week2_bg_NA

 

500za_week3_bg_NA

 

500za_week4_bg_NA


12 Hours Away: Areas of Snow & Ice Pellets For A.M. Commute

December 19, 2013

7pm Thursday…

There are no watches, warnings, or advisories for late tonight and Friday morning, but anyone up and around in the late night and early morning hours may see either snow/sleet.  Either in the air or a dusting on the ground; this MAY end up just being a “conversational snow”, as we like to say, for a good chunk of us in the metro area.

Something should start falling out of the sky sometime between 3-7am.  It’ll start as snow; temps will be right around freezing, maybe slightly above.  Then right around sunrise warmer air moves in above, which means ice pellets (used to be called sleet)  are more likely.  That’s when snowflakes melt into raindrops up above and then refreeze into little chunks of ice before they hit the ground.  It has a “clinky” sound when it hits.

By 8am, the atmosphere will be too warm to support anything frozen since the freezing level will be jumping up to 8,000’.

The Highlights

  •  A brief “wintry” mix between 3-8am.  A dusting is possible anywhere from the metro area to Longview down to the valley floor.  But not everyone will get it.  It’s real light.
  • Snow to sleet, then probably straight to rain.  Freezing rain looks unlikely since temps won’t drop much below freezing (if they do).
  • Some areas may see sleet/snow on roads, depending on the temp.  Best chance would be West Hills, central/north Clark County, Scappoose/St. Helens, and Banks/Vernonia.  Those areas also have the best chance of seeing actual freezing rain at the end of the event around 7-9am.
  • It’s all over after 8am for just about all of us.
  • Gusty south wind tomorrow afternoon, maybe gusts 30-35 mph as temps climb into the 40s.

What We Don’t Expect

  •  A snowstorm; not enough moisture for more than 1-2” of snow even if it did that the whole time.
  • An ice storm; again, just not a whole lot of anything.
  • Widespread frozen roads and a hellish commute.  Probably not cold enough or enough moisture.  Different story up north as mentioned in the highlights
  • More than ½” for 90% of us in the metro area
  • Snow/ice pellets south of the metro area (Salem/Albany) or at the coast.

Here is the latest from this evening’s run of our RPM showing a changeover from snow to ice pellets already at 6am spreading west to east across the metro area

rpm_6am

Then at 9am all frozen precipitation is over in the lowlands unless freezing rain/ice pellets holds on up in northern Clark County.  And, actually it looks mainly dry at that time anyway.

rpm_9am

I’m getting the feeling that Amboy, Yacolt, and Battle Ground are the places to be for this event.  And finally the snow total graphic showing the main accumulation “action” in Clark County:

rpm_snow_9a

The evening NAM model has snow a bit farther south and west into the middle of the metro area.  This is snow accumulation from 7-10am.

nam_snow_10am

The sounding is definitely all snow through the 7am hour.

To wrap it up, here are the percentages I assigned to each of these events…

MarkSnow_PortlandOutlookPercentages2

By the way, for those of you that work the late shift and wake up around 9am like me?  You’ll miss the whole thing!  Go ahead and sleep in.

Chief Meteorologist Mark Nelsen


Snow Chance For Friday Increasing

December 18, 2013

10:30pm Wednesday…

Models have speeded up the timing of the return of moisture Friday morning.  What does that mean?

MarkSnow_PortlandOutlookPercentages

MarkSnow_PortlandOutlookPercentages2

Our RPM model has actually backed off a bit on possible snowfall at that time, showing just about everything north and east of the metro area.  However the UW-WRFGFS model has painted a larger area of snowfall over us sometime after 2am Friday:

wrf_snow

Notice the 2″ forecast for Scappoose, St. Helens, and most of central/north Clark County…more moisture available in those areas.  And if the faster timing continues in the next 2 model runs, just about all of it happens before the sun rises.  As a result it could be snowy morning commute across the far northern part of the metro area.

All models show a rapid warmup several thousand feet up after 7am now.  Snow can’t keep falling after that time for just about all areas.

We’ll be watching closely to see what tomorrow morning’s runs show.

Chief Meteorologist Mark Nelsen

 


Is it going to snow Friday? Briefly, for some

December 17, 2013

If you’re looking for a snowstorm, this isn’t the setup for the Portland Metro area, but a lot of us may see snowflakes at least in the air on Friday morning.  Here’s what’s going on this time around:

A cold front drops through our area tomorrow afternoon, with a nice line of showers, dumping snow down to about 1,500′ just before and around sunset.  Then we dry out and turn chilly as a Canadian air mass descends over the Pacific Northwest for tomorrow night and Thursday.

A strong warm front surges right on in over the leftover cold air late Thursday night and early Friday morning.   This sets us up for a (very) brief period of snow at the lowest elevations from the Portland Metro area north into Western Washington.

The change is going to be most dramatic in the mountains.  Government Camp goes from 52 today, to about 35 tomorrow, 28 Thursday, then back up to 40+ Friday and into the weekend.

Timing will be everything with the possible action on Friday morning.  If the precip arrives late, a mixing south wind may start to develop, if the precip arrives early (before 7am), we could all see a dusting briefly.  Luckily we have 2 more days to figure things out.

I do notice on the evening models (especially the WRF-GFS and our RPM), there is little to no mixing until closer to 10am.  They also both show heavier precip to the north of the metro area.  That’s why I mentioned Clark county in these graphics:

MarkSnow_PortlandOutlookPercentages

MarkSnow_PortlandOutlookPercentages2

Whatever happens, by midday the snow level will be jumping to around 8,000′ and it’ll be raining even at the ski resorts!

My gut feeling is that it’s not going to affect anyone’s life much at all from the Columbia River south…we’ll see.

