A Taste of Summer For Early May

April 30, 2013

It appears that we are headed for an unusually long period of warm and dry weather.   Unusual because it’s rare to have a solid week or more in early May with temps in the 75-85 degree range, and mostly sunny or sunny skies.

The Highlights

  • There is no rain in sight…at least not through the middle of NEXT week.  Every month so far this year has been drier than average, and April ended up a little drier than normal too.
  • Mostly sunny or sunny skies are likely starting tomorrow for at least 6 days!  Maybe longer
  • Temperatures warm dramatically tomorrow, and continue rising through the weekend
  • This weekend will feel like summer; temps should top out in the mid 80s both days

 

Technical info:

I had 3 days off and during that time it was interesting to see how the maps changed…more of the same progression we’ve seen in the models the past few weeks.  Specifically, an upper-level ridge is forecast to build more directly over the West Coast but then ends up back in its favored position a ways offshore.  This leads to a very warm 7 Day forecast and then we have to back off a bit.   Last Thursday and Friday both the GFS and ECMWF were showing 850mb temps (celsius temp near 5,000′) up around +14 to +17 for tomorrow (Wednesday) afternoon.  Instead it’s going to be around +5 to +7.  That’s a huge change.  In the end (for the rest of this week) it won’t matter to the average person because the ridge is still close enough to give us weak offshore low-level flow and warm sunshine.

 

So for the next few days we do have the upper level ridge gradually edging closer, thus the warming atmosphere overhead; we go from that +6 or so tomorrow afternoon to +11-+14 Friday-Saturday afternoon.  Very good agreement on all models with that.  Then a slight change.  Models are forecasting a bit of a “Rex Block” Sunday through much of next week.  That tends to be a very stable upper-level pattern with an upper high centered north of an upper-level low to its south.  The orientation of the upper high north of us may give us good offshore flow Saturday through early next week as well.   Notice the 00z WRF-GFS cross-section showing very little low level moisture until next Tuesday-Wednesday too, thus the very sunny 7 Day forecast:

kpdx.x.th

notice the time goes from right to left, so the right side of the chart is Sunday morning and the left side is Wednesday morning.

The ECMWF does go for more of the offshore ridging instead of a rex block setup over us earlier next week so it isn’t quite as warm.  Here’s the 00z GFS ensemble 500mb forecast for NEXT Wednesday:

m500za_f180_bg_NA

and the 12z ECMWF map for the same time:

m500za_f192_bg_NA

 

Either way, one thing is certain, our drier than normal spring weather is going to continue.  For you gardeners, it’ll be time to start watering this weekend, especially those new plants you’ve put in.  Enjoy the sunshine!

Chief Meteorologist Mark Nelsen

 


A Few Maps for Tuesday Afternoon

April 30, 2013

I had the weekend and Monday off for some kid’s events so a bit delinquent on posting.    So I’m back in the saddle and looking carefully at the weather maps/models…I’ll post a few thoughts later.  I have some other office issues and a project I need to get done.

But for now, here are the latest 18z GFS and 12z ECMWF ensemble charts…very warm for early May:

 

tseries_850t_000-384_Portland

 

tseries_850t_000-360_Portland

And then the monthly ECMWF maps from Sunday night’s run:

500za_week1_bg_NA

500za_week2_bg_NA

500za_week3_bg_NA

500za_week4_bg_NA
  Chief Meteorologist Mark Nelsen