Issued: 3pm on Wednesday, September 2nd 2020
Technical Forecast Discussion
Short Term (Wednesday 9-2-2020 through Saturday 9-5-2020)
Weak PVA in our region along with weak NVA behind it is keeping the jet fairly zonal overhead. This feature is also stirring up showers and thunderstorms across the area for Wednesday. Once synoptically driven morning showers exit the region, sunshine will make its appearance Wednesday afternoon. This will provide destabilization for the area, and may stir up a few convective cells during the evening hours Wednesday. An isolated damaging wind gust will be possible, especially south and east, due to DCAPE values nearing 1000 j/kg. This will work to entrain downdrafts, and accelerate downward motions inside convective cells. Again, this will be more likely the further south and east you are across Ohio. Showers will remain possible tonight due to increasing differential PVA, along with WAA at 500 MB, primairly south of I-70. This pattern looks to continue throughout the day Thursday. Off to our north and west, a strong VORT max will gain strength coming off the Cascades due to conservation of angular momentum Wednesday afternoon and evening. PVA will work to propagate this feature eastward, while positive differential thickness advection will simultaneously work to dig this feature south and eastward. Because of the tightening height gradient caused by this digging, a jet streak will form. At the left exit of this jet streak, strong upper level divergence will occur, and cyclogenesis will begin as a result of continuity. This will form over northern Minnesota. A confluence axis, driven by a VORT axis aloft, will cause frontogenesis of a cold front. This will slide east with its parent cyclone. This front looks to slide eastward across Illinois, Indiana, and eventually into Ohio through Thursday into Friday morning. This front should reach southeast Ohio by about 4 am Friday. Downstream of this front, temperatures should reach the middle and upper 80s for Thursday. Upstream, temperatures will be much cooler–in the upper 60s and 70s. That weather will be likely for Friday. With FROPA Thursday night and Friday morning, don’t expect much, other than a few clouds. This is due to a lack of VORT aloft associated with this front, along with lack of diabatic heating to raise SFC temps enough for convective forcing. While the jet will be overhead, the right exit of an embedded jet streak will drive a strong SFC high. This will locate itself over northern Missouri, and west central Illinois by Friday afternoon, bringing positive omega, and therefore clear skies to the area. Friday will be the day to be out and about this week, with highs in the middle and upper 70s, with mainly clear skies. This high will continue to follow its forcing, and locate its center over Ohio by early Saturday morning. With that said, another beautiful day for this time of year will be present on Saturday, with highs in the middle and upper 70s & lower 80s with mainly clear to partly cloudy skies.
Long Term (Sunday 9-6-2020 through Tuesday 9-8-2020)
A VORT max gaining strength as it comes off the Rockies will advect itself into our region by Sunday morning. This could bring possible rain chances to the state (mainly north, due to stronger WAA over that region) guidance is having trouble resolving this at this time due to differences in temperatures and temperature advection, with the EURO digging this south, and the GFS keeping it north. Much more will be known in subsequent forecasts. In any case, with the high off to our south and east, southerly flow will advect slightly warmer temperatures in for Sunday–lower and middle 80s. Another strong difference in the guidance is a VORT axis feature. The GFS begins to dig a moderately-strong VORT axis down into the US on Sunday evening and night. The EURO on the other hand supports an NVA regime, flattening the jet out over Canada. This will have implication on the possible formation of a sfc cyclone over the upper midwest going into Sunday night. As of this time, the EURO looks a bit more representative of the real atmosphere, but this could definitely change–monitor the latest forecasts. This small feature will have major impacts on the beginning of next week’s weather. If the EURO were to verify, strong ridging will build in toward the end of the weekend into early next week. This would return temperatures to the upper 80s and lower 90s to start next week. If the GFS were to verify, rain and storms would be likely, before a MAJOR cool down would come for the middle of next week. Much more information will be known in later forecasts–stay tuned.