Vancouver, BC, Enjoys Weekend Warmth While Thunderstorms Strike Portland, OR

Friday and Saturday turned out warm, sunny and generally lovely in Southwest BC. At Vancouver International, the temp climbed to 20.3ºC (69ºF) by 1600 on 25 May, even despite a strong WNW to NW wind up to (17 kt) at 1300. On 26 May, the temp climbed to the highest of the year so far, reaching 23.5ºC (74ºF) by 1900 (quite late!), with light SW to WSW winds. The low between these two highs occurred at 0500 with a reading of 8.5ºC (47ºF). Interestingly, our high on Saturday proved warmer than at Sea-Tac with a report of 22ºC (72ºF). Portland also reported a relatively cool high of 20ºC (68ºF) on the same day.

Diurnal thunderstorms afflicted Portland on 25-26 May, with the event of the second day quite spectacular. The Friday event occurred between 1828 and 2010, with light rain amounting to 2.2 mm (0.09"). Maximum winds were E 30 km/h (16 kt) at 1828. The following day at nearly the same time, between 1917 and 2004, a thunderstorm brought with it very heavy rain (for the region). Some 25.9 mm (1.02") fell in the hour ending 1953. NE winds reached 30 km/h (16 kt) gusting 56 (30 kt) at 1932. Vancouver, WA, reported heavy rain from 1929 to 1946, with 21.1 mm (0.83") in the hour ending 1953. According to NWS Portland, both Portland International and Vancouver Pearson set new record daily maximum rainfall due to this convective activity, with the old records of 23.6 mm (0.93") and 16.5 mm (0.65"), respectively, standing since 1953 and 1909. These thunderstorms did not show up in places west, such as Hillsboro. Sea-Tac reported a thunderstorm with light rain between 1851 and 1853 on 25 May, with just a trace of precipitation measured.

The weather up here in Vancouver, BC, changed noticeably on Sunday, 27 May, as a Pacific frontal system approached. Easterly winds picked up dramatically in the morning even as a deep marine layer moved ashore and brought a solid, gloomy stratus deck inland, apparently overriding the offshore surface flow. Winds reached E 37 km/h (20 kt) gusting 54 km/h (25 kt) at 0300, then slowly tapered off into midmorning, and shifting direction to ESE-SE. The clouds fragmented somewhat during the afternoon, allowing a peeks of sunshine at times and helping the temp warm to 18ºC (64ºF). The clouds thickened overnight, and light rain showers began around 0451, continuing until 0900 with the culmination of steady light rain. The temp hovered around 12ºC (54ºF) during the precipitation. Now a gray stratus deck dominates, with light southerly winds and fairly high humidity. In association with the incoming front, the pressure fell to 100.92 kPa (29.80" Hg) at 2000 on 26 May, even with the boundary well offshore. The atmospheric pressure slowly rose afterward as the steadily weakening front approached. During the rain, the barometer indicated 101.75 kPa (30.05" Hg) at 0900 this morning.