A Brief Post

July 22, 2009

A long bike ride between shows plus some serious surgery on a bunch of graphics for tomorrow’s cooler temps means not much time tonight.  Marine air really pouring in tonight, so we lowered tomorrow’s high to 80 here in PDX-Land.  I also notice a cooler trend for Friday and Saturday, and a little Sunday.

Heat Wave Update:  Not much change.  The hottest period is when a thermal trough gets established west of the Cascades Monday-Wednesday.  850mb temps of 20-27 all next week plus the offshore flow mean 100+ temps are more likely now.  I do notice the ECMWF has slightly lower 850mb temps and the thermal trough is not as pronounced.  Sure looks like 95+ temps Sunday through Thursday at least of next week…most likely this is going to be the warmest period this summer.

Chief Meteorologist – Mark Nelsen

Hot Weather Ahead

July 21, 2009

Noctilucent Clouds overhead on the 15th - Ben Monjay

Noctilucent Clouds overhead on the 15th - Ben Monjay

I’m a bit behind the times apparently due to my week of vacation.  Our own Ben Monjay sent this picture which ended up at www.spaceweather.com  Sorry, that’s the largest size I could get the picture to load in.  Update 3:45pm WednesdayWow, I really screwed that one up.  The original picture that I put on there wasn’t Ben’s!  The correct one is now in.  Okay, on to the upcoming weather.  First, a nice push of marine air this evening.  I see Kelso already has low clouds at 10pm!  WRF-GFS implies that we’ll have significant low cloud cover the next 3 mornings.  Our temps through Friday only reflect a weak push, so I’m worried that 85-85-90 is too hot for the next three days.  Gut feeling is 83-83-87.  We’ll see.

So what has changed over the last 24 hours with respect to a possible heat wave?  Looks like it’s back on, then slightly off, now just delayed a bit.  The good times tracking an annoying upper-level low for the weekend continue.  I’m glad we didn’t go crazy on forecast high temps based on the 12z GFS today.  Just between you bloggers and I, my forecast actually started with a 103 on Sunday around 1pm today.  Then I lowered it to 101 around 2:45 after some deep thinking while doing makeup (required for TV).  Then the 18z GFS came out, plus the 12z ECMWF didn’t get me too excited about 100 degree heat.   The final version (what you see on the web and TV) was set around 3:15pm.  That’s how Drew and I ended up with highs below 100 degrees on the 7 Day forecast.
I’m impressed with the length of the upcoming heat regardless of whether we get to 100 degrees or not.  Looks like Saturday through at least next Wednesday we’ll see 90 plus degree weather.  The 00z GFS looks excellent for maximizing offshore flow, more like September than July due to a rare cool surface high over Montana.  If this model were to hold we’d get to 100-105. 
Chief Meteorologist – Mark Nelsen

Hot or Really Hot?

July 20, 2009

Tomorrow's Eclipse: 5pm-8pm Pacific Time

Tomorrow's Eclipse: 5pm-8pm Pacific Time

Don’t worry, you won’t miss an eclipse tomorrow;  all the action will be over Asia.  You can find all the pertinent info at www.spaceweather.com 

So the title shows the main forecasting problem for the last few days.  As I returned from vacation Sunday, I took a gander at the maps.  Whew!  It looked like the heatwave of the decade on the way…but things have sure changed in the last 24-36 hours.  I just took a quick look at the 00z GFS.  It seems to confirm mine and Drew’s “cooler” forecast.  At least cooler compared to the other 7 Day forecasts in Portland.   Right now I don’t see a pattern that pushes us much above 95 degrees unless the pesky upper low suddenly decides to remain offshore.  So the big story is still that our stable and very warm July weather pattern is going to continue for awhile.

Vacation Report:  Family and I went trailer camping for 4 nights in the Cascades late last week and over the weekend.  Two nights at Olallie Lake near Mt. Jefferson and two nights at Clear Lake along Highway 26.  Blood-sucking mosquitos and a hellish road at the first.  No mosquitos, but 3am gunshots plus yelling at the 2nd.  Overall the camping was great, solid sun every single day and the lakes were comfortably warm enough to swim in.  I thought the no-swimming rule at Olallie was one of the dumbest things I have ever heard of.  Really, who goes up to a Cascade lake on an 80 degree day and doesn’t want to jump in???  Luckily the resort has been closed for awhile so no problem until it re-opens I suppose.

Chief Meteorologist – Mark Nelsen

Vacation Extra

July 12, 2009

lightning1Looks like once again models have done pretty well.   Okay, so it was in the 70s instead of 90 yesterday, but who’s counting?  Lots of convection developed over northwest Oregon and southwest Washington early this morning.  This is on top of a VERY thick marine layer.  I see it’s fogged in up at 6,000′ at Timberline.  And I have received .14″ this morning at my home;  only from marine layer drizzle!

