Wet & Wild Week

April 30, 2007

SnapshotCold front slowly moving towards the Pacific Northwest Coast tonight;  it’ll bring a quick end to our warm/dry weather.  This is the leading edge of a chilly airmass.  The cool air itself doesn’t arrive until Wednesday.  As the cold/unstable air sits over us Wednesday and Thursday, we should see the classic heavy shower, hail, and thunder spring weather pattern.
The last 3 runs of the GFS indicate much sharper ridging for this upcoming weekend.  Of course a warm and sunny weekend forecast for May is a dangerous thing to hand out on a Monday, but I feel like living dangerously tonight.

Nice Weekend

April 27, 2007

SnapshotA nice day today…luckily the clouds moved in during the afternoon, otherwise I think we would have been well into the lower 70s.  Very warm night tonight with plenty of cloud cover overhead.  Interesting synoptic pattern tonight with a dying front moving overhead, but little or no moisture.  All models show the atmosphere drying out with a dry northwest wind pushing dewpoints down to or below 40 degrees by afternoon.  So even though technically a cold front arrives during the early morning hours…a drier airmass and afternoon sun should give us high temperatures similar to today’s highs.  Then a wave on the front lifts through the Northwest Sunday morning.  This appears to have little moisture to work with too, so other than a risk of a shower in the morning, that day should be dry too.  Definitely cooler though with 850mb. temps dropping below zero in the morning.  Monday we temporarily bounce back temperature-wise with some sun again by afternoon.  Beginning Tuesday, a cold trough approaches and then sits overhead the rest of the week.  That means a return to March-like weather for the first week of May…Mark

Surprise Showers

April 25, 2007

SnapshotHave I ever mentioned how much I hate forecasting in spring here?  I grew up in our gray and cool spring weather and it still drives me nuts after 16 years of forecasting.  Weak convection broke out this evening and moved out across the metro area.  Amounts were quite light, but nonetheless the public counts that as a wrong forecast when we call for a dry day.  Models show no decent chance for showers the next two days as ridging builds overhead.  A warmer atmosphere overhead means warmer temperatures down at the surface too.  We head well into the 60s tomorrow with more sunshine, then up to around 70 or so Friday with lots of sun.
That ridge gradually pushes off to the east starting Saturday, allowing marine air to flood inland.  That leaves us cooler and cloudier for the weekend.  The 7 Day forecast is dry, but we could easily have a "surprise" shower again in this pattern.  Next week it’s back to cool and wet as troughing sits offshore.  Looks like May is going to start chilly…Mark

Back at the Helm

April 23, 2007

SnapshotA brand new week and a milder weather pattern for the next few days.  A weakening cold front moves inland tomorrow for a very gray day, but not a whole lot of rain involved.  Interesting to note models show a nice wave on the front bringing significant rain to Central and NE Oregon on Wednesday.  That all moves east for Thursday, leading to the first strong ridge of the season over the Western USA.  That ridge is going to be centered over Nevada and Utah, not ON the West Coast.  So we turn warmer, but we will be vulnerable to systems brushing the Northwest.  Highs near 70 or so are likely in this pattern, as opposed to a ridge directly overhead with offshore flow.  That pattern could push us well above 80 degrees this time of year…Mark

More Dry Days Ahead

April 19, 2007

SnapshotI’m trying to wrap things up this evening since I have a day off tomorrow, so a quick post.  Nice day today with lots of sunshine…same thing for tomorrow as we wait for Saturday’s wet system.  Very weak instability gave us a few sprinkles over the Cascades and Coast Range today, exactly as models had shown.  The tough part is that models again show weak convection tomorrow.  This time it supposedly drifts off the Coast Range and into the west side of the metro area in the early evening.  It’ll be
interesting to see if the models nail it again…
    Back to rain Saturday with leftover showers for Sunday.  Models definitely show higher heights now for next week.  Temperature-wise, we should see average to above-average temps next week with only one decent chance for rain…sometime later Tuesday…Mark

Stormy Wednesday

April 18, 2007

SnapshotJust a little something to the left to get you through the chilly April weather.  You may remember that last year we were beginning a month of June-like weather.  It culminated in 4 days of 80-90 degree weather in mid-May.  Much different today.  Cold showers developed once again.  Surprising that even though hail and brief heavy downpours were widespread, there were no lightning strikes west of the Cascades between Seattle and Medford.  Of course current detection only includes strikes from cloud to ground, so there may have been some flashes in the clouds.   The next system is headed into California, leaving us with very weak instability each afternoon.  Most likely we stay dry in the major population centers the next two days.  Another system moves inland later Saturday and Sunday.
Interesting changes MAY be in store for next week.  Most models have higher heights and more ridging of some sort or another starting Monday.  It may not be a sunny week, but it should more like late April…instead of late February like this week…Mark

Cold Showers Continue

April 17, 2007

SnapshotNice convective shower day today, although there were no lightning strikes anywhere west of the Cascades from Seattle to Californiad.  Plenty of hail though as a very cold upper-level trough is now overhead.  It’ll still be overhead tomorrow.  There is no obvious trigger for convection, so it should be strongly diurnal (based on daytime heating).
As I suspected yesterday, with a cold trough still basically overhead Thursday and Friday, it’ll be tough to avoid afternoon showers those days.  And now I see our RPM model shows afternoon convection over the Cascades and Coast Range Thursday afternoon.
More cool weather over the weekend with another trough, then HOPEFULLY a change towards higher 500mb heights will bring us milder and more seasonal late April weather next week.  Some models are showing that.
By the way, April 18th last year (tomorrow’s date) was the beginning of a 3 week stretch of warm and unusually dry weather.  Remember?  Wouldn’t that be nice!  Mark