It was a gloomy end to Thursday with light rain at times from around 2pm onward here in the Portland metro area. Still, it was nice to have some dry weather this morning, at least dry enough to get outside and do some yard cleanup in my case. I sure noticed that spring has sprung even higher up where I live with trilliums just starting to appear in the woods, they look like this: The weather pattern has been quite dull and boring this week. One weak system came through our area today and then several weak waves of moisture (clouds and rain) will move through a developing upper-level ridge Saturday and Sunday. The weekend probably won’t be a total washout, in fact Sunday may be mainly dry SOUTH of the Portland area as the ridge pushes the light rain farther north. What about Monday and beyond? Models are still pushing upper level heights up around 570-576dm at 500mb, a very nice setup in April and May for 70 degree temperatures. 850mb temperatures make it to around 10-12 degrees celsius (ECMWF) both Monday and Tuesday. Even the cooler 8 degree temps on the GFS produce temps in the lower 70s Monday and Tuesday. Now it appears that a trough will pass by to the north on Wednesday, cooling us down and possibly some showers push south into NW Oregon too. However, the generally higher than normal upper-level heights seem to stick around for a few more days. Here’s a very confusing, yet interesting chart from WeatherBell. They provide (for a fee) access to lots of extra model information and they have some really interesting presentations of model data. Everyone got that? I think the forecast is VERY clear from this chart. Just kidding, but stay with me, it actually makes sense if I annotate it a bit: What you are seeing is maximum temperature forecast for each 12 hour period in Portland. The last 11 runs of the ECMWF model are stacked from newest on the bottom to oldest on the top. So the bottom row is the CURRENT forecast from the ECMWF. Notice it shows a high around 70 Monday and 67 Tuesday, then 62 Wednesday. If you go up one line, but stay in the same column, that’s the same time period but one model run back in time. A lineup like this allows a forecaster (or you) to see how the last 11 runs of the model have trended for any one date. In this case you can see the high temp forecast for Monday has been very consistent. You can also see the Tuesday forecast high has trended down the past few days as the ECMWF has gradually weakened the ridging for next week. Maybe most interesting is that for several days the ECMWF was showing high temps around 80 degrees next Wednesday and Thursday. Instead we now have a trough “crashing the ridge” on Wednesday, thus a much cooler temperature forecast. A chart like this is extremely helpful; one can digest many different model runs with just a glance. The minimum temperature chart (not shown) is just as useful for tracking how models are doing with approaching cold weather in the winter too.
This is definitely not a TV graphic…don’t you agree?
BIG PICTURE: 3 more days of cool and wet, then warmer & drier than average next week. Are you a gardener like me? Next week will be our first multi-day dry period in over two weeks…time to get some outside work done! Chief Meteorologist Mark Nelsen