Beautiful Memorial Day Weekend On Tap!

What a beautiful day it is today! With a strong ridge of high pressure centered just off our coast, we have bluebird skies, light winds, and very warm temperatures, with many places around the Portland metro area making it into the 80s! This ridge will move right over us for Memorial Day weekend, meaning our sunniest and warmest days of May are still to come!

One of my all-time favorite charts for forecasting temperatures is a spaghetti plot showing the predicted 850 hPa (around 5,000 feet) temperature amongst all the GFS ensemble members. The spread in the ensembles gives you an idea of how confident the forecast is, and the 850 hPa temperature (as opposed to the 2-meter temperature) is useful because you don’t have to worry as much about the local effects of terrain skewing your temperature readings. As you can see, 850 hPa temperatures at both Seattle and Portland will increase as the weekend goes on, peaking in the low 80s for Seattle and near 90 for Portland on both Sunday and Monday as a thermal trough makes its way into the area.

As the weekend goes on, keep an eye to the Cascades for convection and possible thundershowers developing in the afternoon/evening, particularly on Monday. This is due to moisture over the Pacific slowly making its way eastward as the ridge over our area continues to drift further east.

By Monday evening, CAPE values in excess of 1000 J/kg will be found over the Cascades, which is more than enough CAPE to lead to thunderstorm development. Though the vast majority of these thunderstorms should stay over the Cascades, these storms can occasionally drift northwestward into the lowlands, especially after the sun goes down. Regardless, those with a view of the Cascades should be treated to a good lightning show Monday night!

A big marine push comes through Tuesday, bringing our temperatures back down closer to average for this time of the year. Enjoy the beautiful weekend ahead!