 

By the way here is the snow forecast from our RPM:

RPM_SNOWACCUM

and the 00z WRF-GFS:

wrf_snow
Chief Meteorologist Mark Nelsen


December 15th Snowpack: Lowest in 20+ Years

December 16, 2013

Check out snowpack in the Cascades and other Oregon mountains…pretty bad!  Less than 50% of normal for mid December.

snowpack

Of course it’s very early in the season, and things could turn around quickly.  But as we head toward (and into) Christmas Break, I see no change from the current dry pattern.  In fact most of the precipitation in the Cascades the next week or so will be in the form of rain, not snow.

Right now Timberline and Meadows are partially open.  A coworker that was up there today said it was great with the warm (50 degrees!)  weather, but the snow was so thin he couldn’t go off trails much at all.  Skibowl, Summit, Cooper Spur, Hoodoo, and Willamette Pass are not open yet.  I would be surprised if any of those resorts opened in the next 8-10 days.  The reason?  The same culprit that has given the Portland area only half of our typical wet season rainfall so far.  It’s an upper level ridge that continues to sit over us, or just to our west, blocking storms and/or sending them around us.  Here’s an upper-level map for Friday.  The white lines are air flow (more or less, actually lines of equal height), and the warm colors are high than normal upper heights…or ridging.  You can see the big ridge offshore.

ecm_friday

and again at Day 8, Christmas Day.  Similar setup with the ridge almost right over us:

ecm_xmasday

Not good; no hint of any normal Pacific Northwest winter weather pattern with a bunch of chilly valley rain and good mountain snow.

The best we get is warm and weak systems riding over the top of the ridge.  These produce drippy weather here in the valleys and rain or rain/snow up in the Cascades…yuck.  That’s what we expect for the upcoming Friday-Monday as you can see in our mountain forecast:

MarkSnow_MtHoodFcst_2013

As of tonight, Timberline is reporting 27″ of snow, which is the least of any December 15th since 1989!  Most of you skiers probably remember the winter of 2004-2005…really bad.  That year was a skiing disaster with Skibowl only able to open for a few weeks and I think even Meadows was closed at times mid-winter.  That year we had 47″ on the ground in mid-December at Timberline.  BUT, there were 3 pineapple express events the following couple of months that kept destroying and fresh snow.  We’ll hope that’s not the case this time around.

This is one of just 5 times that Timberline has seen 30″ or less on the ground on December 15th.  So what happened in the other 4 years?  The following includes snowdepth on the 15th and the results:

2002-2003  
30″,   80″+ by January 1st, but then not a very good ski season, poor conditions

1989-1990
15″,   18″ by January 1st, then 105″ by February 1st, massive snowstorms commenced in mid-January

1979-1980
30″,   41″ by January 1st, 85″ by February 1st, ski season limped along…not too bad

1976-1977
2″,  8″  by January 1st,   10″ on February 1st.  Worst drought and ski season (or no skiing) in years.  Hasn’t happened since, hopefully won’t occur again!

So you can see what we’ve had so far is no guarantee of what will come for the rest of the winter.  I remember ’89-’90 real well, all sorts of avalanche issues and highways closed due to feet and feet of snow from mid January to late February.  I think Stevens Pass had 18′ in 3 weeks!

I’m quite confident that we’ll see very little new snow in the Cascades over the next 10 days, but who knows what is out beyond that time.

Here is one hint from the ECMWF model weekly maps.  It’s similar to the map above but a whole week at a time average into one map.  Weeks 1-4, which takes us into the 2nd week of January:

500za_week1_bg_NA

500za_week2_bg_NA

500za_week3_bg_NA

500za_week4_bg_NA

Looks like the ridge wants to continue hanging out…hopefully not.

By the way, we’ll be quite close to a brief episode of freezing rain or snow in the metro area early Friday morning as that warm and moist airmass for the weekend arrives…big question mark on whether it’ll be cold enough or not…more on that tomorrow, since it’s still 4 days away.

Chief Meteorologist Mark Nelsen


This Weekend: Quiet Weather

December 13, 2013

11pm Friday…

After an exciting 2 weeks, the weather is finally very slow this evening.  And, more important, there doesn’t appear to be anything interesting on the horizon.  Upper level ridging wants to remain near the West Coast or a bit farther offshore the next 7-10 days.  Slightly farther west and we’d see a cold trough drop down from the north.  Some model ensembles hint that could happen, but I don’t see anything convincing yet.  Here’s the 00z GFS ensemble chart:

tseries_850t_000-384_Portland

This pattern continues to be very dry for December.   Check out the Mt. Hood snow outlook:

MarkSnow_MtHoodFcst_2013

This implies that Skibowl and Hoodoo wont be able to open for at least the beginning of Christmas Break.  And the pathetic start to the ski season higher up at Meadows and Timberline wont get any better…sorry snow riders!

Enjoy the weekend!


4pm: Freezing Rain (& Rain) Ending: Icy Spots Possible Westside Tonight

December 12, 2013

That wasn’t real exciting…just some light rain this afternoon for most of us.  But some spots of freezing rain on the west side of the Willamette Valley.  Had a few reports of freezing rain in McMinnville, Lafayette, Dayton, and some other patches in western Washington county.

KPTV_Default

As you see on the radar, rain of any sort is about to end as our weak weather system moves on east.

The issue tonight may be the usual case of skies partially clearing behind a cold front; probably only on the west side of the valley again.  Since temps are within a few notches of freezing, any clearing means icy spots could easily develop on roads in those areas…be careful out there later tonight!\

I don’t see a widespread warming southerly wind tonight, but some spots will randomly pop up temp-wise.  I see some mid 40s over on the SE side of the metro area where southerly wind has arrived.  The rest of us stay in the 30s tonight.

Chief Meteorologist Mark Nelsen