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Issued: 8pm on Sunday, September 20th 2020

Technical Forecast Discussion

Short Term (Sunday 9-20-2020 through Tuesday 9-22-2020)

NVA combining with decreasing differential thickness advection will work to amplify a ridge over the forecast area Sunday. This will slightly warm temperatures into the 70s, as opposed to the 60s we’ve been seeing over the area for the past few days. The cold core high resulting from the left entrance of a jet streak will continue to follow its forcing off to the east. This ridge will continue to be present over the area on Monday. Skies should cloud up on Monday resulting from slight PVA and WAA at 500 mb. We should see peaks of sun through the overcast Monday as forcing will not be strong enough for precipitation, or widespread clouds. Monday’s PVA should also work to create slight height falls over the region as the hours tick by on Monday. This will slightly cool temperatures down Monday night into Tuesday. A potent closed upper low, now located over Manitoba, Will begin to lose its punch as it starts to occlude over western Ontario over the next few hours. This is doe to decreasing differential thickness advection aloft. Because of this, the feature will not affect us greatly on Tuesday, outside of a few clouds, and slightly cooler highs. flow will shift to the NW, as hurricane Teddy makes its way to the east coast by Tuesday. This will also be a factor in slight ridge erosion over our area on Tuesday. As height gradients become tighter because of this, mid and upper level winds will slightly begin to pick up. However, these will not become strong enough to produce any form of cyclogenesis on Tuesday.

Long Term (Wednesday 9-23-2020 through Saturday 9-26-2020)

Winds resulting from the slightly tighter height gradient will provide a source of shear vorticity to develop over the southeastern states. This VORT axis will begin to be advected northeastward throughout the day Wednesday. Increasing differential thickness advection will work to deepen these height falls into a subtropical trough over the region for Wednesday. Highs should remain in the lower and middle 70s going into Wednesday. Clouds will be scattered throughout the area, as slightly negative omega will be present due to PVA and very weak WAA aloft. Strong increasing differential PVA and weak WAA should generate enough negative omega to produce widespread clouds, and possible precipitation Thursday morning. On and off rain should continue throughout the day Thursday, as this subtropical toughing feature will continue to affect the area. After this positive VORT axis moves through the area, NVA will begin to occur for Friday. This, along with decreasing differential thickness advection will work to amplify another ridge into the area to start the weekend. Mainly calm weather will persist for Friday, with large-scale sinking motion due to positive omega from NVA and CAA aloft. A strong surface low resulting from the left exit of a jet streak will form over Canada. This cyclone will be so strong due to the Coriolis force that flow over our region will will be affected by this on Friday and Saturday–out of the south. This will advect much warmer temperatures into the area for Saturday. Highs will be in the upper 70s and lower 80s, with partly cloudy skies.