Monday, March 11th, 2019 through Monday, March 18th, 2019
PM-2.5: 24-hour Fine Particulate concentrations are expected to range from Good to middle Moderate through Thursday; mostly Good readings are expected the rest of the forecast period.
Quite conditions start the week with high pressure positioned west of the state. Northwesterly winds should keep fine particulate in the Good range Monday. On Tuesday, the high slides overhead, then east, and southwesterly winds develop. Sunshine, and lighter winds turning southwesterly will cause an increase in fine particulate; readings will range from upper Good to low Moderate.
Southwest winds pick up Wednesday ahead of an approaching weather system and temperatures climb into the 40s. Precipitation could start as snow or freezing rain; however, as temperatures increase precipitation becomes all rain. Warmer temperatures over the snowpack will cause low-level moisture and areas of fog, and these conditions are favorable for Moderate fine particulate. The increase in temperatures continues Thursday with highs expected to range from the 40s north to the 60s south. Precipitation remains in the forecast thanks to an approaching cold front, and a few storms are possible as well. Moderate fine particulate will remain in place.
Extended models show cooler air moving in Friday changing rain showers to snow showers. Cooler temperatures remain through the weekend with an upper level trough in place. A few periods of light winds may allow hourly fine particulate to reach Moderate for a few hours; however, daily averages of fine particulate are expected to be Good to low Moderate through the weekend into early next week.