September 2017 PNW Discussion Thread

[BLI snowman]

I would just say look at the records for Jun 1-15 compared to Sep 20 - 30...one seems less summery than the other to me.

 

The crash into legit fall is way more pronounced and dramatic than the often glacial pace of the spring to summer transition, I think that is pretty obvious.

[epiceast]

Sun angle is a pretty big difference though.  

Have you looked into the Moon angle? I think sometimes it shadows the sun!

[wx_statman]

 

Why would I be talking about that? My response had to do with whether there were actually any studies on hurricanes and jet stream buckles in general. The second comment was simply about the nature of the amateur science that happens on this forum, and every weather forum I've ever seen.

 

If I'm going to take issue with something you personally said, you won't have to read between the lines. 

 

Seems as though you made a response that was prone to misinterpretation. It happens.

[wx_statman]

It almost feels like it's 2/3 a summer month and about 1/3 fall. Probably just a crazy theory though.

 

And October usually feels like 1/2 late September, and 1/2 early November. Another crazy theory.

[Dave]

I can't believe I read the last 6 pages of bickering after not looking at the forum for a day and half.  What a waste of time.

 

I consider September to be the best weather month overall here in Eugene.  Hardly any heat waves, a bit of rain to start greening things up but not too much, comfortable highs in the 70's and low 80's, and much less traffic on the hiking trails and rivers.  It rarely gets too hot, too cool, too wet, or too dry.  It's a goldilocks month.

[Jbolin]

Interesting. We'll be camping out at a farm near Mount Angel tomorrow night, for Oktoberfest. I wonder if they will still be going on then. Would be good to view them away from city lights.

Possibly, CME energy should be waning though, worth a shot.

[BLI snowman]

And October usually feels like 1/2 late September, and 1/2 early November. Another crazy theory.

 

That one's pretty out there.

[wx_statman]

That one's pretty out there.

 

It's chaos in here.

[wx_statman]

It's crisp outside!

[wx_statman]

Seeing some 30's in western WA.

 

37 in Port Townsend and 39 in Forks

[Jesse]

Looks like PDX may have hit their first 40s of the season this morning.

[stuffradio]

It's 42F right now. 6Z GFS shows 5" of rain for me. Crazy.

[TT-SEA]

It's 42F right now. 6Z GFS shows 5" of rain for me. Crazy.

 

Tis the season!  

[SilverFallsAndrew]

Wonders never cease. Down to 40 this morning. 

[Anti Marine Layer]

Have you looked into the Moon angle? I think sometimes it shadows the sun!

It did so on August 21.

[Front Ranger]

Seeing some 30's in western WA.

 

37 in Port Townsend and 39 in Forks

 

At least 38 at OLM and Tacoma McChord, and at least 37 at Shelton as well.

[TT-SEA]

GFS has been backing off on the depth of the trough early next week with each run.   This is actually increasing the rain amounts for the entire area which is probably good news.

 

I just ran a trend GIF for the last 15 runs of the GFS for Monday and it has trended north on each run. 

 

Here was the 12Z run on Wednesday for next Monday afternoon...

 

 

 

And now the 12Z run today...

 

 

 

Much better pattern for rain across the region.  

[Jesse]

Seems like the 06z took a little bit of the punch out of our Monday trough.

[Jesse]

GFS has been backing off on the depth of the trough early next week with each run. This is actually increasing the rain amounts for the entire area which is probably good news.

 

I just ran a trend GIF for the last 15 runs of the GFS for Monday and it has trended north on each run.

 

Here was the 12Z run on Wednesday for next Monday afternoon...

 

 

And now the 12Z run today...

 

 

Much better pattern for rain across the region.

Heights looks more or less just as low. It doesn't dig as far south into California though.

[TT-SEA]

Heights looks more or less just as low. It doesn't dig as far south into California though.

 

Yeah... much more onshore flow as a result.   Particularly up here.   

[Geos]

Elevation is not the entire story though.   I don't think the Lakemont area of Bellevue at the same elevation as this area had anything close to 150 inches that winter.

 

Its a combination of elevation and exposure to outflow through Snoqualmie Pass and some protection from onshore flow (Rattlesnake Ridge).

