First 80 in Portland This Weekend?

April 19, 2012

5:30pm…

I’ve checked out all the maps/models this afternoon and have a few thoughts:

1. This weekend still looks to be the warmest spell of weather we’ve seen this season and the 3rd nice one of the month.

2. Sunday will be the warmest, with light offshore (easterly flow) flow and the warmest airmass overhead.

3. If everything works out just right, we could be in the 80-82 degree range Sunday here in Portland.

4.  Since models have been somewhat inconsistent, and we are right on the edge of the clouds to the west and heat to the east, we decided to keep Sunday’s high at 78 on the 7 Day Forecast.

5.  A significant change in the 12z models was to split the approaching upper level trough later Sunday and Monday.  This has the effect of delaying a cooldown into the middle of next week.

6.  It’s time to see some 70s…look at the past 8 years.  In most Aprils we see at least one day in the 75-85 degree range, except the past two years:

Today turned out pretty much as expected, solid cloud cover and steady rain.  No big surprises there.  Warm fronts are notorious for low cloud decks, light rain, and gloomy conditions all around.  Even a breezy east wind blowing out of the Gorge to remind us that winter weather patterns are never THAT far away…

We get a break in the rain tonight, then the cold front part of this weather system moves south out of Washington and dies right over the top of us tomorrow through early Saturday.  So yes, lots more gloom tomorrow, but after a warmer start we should end up a few degrees warmer.

Saturday, the upper level flow is still expected to amplify offshore, with southerly winds overhead pushing the cold front clouds and rain to our north.  This is a transition day as we go from cloudy and cool to sunny and warm by mid-late afternoon.  Thus a high temp right around 70 as 850mb temps climb to +8 or so.

Sunday things change a bit.  A very light easterly flow in the lower atmosphere throughout the day, abundant sunshine, and 850mb temps between +11 and +15 say June, not April.  According to my “Magic Chart” (not like the Magic Bus up in Alaska), a +12 with offshore flow is somewhere between 78-82 degrees in April.  On April 19-21st, 2009, the last time we had real warm temps in April, temps were 79-83 and 850mb temps were +12 to +16. 

It’ll be interesting to see if we get our first 70 AND first 80 degree temp this weekend; it could happen.

Chief Meteorologist Mark Nelsen