After a seemingly long period of rather warm, humid weather to end the summer, the pattern is finally transitioning to something that is far more recognizable as fall weather. Along with this cooler weather, however, comes the possibility for more organized storm systems, as well as severe weather. In this instance, we have a strong potential for severe weather that could be fairly widespread across the Great Lakes and Ohio Valley regions.
Here's what's going on: A strong trough in west central Canada is digging southward into the United States right now. A shortwave is expected to eject from the trough within the next few hours, causing a developing frontal zone to drop southward and allow rapid cyclogenesis to commence.
Here's the position of the surface low pressure system right now:
Here's what's going on: A strong trough in west central Canada is digging southward into the United States right now. A shortwave is expected to eject from the trough within the next few hours, causing a developing frontal zone to drop southward and allow rapid cyclogenesis to commence.
Here's the position of the surface low pressure system right now:
Today, this low pressure system will continue to organize along the front, and eventually move to the northeast. By tomorrow, the low-pressure system will likely be in Wisconsin, traveling northeast into Canada at a rather rapid pace.
At the same time that this cyclogenesis occurs, a strong cold-front will develop alongside the low-pressure system, drawing colder, drier air out of Canada and into the United States. Warm and moist "return-flow" from the Gulf of Mexico will also be drawn into the "battleground", setting the stage for an unstable and volatile atmosphere in the lower Great Lakes and Ohio Valley region. At the same time, strong winds in the upper atmosphere will allow the system to continue to organize and will also provide the support that tomorrow's thunderstorms will need in order to become severe.
All of this is expected to come together to allow for a decent severe weather outbreak to unfold across the area. However, there are still a few uncertainties as to what will happen.
1.) Cloud-cover/early morning rainfall- Many forecasters are concerned that early morning cloud-cover across the region will remain through the afternoon, suppressing rising temperatures from making it into the 80's. This will lead to a significant reduction in instability for the afternoon hours. While it won't rule out severe weather, it will definitely limit the impact of the severe thunderstorms later in the afternoon and early evening.
At the same time, however, some models, such as the NAM and SREF, are predicting moderate instability to develop across the area, in response to rising boundary-layer moisture and some breaks in the cloud-cover. If this occurs, the severe weather threat will be much more imminent.
2.) Stronger low-level jet winds may shift to the east of the area before the actual cold-front arrives, possibly limiting some of the severe potential. Although I do not see this as a potential problem as of yet, it is something that I will continue to monitor.
Given the above considerations and the factors going into this outbreak, it appears that our main threat will be widespread damaging winds. Even if we don't see enough instability tomorrow, damaging winds will still be a major threat with these thunderstorms. It is also possible that some areas see significant winds above 65 kts [75 mph] in some thunderstorms. If conditions are more unstable than currently forecast, we may in fact see a few isolated tornadoes as well.
I will keep you updated on our FB page.
At the same time that this cyclogenesis occurs, a strong cold-front will develop alongside the low-pressure system, drawing colder, drier air out of Canada and into the United States. Warm and moist "return-flow" from the Gulf of Mexico will also be drawn into the "battleground", setting the stage for an unstable and volatile atmosphere in the lower Great Lakes and Ohio Valley region. At the same time, strong winds in the upper atmosphere will allow the system to continue to organize and will also provide the support that tomorrow's thunderstorms will need in order to become severe.
All of this is expected to come together to allow for a decent severe weather outbreak to unfold across the area. However, there are still a few uncertainties as to what will happen.
1.) Cloud-cover/early morning rainfall- Many forecasters are concerned that early morning cloud-cover across the region will remain through the afternoon, suppressing rising temperatures from making it into the 80's. This will lead to a significant reduction in instability for the afternoon hours. While it won't rule out severe weather, it will definitely limit the impact of the severe thunderstorms later in the afternoon and early evening.
At the same time, however, some models, such as the NAM and SREF, are predicting moderate instability to develop across the area, in response to rising boundary-layer moisture and some breaks in the cloud-cover. If this occurs, the severe weather threat will be much more imminent.
2.) Stronger low-level jet winds may shift to the east of the area before the actual cold-front arrives, possibly limiting some of the severe potential. Although I do not see this as a potential problem as of yet, it is something that I will continue to monitor.
Given the above considerations and the factors going into this outbreak, it appears that our main threat will be widespread damaging winds. Even if we don't see enough instability tomorrow, damaging winds will still be a major threat with these thunderstorms. It is also possible that some areas see significant winds above 65 kts [75 mph] in some thunderstorms. If conditions are more unstable than currently forecast, we may in fact see a few isolated tornadoes as well.
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| Damaging wind threat for the area is at the forty-fifth percentile |
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