Another atmospheric river will bring heavy rain to Western Washington Friday evening and Friday night, potentially soaking trick-or-treaters and creating difficulty for drivers with areas of standing water and flooded roads. KIRO 7 meteorologists have called a Pinpoint Alert Day for Friday due to the heavy rain threat and the potential for disruptive weather for anyone out on Halloween night.
The main threat with this system is the heavy rain, though wind gusts in the 20–35 mph range can also be expected for anyone outside as the system moves through. This will not be a repeat of last weekend’s destructive wind event, and now that trees have already been tested by stronger winds this fall, the scope of power outages is expected to be much more limited.
Those along the coast, Strait, northern islands, and North Sound stand the best chance of getting heavy rain during prime trick-or-treat hours for younger kids in the early to mid-evening. While the timing of the heaviest rain in other areas will be firmed up as we get closer to Halloween, from the Everett area south, we might luck out with lighter showers through the early evening.
Anyone putting together a Halloween costume with plans to be outside should have a weatherproof option ready.
The later we go Friday night, the more areas will get heavy rain, and by midnight Saturday morning, most locations should be seeing rainfall rates that could overwhelm leaf-clogged storm drains. Try to clear drain grates around your home (if it can be done safely) before rain arrives Friday evening. The heaviest rain will have cleared Western Washington by Saturday morning.
Drivers Friday night should be watchful not only for trick-or-treaters and other motorists but also for areas of standing water on roads after dark.
Rainfall totals of a quarter- to a half-inch around the lowlands can be expected by early Saturday morning, with higher amounts across the northern islands, far northern sections, the coast, and the Strait.
In the mountains, this atmospheric river will be warm aloft, bringing heavy rain to the passes before some chances for high-pass snow later in the weekend as showers taper in the lowlands.
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