Frosty Night, then May “Hot” Weather On the Way

May 9, 2012

Tonight should be a perfect setup for a very cold May night.  Clearing sky, wind goes calm after midnight all areas, and an unusually dry air mass.  These all give us a perfect cooling opportunity.  Protect any plants that are considered “warm weather veggies”.  That would be beans, tomatoes, eggplants, cucumbers etc…  I don’t expect it to be cold enough to damage blooming fruit trees.  Usually it needs to be below 30 for that to happen.

Tomorrow morning’s record low in Portland is 37 and we’ll be quite close…we’re forecasting 38-40 right here in the city.  But outlying areas will be a bit colder tomorrow morning than today.  Places like western Washington county and central/northern Clark county could drop to 30 or even a notch colder.

Then it’s on to lots of sunshine the next 6-7 days.  An upper-level ridge builds over the West Coast; it’ll be directly overhead Friday through Monday.  So most of that time we’ll either have a thermal trough (lower pressure) west of the Cascades or at least no onshore flow (Monday).  Combine that with a much warmer atmosphere overhead and it’s going to get real warm.  The GFS would imply we stay below 90 degrees Sunday and Monday, but the ECMWF was a scorcher, showing possible lower 90s both days.  It’s a bit too early to tell, but to be safe we raised both high temps to 88 on our current 7 Day forecast.  Might be a little hot for Mom, but a great afternoon/evening for barbecuing in the shade.

Chief Meteorologist Mark Nelsen