Wind is gradually shifting to easterly across the Cascades. With the additional drying of an east wind, low humidity, and very warm temperatures ahead there is a risk of rapid growth or spread, on our existing wildfires in the Cascades. A Red Flag Warning is issued for this critical fire weather through the day on Monday. A change in wind, temperature and humidity occurs Monday night into Tuesday morning .
Air quality will also be impacted Monday by the east wind carrying wildfire smoke westward. The current air quality forecast is good to moderate for the lowlands but, there is a risk, an increase of smoke in and around the Cascade foothills and through parts of Snohomish, Skagit, and Whatcom Counties will cause Unhealthy for Sensitive Groups Monday afternoon. Anticipate a hazy sky for western Washington Monday with clearing and air quality improvement as the wind returns to a westerly, onshore Monday evening.
Monday will be a sunny, hazy, day with temperatures 5 to 10 degrees above normal for late September. The warmest spot will be through the Cascade foothills and South Sound where highs will be in the low 80s. Most of western Washington will have highs in the 70s, mid to upper 70s from Seattle to Bellevue. High pressure will keep weather dry until Wednesday morning.
Tuesday morning a return to onshore wind will increase cloud cover for the morning hours. Cloudy skies will clear to sunny again Tuesday afternoon and highs will be in the low to mid 70s. A low pressure trough will track over western Washington Wednesday for a round of rain in the morning, a temporary break with sunbreaks early afternoon, then a round of rain showers in the evening. Scattered showers will become focused in a Puget Sound Convergence Zone (Everett to Seattle) by Thursday afternoon and gradually diminish through evening. Highs will be in the 60s. Sunshine returns Friday and Saturday with another low scheduled for rain Sunday.
Meteorologist Rebecca Stevenson
The KOMO 4-Cast Team
Updated Sunday Evening
Today's Record Temperatures