Forecasting is quite simple the next seven days. Strong high pressure is sitting just off the Pacific Northwest coastline. That’s sinking & drying air, keeping weather systems away.
That’s why we hit mid 70s in the metro area today, matching our “warmest of spring so far” 76 degree high.
Tomorrow we lose onshore flow, plus a little warmer atmosphere overhead means we’ll likely see our first 80 degree day of the season. This would be right about on schedule since the 2nd week of May IS the average first 80 degree date for PDX
We get some brief cooling Tuesday/Wednesday with onshore flow but that only brings us down to 10 degrees above average. Thursday through Saturday that upper-level high nuzzles right up to the coastline, amplifying at the same time.
That means surface high pressure develops east of the Cascades and offshore (easterly) low level flow. Offshore wind May through September can REALLY heat us up under sunny skies and that will be the case Thursday through Saturday. Most models show onshore flow returning very late Saturday, or Sunday.
So how warm could we get? Models are generally showing 850mb temps over Salem around 13 to 16 celsius Thursday, then 14 to 18 Friday and Saturday. To hit 90 in May, past cases show (with offshore flow) we need to see at least a +15 or +16. So 90 is definitely in the cards this time around. I’m VERY confident we’re going to hit 85 later this week, far less confident we hit 91-92.
In the past 7 years we’ve seen at least 84 in the first half of May each year. That said, we haven’t seen a 90 before May 11th for about 20 years. There you go, lots of numbers.
Rain is a no-show the next week, which means ending Friday we will have seen only .02″ in three weeks! That will be the driest April 20th-May 10th on record. Let’s hope this isn’t a repeat of last year. It would be nice to see a big soaking at some point between now and mid-June.
Starting midweek I’d say it’s time to begin watering everything you would typically water in summertime; lawns, gardens, very small shrubs/plants you just planted etc… Trees are fine for quite awhile since we had heavy rain just a month ago.
Both the ECMWF & GFS show no rain for the next 8+ days. Click for a better view
That’s through next Monday. There are still hints we turn wetter around the 14th-18th. Both ensemble systems show at least some sort of soaking during that time. That would be later NEXT week
So enjoy the sunshine this week, again, it’s going to feel like July with probably only one “morning clouds” day. That’ll be Wednesday.
I’ll be off the rest of this week, back to work next Sunday. I’m turning 50 Monday (old!), and randomly chose a week in late April or early May to use up 4 vacation days. Wow, I sure didn’t expect the weather to line up like this; I think it’s time to get the Nelsen pool up and running! I’m way too cheap to use a heater so hopefully nature will take care of that Thursday and beyond.
Chief Meteorologist Mark Nelsen