Hot Day Ahead

September 10, 2008

Snapshot  A nice comfortable day again today…after a very chilly start!  I see Hillsboro made it into the upper 30s, so it's definitely moving into Fall with respect to nighttime temps.  We made it up to 81 after a low of 52 at PDX!

So this is part of my new and improved "efficient time-management" era.  Generally someone else will be doing the weather on our sister station KPDX at 8pm.  A nice little break so it seems like a good time to blog don't you think?

We had just about flat pressure gradients from the Coast to Eastside today.  That should change overnight tonight as we get a slightly stronger easterly gradient than what we had Monday.  That will push east wind across the entire metro area by tomorrow afternoon.  So expect a chilly start again, but a very fast warm up.  I see 850mb temps creep up to the +17 to +18 range too.  We MIGHT hit 90 at PDX, close call there.  Either way it'll be briefly hot in the afternoon.

It's back to onshore flow for Friday and most of Saturday…then a change.

Models show the upper level ridge popping back up directly over the Northwest Sunday and Monday.  This time the atmosphere overhead is going to be quite a bit warmer than with the easterly flow conditions over the weekend or coming up for tomorrow.  850mb temps rise to the +22 or +23 mark both afternoons and models have been very consistent the last 48 hours with these temps.  The thermal trough also seems to develop farther to the west, due to a stronger surface high dropping down into the Rockies.  This is beginning to look like a Coastal hot period too.  It all adds up to a brief late season heat wave…time to up the temps on the 7 Day forecast a bit.  The "magic chart" says 93-96!  Since it's not the end of September, this is quite reasonable considering the 850mb temps + offshore flow.

I also notice that there is no sudden onshore push for Tuesday or Wednesday.  It's more of a lingering upper-level high but slowly dropping heights sort of setup.  So summer is going to continue awhile longer…Mark Nelsen