January Heat and High Winds

January 16, 2009

Snapshot Quite a contrast in weather conditions across the area today.  Summer-like temperatures in the 70s in the mountains versus windchill values in the teens in the Gorge.  Let's chat about wind and then temps:

1.  Gradient through the Gorge eased down to around 7mb. earlier today, but has now shot back up to 10mb PDX-DLS as the cold pool east of the Cascades has thickened.  It has pushed up to 3,000' and above…evidenced by the freezing fog and NW wind showing up at Redmond this evening, plus I notice Mt. Wilson on the Warm Springs Reservation at 3800' is 10 degrees colder tonight.  Wind is now as strong as it was during the arctic blast at the west end of the Gorge…regularly gusting 60-70 mph at Corbett, with one gust to 72 mph.  It generally doesn't get much stronger than that without a deep low approaching the coast.  The strong wind is confined pretty close to the Gorge…probably due to the very low inversion top.  WRF-GFS implies a more widespread east wind across the metro area tomorrow…we'll see.  Either way, for those of you out in the Gorge wind "blast zone", it's going to stay rough through early next week.

2.  Temps…airmass coming through the Gorge has cooled a bit further compared to 24 hours ago, so I dropped high temps for tomorrow a few degrees further as well.  Highs should range from upper 30's in Gresham to the upper 40's on the far west/south sides of town.  It's going to be a cold day in the windy areas, and comfortably cool elsewhere.  Fun temp forecast challenge for a couple spots.  For one, Redmond, which was in the lower 60's today will probably be within the cold pool tomorrow.  That would give a high in the lower 20s!  So about a 40 degree drop over there.  Bend may stay above the cold air, so highs there still make it into the 50s.  This happens a couple times a winter.  Good times.  The other spot is Government Camp.  It made it well into the 60s today, but if the cold airmass deepens to 4,000', the very cold air could spill through the pass there.  So Govy should be somewhere between 35 and 65 for a high…"where she stops, no one knows"!

Okay, I need to finish the show.  It's a tough evening with the 1st of the last 10 episodes of Battlestar Galactica starting during the 10pm show.  I'm going to force myself to leave it off and just record.  I don't know if I can handle that…Mark Nelsen

By the way, I'm guessing some of you might consider driving up to Crown Point or Women's Forum Viewpoint to check out the wind tomorrow.  I might be interested in a brief (cold) get together since it's only a mile or so from home.  Maybe midday?  If so, let me know via email.


The Chilly Wind Is Back

January 15, 2009

Snapshot A few tweaks to the forecast tonight.  First, it looks as if a nice cold pool IS developing east of the Cascades, more than I would have expected considering how little snow is on the ground in the Columbia Basin.  A surface high has strengthened in the Columbia Basin with just about 10 millibars easterly gradient from PDX-DLS.  The depth of the cold air east side is almost 3000' now…for example I noticed Middle Mountain (in the MIDDLE of the Hood River Valley), around 2400' is running 8 degrees colder tonight compared to last night.  Corbett at the west end of the Gorge, which is "well-mixed" due to the strong wind, is running 8 degrees colder compared to 24 hours ago as well.  So…I have a feeling high temps will be cooler in at least the eastern 1/2 of the metro area tomorrow.  I went 48 for PDX, but it may only be 44-46.  For sure it'll be windy and chilly east of I-205.  With no change in the upper-level pattern through Monday, I think we'll cool a few degrees through that time.  So forecasts of 50-55 degrees are sure not going to happen.  And for those of you in the windy areas, it's going to be a long period of annoying east wind.

With 10 millibars gradient, the dry air has sure been slow working it's way across the metro area.  Dewpoints in the 20s in Gresham/East Portland are a good sign that eventually we'll get rid of the fog though.  I think it'll be a non-story by midday tomorrow.

If you want warm weather, head up or west.  The Coast should be in the 60-65 degree range the next few days, and some spots in the Cascades made it into the lower 70s today!

