April 28, 2006
It wasn’t expected of course, but we finally hit 80 degrees today. And that was without warm easterly winds! We could have been 85 with the same atmosphere overhead plus offshore flow.
The big story tonight is the weak looking cold front offshore. It may be weak, but there is a lot of cold air behind it. The front should pass through NW Oregon during the daytime tomorrow, bringing a few showers, but no big soaking. BUT, the double whammy of strong onshore flow plus a much colder airmass arriving by afternoon equals a good 20 degree drop in temperatures.
Even though the air flowing in Saturday afternoon is cold, it’s quite dry, so Sunday we start chilly, but end mild with a mostly sunny day.
A 2nd front moves through Monday for at least partly cloudy skies, but once again pretty dry. Then it’s on to ridging Tuesday-Thursday or possibly Friday too. One more round of warm summery weather coming then…Mark
April 27, 2006
Of course it happens this way: Yesterday the low clouds wouldn’t go away, but this morning they were already mostly gone at sunrise. I can’t win! Temps made it into the lower 70s today across the metro area as a result.
With all models forecasting several degrees of atmospheric warming tomorrow, we should easily hit 75-76. I notice ETA MOS at 00z has 78 for tomorrow. Could happen, but I hate to get too wild and crazy. In my younger days at a local TV station I would have gone for 78 or so, but I’m getting old & conservative (weatherwise) lately.
Massive marine push + weakening cold front Saturday keeps us in clouds through midafternoon with a few sprinkles or a shower. MUCH cooler the big story then. But by Sunday we’re back to northerly low-level flow, which means quite a bit more sun.
Long range models have either a flat or strong ridge over us starting Tuesday and continuing through Thursday next week. We could anywhere from 74-86 depending on which model you believe, so I’ll stick with 76. No good chance for widespread rain until later next week.
April 26, 2006
They are back! The most hated part of forecasting in the warm season…those marine clouds. They moved inland nicely overnight as expected, but like an unwanted house guest they never completely dissipated over and north of the Portland Metro Area.
You may remember last night I was afraid the push would be too weak again, so I raised the forecast high from 61 to 63. Instead we only hit 59. This happens quite a bit in the summer. The thickness of the marine layer is always hard to predict. Not exactly a life-threatening forecast problem, but still a problem here west of the Cascades.
But there is always tomorrow right? Rising 500mb heights are the story through Friday as a strong ridge of high pressure builds over the West Coast. Higher heights tend to "squash" the marine layer as subsidence increases. For this reason, the clouds tomorrow and Friday should dissipate much faster. At least that’s the plan. No offshore flow Friday means mid 70′s will be hard to do. Then another wave passes by Saturday, giving us a major push again.
00z models stay with the return to stronger ridging beginning Monday and continuing the rest of next week. ECMWF & GEM (Canadian) models have much higher 850mb. temps, up to 14 degC in the ECMWF. Combine that with offshore flow in early May and we can hit 85 degrees in Portland. But for now the GFS is not nearly so strong with the ridge, so I’ll stay with mid 70′s Tuesday-Wednesday.
Either way the generally dry weather continues. That shortwave disturbance Saturday could give us a shower, but not enough to make me bring in all the yard tools in my case. Get your dry weather activities finished up…it’s always possible we get wet again in May for quite awhile…Mark
April 25, 2006
The first forecast concern tonight is the amount of marine air moving inland. Gradients at 5pm are only 2-3millibars from the coast into the valley. Not very impressive for a good push. Combine that with the last visible satellite pictures of the day showing only scattered stratus offshore and I’m thinking we may not have much thicker cloud cover tomorrow. I may revise to warmer/sunnier Wednesday if the 00z runs this evening weaken the onshore flow or the after dark fog imagery shows no movement onshore.
Strong ridging builds in behind a passing shortwave Thursday-Saturday morning, which should warm us up quite a bit again. Significant for this warm spell is the fact that no easterly wind develops. So even with a +12 or +13 850mb temp forecast for Friday, we may not get above 75 degrees. Solid easterly flow like last weekend COULD give us 80 in this warm of an atmosphere, but I think that’s unlikely.
After 2 more waves Saturday PM & Monday AM bring onshore flow back over the weekend, strong ridging returns for the middle of next week. Our unusual dry spell should last at least 7-9 more days!
April 24, 2006
After taking a little break this weekend, I come back to very June-like weather maps. So what kind of weather map looks like June?
500 millibar heights through the next 7-10 days remain quite high with just weak disturbances passing by to the north from time to time. It’s quite possible that we won’t see a soaking rain for 10 days. That is very unusual for late April or early May.
00z GFS has ridging over us late this week and again the middle of next week. These periods will be the warmest days of the next 7-10, then we cool off inbetween with onshore flow.
In the short term, onshore flow tonight shouldn’t be strong enough to push cloud cover inland much, but tomorrow night’s push will be much stronger. We may struggle to get any sun on Wednesday as a result.
April 20, 2006
A very weak front moves through tonight, so weak that we may see more showers in the unstable southerly flow just ahead of the system overnight. All models show and, satellite imagery confirms the airmass behind the front is very dry, more like a continental cold front. If you’re from east of the Rockies, you’re familiar with rain ahead of and with cold fronts, then it dries out and sunshine returns behind. That’s what I expect tomorrow.
Then it’s on to a warm and sunny weekend. 00z GFS & ETA both have 850 mb. temps Sunday afternoon around +8 deg. C. That still puts us in the mid 70′s if easterly flow dips down into the city. I expect that to occur, so 75 still looks good (I wimped out on the 76 eh?).
Enjoy the upcoming weekend, I have a day off tomorrow, so I’ll be back Monday…Mark
April 19, 2006
Looks like PDX hit 70 at 6pm today, the first 70 degree temperature this season. Spring so far (March & April) has been pretty average, but we’ve had a real lack of ridging or offshore flow for very warm temps. If you think about it, the average high of 62 for today is really a compilation of lots of 55-60 degree days plus a few 70-80 degree days in the past thrown in.
Still warm tomorrow since the wavy front offshore is still there. A final wave should push it onshore late Thursday. But as I mentioned last night it will be a fast mover and we won’t see much rain.
Warm weekend still on track too with our first very warm east wind event of the spring. 850 mb. temps on the 12z/18z GFS and ECMWF rise up to around +8 C by Sunday afternoon. Mark’s Magic Chart we look at here in the newsroom gives us mid 70′s when that is accompanied by easterly flow at the surface. That’s where I get the 75 degree forecast high. NWS is going 65 and partly-mostly cloudy…hmm. They’ll come around right? I still remember the 90 degree high on April 30th back in 1998. That was an easterly wind event with a +18 C temperature. Am I getting old when I can remember 8 years ago as "just yesterday"?
During my morning wanderings through the yard/garden I noticed my peach and nectarine trees are blooming, the 30 at my home yesterday morning apparently didn’t affect them. I’m always amazed at microclimates here in the metro area. I saw peach trees blooming 3 weeks ago in Canby, amazing how just 1000′ elevation can slow things down. Everything runs behind at home. If you want early tomatoes, live right in the middle of the city. If you don’t want to mow until April each year, live at 1000′ or above. Choose your own climate.
By the way…someone in the last post mentioned a forecast for Bend. We have a sister station there and here’s the link to the 7 Day Forecast for Bend: http://www.foxcentraloregon.com/home/1624692.html