After a long dry period, western Washington and Oregon are finally getting some significant rain.
The radar image at 7 AM shows a mass of precipitation extending roughly from Seattle to Portland, some of it of moderate intensity (yellow colors). This precipitation is coming from an unusual direction: from the east.
The infrared satellite image at the same time shows the extensive clouds over the region, some of it clearly convective. But none of it is deep enough for lightning.
As of 8 AM, there has been significant 24-h precipitation over the Cascades and southwest Washington (see below)
The latest NOAA HRRR forecast of accumulated rain from 5 AM Friday until 8 PM tonight, predicts up to approximately half an inch from the Olympics to the south Cascades.
An Admission
This situation has not been particularly well forecast. On Wednesday afternoon our model prediction had the rain heading further northward (the 72h rainfall total ending 5 AM Saturday is shown below).
On Thursday morning, our prime tool for understanding forecast uncertainty...ensembles of many high-resolution forecasts, was starting to show the potential for rain with about half of the ensemble members going for significant precipitation (see accumulated precipitation plots for forecasts starting 5 AM Thursday, time increases to the right). Each line is one model, the black line is the average of all of them.
By last night, the ensembles were going wet (see the forecasts below).