Long range, not much to talk about…either ridging or split flow is the story through the end of next week…Mark Nelsen


A Warm Ridge

January 14, 2009

Snapshot  The weather may be boring, but for those temperature freaks, lots to talk about!  A very strong valley inversion has developed across the Pacific Northwest.  As you can see from the image, some spots in the 2,000-4,000' range made it close to 70 degrees today while the valleys sat in the 40s.  The layer of cold air is pretty shallow and has become a bit shallower this evening.  I see the temp on our tower at 1,800' has jumped to 60 degrees at 10:45pm. 

     This is all being driven by a strong upper-level ridge centered over SW Oregon.  Nothing changes the next few days except the center of the upper-level high moves north over Washington by Saturday afternoon.  850mb temps are astounding for mid-January.  They peak out in the +16 to +18 deg C. range.  For kicks, I pulled out the warm season "magic charts" for May and March.  For one, there are no temps that warm for the month of March.  For May, those temps plus easterly wind would get us up to about 90 degrees here in Portland!  So then you might think "we're going to get east wind the next few days, how come the warm air doesn't mix down?".  Well, between now and late February, the east wind is coming in through the Gorge BELOW the inversion top.  It's just bringing in cool air from east of the Cascades, not mixing down warm air from above.  This generally makes forecasting high temps at PDX simple in east wind events in the dead of winter (now).  Except for maybe the 1st day the wind arrives, you can add about 10 degrees from the DLS high to get the number.  Better to remember that in January you're not going to get much above 50 degrees on a good east wind day (except for maybe that 1st day).  45-50 is most common unless/until a good cold pool develops eastside.  I don't see that this time around, so I kept high temps at/above 45 degrees through early next week.

Looks like the surface high is now strengthening quickly in the Intermountain region.  The PDX-DLS gradient has gone from around 2 millibars late this afternoon to about 6 millibars now.  The wind hasn't made it to the Troutdale airport yet, but I would guess it's started blowing a bit up above in "upper" Troutdale and Gresham.  If not, it'll arrive soon.  6 millibars is enough to push wind all the way to downtown Portland by tomorrow afternoon.  With lower dewpoints spreading across the metro area, I have a feeling that tonght's patchy areas of fog will be the last until sometime early next week.  Lots of sunrises and sunsets will be seen from the Portland Metro area through the weekend!  Mark Nelsen


A Warm Ridge

January 14, 2009

Snapshot  The weather may be boring, but for those temperature freaks, lots to talk about!  A very strong valley inversion has developed across the Pacific Northwest.  As you can see from the image, some spots in the 2,000-4,000' range made it close to 70 degrees today while the valleys sat in the 40s.  The layer of cold air is pretty shallow and has become a bit shallower this evening.  I see the temp on our tower at 1,800' has jumped to 60 degrees at 10:45pm. 

     This is all being driven by a strong upper-level ridge centered over SW Oregon.  Nothing changes the next few days except the center of the upper-level high moves north over Washington by Saturday afternoon.  850mb temps are astounding for mid-January.  They peak out in the +16 to +18 deg C. range.  For kicks, I pulled out the warm season "magic charts" for May and March.  For one, there are no temps that warm for the month of March.  For May, those temps plus easterly wind would get us up to about 90 degrees here in Portland!  So then you might think "we're going to get east wind the next few days, how come the warm air doesn't mix down?".  Well, between now and late February, the east wind is coming in through the Gorge BELOW the inversion top.  It's just bringing in cool air from east of the Cascades, not mixing down warm air from above.  This generally makes forecasting high temps at PDX simple in east wind events in the dead of winter (now).  Except for maybe the 1st day the wind arrives, you can add about 10 degrees from the DLS high to get the number.  Better to remember that in January you're not going to get much above 50 degrees on a good east wind day (except for maybe that 1st day).  45-50 is most common unless/until a good cold pool develops eastside.  I don't see that this time around, so I kept high temps at/above 45 degrees through early next week.

