WeatherWatcher: Heat Advisory In Effect

National Weather Service, Seattle, WA.

Heat Advisory is in effect until 10pm Tuesday evening. A heat advisory means a period of hot temperatures is expected. The combination of high humidities and temperatures combine to create a situation where heat illnesses are possible. Shoreline and Lake Forest Park will see high temperatures peaking probably between the 3pm-5pm time frame at the mid-upper 80s, maybe even a stray 90°F.

The thick smoke cover is reducing the amount of surface heating that is forecasted, most of the forecast models do not calculate the amount of solar radiation reduction caused by the smoke layer. We would otherwise make it into the low to mid 90's for a high temperature.

Source of the smoke is from wildfires in eastern Washington and eastern Oregon this time. Heat waves are generally caused by an offshore air flow patterns. This means winds are traveling from the east to the west. On a normal summer day here, we have an onshore wind, which means the winds are traveling from the west to the east. These winds keep the wild fire smoke east of the Cascade mountain range, and bring us our morning fog and afternoon sunny days, with cooler temperatures. Some even call onshore winds our natural air conditioner.

Forecast: Beyond Tuesday evening and Wednesday, onshore flow comes back, bringing us areas of fog and low clouds, and clearing out the smoke. Highs will still make it into the 80's during the day. Wednesday night, however, gets a little more interesting.

Wednesday night some clouds come in with showers, and there might be a slight chance of some thunderstorms. The threat of thunderstorms will last through Thursday evening, and the threat of showers will continue through the next weekend. High temperatures are expected to return to the 70's with lows dipping back down to the 50's.

For current weather conditions visit www.ShorelineWeather.com