Slowly Drying Out Tonight

September 28, 2010

I see dewpoints are SLOWLY dropping off this evening as we get a drift of drier air coming down from the north.  The good news is dewpoints are much lower to our north (low-mid 50s in Puget Sound), and we get increasing north and northeast wind the next 48 hours.  That should bring us back down into “normal” territory by midday tomorrow.  Basically the humid weather is finishing up this evening.  Temperatures are dropping more quickly this evening as a result too.  We had 3 consecutive record warm lows (61, 63, 63) at PDX, which appears to be the first time in 10 years we’ve seen such a warm stretch…and highly unusual for the last half of the month too. 

Two real nice days ahead with slight offshore flow tomorrow and stronger easterly flow on Thursday.  850mb temps peak out near +20 C on Thursday too.  That should push us well into the 80s.  With the decreasing sun angle and daylight hours, it becomes very hard to get temperatures much above 80 over the next couple of weeks.  But conditions are perfect for that to happen on Thursday.  A weak shortwave trough passing overhead Friday morning gives us a southwest push.  Our RPM model and the WRF-GFS say widespread low clouds in the Valley the first part of the day.  That’s a tricky forecast because in early October once you get the low clouds in the Valley they can easily be stuck there most of the day.  I’ll ignore that for now and go for mid 70s.

Beyond that a stronger trough comes through here very late Sunday or Monday.  That’s the next chance for rain.  But it’s not the start of a wet spell…it appears a longwave ridge wants to stay nearby for a good chunk of next week too.   Hopefully it’ll be nice and dry again, although I see the 00z GFS is looking similar to the humid pattern we just had…plenty of rain to the north and warm air down here.

Chief Meteorologist Mark Nelsen