Issued: 12am on Thursday, January 1st 1970
Technical Forecast Discussion
Short Term (Wednesday 10/9 through Saturday 10/12)
In conjunction to subjectively zonal and diminished flow aloft, weak upper ridging will briefly remain in control over SE Ohio before breaking down late Friday. Simultaneously, the previously projected upper level trough will continue to deepen over the Western Central U.S and take on a negatively tilted axis by 06z Friday. Its strengthening surface low ~996mb will begin to ingest cooler air and become vertically stacked over NE North Dakota by about 06z Saturday. This disturbance will extend a well-defined cold front that will eventually encroach on the region by Saturday morning and introduce some gusty winds and a cooler air mass…Wednesday night, proper radiational cooling and inverting near the surface will ensue as winds will remain weak in addition to any minimal cloud cover. Patchy fog development will be possible for the mornings of Thursday and Friday and likely be seen within the valley locations. The development early Thursday morning is likely, but with a pocket of moisture projected within the 875-850mb may slightly hinder its development and offer an increase to overnight cloud cover. Higher pressure ~1024mb will briefly remain located NE and SE of Ohio, which will continue to influence drier, but warmer conditions for Thursday and Friday. Temperatures will climb into the upper 70s as weak-calm surface winds reduce the efforts of daytime mixing and gradually introduce weak WAA. Cloud cover and moisture will slowly increase late Friday evening as the aforementioned upper disturbance will introduce its quickly moving cold front between 12-14z Saturday. The intensity of the precipitation, if any will remain fairly low as instability parameters and lapse rates will be extremely weak. Although, some weak-moderate rainfall will still be considered possible slightly ahead and along the front itself as the lower-mid levels significantly moisten at that time. Drier and much cooler air will quickly filter in aloft (850mb) with its passage and significantly confine the afternoon high to near 60. CAA and high pressure ~1020mb will quickly filter in for Saturday afternoon and into the early evening. Depending on how quickly the low-level moisture and cloud cover can evacuate mid-afternoon may influence a slight increase to this temperature…Temperatures will gradually warm into the upper 70s for Thursday and Friday in before a cold front sharply reduces the temperatures to near average for the weekend. Saturday night’s low may drop further into the mid-30s and possibly introduce the first frosting of Fall.
Long Term (Sunday 10/13 through Tuesday 10/15)
The previous upper level disturbance will stall out just north of the Great Lakes as high pressure ~1016mb situates just east of the region on Sunday. In combination, strong SW’ly flow will bring in more WAA and temperatures back near the lower 70s for Sunday and Monday. This high pressure will progressively break down over Sunday and into Monday as another cold front quickly advances on the region for Tuesday. As another shortwave trough pushes east into the Great Lakes region, the Jet stream will be positioned W-E along the southern U.S and offer favorable convergence over northern Indiana 12z Tuesday. A surface low is expected to develop over this region as it extends a SW’ly cold front. Future guidance shows this low lifting further NE as its cold front advances onto the region and makes passage by late Tuesday night/early Wednesday morning.
