Warming Through Thursday, Then A Colder Regime

Early spring is upon us! I went hiking on Friday in Forest Park with fellow WeatherTogether blogger (and music buddy… he’s a great sax/french horn player!) Karl Bonner ahead of the cold front that swept through later that evening, and we had a great time looking at the budding flora, most of which had not yet flowered. The pictures we took on our phones did a pretty poor job capturing the buds, but here’s an example of a budding Bigleaf Maple anyway.

Those more knowledgeable than me say that most trees are a bit ahead of schedule in the flowering department. The Magnolia Tree outside Union Station is already beginning to bloom, and I’ve even seen a few early cherry blossoms scattered throughout the city. I surmise this is due to the exceptionally warm winter we had, even though we didn’t see a great deal of sun through mid-February!

We currently have a moderate ridge of high pressure in the Eastern Pacific that is helping nudge a moderate/strong system into British Columbia. The Washington Cascades have seen orographically-enhanced precipitation courtesy of moist/strong mid-level westerly flow with this system, with several inches of snow falling above 3,500 – 4,000 feet.

Precipitation will weaken dramatically overnight and the Cascades should be mostly dry by Tuesday morning as tonight’s system moves east into the Canadian Rockies. However, another system will approach from the northwest Tuesday night, spreading rain once again into northwest Washington and perhaps giving some light drizzle to the Portland metro area Wednesday morning. Like tonight’s system, this storm is primarily headed to our north and is embedded in strong westerly flow, and as such, the Cascades will see the most precipitation due to orographic enhancement on their western slopes.

We’ll see clearing skies Wednesday evening, and Thursday will be our nicest day of the week as a ridge of high pressure builds ahead of an incoming cold front. However, this front will come crashing through on Friday, sending temperatures from near 60 on Thursday to the upper 40s on Friday. Just like this past Saturday, Friday’s airmass will be unstable, and any particularly heavy showers could contain small hail and maybe even a rumble of thunder.

The GFS ensembles (below) are in good agreement that a deep trough will settle behind Friday’s cold front and persist through Tuesday of next week. Though highs should moderate from near 50 on Saturday to the low or even mid 50s by Tuesday, lows will stay in the mid 30s and could even dip below freezing in outlying areas, particularly if we see a clear night and excellent radiational cooling.

To summarize: Expect an improving trend through Thursday, but another dramatic cold front to finish off the week, with cooler-than-average temperatures persisting through early next week as a deep trough moves over the area. As a side note, California will get some much-needed snowpack later next week as this trough deepens and the storm track heads south – they started off the water year with a bang but their snowpack is now well-below-average.

Thanks for reading and have a great week!
Charlie