Cold, then A Taste of Summer Again

May 1, 2012

Our latest 7 Day forecast is quite chilly (4 more days), then shows a dramatic warm up.  That seems to stick out a bit compared to other Portland station’s forecasts:

First the chilly weather, I see the 00z NAM is showing -5 to -6 temps at 850mb late Friday night and early Saturday morning.  Pray for skies remaining mostly cloudy Friday night because all my fruit trees are in full bloom right now and I don’t want a late season frost.   With a few leftover showers Saturday morning, there could be sticking snow down around 2,000′.

The ECMWF has been leading the way showing a quicker exit of the cold upper trough later Saturday and Sunday.  Plus it and the Canadian model have been sticking to a stronger ridge for Monday and Tuesday.  Now the 00z GFS is also quite similar.

This means we actually get a thermal trough west of the Cascades at least on Monday…note the WRF-GFS for Monday at 7am:

You can see a decent easterly gradient through the Gorge and over the Cascades.  My chart for May shows easterly flow, 850 mb temps about +10 Monday afternoon, plus full sunshine = 77-81 degrees.  That’s why I pushed forecast high temps up a bit.

Not sure how long it’s going to last, GFS wants to get “all troughy” on us while the ECMWF and Canadian rebound the ridging a bit for the latter half of next week.

Chief Meteorologist Mark Nelsen