Issued: 12am on Thursday, January 1st 1970
Technical Forecast Discussion
Short Term (Sunday 7/28 through Wednesday 7/31)
Fog development may become possible for early Monday morning as radiational cooling will once again occur overnight. Favorable decoupling of the surface boundary will look to transpire depending on how much the winds weaken overnight, but between the 6am-8am, patchy fog in the low-lands and valleys may develop. Shifting focus, upper-level ridging that has been providing the region dry and warmer weather will begin to break down and shift further northeast. This pattern with its weak zonal flow will vacate mid-late on Monday in presence of the incoming shortwave from the northwest. This upper shortwave trough will dig further into the central Great Lakes region by the afternoon on Monday and continue to progress further NE. In its progression, the mid-level trough axis tilts negatively, giving sign of further strengthening of the surface low. Despite the given strengthening and mature stage of this disturbance, upper-level winds, lapse rates and moisture/pressure gradients remain relatively weak. By Monday afternoon, winds will predominantly shift southerly and begin to advect WAA and low-level moisture into the region. With a fairly unstable environment ahead of the system, showers and even a thunderstorm may pop-up into the afternoon and evening hours. Severity will be very much limited, but not completely ruled out as CAPE parameters, lapse rates and upper level forcing remains weak. The associated surface low will drape a cold front from the WNW, approaching the region by late Tuesday night. With the nearing presence of the front, Tuesday will see a southwesterly shift in winds, which will hold for better chances of thunderstorm activity. As shearing and lapse rates remain weak, CAPE values may end up reaching 2000-2500 J/kg Tuesday afternoon and offer some multi-cellular development ahead and along the front. The cold front then drops southwest of the region by early morning on Wednesday. Cloud cover and low-level moisture will begin to decrease as Wednesday progresses, but current NAM and GFS runs agree on possible weak diurnal convection in the afternoon/evening hours. Still remaining fairly unstable and absent of strong and organized flow, the risk of slow-moving convective storms could bring some heavy downpours. High pressure will finally fill in over the Great Lakes by midweek as the temperatures stay consistently near average.
Long Term (Thursday 8/1 through Saturday 8/3)
Exceedingly broad upper-level ridging continues to take place across the western U.S, extending through the Great Plains and into the Midwest regions. Dry and mostly sunny conditions will be expected for the beginning of this forecast period as a dominating high pressure (~1021mb) fills in eastward across the Great Lakes. Also, temperatures continue to remain near average with highs into the mid-upper 80s. Southerly flow once again will take shape for late weekend/early work week as a high pressure develops for southeastern U.S. Interestingly, the previous cold front that looks to push south of the region early Wednesday (7/31) will interact with an influx of warm and moist air from the south and form a stationary boundary along the Ohio river. Very weak upper-level forcing will be present just south and east of the region, but with the presence of this boundary, diurnal thunderstorm activity may exist into Sunday.
