Those Darn Marine Clouds

April 26, 2006

They are back!  The most hated part of forecasting in the warm season…those marine clouds.   They moved inland nicely overnight as expected, but like an unwanted house guest they never completely dissipated over and north of the Portland Metro Area. 

You may remember last night I was afraid the push would be too weak again, so I raised the forecast high from 61 to 63.  Instead we only hit 59.  This happens quite a bit in the summer.  The thickness of the marine layer is always hard to predict.  Not exactly a life-threatening forecast problem, but still a problem here west of the Cascades.

But there is always tomorrow right?  Rising 500mb heights are the story through Friday as a strong ridge of high pressure builds over the West Coast.  Higher heights tend to "squash" the marine layer as subsidence increases.  For this reason, the clouds tomorrow and Friday should dissipate much faster.  At least that’s the plan.  No offshore flow Friday means mid 70’s will be hard to do.  Then another wave passes by Saturday, giving us a major push again.

00z models stay with the return to stronger ridging beginning Monday and continuing the rest of next week.  ECMWF & GEM (Canadian) models have much higher 850mb. temps, up to 14 degC in the ECMWF.  Combine that with offshore flow in early May and we can hit 85 degrees in Portland.  But for now the GFS is not nearly so strong with the ridge, so I’ll stay with mid 70’s Tuesday-Wednesday.

Either way the generally dry weather continues.  That shortwave disturbance Saturday could give us a shower, but not enough to make me bring in all the yard tools in my case.  Get your dry weather activities finished up…it’s always possible we get wet again in May for quite awhile…Mark