 

North Bend did not have nearly as much snow as we did here in 2007-08 but it had way more snow than the Seattle area due to exposure to outflow.    Still... there were many days when there was nothing in town while we were buried up here.  

 

Yeah I have studied the terrain and looked at observations during rain/snow events and I see the cold outflow down from the pass really helps North Bend and Snoqualmie (sometimes) cool off to freezing or below.The Issaquah Alps are a nice barrier to the SW flow except for those gaps like above Issaquah and Rattlesnake Lake. I'd imagine you and North Bend would get even more snow if it wasn't for that gap right there.

I bet you had to go a bit higher up Squak Mountain in Bellevue to see those 150"+ amounts that winter. Say above 1000 ft. 

 

My location is probably the best spot for seeing snow west of I-405. Eventually I would like to get some property higher up and in the mountains, maybe in the Skykomish Valley.

[TT-SEA]

Yeah I have studied the terrain and looked at observations during rain/snow events and I see the cold outflow down from the pass really helps North Bend and Snoqualmie (sometimes) cool off to freezing or below.The Issaquah Alps are a nice barrier to the SW flow except for those gaps like above Issaquah and Rattlesnake Lake. I'd imagine you and North Bend would get even more snow if it wasn't for that gap right there.

I bet you had to go a bit higher up Squak Mountain in Bellevue to see those 150"+ amounts that winter. Say above 1000 ft. 

 

My location is probably the best spot for seeing snow west of I-405. Eventually I would like to get some property higher up and in the mountains, maybe in the Skykomish Valley.

 

 

If we were even more protected from the SW wind... it would be like Skykomish here.   That location is absolutely amazing at keeping snow... much better than my location.   We can get buried and we can keep snow much longer than other places... but eventually we get blasted by the SW wind and it disappears fast.   Skykomish is completely protected from the SW wind.

 

Snoqualmie Parkway (exit 25 on I-90) is usually the line when there is a battle between onshore and offshore flow.   We get way more snow here than Tiger Mountain on Hwy 18 despite being 250 feet lower... because that area is much more exposed to onshore flow.   

 

There have been MANY times when I have seen it pouring rain right up to the Snoqualmie Parkway exit and then it starts dumping snow as you go downhill towards North Bend and into the offshore flow.  

[TT-SEA]

12Z GFS this morning has definitely come around to the ECMWF solution that we discussed in great detail yesterday.   

 

Here was the 12Z GFS run from yesterday morning for next Friday:

 

 

 

And the 12Z GFS run this morning for the same time:

 

[Front Ranger]

Here's the 0z EPS for day 8.

 

[Front Ranger]

0z Euro 850 temps for day 9.

 

[richard mann]

(.. cross-reference.)
 
http://theweatherforums.com/index.php/topic/1582-summer-2017-colder-air-mass-movement-and-distribution-projections/?p=256243

[epiceast]

If we were even more protected from the SW wind... it would be like Skykomish here.   That location is absolutely amazing at keeping snow... much better than my location.   We can get buried and we can keep snow much longer than other places... but eventually we get blasted by the SW wind and it disappears fast.   Skykomish is completely protected from the SW wind.

 

Snoqualmie Parkway (exit 25 on I-90) is usually the line when there is a battle between onshore and offshore flow.   We get way more snow here than Tiger Mountain on Hwy 18 despite being 250 feet lower... because that area is much more exposed to onshore flow.   

 

There have been MANY times when I have seen it pouring rain right up to the Snoqualmie Parkway exit and then it starts dumping snow as you go downhill towards North Bend and into the offshore flow.  

I've seen that as well!

[Geos]

If we were even more protected from the SW wind... it would be like Skykomish here.   That location is absolutely amazing at keeping snow... much better than my location.   We can get buried and we can keep snow much longer than other places... but eventually we get blasted by the SW wind and it disappears fast.   Skykomish is completely protected from the SW wind.

 

Snoqualmie Parkway (exit 25 on I-90) is usually the line when there is a battle between onshore and offshore flow.   We get way more snow here than Tiger Mountain on Hwy 18 despite being 250 feet lower... because that area is much more exposed to onshore flow.   

 

There have been MANY times when I have seen it pouring rain right up to the Snoqualmie Parkway exit and then it starts dumping snow as you go downhill towards North Bend and into the offshore flow.  