Looks like the surface high is now strengthening quickly in the Intermountain region.  The PDX-DLS gradient has gone from around 2 millibars late this afternoon to about 6 millibars now.  The wind hasn't made it to the Troutdale airport yet, but I would guess it's started blowing a bit up above in "upper" Troutdale and Gresham.  If not, it'll arrive soon.  6 millibars is enough to push wind all the way to downtown Portland by tomorrow afternoon.  With lower dewpoints spreading across the metro area, I have a feeling that tonght's patchy areas of fog will be the last until sometime early next week.  Lots of sunrises and sunsets will be seen from the Portland Metro area through the weekend!  Mark Nelsen


Flooding Winds Down

January 8, 2009

Snapshot Looks like the Chehalis River is the last to crest in our viewing area this evening.  Once again the Twin Cities are getting nailed by flooding.  A bit of an editorial here, but maybe it's time to stop filling in the flood plain?  Okay, enough of that before I get in trouble.  All other rivers are falling quickly at 10pm, so flooding should be over with most spots by tomorrow.

Big ridge of high pressure settles in this weekend, but one system slips through and sits over us Sunday.  Saturday looks like a real nice day, but Sunday should be cool, gloomy, and wet.  Snow levels climb up to around 7,000' or higher at that time.  So make sure you head up to the mountain for skiing Saturday, not Sunday.

The amount of offshore flow to get rid of the fog is in question for next week.  For now it sure doesn't look like much easterly wind.  Hopefully that will change or it's going to be a very gray week in the lowlands.

I'm taking the next 3 "business" days off…so no new blog posts until next Wednesday…we can all take a break with the dead weather!  Mark Nelsen


Lots of Rain

January 7, 2009

Snapshot  Quite a flooding event AGAIN for S.W. Washington.  In fact the significant rainfall has been confined to only that area and the extreme NW tip of Oregon.  It poured all last night and most of today from Longview north, which explains the widespread flooding in those areas.  Looks like NW Oregon is mainly dodging the bullet this evening.  We will have some heavy rain the next few hours, but it won't last long…the satellite looper shows that pretty clearly.  Models also only give us maybe another .50-.75" here in Portland.

Wind has increased again this evening just ahead of the cold front.  Peak gust last hour at PDX was 43 mph.  I don't think it'll go much higher.  After the cold front passes, rain turns to just light showers.

Still very little to talk about beyond tonight.  High pressure takes hold Friday and that's going to last at least a week, probably longer, giving us our driest stretch of weather since November…Mark Nelsen


Rainy and Warm Night Ahead

January 6, 2009

Snapshot  Now I'm really annoyed.  This is the 2nd time for this post.  I got all the way to my name, hit the post button, but apparently clicked something else on the keyboard at the same time.  Poof!  The post was gone.  But at least it's still mostly in my head.  Check out those wind gusts on Mt. Hood today!  Drew Jackson mentioned that parts of all 3 ski areas were closed today.  Rain plus strong wind isn't fun and those gusts of 50-100 mph aren't the best for the ski lifts either.  The 129 mph gust was at the top of the Magic Mile chairlift.

The melt continues in the hills today…I'm down to just spots of snow in the woods and the shoveled areas at home after a night in the 40s.  The lawn looks REALLY flat after having 5"+ snow on it for 3 weeks!

The big message that hopefully I'm getting across is that most of the Pineapple Express is heading into Washington this time around.  Heavy and flooding rains fall from tonight through Thursday morning in Southwest Washington, but I don't expect heavy rain here in most of Northwest Oregon until tomorrow evening.  The firehose is mainly aimed just to our north.  I'm assuming that the main reason for the Flood Watch from Portland south is due to already high rivers that will rise back to flood stage easily.

The Nehalem river already has a flood warning this evening.  It is forecast to rise to 26', which would be the 2nd highest on record after 1996.  Now last week the forecast was way off, by about 9' as the rainfall cut off quickly.  This week though, heavy rain combined with quite a bit more melting snowfall may push it much higher.  It'll be an interesting one to watch.

There is NO weather to discuss beyond Thursday.  The well-advertised big ridge sits over us from Friday through at least late next week.  It's not in a position to get strong surface high pressure east of the Cascades (at least initially), so fog is going to be a big issue with the very wet ground and little wind.  This time of the year we can stay fogged in all day, so forecasting high temps on the 7 Day forecast is challenging…Mark Nelsen