Monday, August 31 - Wednesday, September 2, 2026 Convective Episodes

[weatherwiz]

The weather pattern across the CONUS the past few months has been dominated by a large ridge of high pressure across the southern Plains with the ridge centered within the New Mexico - Louisiana vicinity. This has resulted in a prolonged period of some extreme heat within this region while also yielding convectively active periods within portions of the Great Plains, upper-Midwest, and Ohio Valley region. Computer forecast models have been consistent in the eastward expansion of this ridge across the deep South with an eastwards shift in the ridge axis farther northeast, potentially into the Mississippi or Tennessee Valley region (this does greatly impact us). The shift in the ridge axis would push the periphery of the jet stream across the northern tier of the Great Lakes region and across New England. 

As we speak, high pressure is building into the region and will dominate through the weekend, however, late Sunday a weak cold front approaches from the north. Computer forecast models then stall the front within the region on Monday and this is where the fun begins. An unseasonably strong northwesterly flow is expected to overspread the region along the periphery of the upper-level ridge early in the week, meanwhile a more westerly surface flow (south of the weak stationary front) will advect warmer and more humid air from the Ohio Valley into the region. Multiple shortwave impulses will traverse the jet, originating from the upper-Midwest/Canada. This will offer the opportunity for multiple thunderstorm clusters to develop across southern Canada and the northern Great Lakes which and traversing the region Monday and again on Tuesday. The biggest key here is where will the instability gradient reside? Historically, this seems to favor New York, Pennsylvania, New Jersey, and perhaps far southwest Connecticut but this is going to be highly dependent on where that stationary front resides and how strong is the push of warmer and more moist low-level air.

The more intriguing day is expected to be on Wednesday. This is when computer forecast model guidance advances a sharper trough across southeast Canada with a cold front moving into the region at the surface with the stationary front perhaps lifting back northeast as a warm front. In addition, there have been some hints at the potential advection of remnant elevated mixed-layer air. In addition, flow aloft, particularly  in the lower levels is expected to increase and should the low-level flow become more southwesterly or southerly, this would result in a greater surge of moisture into the region and potential for moisture pooling. Within the warm sector, 850mb temperatures are forecast to climb to +17C to +20Cwith 850mb dewpoints +15C to +17C. This would yield potential for surface temperatures well into the 80's and surface dewpoints well into the 60's to lower 70's. This combination, potentially under the presence of steep mid-level lapse rates under the presence of an advecting elevated mixed-layer would yield potential for moderate instability (MLCAPE > 2500 J/KG) to develop. 

The combination of a moderate unstable airmass with increasing shear and forcing would net the likelihood for scattered-to-numerous thunderstorms developing during the afternoon on Wednesday; including potential for line-segments and supercells with hazards of damaging wind gusts, large hail, and perhaps even the risk for a few tornadoes if we can get some turning of the low-level flow and enlarged hodographs. At this time, the greatest potential seems to be across Pennsylvania, New York, and northwest New Jersey, however, this is all highly dependent on key surface features but western southern New England would definitely be in play. While the threat for strong-to-severe thunderstorms would gradually wane with the loss of daytime heating, showers and thunderstorms could work their way through the coast Wednesday night. 

Lots of details to iron out over the coming days!