 

So that exit there is 950 feet and your a couple hundred feet above that. 

Yeah the upper part of the Skykomish Valley is well insulated from the SW flow. I know several times last winter going up to Stevens where it was raining and/or there was snow on the ground starting near Index and it just got deeper as you went up the valley. Each time is was like low 40s and pouring in Monroe. As the valley narrows after Gold Bar that's where the snow is a lot more common in the winter. 

 

Chilly this morning. Low of 42 at my house.

[ShawniganLake]

If we were even more protected from the SW wind... it would be like Skykomish here. That location is absolutely amazing at keeping snow... much better than my location. We can get buried and we can keep snow much longer than other places... but eventually we get blasted by the SW wind and it disappears fast. Skykomish is completely protected from the SW wind.

 

Snoqualmie Parkway (exit 25 on I-90) is usually the line when there is a battle between onshore and offshore flow. We get way more snow here than Tiger Mountain on Hwy 18 despite being 250 feet lower... because that area is much more exposed to onshore flow.

 

There have been MANY times when I have seen it pouring rain right up to the Snoqualmie Parkway exit and then it starts dumping snow as you go downhill towards North Bend and into the offshore flow.

I've noticed many times how fast you melt out on a SW wind therre. Seems like 2ft melts out overnight there, when 6" here lasts a week or more.

[TT-SEA]

So that exit there is 950 feet and your a couple hundred feet above that. 

Yeah the upper part of the Skykomish Valley is well insulated from the SW flow. I know several times last winter going up to Stevens where it was raining and/or there was snow on the ground starting near Index and it just got deeper as you went up the valley. Each time is was like low 40s and pouring in Monroe. As the valley narrows after Gold Bar that's where the snow is a lot more common in the winter. 

 

Chilly this morning. Low of 42 at my house.

 

 

The fun part is going from pouring rain at that exit at 950 feet to heavy snow at 450 feet in North Bend.   

[Jesse]

Once again the operational GFS shows riding in the long range, but there is very little in the way of ensemble support. You do have to wonder when the op spits out a patcular solution so many times, though.

[Jesse]

12z Canadian looks much troughier than the 00z for later next week.

[Jesse]

Tim will love the 12z Euro at day 9 and 10.

[Geos]

The fun part is going from pouring rain at that exit at 950 feet to heavy snow at 450 feet in North Bend.   

 

Yeah that goes against the logic of temperature dropping with height. 

 

Was just thinking if Snoqualmie Pass wasn't as high as it was, then there would be more cold air drainage down into central King County. Would totally increase snowfall in your area.

[TT-SEA]

Yeah that goes against the logic of temperature dropping with height. 

 

Was just thinking if Snoqualmie Pass wasn't as high as it was, then there would be more cold air drainage down into central King County. Would totally increase snowfall in your area.

 

Not sure... it might increase the snowfall for all of King County.

 

On the other hand... without that gap in the Cascades my area would see much less snow and be dependent entirely on elevation.  

[TT-SEA]

Tim will love the 12z Euro at day 9 and 10.

 

I do like the idea of an alternating trough/ridge scenario rather than just a complete descent into wet and cold this early.  

[TT-SEA]

Tim will love the 12z Euro at day 9 and 10.

 

ECMWF control run sure agrees... this is day 9.

 

[Phil]

The new EPS weeklies do revert to the ridge west/trough east pattern next month. Looks like some Pacific convection, though it appears to be transitory in nature.

 

Will be interesting to see how it unfolds. Looks like a difficult pattern to forecast either way with tropical cyclones everywhere.

[TT-SEA]

The new EPS weeklies do revert to the ridge west/trough east pattern next month. Looks like some Pacific convection, though it appears to be transitory in nature.

 

Will be interesting to see how it unfolds. Looks like a difficult pattern to forecast either way with tropical cyclones everywhere.

 

A nice October works for me.  

 

November can do whatever it wants.   

[Jesse]

The new EPS weeklies do revert to the ridge west/trough east pattern next month. Looks like some Pacific convection, though it appears to be transitory in nature.

 

Will be interesting to see how it unfolds. Looks like a difficult pattern to forecast either way with tropical cyclones everywhere.

God f***** D****T.