FORECAST SUMMARY:
Monday, December 21st, 2020 through Monday, December 28th, 2020
PM-2.5: 24-hour average Fine Particulate concentrations will be upper Good to middle Moderate through mid-week, then Good Christmas Eve and Christmas Day. Moderate levels may move back in for the weekend.
FORECAST DISCUSSION:
A clipper system tracking northwest to southeast Monday will bring with it some light precipitation, mostly falling as snow. A high-pressure ridge slides through Tuesday. As it tracks east, northerly winds turn southwesterly and increase in speed early Wednesday ahead of the next approaching system. For the Christmas Holiday, we can expect dropping temperatures late Wednesday, into Christmas Eve as a cold front brings in strong northwesterly winds in its wake. The cold front will have some precipitation associated with it, but what will be most noticed will be the drop in temperatures Christmas Eve and Christmas Day, and lake effect snows kicking in.
As for air quality, fine particulate levels have been lingering mostly in the low to middle Moderate range since this past weekend. While levels should improve some behind the Monday system, 24-hour readings Monday and Tuesday may still linger in the low Moderate range. Stronger southwesterly winds Wednesday will hamper a significant fine particulate building up. Readings statewide will improve to Good late Wednesday as cold artic air ushers in on a northwest wind. Good fine particulate readings can be expected both Christmas Eve and Christmas Day.
EXTENDED FORECAST:
Extended forecast models show lake effect snows ending Saturday as high pressure moves in. Generally quiet weather is expected Saturday and early Sunday with the next system approaching by Monday. Without a noteworthy period of stagnation, fine particulate during the weekend into early next week will range from middle Good to low Moderate.