Transition weekend, stormy conditions next week

After strong to severe storms blew through the area on Wednesday evening, Canadian high pressure is back in control on Thursday. Cooler than normal air will slide back into the area over the next few days, with generally pleasant conditions. High temperatures in the 80’s will be more common than the 90’s from earlier in the week, but the lower humidity will make it feel much more comfortable. A transition in the pattern won’t occur until late this weekend into early next week, when unsettled weather will be poised to make a return.

As a mid level disturbance slides eastward through the Great Lakes, actually a part of a larger upper level trough, a warm front will slide northeastward from the Ohio Valley through the Northeast US. This will be the first sign of forthcoming unsettled weather, as increasing temperatures and forcing along the front will aid in the development of storms as early as Sunday morning. Multiple disturbances moving northeastward through the area will provide chances for storms on Sunday — but the main event would come on Monday as a low pressure system shifts through the Northeast US.

GFS model showing disturbances in the mid levels of the atmosphere approaching the area early next week.

The exact track of this low pressure system will have major impacts on the sensible weather which occurs, but forecast models have come into better agreement on a track from the Northeastern Ohio Valley into Northern Pennsylvania and Upstate New York. Such a track would allow for an increase in instability near our area and much of the Mid-Atlantic states, owing to an increasing southerly flow. But the timing, as modeled currently, doesn’t support a widespread severe weather threat with the front coming through during the morning hours on Monday.

GFS model showing a low pressure system to our northwest on Monday.

This obviously leaves us with increasing confidence in an unsettled period of weather, but uncertainties regarding exactly where severe weather may occur and the extent/areal coverage of those severe thunderstorms. If the front stays back to the west of the area until Monday afternoon, potential for severe weather could increase. But a faster timed front will bring us unsettled weather on Sunday and early Monday, but clearing thereafter.

A near certainty behind the front early next week is the fact that cooler than normal temperatures will overtake the Eastern 1/3 of the United States. A large upper level trough will shift through the Great Lakes and into the Northeast US, and establish itself near our area as ridging over the West Coast builds and high latitude blocking over Canada slows down the pattern. This means a higher than normal likelihood of cooler temperatures for a large part of next week.