Okay, that’s all, mainly I just wanted to save this image for the future.

Chief Meteorologist – Mark Nelsen

More Thunderstorms

July 10, 2009

A "near" Severe Thunderstorm This Afternoon over Detroit Lake

A "near" Severe Thunderstorm This Afternoon over Detroit Lake

A nice little snapshot of a briefly strong storm over Detroit Lake this afternoon shows how a nice sunny day can turn dangerous over a Cascade Lake.  At this point the cell appeared to peak out around 63 dBz or so.  Looks like about 10 cloud to ground lightning strikes within 15 minutes in the area.

Then about one hour later a storm briefly pulsed up around Molalla on it’s way north, producing 4-5 strikes close to town.

There is obviously still some mid-level instability out there this evening (10:30pm).  There have been 5 strikes in the last 15 minutes between Newport and Yachats.  That would be OVER a cold marine layer.  It must look neat to see the lightning strikes come punching down through the low clouds and drizzle.

Tomorrow looks very similar to today with the upper low remaining well offshore.  I don’t see any good trigger for widespread convection…very much like today.  I notice our RPM has almost no convection at all. 

One change in the lower atmosphere is that some marine air is flooding into the southern/central part of the Willamette Valley.  Models show some of this filtering into the north valley by morning.  Will it still make it to 90 tomorrow?  The push does look very shallow, and it is coming in from the southwest…notice Kelso never had a big push this evening?  So I left the temperature the same in the forecast, but I could easily see only 87 at PDX.

Tomorrow night could be fun as the upper low makes it’s move inland to our south.  Our RPM shows showers suddenly breaking out 8-11pm and continuing overnight in the southerly flow.   I also notice the big southwest low level surge of marine air doesn’t come in until around daybreak Sunday.  So it may be a warm and humid Saturday night with some thunderstorms around.

Next week looks very typical and boring summer weather, which means a great vacation week.  I have some “home time” and some camping planned in the Cascades, no  big extravaganzas.  I’ll be back Monday the 20th.  No posts until that time unless Drew or Rob get really inspired by the sunshine.

Chief Meteorologist – Mark Nelsen

A Few Thunderstorms

July 9, 2009

A brief "pop-up" thunderstorm near Mt. Hood
A brief “pop-up” thunderstorm near Mt. Hood

A nice little burst of convection early this afternoon to the east of Mt. Hood spit out a dozen or so strikes on the Mt. Hood National Forest.  One hour later though it’s gone.  I think that will be the story the rest of today and maybe tomorrow afternoon as well.  Lots of brief thunderstorms over the Cascades and east of the mountains.  I have a feeling we need to wait until Saturday for a better chance westside.  I do think Saturday is going to be a surprisingly hot day…maybe well into the 90s.  I’ll post more thoughts later. 

And…apparently those thoughts will be brief since it’s 11pm:

Upper level low is going to be slightly farther offshore the next 48 hours than what was forecast 24 hours ago, so heights are higher over us which means warmer temps.  Offshore flow looks real nice tomorrow and Saturday as well.  According to the “magic chart”, an 850 temp of 18-20 with offshore flow CAN get us to 95 degrees in perfect conditions.  90-93 is a better bet so obviously I’m shooting a bit high.  The 00z WRF-GFS has a strange shallow surge of marine air Saturday morning.  The NAM doesn’t show that and neither does the GFS.  As for thunderstorms, maybe something comes in Saturday night as the upper flow turns more southeasterly, especially if a major marine push holds off until sometime Sunday.  Lots of details to be resolved for Saturday night and Sunday…seems to be a low-confidence forecast for the 2nd half of the weekend.  Chief Meteorologist – Mark Nelsen

The Dry Month Begins

July 8, 2009

junkI have to admit that I stole the idea for this graphic from Cliff Mass’s blog up in Seattle.   This is a graph of the rainfall probability for any one day throughout the entire year at PDX.  Notice the sharp dropoff after the 4th of July.  The month from July 10th to August 10th is the driest of the year here in the Portland area.  Of course each year is different, but the average numbers sure don’t lie do they?  I also see that September is a bit drier than June, but we quickly turn wetter after October 1st.   Basically we turn wetter faster in the fall than we dry out in the Spring and early Summer.

Coming up…looks like possibly some interesting weather for the end of the week.   The upper level low off of Vancouver Island is going to sag to the south and be sitting off the Oregon Coast Friday and Saturday.  It fills a bit as heights rise, but it’s definitely still there through Saturday.  Of course then that sets up the preferred south or southeasterly “thunderstorm” flow that we like to see.  Our RPM model and WRF-GFS imply something could drift off the Cascades Friday and/or Saturday afternoon.  But as we saw in June, we can have this pattern and still get no significant storms west of the Cascades.  It’s something to keep an eye on.

Mark Nelsen