Thunder, rain, and more! Here’s what to expect from this week’s fall weather

SEATTLE — With another quarter-inch of rain so far today at Sea-Tac Airport as of 3 p.m., the official tally for September is now 2.55″, nearly an inch more than the average September rainfall of 1.61.” In fact, the last three days have seen more rain than the entire period June to August!

More showers and isolated thunderstorms are likely Tuesday night with the chance for ponding of water on roadways, lightning, and possibly some urban flooding for a time.

However, eyes are on a developing storm system in the Pacific that will rapidly intensify in the coming hours and come ashore on Wednesday morning.

There is still uncertainty as to the track of the low – with the location of landfall Wednesday morning possible anywhere from the central or north coast of Washington to the mouth of the Columbia River. The stronger this low pressure can get, the more likely it tracks farther north – and with greater impacts to Western Washington.

However, as of 3 p.m., the best forecast has the low moving shore in the central or southern Washington coast near or just before sunrise Wednesday. It would quickly track eastward through the morning hours. On this trajectory, the strongest winds would be from the Seattle or Tacoma areas south. It is quite possible a farther south track is taken, which would significantly lessen impacts across Western Washington. But we have to prepare nonetheless.

Wind gusts near and to the south of the storm track would likely be in the 30 to 40 mph range with isolated higher gusts. Later in the fall, this storm would be of only moderate impact, but given trees still have all their leaves and some were weakened by the drought, we’re likely to see tree damage and some power outages near and to the south of the track of the low.

As of the 3 p.m. forecast, the most likely range of peak wind gusts is Wednesday morning but is highly subject to change as the storm evolves.

  • North coast/Strait/Islands: 20-35 mph.
  • North Sound, including Everett: 20-30 mph.
  • Central Sound, including Seattle: 25-35 mph.
  • South Sound and south interior, including Tacoma, Olympia, and Chehalis: 30-40 mph.
  • Central and south coast of Washington: 35-45 mph with isolated gusts to 50 mph+ on the beaches of Grays Harbor and Pacific counties.

People should prepare for possible power outages Wednesday morning through midday Wednesday with flashlights, charged phones, etc. There could also be tree damage that causes travel disruption.

Also, plenty of rain will come in with this system, especially near and to the south of the track.

Beyond Wednesday’s potential wind event, we’ll have some showers and sun breaks the remainder of Wednesday through Thursday and it stays a little blustery.  Highs will be near 60.

Friday through the weekend, expect more sunshine after morning clouds or fog and rain-free conditions. It will remain cool with highs in the low to mid-60s in Seattle but the sunshine will make it feel a little warmer.

Another rain chance could come our way around Tuesday of next week.