Forecast: Cold air intrudes this week

The Northern Hemispheric pattern change, which we discussed last week, will finally come to fruition in terms of sensible weather in our area late this week. Several rounds of cold fronts have helped us “step down” into a much colder pattern, with arctic air intruding the Northern 1/3 of the United States during the middle to latter part of this upcoming week. The cold air will peak over the Northeast US late this week and into the weekend, as a mid level ridge on the West Coast of the US flexes its muscles, and multiple disturbances slide southeast into a large trough over the Eastern 1/3 of the US, reinforcing the cold air.

A weak coastal storm system is forecast to slide off the coast of the Mid-Atlantic states on Wednesday, but forecast models are not impressed with the strength or potential precipitation from the system. Owing to the suddenly fast and progressive nature of the pattern, the storm is expected to slide east/northeast quickly off the coast, after a cold front passes the area. Behind the system, stiff west-northwesterly winds will push in the cold air. Overnight and morning low temperatures on both Thursday and Friday mornings will be the coldest of the season to date.

NAM model forecasting morning low temperatures in the 30's and 40's on Thursday morning. Friday morning may be several degrees colder.

NAM model forecasting morning low temperatures in the 30’s and 40’s on Thursday morning. Friday morning may be several degrees colder.

Through the weekend, the cold air will be noticeable. For the first time this year, the cold won’t be a nighttime or morning only event. The still west-northwesterly winds and very cold air above the surface (850mb temperatures fall between -4 C and -6 C on Thursday) will keep high temperatures in the 50’s throughout the area on Thursday and Friday. Such a change will certainly sting a bit, after several weeks of pleasant weather and high temperatures reaching into the 60’s and 70’s despite very cool mornings.

Through the end of the week, chances for heavy precipitation seem minimal. More clouds than Monday are expected on Tuesday and early Wednesday with the passing storm system. A few sprinkles can’t be ruled out, either, as the system scoots eastward. But all in all, the pattern looks cold and blustery beginning late Wednesday and continuing through this upcoming weekend.