I feel very good about the forecast for today. Easterly gradient from PDX-DLS was over 6 millibars this morning, which is unusually strong for the warm season. But, just as models had predicted, the gradient backed off quickly and at 5pm is down to just 2 millibars. It was a perfect set up…warming from the downslope wind overnight and this morning, then the wind shuts down just in time for peak heating so we don’t get too much mixing. The final highs for the metro area are to the left. Portland, Hillsboro, and Vancouver all set new record highs for the date.
This is all real nice, but unfortunately the weekend forecast needs some major invasive surgery this evening. That "cutoff" upper level low that was scheduled to harmlessly track through N. California has decided to remain a bit more attached to the trough moving by to the north instead. This allows a somewhat organized frontal band sitting offshore to pass overhead as it’s dying tomorrow. Lots of clouds and off/on showers is now the forecast for Saturday. And instead of 70’s, we’ll be in the mid 60’s or so. By evening a strong onshore (southwesterly) push has begun too. That brings in cooler air for Sunday. The only good news is that we wait until sometime Sunday afternoon for the next system to move inland. We get a dry window from Saturday night through early Sunday afternoon, then the chilly rains return. As for thunderstorms…the southeasterly flow is always good for storms in the warm season, even when models aren’t too keen on the idea west of the Cascades (as they are tonight). However, I notice both the MM5 and our own 21z RPM model just out show a sudden "blowup" of moisture moving up the Valley from 3am-8am. The look of it on the two models looks "thundery" to me, so there is a chance later tonight. Tomorrow though should just be plain old showers after 10am…I’ll post later if anything changes, otherwise enjoy the Easter Weekend…Mark
11pm Update: Forecast (unfortunately) appears to be on track with IR satellite and radar showing things beginning to fill in across Western Oregon. Some nice pulsing storms moving up the east side of the valley too. Looks live movement is due south or beginning to turn slightly southeast. That’s exactly what the MM5 and our own RPM model show…lots of showers and the flow turning southeast by daybreak overhead. Looks like a good morning to sleep in…after hopefully some lightning sometime after 1am???