Frontal system to affect Central/Eastern US weather into the work week

An upper level low pressure system moving east across the southern portion of Canada drags its frontal system across the northern portion of the United States during the weekend into the early next work week.

Forecast position of the low pressure system and attendant frontal system over the Great Lakes and Ohio River Valley by later Sunday. Courtesy of the WPC.
Forecast position of the low pressure system and attendant frontal system over the Great Lakes and Ohio River Valley by later Sunday. Courtesy of the WPC.

 

On Sunday, the warm front will be followed by the cold front allowing for showers and thunderstorms in the Great Lakes, Eastern of the Middle Mississippi Valley and northwestern portions of the Ohio River Valley with wind and hail damage being the main threats with any severe thunderstorms that form. However, the area with the best combination of shear (turning winds) and (CAPE) convective energy appears to be over northern Lower Michigan later Sunday. The main problem with this severe weather situation will be the lack of low level wind strength contributing to lower shear especially south of Lower Michigan. In addition to wind and hail threats, precipitable water values will approach 2 inches meaning poor drainage flooding may be possible especially in any thunderstorms especially over Lower Michigan where the largest area of large scale lift is being modeled.

 

Shear wind barbs and CAPE contours and coloring over Lower Michigan indicate the best chance for severe weather in Northern Lower Michigan Sunday.
Shear wind barbs and CAPE contours and coloring over Lower Michigan indicate the best chance for severe weather in Northern Lower Michigan Sunday.

 

On Monday, the cold front moves east with the Mid-Atlantic and New York being the main areas with the greatest combination of shear and CAPE along this front alluding to the best chance for severe weather. Wind damage will be the greatest threat with any severe weather in the aforementioned area. Precipitation of the pop-up variety is being modeled with the first front entering western Massachusetts later Monday into Monday night.

Energy plot showing the energy off the Eastern US with the cold front's energy entering Eastern New York early Monday.
Energy plot showing the energy off the Eastern US with the cold front’s energy entering Eastern New York early Monday. Courtesy of AccuWeather.

 

GFS Ensemble model output for Tuesday still showing a chance for precipitation in most of Eastern New England for Tuesday.
GFS Ensemble model output for Tuesday still showing a chance for precipitation in most of Eastern New England for Tuesday.

 

Beyond Monday, an area of vorticity east of the East Coast backs towards the East Coast helps to slow up the aforementioned cold front’s energy and may even affect the next cold front that enters the Northeast later in the day. Some pop-up showers and thunderstorms are modeled, but may not result in much because of how some dynamics result in this situation. Models have varying solutions modeled as a result of a few different things. Interacting energy involves dynamics on scales much smaller than models can simulate. Many times, an ensemble of varying solutions with slightly tweaked starting points (like the GFS ensemble or Euro ensemble) can simulate the correct, or close to correct solution, so interrogating those solutions can often lead toward the correct outcome. In addition, because the atmosphere acts in a wave-like system, the resulting energy may work to counter any precipitation within Eastern New England. For example, the front would get stalled over eastern New York with precipitation there and the energy off the East Coast would also have precipitation, but the lack of energy in between would just allow clouds over Eastern New England. An example of this would be Tuesday as portrayed by the GFS. This would all depend on how the energy does evolve during this period so it does appear at least some precipitation could fall on Tuesday and Wednesday over Eastern New England. It also appears that it should become increasingly sunnier on Thursday as the energy moves away from the region.

 

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