Valley eludes hailstorm but gets natural fireworks shows

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It was an active weekend of weather for the Walla Walla Valley. A Pacific low pressure system just west of the California/Oregon border spun spokes of moisture from the southwest to the northeast through Oregon and Washington, touching off rounds of showers and thundershowers on both Saturday and Sunday.

In the Umatilla National Forest south of Heppner, where your forecaster was camping with his usual cadre — consisting of a comely companion and a couple of clever canines, Saturday began benignly enough. But as the day wore on, gathering clouds to the south were a portent of a decidedly less friendly turn in the weather, and by 6 p.m. the distant, low-throated rumble of the first thunder signaled that it was time to put down that third glass of verdicchio and spring into action if we were to keep our well-exposed gear from getting soaked. With lightning and thunder getting ever closer, we rushed to and fro to stow as much of it as we could and covered the rest with a tarp in anticipation of the deluge to come, then retreated to the camper to wait out the storm. One hundred-fourteen raindrops later, it became rather obvious that the brunt of the action had passed us by to the west, and we toasted our small victory with the last of the wine.

It was much the same story in Walla Walla, where thundershowers played around the periphery of the city all weekend, teasing our town with occasional lightning and thunder but ultimately delivering precious little in the way of precipitation. Saturday afternoon brought a trace of rain to the airport, and Sunday’s action did the same, with the addition of a period of very gusty winds that reached 40 miles per hour and kicked up plenty of dust and debris. These winds originated from a severe thunderstorm to our west that brought hail and high winds along with more than one-quarter of an inch of rain to parts of extreme western Walla Walla County and neighboring portions of Benton and Franklin counties.

The downrush of cold air entrained in the rain and hail falling from the upper reaches of the storm cell was responsible for the chilly wind that blew into the city, though the cell itself was too far away to provide anything more than a few drops of rain. Temperatures plummeted from the low and mid-80s to the mid- and upper 60s in a matter of just a few minutes as the downdraft swept through the Walla Walla Valley. It is downbursts such as these that can play havoc with aircraft that are caught flying in them, as they are capable of negating any lift whatsoever — a particularly dangerous scenario at takeoff and landing.

The coming week’s weather will feature a transition from summer to fall as we flip the calendar to September. A fairly deep area of low pressure is forecast to set up off the Pacific Northwest coast this weekend — but just how far off the coast is a matter of some discussion between the two forecast models that we most commonly rely on. The Global Forecast System has the low just off the coast, a setup that would bring a good chance of showers and thundershowers to much of the area. In contrast, the European Center for Mid-range Weather Forecasting model holds the low well west of the coast, with a considerably lower possibility of precipitation. On Sunday, the GFS brings the system across the state while the ECMWF keeps it just off the coast.

Though the sports book at Harrah’s Las Vegas won’t take weather-related bets, your prognosticator has his hard-earned money on the GFS and considers the chance of some measurable rainfall this weekend about equivalent to your need for a few sessions of chiropractic after a couple of trips up or down Pleasant Street, which is about as bad a misnomer for that currently busted-up thoroughfare as can be imagined.

Much cooler air will also invade our part of the state owing to the northern origins of the low pressure system. Labor Day may end up considerably cooler than the normal low-80s we expect on that holiday from year to year, though it now appears as if we will warm up nicely in the following days.

Your weatherperson will be taking a pre-harvest vacation at the coast and hopes that September’s arrival there does not coincide with a general downturn in the weather courtesy of that same low pressure. If so, eating and drinking must necessarily replace outdoor activities — much to the dismay of his ever-expanding waistline.

A lifelong fan of both the weather and the Baltimore Orioles, Jeff Popick is an instructor at the Center for Enology and Viticulture at Walla Walla Community College and manages the school’s teaching vineyard. Send your questions and comments to him at jeffrey.popick@wwcc.edu.

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