Issued: 12am on Thursday, January 1st 1970
Technical Forecast Discussion
Short Term (Wednesday 8/21 through Saturday 8/24)
Objectively meridional flow across southern Canada has been hindering further progression of the now-present shortwave over the northern Great Lakes. A SW’ly to NE’ly positioned Jet across the central Great Lakes has its right entrance region located in northwest Illinois and more pronounced left exit north of New York. The strengthening surface low just north of the state of New York has been slowly dragging its extended cold front southeasterly through the lower Great Lakes. Wednesday night, the positive trough axis will be accompanied by weak to moderate flow, but vaguely increase throughout the day on Thursday as it treks further NE. The aforementioned cold front will encroach on the region Thursday morning with intentions of becoming somewhat static near southern Ohio late Thursday. Cloud cover will thicken in addition to showers and thunderstorms forming ahead of the front early on Thursday (approximately 12z-14z). The timing of this early prefrontal precipitation/extensive cloud cover may affect the projected high temperatures and influenced afternoon convection across the region. As of now, this Thursday afternoon convection ahead and along the frontal boundary will be aided by a strong southwesterly flow, 2000 J/kg – 2500 J/kg CAPE values, moderate wind shearing (35knots) and well saturated profiles. Some severity is considered for the afternoon and early evening hours with strong and gusty winds being the primary considered threat. Heavy rainfall and potential flooding concerns will again be considered with this moisture loaded atmosphere. Dew points will once again reach into the upper 60s alongside precipitable water values up to 2.2in. The cold front takes passage through southern Ohio by early Thursday evening, but leaving some secondary low-level moisture and rain chances through the first part on Friday. In addition to the frontal passage, northerly flow and CAA follows suit Friday and into the first part of the weekend as high temperatures will be seasonably cooler. The end of the short term will also be drier as strong high pressure briefly (about 1027mb) fills in over the northern Great Lakes before being influenced eastward on Sunday.
Long Term (Sunday 8/25 through Tuesday 8/27)
Drier and much cooler conditions will persist throughout Sunday as the high temperatures fluctuate around the low 80s. The projected high pressure to the north will push eastward and out of the region as upstream upper level ridging takes shape for the second half of Sunday. Southwesterly flow and prominent moisture advection return out ahead of another shortwave trough digging its way across the upper Great Plains early on Monday. Temperatures will gradually rise back into the mid-80s on Monday and Tuesday, but at cost of higher dew points readings. Late forecast period and into midweek will hold for more warm and unstable environments, which will promote afternoon convection and more spotty rain/thunderstorm chances.
