Issued: 12am on Thursday, January 1st 1970
Technical Forecast Discussion
Short Term (Wednesday 9/25 through Saturday 9/28)
High pressure ~1017mb was once over SE Ohio earlier this morning and will progressively break down as it newly positions westerly along the Mid-Atlantic coast. In response, an upper shortwave trough currently located over the northern Mid-West will quickly propagate easterly over the Great Lakes by 21z Thursday as prominent zonal flow fills in behind… A fairly weak cold front from the WNW will begin its approach onto the region late Wednesday evening as it currently resides along the Indiana/Ohio border. Cloud cover will begin to thicken overnight as the lower levels (850mb – 700mb) gradually moisten by 07z Thursday. In addition to the cloudy conditions, fairly weak SW’ly flow near the surface will help maintain a slightly warmer low into the low 60s. ‘Absolutely Stable’ lapse rates and well-limited energy/moisture values will keep the QPF and the intensity of any frontal precipitation very low. The heavily hindered cold front will introduce weak-moderate rain showers slightly ahead and along the boundary itself before seeking a quick and timely passage by 13z-15z Thursday. Leftover moisture and cloud cover within the lower levels will linger into the early afternoon before mixing out with prominent NW’ly CAA and stronger zonal flow aloft. The timing of this FROPA and introduction to a cooler air mass will limit the afternoon high to the upper 70s. Moderate high pressure ~1016mb briefly fills in over the region for the remainder of Thursday and Friday. This brief high will quickly propagate further east and offer a veering southerly flow and increase in moisture that will return the risk for showers and thunderstorms Friday night into Saturday. Warm and unstable conditions will exist late short term as another cold front from the NW approaches SE Ohio Saturday afternoon…500mb heights will steadily be on the rise through late week/weekend with temperatures greatly warming into the mid and upper-80s.
Long Term (Sunday 9/29 through Tuesday 10/1)
Throughout Sunday, strong downstream flow will exist along the Pacific West coast as a deepening upper-level low develops over the Pacific NW. In conjunction, strong mid-level ridging will develop and persist over the lower Mississippi river valley for the remainder of this term. The recently mentioned upper level convergence and divergence zones will direct the strong flow aloft in a SW”ly-NE’ly fashion across the continental U.S. Therefore, strong ridging and a persisting high pressure ~1020mb (over SE U.S.) will continue to influence ‘drier’ weather and advect hot and humid conditions into the region. Dewpoints will consistently reach into the lower 60s as temperatures greatly warm well-above average with highs nearing 90. This relatively absent flow aloft with unstable conditions near the surface may introduce some diurnally driven (isolated) convection through late long term.
